Historically, everything from autogenous bone to xenografts, allografts, and alloplastic materials has been used and studied in dentistry when a graft or graft substitute is needed. These different materials have all been used with great success over the years, and they continue to provide clinically successful results. The alloplastic class over the years has become an exciting class since it is continually being advanced at a greater rate by new products than the allograft and xenograft classes.

Everyday, practitioners are faced with the need to graft and regenerate new bone. This can be an extraction site, an existing defect, or in combination procedures such as immediate implant placements or sinus elevations. The purpose of a graft material is to not only maintain clinical bone volume but also also to provide a framework for new bone growth as the particles are resorbed for new bone regeneration. Only in the case of an autograft will osteogenesis occur, as there are live cells capable of proliferating to create new bone. Therefore, a bone substitute is a natural or synthetic material, often containing only a mineralized bone matrix with no viable cells.¹ 

In studies, the 3 main classes of graft materials (allograft, xenograft, and alloplast) all showed the presence of newly formed bone with residual graft particles and connective tissue in greater or lesser amounts. The presence of newly formed bone in direct contact with residual particles of each bone substitute material indicated the adequate osteoconductive capacity.² 

This article will compare the makeup and advantages/disadvantages of the materials noted above and then focus on a material consisting of non-ceramic, synthetic, bioactive resorbable calcium apatite crystals known as OsteoGen (IMPLADENT LTD). These hydrophilic cluster particulates have physicochemical and crystallographic properties similar to human minerals. The low-temperature, bioactive calcium phosphate mineral also has the ability to control the migration of connective tissue.³ 

We are now going to look at and compare individual classes of graft materials to better understand the advantages of OsteoGen.

AUTOGENOUS BONE

Autografts remain the gold standard for grafting materials as they are still the only graft material that possesses the 4 fundamental biological properties required for bone regeneration, but they are not without issues.^1,4

An advantage of the use of autogenous bone graft materials is that they represent the highest degree of biological safety, and there are no histocompatibility or immunogenicity issues associated with their use.

Even with autogenous bone grafts being considered the optimal choice for augmentation, the procedure usually requires harvesting bone from a distant donor site. This resulting second site morbidity can, has, and will continue to lead to patient dissatisfaction. 

ALLOGRAFTS

Allograft materials, which are derived from cadaveric sources, have been used for decades with great success. These materials come in many forms, including mineralized and demineralized particulates and puttys. They are also available in cortical and cancellous formulations or a blend of the 2.

On their own, cancellous autografts and allografts have poor mechanical strength in addition to exhibiting inadequate healing capacity. The tissue-processing techniques, including treatment with alcohol, acetic acid, or nitric acid, reduce the materials’ osteoinductive capabilities.^1,5 These graft materials can also cause local host inflammatory responses, which can result in fibrous tissue formation rather than healthy bone. This is of concern and can produce up to 62% connective tissue, which is not conducive to good implant support after load (Figure 1).

Figure 1. Four clinical studies of allografts (mineralized or demineralized) conducted at New York University College of Dentistry and the University of Texas San Antonio from 2002 to 2012.

Cortical particles, on the other hand, do provide structural support and provide a mineral storehouse, but these take longer to resorb. This increased resorption time is a distinct advantage when trying to either rebuild height/width or maintain osseous architecture when thin cortical plates are present after an extraction. 

The downside, a common issue with all types of particulate grafts, is the possibility of migration or loss of material. Even if the particles are bound, as in bone putty by a binder, the addition of fluids, including blood, can wash these products out during clinical delivery. Finally, the literature supports the possibility of disease transmission by this class of products.⁶ 

Caution: Not all mineralized graft materials are the same.

ALLOPLASTS 

Historically, many substances have been used as components for grafting in dentistry, either by themselves or as a binder with other graft materials. This author has used many of these with varying results. Calcium phosphate is one substance that has been used as a bone cement either to deliver antibiotics locally or to bind allograft or xenograft particulates. One example of this type of product is Fusion Bone Binder (Park Compounding Pharmacy). Bi-phasic calcium phosphate products such as Augma Biomaterials’ 3D Bond (Augma Biomaterials) and Bond Apetite are products that are used alone as a graft material. Beta-tricalcium phosphate (β-TCP) products such as Cerasorb M (Curesan) is another material used alone to graft sockets or defects around implants. 

DENSE SINTERED ALLOPLASTS AND XENOGRAFTS

The Food and Drug Administration refers to dense, non-resorbing products as bone filler and augmentation materials (BFAM), and these have been used extensively for many years. To overcome potential immunogenicity and morbidity at donor sites, artificial synthetic bone substitutes and natural materials are manufactured to closely mimic the biological properties of natural bone.¹ These alloplast materials are either derived from natural substances (ie, coralline) or man-made and can be a homogenous product or a mix of materials. A variety of synthetically and organically derived dense bone formulations have been used in dentistry and medicine. In dentistry, they are used for the therapeutic repair and restoration of osseous ridge defect sites, post-tooth extraction (including periodontal reconstruction), sinus augmentation with and without implants, and post cyst removal with questionable results. Since these products have weak regenerative abilities on their own, highly sintered alloplastic and organic bone substitutes are often augmented with growth factors and membranes at an increased cost to the practitioner.

When evaluating the rates of resorption of ceramic hydroxyapatite (HA) alloplastic materials, the results are questionable. Densely sintered at high temperatures, pure ceramic HA has low microporosity and high density and is prepared in relatively large particle size with long resorption times. Essentially, these materials closely resemble ceramics. Sintered (non-resorbable) HA materials,⁷ xenografts, and allografts are often subject to fibrous tissue encapsulation rather than becoming a viable part of the host bone.⁸ 

Upon tooth extraction, the goal is complete regeneration while preventing pathology from arising that could signal the patient’s immune response against getting involved, depending upon the type of graft material used. One consequence is the involvement of macrophage cells. In extraction sites where dense products such as ceramic HA, TCP, glass, polymers, coralline, and xenografts are placed, these macrophages are recruited. This is in contrast to the normal mechanism of osteoclastic breakdown. 

These cells are signaled by an immune response to remove the graft material as foreign matter, and these 18-µm cells will continue to enter the socket area through the nutrient canals in the lamina dura (Figure 2).

Figure 2. The tooth-alveolous construct.

This immune response is inevitable in the use of these products, and the immune system’s mechanism is to eventually produce multi-nucleated giant cells to fragment (not phagocytose) these dense graft materials and transport the residual pieces to larger filters in the body (ie, lymph nodes, lungs, and the spleen), resulting in the patient’s compromised immune system.^9,10

Studies have shown that highly dense bovine xenografts have also been shown to induce the formation of giant cells relatively early in the healing process.¹¹ 

Compared with allogeneic and xenogenic bone grafts, common advantages of non-resorbable alloplastic bone substitutes are the standardized product quality and absence of infectious disease risk. The main advantages of alloplastic non-resorbing bone substitutes involve their biological stability and volume maintenance, which allow cell infiltration and remodeling.¹² Originally HA ceramic and β-TCP products comprised 80% of all alloplastic bone graft products in the market. 

Xenografts can be derived from sources including bovine and porcine origins, with bovine being the most prominent graft source in the industry. Xenografts carry with them the potential for immunologic reaction resulting in the patient mounting a host immune response against the grafting material. The long-term clinical use and safety of xenografts and their potential association with severe immune responses, as well as objections to their use for both religious and ethical reasons, are valid concerns.

Dental literature has rarely addressed the clinical risks and complications of anorganic bovine bone as a grafting material. However, the scarce literature on complications does not mean that such events are unusual. Often, the negative findings are not published or are not being submitted for publication in dentistry; ignoring the negative outcomes is worrisome as it skews the scientific literature. To the authors, a major concern was the late complications caused by product not resorbing, extending from 2 to 13 years after what was considered to be a successful treatment outcome. In the study, adverse effects presented in the case series report included sinus and maxillary bone pathoses, displacement of the graft materials, oroantral communications, implant failure, foreign body reactions, encapsulation, chronic inflammation, soft-tissue fenestrations, and associated cysts.¹³

Finally, the amount of time it takes for full “resorption” of the bovine xenograft material is a potential issue due to the fragmentation of the particulate by multi-nucleated giant cells, which is of immunologic concern. Human biopsies after sinus augmentation confirm that particles of bovine-derived bone substitutes can still be found up to 10 years postoperatively.¹⁴

RESORBABLE CALCIUM APATITE CRYSTALS AND CLUSTERS

OsteoGen has been used as a particulate graft material since 1984 and has documented clinical success for use with implants, general osseous repair,¹⁵ periodontal procedures,¹⁶ and sinus lifts.¹⁷ When first developed and brought to market, OsteoGen crystals and clusters were used either alone or mixed with other graft materials to extend the amount of graft and to enhance new bone growth. Over the years, product development to address the needs of practitioners has driven new products that contain the OsteoGen crystals mixed with highly purified Achilles tendon collagen. These products include OsteoGen Plugs, OsteoGen Strips, OsteoGen Blocks, and OsteoGen Plates (Figure 3).

Figure 3. Available OsteoGen (IMPLADENT LTD) products.

The bioactive crystal is grown utilizing a unique low-temperature production process that generates osteoconductive and resorbable low-density crystals and crystal clusters (Figure 4). It has a unique calcium-to-phosphate ratio similar to human bone that is neither a β-TCP nor a dense, non-resorbable ceramic HA. 

Figure 4. Scanning electron micrograph of the OsteoGen crystal.

Figure 5. A 3-month histology by Dr. Kyle Hale at the University of Texas Health and Science Center.

As discussed previously, a non-autogenous bone graft material should ideally be non-antigenic, bioactive to control migration of connective tissue, osteoconductive, and synthetically derived with a clinically acceptable time frame of resorption of the majority of such material (Figure 5). The material does have physicochemical and crystallographic properties relatively similar to the host bone (Figure 6) and possesses a bioactive resorptive chemical potentiality to induce favorable cellular response for new bone formation by the action of ionization into calcium and phosphate ions in a chemotactic state.³ What this means is that the breakdown of the clusters produces the optimal environment on a cellular level for bone regeneration. 

Figure 6. A fractured cross section of OsteoGen bioactive crystal with similarity to natural bone.

The clusters are a highly microporous, non-sintered, non-ceramic material composed of small and large crystals and hydrophilic clusters with a controlled, predictable rate of resorption based on the patient’s age and metabolism. 

As opposed to particulate grafting materials on the market today, the plugs and strips prevent the migration of the OsteoGen crystals from the recipient’s surgical site by binding the crystals with collagen. With an approximate ratio of 60/40 mineral to collagen, it is similar to the makeup of native bone, and the distribution of OsteoGen crystals to porous collagen matrix creates an environment conducive to angiogenesis, cell proliferation, and new bone growth. The bioactive definition relates to the nature of the graft’s ability to form new bone by controlling migration of connective tissue and releasing calcium ions to stimulate new bone formation.

One of the main advantages of OsteoGen bioactive crystals is the ability to provide Ca⁺ ions directly into the site where bone growth and maturation will occur. When the composite is fully saturated with blood, these ions are released at an optimal level to facilitate healthy bone regeneration. 

Local Ca⁺ levels in the grafted area control osteoblastic viability, proliferation, and differentiation and are concentration-dependent.

• Too high: >10mM results in apoptosis.
• Optimum: 6 to 8mM results in proliferation.
• Too low: 2 to 4mM results in proliferation and survival without differentiation.

Various clinical studies and recently published papers have confirmed OsteoGen’s bioactivity.

In a split-mouth study conducted by Yosouf et al,¹⁸ it was shown that, when compared to healing without a graft (control), ridge preservation was greatly enhanced by the use of an OsteoGen Plug. Results showed a 60% improvement when grafting with an OsteoGen Plug as 0.56 mm was lost vertically with the plug compared to 1.47 mm lost in the control. When looking at horizontal grafting, 0.9 mm was lost horizontally compared to 2.26 mm in the control. This minimal amount of bone loss is comparable to levels lost when utilizing an allograft and a membrane,¹⁹ although Yosouf et al¹⁸ achieved these results with the use of a Plug alone and no membrane. 

Jones et al²⁰ directly compared an OsteoGen Plug to a Collagen Xenograft Plug (Salvin Dental Specialties) and human bone allograft. It was found that osteoblast proliferation throughout the OsteoGen Plug was between 3 and 6 times greater compared to the xenograft plug or allograft. Additionally, live cell images showed significantly greater osteoblast activity at multiple time periods compared to the xenograft material, which could not sustain the cells. Also, this study showed significantly higher porosity levels (94.4%) for the OsteoGen Plug compared to xenograft material (75.2%) and allograft (55.8%). The study concluded that the OsteoGen Plug demonstrated significantly better biocompatibility compared to the xenograft option and the allograft option alone. 

Jafarian²¹ compared the bone quality attained when using an OsteoGen Plug without a membrane to the bone quality attained using Biohorizons’ MinerOss corticocancellous allograft particulates and a dense PTFE membrane. The author concluded that there was no significant difference in bone quality measured by histomorphometry for placing an implant at 3 to 5 months between the OsteoGen Plug without a membrane and the current gold standard of corticocancellous allograft covered with a membrane.²⁰

The following case series will reinforce the literature with regard to the uses and results of this alloplast plug.

RIDGE PRESERVATION

The most common observation of insufficient quantity of bone in dentistry is following tooth loss, where rapid resorption of alveolar bone occurs due to an absence of intraosseous stimulation that would typically occur via the periodontal ligament fibers.^1,22,23 The amount of resorption is greatly dependent upon the reason for the extraction and the length of time pathology has been present. Studies and anecdotal clinical evidence provide the rationale for grafting fresh extraction sockets. 

During the first year after tooth loss, a patient can see possibly 40% to 60% of the width and height of the alveolar ridge resorb after tooth extraction. Preserving the alveolar ridge offers patients choices in their restorative treatment plans, including endosseous implants.²⁴

All successful ridge preservations have a common starting point, and that is the atraumatic extraction.²⁵ There are a plethora of instruments available, and practitioners use just as many techniques to remove teeth. Though the specific techniques to achieve this will not be discussed in detail, the result by the use of any instrument or technique should minimize soft- and hard-tissue trauma.

SOCKET PRESERVATION CASE 

The patient presented with a non-restorable maxillary right second molar (Figure 7a). Although the patient would likely not suffer any functional deficiency when chewing, he chose to have the site grafted in order to keep the possibilities open for an implant placement at a later date. After sectioning the roots for a less traumatic extraction (Figure 7b), the individual roots were removed while being careful not to damage the buccal plate (Figure 7c).

Figure 7. Socket preservation case.

Once the roots were removed, the sockets were thoroughly debrided to not only clean out any granulation tissue but also to produce copious bleeding. This bleeding is extremely important to kick off healing through what is known as the Regional Acceleratory Phenomenon by making holes through the lamina dura into cancellous bone and recruiting osteoclast cells. The OsteoGen Plug was then cut with scissors (Figure 7d) into a 3-root-like plug and placed into the socket (Figure 7e). The blood was allowed to soak into the plug by compacting the plug very gently into the socket to allow it to conform to the site (Figure 7f). A figure 8 chromic gut suture was utilized to hold the plug in place (Figure 7g). A primary closure or use of a membrane was not necessary. The compacted plug creates a bioactive-crystal, “wall-like” membrane to control the downward migration of connective tissue. 

A radiograph taken immediately post-op showed that the plug itself was radiolucent (Figure 7h) and would become more radio-opaque as it was replaced by native bone. This unique aspect allows a practitioner to easily know when the site is ready for further treatment.

An intraoral photo of the site at one month demonstrates the complete closure of the site by secondary healing (Figure 7i). The 3.5-month radiograph is indicative of how the socket radio-opacity changes during healing by showing bony reconstruction of the socket (Figure 7j).

GRAFTING THE GAP WITH IMMEDIATE IMPLANT PLACEMENT

Much has been written regarding how to manage the “gap” that results when an implant is placed in an extraction socket. When a dental implant is placed into a fresh extraction socket, the space between the implant periphery and surrounding bone is called the “gap” or “jumping distance.” Bone filling in the gap between the implant and the peripheral bone is important for integration and long-term success. The buccal aspect of an implant is of great concern, especially in the aesthetic zone, because the buccal bony plate is usually thin, and its resorption can result in soft-tissue recession.¹⁷

The horizontal gap, if less than 2 mm, will likely fill in without any intervention by the practitioner. In fact, it has been shown that it is possible to have complete fill-in with a gap of up to 4.2 mm, but this is not predictable. Due to this unpredictability, grafting the gap is a belt-and-suspenders approach to assuring that both hard and soft tissue remain stable through the healing process and result in the optimal aesthetics when treatment is completed.²⁶ 

In 2012, Chu et al²⁷ showed that the most predictable hard- and soft-tissue changes and aesthetic results when immediately placing implants in a fresh extraction socket occurs when the gap between the implant and the alveolus is grafted. 

IMMEDIATE PLACEMENT CASE 

Presenting with a failing maxillary right central (Figure 8a), this patient opted for extraction and immediate placement of an implant. After an atraumatic extraction of the tooth (Figure 8b), the tooth was evaluated to determine the amount and position of graft material to be placed. By laying an osteotomy bur on the root, this calculation is very easy to perform (Figure 8c).

Figure 8. Immediate placement case.

The osteotomy was prepared following standard protocol to ensure proper prosthetic position, and the site was checked for any inadvertent perforation. A portion of an OsteoGen Strip was rehydrated with sterile saline in preparation for use. As opposed to the plug, which is delivered dry into an extraction socket, the OsteoGen Strip is rehydrated beforehand to enhance its moldability to fill the gap between the implant body and the alveolus (Figure 8d). 

The position of the implant preparation had been distalized to take advantage of bone contact on the distal wall of the socket and to place the long axis of the implant in the correct prosthetic position for a central incisor with a midline diastema (Figure 8e). After placement of the strip, the implant was driven into place, causing the moldable strip to fill in any gaps (Figure 8f). Placing the strip first will be easier in these kinds of cases rather than trying to place it after the implant is in place. A check film was taken to verify the position (Figure 8g) and show the area of graft placement in the remaining socket. A 3-mm-tall healing abutment was placed, and the site was sutured with PGA sutures (Figure 8h). At the time of placement, the stability was not at a level that would have allowed for direct, immediate temporization. 

After 3.5 months of healing, the healing abutment was removed (Figure 8i), a digital impression post was placed, and the site was scanned for the final restoration. A custom titanium abutment with a full zirconium restoration was chosen for the final restoration and delivered a few weeks later (Figure 8j). The soft-tissue quantity and quality was excellent, and the patient was pleased with the outcome. 

SINUS ELEVATION

Everything from autogenous bone to allografts, xenografts, and alloplasts has been successfully used as graft material in the sinus. The osteoconductive activity of various bone substitutes has been assessed according to the quality and quantity of newly formed bone in the augmented areas.^28,29

The successful use of OsteoGen crystals in sinus elevation has been well-established for more than 30 years. In 1991, Wagner³⁰ showed the efficacy of this material in a 3.5-year follow-up study, and Manso and Wassal¹⁷ expanded on this work with a 10-year longitudinal study.The introduction of OsteoGen Plugs and Strips simplifies both vertical and lateral approach subantral lifts. The issues of material migration due to settling or loss due to the presence of a perforation have been mitigated due to the collagen makeup of the products. 

The use of these products as a graft material is independent of the type of lift or technique used. Either plugs, strips, or malleable OsteoGen blocks can be used depending on the clinical situation. This author prefers to use plugs for vertical lifts and strips for lateral approach lifts. 

SUBANTRAL AND LATERAL SINUS LIFTS 

In this case, the sinus floor needed a sub-5-mm lift to accommodate the apex of the implant to be placed (Figure 9a). An osteotome was used to up-fracture the floor after creating an osteotomy approximately 1 mm short of the sinus floor. A regular-size OsteoGen Plug (Figure 9b) was cut to the appropriate dimension needed for the lift (Figure 9c) and placed into the osteotomy using an osteotome (Figure 9d). The resulting lift showed a smooth membrane without any indications of a tear (Figure 9e). With the use of these plugs, even if there was a small perforation or tear, the plug would allow for healing of the Schneiderian membrane without loss of the graft. 

The Caldwell-Luc procedure, or lateral approach lift, is used when the clinical amount of crestal bone is less than 3 to 4 mm and placement of an implant would result in very little stability or exposure into the sinus cavity. The use of OsteoGen Strips rather than plugs to graft this type of case was decided upon in order to allow better conforming to the walls of the sinus cavity. 

Figure 9. Sinus elevation cases.

In this case, the sinus had pneumatized after extraction of the maxillary right first molar (Figure 9f) and required a lift of approximately 10 mm to accommodate the length of the intended implant to be placed. 

After a window was cut in the lateral wall of the sinus with a #2 round diamond (Figure 9g), the OsteoGen Strips were soaked in sterile saline (Figures 9h and 9i) to rehydrate them and make them malleable. Strips are first placed against the medial wall, then superiorly (Figure 9j), anteriorly, and posteriorly. This ensures that there will be grafting material 360° around the implant (Figures 9k and 9l) prior to placing additional strips laterally.

The final radiograph, taken 4 months later, indicated the growth of bone around the implant and the successful lift (Figure 9m). 

CONCLUSION

Many times, it is a patient preference or refusal of a material that will guide a practitioner toward the type of grafting material he or she can use in a case. Studies have shown the highest rate of refusal was observed for allografts and xenografts. The grafts with the lowest rates of refusal were autologous grafts (3%) and dense alloplastics (2%).³¹ 

An advanced composite graft material such as OsteoGen, in all its prefabricated shapes and formulations, has the advantages of ease of use, cost-effectiveness, clinical ease of delivery, and adaptability to its intended site when compared to the other grafting particulate options on the market today. It is a viable and, in many circumstances, a better long-term option for grafting than traditionally used xenografts and allografts. 

Currently, and in the future, combining this product with growth mediators such as PRF or other substances will open new chapters of outstanding clinical results. It is very likely that, in the future, the use of allografts and xenografts will likely diminish, and alloplastic bioactive materials, which have high quality, safety, and ease of clinical delivery, will be the regenerative materials of choice.

REFERENCES

1. Zhao R, Yang R, Cooper PR, et al. Bone grafts and substitutes in dentistry: a review of current trends and developments. Molecules. 2021;26(10):3007. doi:10.3390/molecules26103007
2. Nappe C, Rezuc A, Montecinos A, et al. Histological comparison of an allograft, a xenograft and alloplastic graft as bone substitute materials. J Osseointegration. 2016;8(2):20–6. doi:10.23805/jo.2016.08.02.02
3. Valen M, Ganz SD. A synthetic bioactive resorbable graft for predictable implant reconstruction: part one. J Oral Implantol. 2002;28(4):167–77. doi:10.1563/1548-1336(2002)028<0167:ASBRGF>2.3.CO;2
4. Misch CM. Autogenous bone: is it still the gold standard? Implant Dent. 2010;19(5):361. doi:10.1097/ID.0b013e3181f8115b
5. Roberts TT, Rosenbaum AJ. Bone grafts, bone substitutes and orthobiologics: the bridge between basic science and clinical advancements in fracture healing. Organogenesis. 2012;8(4):114–24. doi:10.4161/org.23306
6. Simonds RJ, Holmberg SD, Hurwitz RL, et al. Transmission of human immunodeficiency virus type 1 from a seronegative organ and tissue donor. N Engl J Med. 1992;326(11):726–32. doi:10.1056/NEJM199203123261102
7. Linkow LI. Bone transplants using the symphysis, the iliac crest and synthetic bone materials. J Oral Implantol. 1983;11(2):211–47.
8. Toloue SM, Chesnoiu-Matei I, Blanchard SB. A clinical and histomorphometric study of calcium sulfate compared with freeze-dried bone allograft for alveolar ridge preservation. J Periodontol. 2012;83(7):847–55. doi:10.1902/jop.2011.110470
9. Ahmadzadeh K, Vanoppen M, Rose CD, et al. Multi-nucleated giant cells: current insights in phenotype, biological activities, and mechanism of formation. Front Cell Dev Biol. 2022;10:873226. doi:10.3389/fcell.2022.87322
10. Miron RJ, Zohdi H, Fujioka-Kobayashi M, et al. Giant cells around bone biomaterials: Osteoclasts or multi-nucleated giant cells? Acta Biomater. 2016;46:15-28. doi:10.1016/j.actbio.2016.09.029
11. Barbeck M, Udeabor SE, Lorenz J, et al. Induction of multi-nucleated giant cells in response to small-sized bovine bone substitute (Bio-Oss) results in an enhanced early implantation bed vascularization. Ann Maxillofac Surg. 2014;4(2):150–7. doi:10.4103/2231-0746.147106
12. Fukuba S, Okada M, Nohara K, et al. Alloplastic bone substitutes for periodontal and bone regeneration in dentistry: current status and prospects. Materials (Basel). 2021;14(5):1096. doi:10.3390/ma14051096
13. Rodriguez AE, Nowzari H. The long-term risks and complications of bovine-derived xenografts: A case series. J Indian Soc Periodontol. 2019;23(5):487–92. doi:10.4103/jisp.jisp_656_18
14. Piattelli M, Favero GA, Scarano A, et al. Bone reactions to anorganic bovine bone (Bio-Oss) used in sinus augmentation procedures: a histologic long-term report of 20 cases in humans. Int J Oral Maxillofac Implants. 1999;14(6):835–40.
15. Wagner JR. Clinical and histological case study using resorbable hydroxylapatite for the repair of osseous defects prior to endosseous implant surgery. J Oral Implantol. 1989;15(3):186–92.
16. Epstein SR, Valen M. An alternative treatment for the periodontal infrabony defect: a synthetic bioactive resorbable composite graft. Dent Today. 2006;25(2):92–7.
17. Manso MC, Wassal T. A 10-year longitudinal study of 160 implants simultaneously installed in severely atrophic posterior maxillas grafted with autogenous bone and a synthetic bioactive resorbable graft. Implant Dent. 2010;19(4):351–60. doi:10.1097/ID.0b013e3181e59d03
18. Yosouf K, Heshmeh O, Darwich K. Alveolar ridge preservation utilizing composite (bioceramic/collagen) graft: A cone-beam computed tomography assessment in a randomized split-mouth controlled trial. J Biomed Eng. 2021;14(2):64-73. doi:10.4236/jbise.2021.142007
19. Cheon GB, Kang KL, Yoo MK, et al. Alveolar ridge preservation using allografts and dense polytetrafluoroethylene membranes with open membrane technique in unhealthy extraction socket. J Oral Implantol. 2017;43(4):267–73. doi:10.1563/aaid-joi-D-17-00012
20. Jones K, Williams C, Yuan T, et al. Comparative in vitro study of commercially available products for alveolar ridge preservation. J Periodontol. 2022;93(3):403–11. doi:10.1002/JPER.21-0087
21. Kumar P, Vinitha B, Fathima G. Bone grafts in dentistry. J Pharm Bioallied Sci. 2013;5(Suppl 1):S125–7. doi:10.4103/0975-7406.113312
22. Misch CE, Dietsh F. Bone-grafting materials in implant dentistry. Implant Dent. 1993;2(3):158–67. doi:10.1097/00008505-199309000-00003
23. Murray VK. Anterior ridge preservation and augmentation using a synthetic osseous replacement graft. Compend Contin Educ Dent. 1998;19(1):69-74, 76–7.
24. Schlesinger C. Ridge preservation technique: there’s more than one way to fill the hole! Dent Today. 2019;28(3)42-27.
25. Schlesinger C. A novel approach to grafting around implants. Dent Today. 2017;26(12):50-54.
26. Chu SJ, Salama MA, Salama H, et al. The dual-zone therapeutic concept of managing immediate implant placement and provisional restoration in anterior extraction sockets. Compend Contin Educ Dent. 2012;33(7):524–32, 534.
27. Berberi A, Nader N, Noujeim Z, et al. Horizontal and vertical reconstruction of the severely resorbed maxillary jaw using subantral augmentation and a novel tenting technique with bone from the lateral buccal wall. J Maxillofac Oral Surg. 2015;14(2):263–70. doi:10.1007/s12663-014-0635-7
28. Artzi Z, Nemcovsky CE, Tal H, et al. Histopathological morphometric evaluation of 2 different hydroxyapatite-bone derivatives in sinus augmentation procedures: a comparative study in humans. J Periodontol. 2001;72(7):911–20. doi:10.1902/jop.2001.72.7.911
29. Wagner JR. A 3 1/2-year clinical evaluation of resorbable hydroxylapatite OsteoGen (HA Resorb) used for sinus lift augmentations in conjunction with the insertion of endosseous implants. J Oral Implantol. 1991;17(2):152–64.
30. Fernández RF, Bucchi C, Navarro P, Beltrán V, Borie E. Bone grafts utilized in dentistry: an analysis of patients’ preferences. BMC Med Ethics. 2015;16(1):71. doi:10.1186/s12910-015-0044-6

ABOUT THE AUTHOR

Dr. Schlesinger has been placing implants for the past 28 years, and as an educator for the past 19 years, he has taught doctors worldwide about dental surgical procedures. Along with running a busy private practice in Rio Rancho, NM, he maintains a clinical advisory role with numerous dental product manufacturers. He can be reached at  cdschlesinger@gmail.com. 

Adj. Prof. Valen is the founder and CEO of Impladent. He can be reached at maurice@impladentltd.com. 

Disclosure: Dr. Schlesinger is a paid consultant for Impladent. Mr. Valen is a nonpaid consultant for Solmetex and CEO of Impladent.

WEBINAR

Dr. Schlesinger will present a FREE CE WEBINAR on July 10, 2024 expanding on this article’s topic.

CLICK HERE TO REGISTER NOW.

Osseointegration, as defined by Brånemark, is a direct structural and functional connection between ordered, living bone and the surface of a load-carrying implant.¹ The process of osseointegration is very much dependent on the quantity and composition of osteoblast attachment to the implant surface. The quantity of osteogenic cells in contact with the titanium surface directly correlates to the amount of peri-implant bone and, as a result, the percentage of bone to implant contact (BIC). Extracellular proteins such as fibronectin are integral in the attraction and attachment of osteoblasts to the titanium surface.² The aging of titanium results in the deposition of hydrocarbons on the surface, hydrophobicity, and conversion of the surface charge from positive to negative.³ This diminishes the bioactivity of the titanium so that proteins have less of an affinity for the implant surface and, consequently, inferior osteoblast proliferation, migration, and attachment compared to new titanium.³ The percentage of BIC is highly dependent on the bioactivity of the implant surface and its ability to interact biologically with the host’s mediators of osteogenesis.^4,5 The osseointegration speed index (OSI), as measured by sequential implant stability quotients (ISQs), is also affected by the decreased bioactivity. This process has been researched and reported, and the ISQ is generally expected to be adequate at 3 to 6 months, depending upon the bone quality or type and characteristics of the implant surface.^6-8 Implant surfaces have been modified over the years to enhance osseointegration by various methods, including plasma spraying, acid etching, or sandblasting the surface to gain improved adhesion, migration, and differentiation of osteoblasts, which increased the OSI and BIC.^7,8 However, these modifications to the implant surface design do not prevent the accumulation of hydrocarbons on the titanium implant surface that occurs with aging.^8-10 Aged titanium surfaces show less protein absorption (fibronectin, albumin) and consequently inferior osteoblast proliferation, migration, and attachment than a newly manufactured titanium implant.¹¹ This results in a decrease in both the BIC and the biomechanical strength of the bone-titanium interface.^10,12-14 A titanium implant that has aged has a BIC of 58%, whereas a newly manufactured implant has BIC of 90%.^10,12-14

Modification of the aged implant surface is clinically desirable to increase the OSI and BIC through the reversal of titanium degradation caused by aging. A novel surface treatment termed photofunctionalization (PFZ) has been shown to accomplish this modification.^10,14-22 The process of PFZ removes hydrocarbons, restores hydrophilicity, alters physiochemical properties, and restores bioactivity.

This article will present a case of UVCL treatment of a dental implant for the enhancement of the osseointegration process, reducing the functional osseointegration time from 12 to 16 weeks to 6 weeks.

CASE REPORT

A 47-year-old female patient reported to the Midwestern University College of Dental Medicine for replacement of her missing tooth No. 19. Restorative options, including fixed, removable, and implant-borne prosthetics, were presented, and the patient chose a dental implant. Her medical history was non-contributory, with no history of diabetes, tobacco use, or any immunosuppressant or anti-resorptive therapy and no past or present history of periodontal disease. She exhibited good oral home care and was committed to professional maintenance care every 4 months. She had lost tooth No. 19 from a periapical infection due to recurrent decay under a restoration she had received years ago. Tooth No. 19 was extracted without complication, followed by ridge preservation using mineralized/demineralized cortico-cancellous bone allograft (AlloOss [ACE Surgical Supply]) 7 months prior to implant placement surgery (Figure 1). 

Figure 1. Residual ridge No. 19 seven months post extraction and ridge preservation.

Figure 2. CBCT scan showing residual ridge No. 19 seven months post extraction and ridge preservation.

Figure 3. The implant workup from the DIOnavi dental laboratory (DIO Implant).

Figure 4. Surgical guide fabricated for the case.

Figure 5. DIOnavi drilling sequence provided by the laboratory.

Figure 6. DIOnavi UVC vacuum light.

Figure 7. Implant with healing abutment immediately after placement.

Figure 8. Restored implant.

A full maxillary and mandibular CBCT scan was acquired (3D Accuitomo 170 [J Morita]) (Figure 2) as well as intraoral scans (Emerald S scanners [Planmeca]), and the case was worked up in Romexis (version 6.3) implant planning software (Planmeca) to determine implant placement viability from a restoratively driven perspective. After that initial workup proved favorable, all data were electronically uploaded to the DIOnavi (DIO Implant, Busan, South Korea) portal for implant placement design and surgical guide fabrication (Figures 3 and 4). On the day of surgery, the DIO drilling protocol was followed (Figure 5). Before placement, the implant body was treated in a novel UVC vacuum light (DIO Implant) (Figure 6). A 5.0- × 11.5-mm DIO implant fixture was placed in site No. 19 with a seating insertion torque value of 50 Ncm. For investigative purposes, a CBCT scan was again taken on the day of implant placement (Figure 7), confirming the implant to be in a favorable position for restoration. At the 6-week mark, the patient returned; the healing abutment was removed; and ISQ readings were taken from the mesial, distal, buccal, and lingual, all registering at 85 (Osstell). The healing abutment was replaced, and the patient was then scheduled to begin the restorative phase of treatment at 6 weeks post implant placement. The final restoration is seen in Figure 8. 

DISCUSSION 

Ultraviolet light (UVL) is a form of radiation found on the electromagnetic spectrum. The spectrum consists of light types based on their wavelengths. These are radio, microwave, infrared, visible, ultraviolet A, ultraviolet B, ultraviolet C, x-ray, and gamma-ray waves. These wavelengths vary across the spectrum, with radio waves having the longest and gamma rays having the shortest. UVL is shorter than visible light, so it is invisible to most vertebrates, including humans, and the wavelengths range from 200 to 400 nm within this spectrum (Figures 9 and 10). In 1997, Wang et al,²³ reported on the effects of UVL on the superhydrophilicity of TiO₂, and applications were developed in many areas of industry, including anti-fogging, stain resistance, and antibacterial treatments, because of this research.²⁴ Funato and Ogawa²⁵ were the first to publish on the clinical application of PFZ to alter the surface of a titanium implant in 2013. Their study followed 7 implants that had micro-roughened surfaces that were photofunctionalized through exposure to UVL for 15 minutes chairside. All 7 implants were loaded early, and it was found that their ISQ values increased from insertion to loading. At one year, they found that all implants were integrated and under function after early loading. Funato et al²⁶ researched the effects of PFZ through a retrospective study. They found that healing times can be shortened to 3.2 months from 6.6 months using PFZ, effectively increasing the OSI. The work of Suzuki et al²⁷ has also shown that PFZ increases the OSI. While these reports showed clinical promise in the use of PFZ, 15 minutes to modify an implant chairside is not clinically applicable. However, research has continued, and a novel UVL activator (Figure 6) is now available to photofunctionalize implants chairside, according to the manufacturer (DIO Implant). This activator utilizes a 172-nm xenon excimer-generated vacuum ultraviolet light (VUV). The implants are stored in quartz ampules following manufacturing and subsequently modified in the VUV activator in these ampules as the quartz allows for the UVC light to exert maximum effect. This activator was tested against other commercially available devices, and it was found to accomplish greater than 90% decomposition of organic materials in the form of hydrocarbons.²⁸ PFZ allows for the reversal of titanium degradation, and this restores the TiO₂ layer, which restores bioactivity. Hydrocarbons are removed, hydrophilicity is restored, and the surface charge returns to positive. This, in turn, promotes protein adsorption, which enhances osteoblast migration, proliferation, and attachment to the implant surface. This results in improved biomechanical strength of the bone implant interface through increased BIC.²⁹ By accomplishing this, the osseointegration stability curve is shifted to the left (Figures 11 and 12).

Figure 9. Partial light spectrum in nanometers.

Figure 10. Ultraviolet light spectrum information.

Figure 11. Typical stability curve associated with osseointegration.

Figure 12. Stability curve demonstrating the shift to left for UVL-treated implants.

CONCLUSION

This case demonstrates the successful implementation of a novel UVL activator in modifying a dental implant surface. In addition, this shows that it may be clinically applicable to photofunctionalize dental implants chairside and, as a result, increase the BIC and the OSI, effectively shortening treatment time and providing predictable results.

REFERENCES 

1. Park NI, Kerr M. Chapter 2: Terminology in implant dentistry. In: Resnick R, ed. Misch’s Contemporary Implant Dentistry. 4th ed. Elsevier; 2020:20–2. 

2. Hori N, Att W, Ueno T, et al. Age-dependent degradation of the protein adsorption capacity of titanium. J Dent Res. 2009;88(7):663–7. doi:10.1177/0022034509339567 

3. Sugita Y, Saruta J, Taniyama T, et al. UV-pre-treated and protein-adsorbed titanium implants exhibit enhanced osteoconductivity. Int J Mol Sci. 2020;21(12):4194. doi:10.3390/ijms21124194 

4. Lian Z, Guan H, Ivanovski S, et al. Effect of bone to implant contact percentage on bone remodelling surrounding a dental implant. Int J Oral Maxillofac Surg. 2010;39(7):690–8. doi:10.1016/j.ijom.2010.03.020 

5. Pyo SW, Park YB, Moon HS, et al. Photofunctionalization enhances bone-implant contact, dynamics of interfacial osteogenesis, marginal bone seal, and removal torque value of implants: a dog jawbone study. Implant Dent. 2013;22(6):666–75. doi:10.1097/ID.0000000000000003 

6. Colnot C, Romero DM, Huang S, et al. Molecular analysis of healing at a bone-implant interface. J Dent Res. 2007;86(9):862–7. doi:10.1177/154405910708600911 

7. Davies JE. Understanding peri-implant endosseous healing. J Dent Educ. 2003;67(8):932–49. 

8. Misch C. Dental Implant Prosthetics. 2nd ed. Mosby; 2015.

9. Albrektsson T, Zarb G, Worthington P, et al. The long-term efficacy of currently used dental implants: a review and proposed criteria of success. Int J Oral Maxillofac Implants. 1986;1(1):11-25. 

10. Att W, Ogawa T. Biological aging of implant surfaces and their restoration with ultraviolet light treatment: a novel understanding of osseointegration. Int J Oral Maxillofac Implants. 2012;27(4):753–61.

11. Att W, Hori N, Takeuchi M, et al. Time-dependent degradation of titanium osteoconductivity: an implication of biological aging of implant materials. Biomaterials. 2009;30(29):5352–63. doi:10.1016/j.biomaterials.2009.06.040 

12. Hori N, Att W, Ueno T, et al. Age-dependent degradation of the protein adsorption capacity of titanium. J Dent Res. 2009;88(7):663–7. doi:10.1177/0022034509339567 

13. Att W, Hori N, Takeuchi M, et al. Time-dependent degradation of titanium osteoconductivity: an implication of biological aging of implant materials. Biomaterials. 2009;30(29):5352–63. doi:10.1016/j.biomaterials.2009.06.040 

14. Hirota M, Ozawa T, Iwai T, et al. UV-mediated photofunctionalization of dental implant: a seven-year results of a prospective study. J Clin Med. 2020;9(9):2733. doi:10.3390/jcm9092733 

15. Takeuchi M, Anpo M. Effect of UV light irradiation of different wavelengths on the surface wettability of titanium metal for dental implants. J Mater Sci Res. 2018. doi:10.29011/ JMSR-109/100009

16. Huang Y, Zhang H, Chen Z, et al. Improvement in osseointegration of titanium dental implants after exposure to ultraviolet-C light for varied durations: an experimental study in beagle dogs. J Oral Maxillofac Surg. 2022;80(8):1389–97. doi:10.1016/j.joms.2022.04.013

17. Chang LC. Clinical applications of photofunctionalization on dental implant surfaces: a narrative review. J Clin Med. 2022;11(19):5823. doi:10.3390/jcm11195823 

18. Arroyo-Lamas N, Arteagoitia I, Ugalde U. Surface activation of titanium dental implants by using UVC-LED irradiation. Int J Mol Sci. 2021;22(5):2597. doi:10.3390/ijms22052597 

19. Tabuchi M, Hamajima K, Tanaka M, et al. UV light-generated superhydrophilicity of a titanium surface enhances the transfer, diffusion and adsorption of osteogenic factors from a collagen sponge. Int J Mol Sci. 2021;22(13):6811. doi:10.3390/ijms22136811

20. Sugita Y, Saruta J, Taniyama T, et al. UV-pre-treated and protein-adsorbed titanium implants exhibit enhanced osteoconductivity. Int J Mol Sci. 2020;21(12):4194. doi:10.3390/ijms21124194 

21. Camolesi GCV, Somoza-Martín JM, Reboiras-López MD, et al. Photobiomodulation in dental implant stability and post-surgical healing and inflammation. A randomised double-blind study. Clin Oral Implants Res. 2023;34(2):137–47. doi:10.1111/clr.14026 

22. Suzuki S, Kobayashi H, Ogawa T. Implant stability change and osseointegration speed of immediately loaded photofunctionalized implants. Implant Dent. 2013;22(5):481–90. doi:10.1097/ID.0b013e31829deb62 

23. Wang R, Hashimoto K, Fujishima A, et al. Light-induced amphiphilic surfaces. Nature. 1997;388:431–2. doi:10.1038/41233

24. Aita H, Hori N, Takeuchi M, et al. The effect of ultraviolet functionalization of titanium on integration with bone. Biomaterials. 2009;30(6):1015–25. doi:10.1016/j.biomaterials.2008.11.004 

25. Funato A, Ogawa T. Photofunctionalized dental implants: a case series in compromised bone. Int J Oral Maxillofac Implants. 2013;28(6):1589–601. doi:10.11607/jomi.3232 

26. Funato A, Yamada M, Ogawa T. Success rate, healing time, and implant stability of photofunctionalized dental implants. Int J Oral Maxillofac Implants. 2013;28(5):1261–71. doi:10.11607/jomi.3263 

27. Suzuki S, Kobayashi H, Ogawa T. Implant stability change and osseointegration speed of immediately loaded photofunctionalized implants. Implant Dent. 2013;22(5):481–90. doi:10.1097/ID.0b013e31829deb62

28. Suzumura T, Matsuura T, Komatsu K, et al. A novel high-energy vacuum ultraviolet light photofunctionalization approach for decomposing organic molecules around titanium. Int J Mol Sci. 2023;24(3):1978. doi:10.3390/ijms24031978 

29. Pyo SW, Park YB, Moon HS, et al. Photofunctionalization enhances bone-implant contact, dynamics of interfacial osteogenesis, marginal bone seal, and removal torque value of implants: a dog jawbone study. Implant Dent. 2013;22(6):666–75. doi:10.1097/ID.0000000000000003 

ABOUT THE AUTHORS

Dr. Beals earned his BS, MS, and DDS degrees at The Ohio State University. He remained at Ohio State to complete a residency in oral and maxillofacial surgery, then relocated to Phoenix, where he entered private practice. He is currently a clinical associate professor at Midwestern University Dental Institute in Glendale, Ariz. He can be reached at dbeals@midwestern.edu.

Dr. Francis is a clinical associate professor at the College of Dental Medicine, Midwestern University in Glendale. He can be reached at jfranc@midwestern.edu.

Dr. Barber is a clinical associate professor at the College of Dental Medicine, Midwestern University. He can be reached at hbarbe@midwestern.edu.

Dr. Siu is a clinical associate professor at the College of Dental Medicine, Midwestern University. He can be reached via email at tsiu@midwestern.edu.

Dr. Cianciola is a clinical assistant professor at the College of Dental Medicine, Midwestern University. He can be reached at jcianc@midwestern.edu.

Disclosure: The authors report no disclosures. 

Implant dentistry has become a discipline in health care to reconstruct lost soft and hard tissues to facilitate dental rehabilitation. Endosseous implants demonstrate high success rates when placed in an adequate volume of bone.¹ Bone resorption is a common sequel after the loss of a tooth.² Tooth loss is a result of caries, trauma, periodontal disease, perio-endo lesions, or congenitally missing teeth. Several approaches to managing alveolar ridge deficiency have been described, including ridge expansion, guided bone regeneration (GBR), and autogenous and allogenic block grafting.^3-5 

Autogenous block grafts are considered the gold standard approach for bone grafting because they provide osteogenic, osteoinductive, and osteoconductive properties.⁶ This source of bone can be procured from intraoral sites, such as the mandibular symphysis, ramus, or maxillary tuberosity. Extraoral sites can be utilized for larger recipient areas harvested from the iliac crest, calvarium, or tibia. The limitations of autogenous block grafting are morbidity, limited quantities, resorption potential, and a high skill level needed by the clinician.⁷ 

Allographic block grafting has gained wide acceptance because of reduced morbidity and unlimited availability if a large quantity of bone is needed.⁸ Allogenic grafts may be utilized in a particulate or block form, depending on the nature of the surgical objective. There is evidence of high success rates of graft integration with minimal resorption. In addition, implants placed into allogenic bone have demonstrated high survival rates.^9,10 

This case report discusses the management of a congenitally missing maxillary lateral incisor with a horizontal alveolar ridge deficiency. A staged approach encompassing an allogenic block graft followed by implant placement and prosthetic reconstruction was employed. This technique is for consideration for horizontal ridge augmentation for dental implant reconstruction.

CASE REPORT

A 21-year-old female patient presented to my office with an edentulous space associated with the maxillary right lateral incisor (tooth No. 7). The patient’s history revealed that the tooth was congenitally missing, and orthodontic therapy was completed 10 years ago. The medical history revealed no significant findings except for the daily intake of the medication Escitalopram (Lexapro) to manage episodes of depression. The clinical and radiographic examination revealed a Class I occlusion, adequate keratinized gingiva, and a deficiency in the buccal-palatal alveolar ridge (Figures 1 to 3). A diagnosis of horizontal ridge atrophy was made. The agreed-upon treatment plan was endosseous implant therapy post allogenic block grafting in a staged approach.

Figure 1. Presurgical site, maxillary right lateral incisor (tooth No. 7).

Figure 2. Buccal-palatal deficiency.

Figure 3. CBCT image, section view.

The surgical phase was initiated with a 20-mL blood draw from the median cubital vein to develop platelet-rich fibrin (PRF) and buffy coat platelet-rich plasma (BC-PRP). BC-PRP and PRF were produced with a single-spin centrifuge at 3,100 rpm for 12 minutes and processed. Local anesthesia—one carpule 3% Polocaine (54 mg) without epinephrine and one carpule 2% Lidocaine (36 mg) with epinephrine (Benco Dental)—was administrated in an infiltration manner. A full mucoperiosteal flap was raised after a midcrestal and intrasulcular incision design was made with a 15C Bard Parker blade (Figure 4). Vertical releasing incisions were made, including in the dental papilla one tooth mesial and distal to the surgical site. Collagen and elastin fibers were released and separated utilizing the dull side of a 15C blade in a back-action sweeping technique.

Figure 4. Full mucoperiosteal flap.

The recipient site was prepped with a 700 XL bur in an attempt to create a positive seat for the block graft. Perforations utilizing a No. 4 round bur on the alveolar ridge to promote bleeding points were made. A 10- × 10- × 5-mm corticocancellous allogenic block graft (Rocky Mountain Tissue Bank) was secured by placing a 1.5- × 10-mm machined TriStar Bone Graft Fixation System (IMPLADENT LTD) through the graft and into the palatal bone (Figure 5). After fixation was confirmed, the bony edges were rounded with a No. 6 round bur.

Figure 5. Allogenic block with fixation screw.

Figure 6. Collagen membrane.

Figure 7. Particulate allographic (particulate mineralized irradiated bone) and platelet-rich fibrin.

Particulate mineralized irradiated bone (MIRB) cancellous allograph (Fine [Rocky Mountain Tissue Bank]) was mixed with PRP and mortised into all voids existing between the block and host site. The entire graft was covered with PRF and a type 1 collagen resorbable membrane (OSSix Plus [OraPharma]) (Figures 6 and 7). A fixed transitional appliance (Essix) was placed. The flap was closed, consisting of a dual technique encompassing a horizontal mattress and interrupted 3.0 d-PTFE sutures (Figure 8). A 4-month healing period prior to implant surgery was established (Figure 9).

Figure 8. Primary closure, d-PTFE.

Figure 9. Surgical site after 4 months of healing.

The implant surgery procedure was prepared concerning PRP/PRF and local anesthesia exactly in the same manner as for the block graft. A midcrestal incision was made with a 15C Bard Parker blade extending distal to the maxillary right canine and mesial to the right maxillary central incisor. A full mucoperiosteal flap was reflected to expose the block retention screws and removed with the appropriate driver (Figures 10 and 11). The implant osteotomy was developed utilizing osseodensification (OD) Densah drills (Versah). The sequence was a 1.6-mm pilot drill rotating clockwise (forward), followed by 2.0-, 2.5-, and 2.8-mm Densah drills rotating in a counterclockwise (reverse) OD mode to a depth of 13 mm. A 3.2- × 13-mm SBM Legacy2 (Implant Direct) implant was inserted utilizing a straight driver to the level of the bony crest (Figure 12). A 3.2-mm transfer pin was placed, and a radiograph was taken prior to taking an impression with a heavy-body polyvinyl siloxane (Imprint III [3M]) material (Figures 13 and 14). A maxillary-mandibular relation and a shade B2/B1 were taken. A 3.2- × 2-mm healing collar was placed with a 1.25-mm hex tool and covered with a PRF bioactive membrane. The flap was approximated in a dual-closure approach with a horizontal mattress and interrupted 4.0 Vicryl sutures.

Figure 10. Full mucoperiosteal flap and allogenic block after 4 months of healing.

Figure 11. Fixation screw.

Figure 12. A 3.2- × 13-mm SBM Legacy2 implant (Implant Direct).

Figure 13. Impression transfer pin.

Figure 14. Periapical radiograph of the 2-mm healing collar.

Figure 15. Healing collar after 4 months of healing.

The restorative stage was initiated 4 months post-implant fixture placement (Figure 15). After infiltration anesthesia, the 2-mm healing collar was removed with a 1.25-mm hex tool to expose the fixture (Figure 16). A titanium abutment was placed, a periapical radiograph was taken, and an abutment screw was torqued at 30 N/cm twice over a 5-minute time interval (Figures 17 and 18). The final porcelain-fused-to-metal crown was permanently cemented with zinc oxide phosphate cement (Figures 19 and 20).

Figure 16. The fixture at 4 months.

Figure 17. Titanium abutment.

Figure 18. Periapical radiograph of the abutment/implant.

Figure 19. Final prosthesis, a porcelain-fused-to-metal crown (lateral view).

Figure 20. The porcelain-fused-to-metal crown (facial view).

DISCUSSION

Implant dentistry has provided many individuals with the opportunity to reconstruct lost oral structures.¹ The need to reconstruct a deficiency in hard and soft tissue prior to the placement of dental implants is a common prerequisite.¹¹ Many treatment approaches have been described in the literature, such as ridge expansion, GBR, and autogenous and allographic block grafts.¹² The selection of a specific technique is based on the volume of alveolar ridge reconstruction needed or whether a staged or simultaneous implant placement can be achieved.

The utilization of block grafting for the reconstruction of a horizontal ridge deficiency has demonstrated high success rates.^13,14 Autogenous block grafting is considered the gold standard because all bone development processes are involved in regeneration.¹⁵ Autogenous block grafts can be harvested from intraoral sites, such as the symphysis, ramus, or maxillary tuberosity.¹⁶ Extraoral sites utilized for grafting are the iliac crest, calvarian, and tibia. Autogenous grafts exhibit a high incidence of morbidity, paresthesia, devitalization of teeth, hospitalization, and costs.

Allogenic block grafts have become widely used in implant dentistry due to reduced morbidity and advances in processing for sterilization.¹⁷ Allogenic block grafts meet the pass criteria for bone regeneration development described by Wang and Boyapati.¹⁸ The cortical-cancellous nature of the block creates physical space, including porosity to foster vascularity to develop within the graft. The block can be fixated to the host site to create stability needed for bone growth. Allogenic block grafts have demonstrated high success rates histologically by the amount of vital bone growth they’ve enhanced.¹⁹ Furthermore, high implant survival rates are exhibited when implants are placed in allogenic block grafts.

This case report utilized a cortical-cancellous block graft sterilized via gamma radiation at 2.5 to 3.8 mrad to kill bacteria, viruses, and cells, and it was provided in a hydrated form. The hydrated form and cancellous component allow for compression with less breakage during the fixation process. The block graft is procured from the vertebra column exhibiting a curved anatomical shape.^12,20

The techniques of the block graft procedure depend highly on the execution of the flap and block protocols.²¹ A tension-free closure is needed, requiring vertical releasing incisions and release of the periosteum. Release of collagen from the periosteum and elastin fibers in the mucosa is required to coronally advance the flap for a tension-free closure. The allogenic block is placed in a surgically developed area to enhance a positive seat in the host bone. The host bone is decorticated with multiple perforations to release growth factors via the regional acceleratory phenomenon.²²

A Ti-machined fixation screw is placed through the block and into the host bone to eliminate any movement of the block graft. It is paramount that the block graft is in close approximation with the recipient site. The voids that exist around the block are filled in with particulate MIRB allograph and PRP.^23,24 PRF bioactive and collagen type 1 membranes are utilized to cover the allogenic block and particulate graft. The membranes serve to promote soft- and hard-tissue healing as well as prevent epithelial migration into the allogenic block graft sites.^25,26 

The resorption of allogenic and autogenous block grafts has been under discussion for several years. Systematic reviews demonstrate minimal resorption of both types of grafts after 12 months and that they remain stable for 5 years.²⁷ More importantly, implant survival rates in block grafts have been higher than 95%.²⁸ Further studies have exhibited the presence of new bone formation histologically after 4 months, with a diminished residual graft bone. These studies are confirmed by the presence of osteogenic markers such as bone morphogenic protein (BMP), osteocalcin, and alkaline phosphate.²⁹

Patient evaluation prior to block grafting is critical in developing a proper diagnosis. A diagnosis will guide the clinician in decision making concerning which horizontal ridge augmentation technique will accomplish a favorable outcome. A prophylaxis of adjacent teeth and an evaluation of the amount of keratinized tissue should be performed. A CBCT scan is ideal for evaluating the buccal palatal volume and shape of the ridge.³⁰ The 3D image is helpful in determining the amount of bone regeneration needed to place an implant in the ideal position. Most importantly, it assists the clinician in making the proper decision on the surgical approach. The patient was prescribed a Cephalosporin (Keflex) antibiotic, ibuprophen, and chlorhexidine prior to surgery. The patient in this report was taking the medication Escitapram (Lexapro). Individuals prescribed selective serotonin reuptake inhibitors have exhibited a higher risk for implant failure. A study has demonstrated twice the failure rate for individuals taking the medication vs non-users. The clinical failure is evident at second-stage surgery or at the restorative stage, suggesting a negative biological remodeling effect.³¹

Platelet concentrates and allographic bone serve as a synergistic combination for bone growth. A single platelet contains an excess of 1,000 growth factors, including BMP, platelet-derived growth factor, insulin-derived growth factor, endovascular growth factor, and fibroblast growth factor. Growth factors enhance the recruitment and differentiation of cells associated with soft- and hard-tissue development.³² BC-PRP, utilized in this case with an allographic block and particulate bone, provides osseoinductive and osseoconductive properties for bone development. The graft utilized for this report was derived from the human vertebral column and gamma-irradiated at 2.5 to 3.8 mrad to sterilize the graft from viruses, bacteria, and cells. It was provided in a hydrated form that maintained flexibility, thereby preventing fracture during the fixation stage.

The implant surgical stage is performed after 4 months of healing. Studies have determined that approximately 45% of the graft is replaced with new vital bone after this time interval.^29,33 In this case, the fixation screw was visible but not perforated through the mucosa. Although some resorption was evident around the head of the screw, the overall volume of the block was sufficient for implant placement. The osteotomy procedure was performed utilizing an osseodensification method due to a lower degree of drill chatter. The osteotomy was not undersized but developed using a hard-bone protocol to reduce internal forces during implant placement. This approach is utilized to prevent disturbance of the allograph and host-bone interface, which could potentially dislodge the grafted bone. The restorative stage was initiated at implant surgery due to a fixture stability of greater than 35 N/cm. 

After a 4-month osseointegration period, second-stage surgery was performed with simultaneous placement of the final abutment and crown placement. Implant occlusal principles were completed prior to the patient being discharged.³⁴

ACKNOWLEDGMENTS

The author wishes to acknowledge Tatyana Lyubezhanina, DA, and LeeAnn Klots, DA, for their assistance in preparation of this article.

REFERENCES

1. Albrektsson T, Brånemark PI, Hansson HA, et al. Osseointegrated titanium implants. Requirements for ensuring a long-lasting, direct bone-to-implant anchorage in man. Acta Orthop Scand. 1981;52(2):155–70. doi:10.3109/17453678108991776 

2. Van der Weijden F, Dell’Acqua F, Slot DE. Alveolar bone dimensional changes of post-extraction sockets in humans: a systematic review. J Clin Periodontol. 2009;36(12):1048–58. doi:10.1111/j.1600-051X.2009.01482.x 

3. Leonetti JA, Koup R. Localized maxillary ridge augmentation with a block allograft for dental implant placement: case reports. Implant Dent. 2003;12(3):217–26. doi:10.1097/01.id.0000078233.89631.f8 

4. Starch-Jensen T, Deluiz D, Tinoco EMB. Horizontal alveolar ridge augmentation with allogeneic bone block graft compared with autogenous bone block graft: a systematic review. J Oral Maxillofac Res. 2020;11(1):e1. doi:10.5037/jomr.2020.11101 

5. Elgali I, Omar O, Dahlin C, et al. Guided bone regeneration: Materials and biological mechanisms revisited. Eur J Oral Sci. 2017;125(5):315–37. doi:10.1111/eos.12364 

6. Sakkas A, Wilde F, Heufelder M, et al. Autogenous bone grafts in oral implantology-is it still a “gold standard”? A consecutive review of 279 patients with 456 clinical procedures. Int J Implant Dent. 2017;3(1):23. doi:10.1186/s40729-017-0084-4 

7. Lampert RC, Braidy HF, Zweig BE, et al. Intraoral augmentation vs allogenic block graft to preparation for dental implants placement: A retrospective cohort study. J Oral Maxillofac Surg. 2015;73:E30–1. doi:10.1016/j.joms.2015.06.050

8. Peleg M, Sawatari Y, Marx RN, et al. Use of corticocancellous allogeneic bone blocks for augmentation of alveolar bone defects. Int J Oral Maxillofac Implants. 2010;25(1):153–62. 

9. Motamedian SR, Khojaste M, Khojasteh A. Success rate of implants placed in autogenous bone blocks versus allogenic bone blocks: A systematic literature review. Ann Maxillofac Surg. 2016;6(1):78-90. doi:10.4103/2231-0746.186143 

10. Petrungaro PS, Amar S. Localized ridge augmentation with allogenic block grafts prior to implant placement: case reports and histologic evaluations. Implant Dent. 2005;14(2):139–48. doi:10.1097/01.id.0000163805.98577.ab 

11. Tolstunov L. Classification of the alveolar ridge width: implant-driven treatment considerations for the horizontally deficient alveolar ridges. J Oral Implantol. 2014;40 Spec No:365–70. doi:10.1563/aaid-joi-D-14-00023 

12. Troeltzsch M, Troeltzsch M, Kauffmann P, et al. Clinical efficacy of grafting materials in alveolar ridge augmentation: A systematic review. J Craniomaxillofac Surg. 2016;44(10):1618–29. doi:10.1016/j.jcms.2016.07.028 

13. Fretwurst T, Nack C, Al-Ghrairi M, et al. Long-term retrospective evaluation of the peri-implant bone level in onlay grafted patients with iliac bone from the anterior superior iliac crest. J Craniomaxillofac Surg. 2015;43(6):956–60. doi:10.1016/j.jcms.2015.03.037 

14. Keller EE, Tolman DE, Eckert S. Surgical-prosthodontic reconstruction of advanced maxillary bone compromise with autogenous onlay block bone grafts and osseointegrated endosseous implants: a 12-year study of 32 consecutive patients. Int J Oral Maxillofac Implants. 1999;14(2):197-209. 

15. Nkenke E, Neukam FW. Autogenous bone harvesting and grafting in advanced jaw re5sorption: morbidity, resorption and implant survival. Eur J Oral Implantol. 2014;7 Suppl 2:S203-17.  

16. Misch CM. Comparison of intraoral donor sites for onlay grafting prior to implant placement. Int J Oral Maxillofac Implants. 1997;12(6):767–76.  

17. Fuglsig JMCES, Thorn JJ, Ingerslev J, et al. Long term follow-up of titanium implants installed in block-grafted areas: A systematic review. Clin Implant Dent Relat Res. 2018;20(6):1036–46. doi:10.1111/cid.12678 

18. Wang HL, Boyapati L. “PASS” principles for predictable bone regeneration. Implant Dent. 2006;15(1):8-17. doi:10.1097/01.id.0000204762.39826.0f 

19. Waasdorp J, Reynolds MA. Allogeneic bone onlay grafts for alveolar ridge augmentation: a systematic review. Int J Oral Maxillofac Implants. 2010;25(3):525–31. 

20. Tatum OH Jr. Osseous grafts in intra-oral sites. J Oral Implantol. 1996;22(1):51–2. 

21. Kleinheinz J, Büchter A, Kruse-Lösler B, et al. Incision design in implant dentistry based on vascularization of the mucosa. Clin Oral Implants Res. 2005;16(5):518–23. doi:10.1111/j.1600-0501.2005.01158.x 

22. Frost HM. The regional acceleratory phenomenon: a review. Henry Ford Hosp Med J. 1983;31(1):3-9. 

23. Rutkowski JL, Thomas JM, Bering CL, et al. Analysis of a rapid, simple, and inexpensive technique used to obtain platelet-rich plasma for use in clinical practice. J Oral Implantol. 2008;34(1):25-33. doi:10.1563/1548-1336(2008)34[25:AAOARS]2.0.CO;2

24. Soni R, Priya A, Agrawal R, et al. Evaluation of efficacy of platelet-rich fibrin membrane and bone graft in coverage of immediate dental implant in esthetic zone: An in vivo study. Natl J Maxillofac Surg. 2020;11(1):67-75. doi:10.4103/njms.NJMS_26_19 

25. Omar O, Elgali I, Dahlin C, et al. Barrier membranes: More than the barrier effect? J Clin Periodontol. 2019;46 Suppl 21(Suppl Suppl 21):103–23. doi:10.1111/jcpe.13068 

26. Machtei EE. The effect of membrane exposure on the outcome of regenerative procedures in humans: a meta-analysis. J Periodontol. 2001;72(4):512–6. doi:10.1902/jop.2001.72.4.512 

27. Novell J, Novell-Costa F, Ivorra C, et al. Five-year results of implants inserted into freeze-dried block allografts. Implant Dent. 2012;21(2):129–35. doi:10.1097/ID.0b013e31824bf99f 

28. Schlee M, Rothamel D. Ridge augmentation using customized allogenic bone blocks: Proof of concept and histological findings. Implant Dent. 2013;22(3):212–8. doi:10.1097/ID.0b013e3182885fa1 

29. Correa LR, Spin-Neto R, Stavropoulos A, et al. Planning of dental implant size with digital panoramic radiographs, CBCT-generated panoramic images, and CBCT cross-sectional images. Clin Oral Implants Res. 2014;25(6):690–5. doi:10.1111/clr.12126 

30. Wu X, Al-Abedalla K, Rastikerdar E, et al. Selective serotonin reuptake inhibitors and the risk of osseointegrated implant failure: a cohort study. J Dent Res. 2014;93(11):1054–61. doi:10.1177/0022034514549378 

31. Bölükbaşı N, Yeniyol S, Tekkesin MS, et al. The use of platelet-rich fibrin in combination with biphasic calcium phosphate in the treatment of bone defects: a histologic and histomorphometric study. Curr Ther Res Clin Exp. 2013;75:15-21. doi:10.1016/j.curtheres.2013.05.002 

32. Schlee M, Rothamel D. Ridge augmentation using customized allogenic bone blocks: proof of concept and histological findings. Implant Dent. 2013;22(3):212–8. doi:10.1097/ID.0b013e3182885fa1 

33. Jun CM, Yun JH. Three-dimensional bone regeneration of alveolar ridge defects using corticocancellous allogeneic block grafts: Histologic and immunohistochemical analysis. Int J Periodontics Restorative Dent. 2016;36(1):75-81. doi:10.11607/prd.1950

34. Misch CE. Chapter 31: Occlusal considerations for implant-supported prosthesis. In: Misch CE, ed. Contemporary Implant Dentistry. 2nd ed. Mosby;1993:705–33.

ABOUT THE AUTHOR

Dr. Jackson graduated from Utica University with a BS degree in biology, cum laude. He received his DDS degree at the State University of New York at Buffalo School of Dental Medicine. He completed postgraduate training at St. Luke’s Memorial Hospital Center’s General Practice Residency Program. He completed his formal implant training through the New York AAID MaxiCourse in oral implantology at the New York University College of Dentistry. He is board-certified and a Diplomate of the American Board of Oral Implantology/Implant Dentistry and an Honored Fellow of the American Academy of Implant Dentistry (AAID). Dr. Jackson is the past president of the AAID. He is attending staff dentist for Faxton St. Luke’s Healthcare General Practice Residency Program. He is a member of the ADA and director of the AAID Boston MaxiCourse in oral implantology and the East Coast Implant Institute. Dr. Jackson has published several articles in peer-reviewed journals on the topic of oral implantology and implant dentistry. He can be reached via email at bjjddsimplant@aol.com.

Disclosure: Dr. Jackson is a speaker for Implant Direct but did not receive compensation for this article. 

Implant placement in an edentulous posterior maxillary site faces challenges related to the resorption of the crestal ridge and enlargement of the maxillary sinus. Both of these events are normal occurrences following the loss of the premolar or molar in the posterior maxilla. The result is insufficient crestal height to accommodate implant placement.

In 1994, Summers^1,2 was the first to publish on the use of osteotomes utilizing a crestal approach to elevate the maxillary sinus membrane and place osseous graft material to increase the crestal height to allow implant placement in the deficient posterior maxilla. Prior to this innovation, a lateral approach was utilized to elevate the sinus in preparation for implant placement. Dr. Hilt Tatum had developed the lateral window sinus approach in the 1970s, but the technique was not published until 1980.^3,4

The lateral approach is more complicated surgically, has more postoperative issues during initial healing, and has more potential problems than the crestal approach. Lateral sinus elevation is still indicated when the crestal bone is less than 3 mm, and multiple implants will be placed in the quadrant, requiring a larger area to be elevated, whereas the crestal approach is well-suited when the current crestal height is 3 mm or greater and either a single or 2 adjacent implants are planned. When the current crestal height is 4 mm or greater, sufficient elevation and grafting may be performed in conjunction with simultaneous implant placement, as stability of the implant is possible, and allowed to heal before the restorative phase is initiated. Should the existing crestal height be between 3 and 5 mm, crestal augmentation may be performed, and delayed implant placement can be performed. Following initial healing of the sinus augmentation, at the subsequent surgery, additional crestal elevation can be performed, and implants can be placed.

Contraindications to the crestal approach include, as mentioned, a crestal height of less than 3 mm and a ridge width of 3 mm or less than the planned implant width. When those factors are present, a lateral approach should be utilized.

A CRESTAL SINUS ELEVATION PROCEDURE 

Depth stop drills improve accuracy and, in combination with non-cutting drill tips, aid in preventing the tearing of the sinus membrane during the elevation process.

The drills are designed so that autogenous bone particles are pushed up through the opening in the sinus floor beneath the membrane as each progressive (larger diameter) drill is used. The drill removes bone from the inner wall of the osteotomy with a counterclockwise rotation. (Drill sets are available for both clockwise or counter-clockwise rotation.) This pushes the bone apically to elevate the membrane. The use of a sinus elevation probe after each drill in the 1.5- to 2.2-mm gold series depth is done to feel/check for a perforation through the bone at the sinus floor. The drills should not penetrate the floor of the sinus by more than 1 mm, leaving the membrane intact.

The Guide Right Sinus Elevation kit (DePlaque) contains all the components, drills, and tools to perform the crestal sinus elevation procedure (Figure 1). The Guide Right drills are available in 5 series of diameters with a 2° taper in lengths of 4, 5, 6, 7, 8, 9, and 10 mm (Figure 2). Each drill is run at 600 to 800 rpm in the surgical handpiece. The drills may be used with a guided approach or freehand, depending on the surgeon’s preference.

Figure 1. The Guide Right Sinus Elevation kit and its components (DePlaque), available for both clockwise and counter-clockwise rotation.

Figure 2. Drill series for crestal sinus elevation with 2° tapered depth stops utilized.

CRESTAL SINUS ELEVATION PROTOCOL

When using a guided approach or a flapless protocol, the crestal sinus elevation drill sequence is followed (Figure 3, steps 1, 2, and 3). Subsequent gold drills that are 4 and 6 mm long are used to depth until the bone is penetrated and the membrane is felt. After the use of each 4- to 6-mm-length gold drill, the site is evaluated with a sinus elevation probe to tacitly feel if the membrane has been contacted. The probe should be used gently to avoid perforation of the sinus membrane. If the membrane can be felt, longer drills are not utilized, and further site preparation is done with the wider Guide Right Sinus drills of the same length. For illustration purposes, we will assume that the depth before membrane contact is 6 mm.

Figure 3. Steps 1 to 3: initial steps to determine the level of the sinus membrane and thickness of the crestal bone.

To verify an intact sinus membrane, it can be checked using the Valsalva Maneuver. This maneuver involves pinching the patient’s nose and having the person try to blow his or her nose while you watch to see if any bubbles escape from the osteotomy site. If no bubbles or blood escape, the membrane has most likely not been perforated. This should be checked prior to any graft material being placed into the osteotomy. After testing with the Valsalva Maneuver, if the membrane has been perforated, select a drill 1 mm shorter than the working length that is wider than the prior drill. Use those larger diameter drills, 1 mm shorter in length, until you reach the final diameter needed.

A Rose series drill (2 to 2.9 mm) in 6 mm length is used until the drill stop contacts the crest, which pushes the autogenous bone particulate to further elevate the sinus membrane.

Cut an OsteoGen Plug (OPS625-10 Slim [IMPLADENT LTD]) into small pieces that are 3 to 4 mm long. Using the Concave Plugger (small end), compress all pieces, one piece at a time, into the osteotomy. Check again for sinus membrane perforation with the Valsalva Maneuver. Continue to increase the sinus elevation with more of the collagen or bone product until you have reached the desired implant length. Check the site with a periapical radiograph prior to placing the implant to verify the graft is confined in the area and not dispersed throughout the sinus.

Subsequent drills increasing in diameter, from Blue series (2.7 to 3.2 mm) to the Silver series (3 to 3.9 mm) in 6 mm length, are utilized to push additional autogenous particulate, widening the diameter of the osteotomy to elevate the sinus membrane (Figure 4, step 4).

Figure 4. Steps 4 to 6 utilized to push additional autogenous bone particulate into the sinus.

The final diameter of the Guide Right Sinus Elevation drills should be narrower than the planned implant’s diameter so that the implant, upon placement, engages the osseous walls crestally, providing initial implant stability (Figure 4, steps 5 and 6).

When the planned implant is a greater diameter than 4.7 mm, the Black series drills are used, which have a diameter of 3.7 mm at the tip and 4.7 mm at the drill stop. This drill is then used after filling the osteotomy with additional graft material, in this illustrated case to the 6-mm drill stop (Figure 5, step 7). The Concave Plugger is then used to add additional graft material and gently apply apical pressure to further lift the sinus membrane, allowing the graft material to elevate the membrane circumferentially and apically (Figure 5, step 8). The implant is then placed, achieving lateral compression with the crestal walls and achieving initial stability (Figure 5, step 9). A cover screw or healing abutment is placed, and soft tissue is sutured around to get primary closure if a flap is reflected. Due to the less dense bone of the posterior maxilla, it is not recommended to immediately load these implants but to allow the graft material to mineralize and the implant to osseointegrate for 4 to 6 months before the restorative phase is initiated.

Figure 5. Steps 7 to 9 utilized to push additional graft material with apical pressure to further elevate the sinus membrane.

DRILL TEMPERATURE AND ITS EFFECTS

A study on the effects of drill sharpness completed by Ercoli et al⁵ examined temperature increases with different drilling protocols. One of the parameters examined was the temperature of the drilling protocol. The results indicated drills were not significantly different at depths of 5 mm or 15 mm, or between 2- or 3-mm-diameter drills. The temperatures generated by the different types of drills were not significantly different. Clinically harmful temperatures were detected only at a depth of 15 mm during osteotomy preparations and coincided with a marked decrease in the rate of drill advancement with a resulting continuous drilling action. They concluded the properties significantly affect cutting efficiency and durability. Coolant availability and temperature were the predominant factors in determining bone temperatures. Continuous drilling in deep osteotomies can produce local temperatures that might be harmful to the bone.⁵ It has been shown in an in vitro study in bovine ribs that the use of a refrigerant solution at a temperature of 6°C reduces the increase of bone temperature during the preparation of implant sites compared with the physiological solution at the temperature of 23.7°C.⁶

There are benefits of cold drilling when creating osteotomies, especially when a flapless approach is being used with a surgical guide. Irrigation is unable to reach apical to the soft tissue during a flapless approach, and a surgical guide may hamper the irrigant from cooling the drills. Because flapless protocols involve serial drilling by increasing drill lengths at 1-mm intervals, the drills are pre-cooled, and irrigation is not necessary nor required. The drills can be pre-cooled by placing them in a refrigerator’s freezer for one hour prior to surgery. The sinus elevation protocol calls for serial drilling, increasing the depth by 1 mm at a time, which is hardly long enough for the drill to heat up to significantly injure the bone cells. Once the depth of the osteotomy is reached, the width of the osteotomy is increased by less than 1 mm with each increasing drill diameter, also using cooled drills. In serial drilling of 1-mm increments of bone depth (4-, 5-, 6-, 7-, 8-, 9-, and 10-mm lengths), switching to a fresh cooled drill for each step until the final depth is reached results in less trauma to the alveolar bone and less discomfort to the patient. After the appropriate depth is reached, the osteotomy width is also increased in small steps, limiting the trauma and heat produced by using pre-cooled drills to remove a very small amount of bone pushed apically.

CASE REPORTS

Case 1

A 70-year-old male patient presented with missing molars in the maxillary right posterior, desiring replacement to improve mastication. The first and second molars had been extracted several years before. A periapical radiograph was taken, and pneumatization of the sinus was noted. The crestal height was estimated at 6 mm (Figure 6). Treatment was discussed, and it was recommended to place an implant at the first molar site without implant placement at the second molar site. The patient was advised sinus elevation would be required for implant placement, and treatment recommendations were accepted.

Figure 6. Periapical radiograph demonstrating an estimated crestal height at site 3 of 6 mm.

An impression was taken, and a study model was made to fabricate a diagnostic guide utilizing Guide Right sleeves to be utilized during the CBCT. A cone-beam radiograph was taken with the diagnostic guide in place. The scan was imported into CS 3D Imaging planning software (Carestream Dental). A virtual implant was placed in the preferred position (Figure 7). It was determined an angle correction of 12° would be required based on the anatomy present to be incorporated into the surgical guide design (Figure 8). A corrected surgical guide was fabricated to place the planned implant in an ideal position related to the anatomy, and it was prosthetically driven.

Figure 7. CBCT views during the planning stage with Guide Right sleeves in the diagnostic stent with measurement of the crestal bone height and overlaying soft tissue available at site 3.

The patient returned, and consent forms were reviewed and signed by the patient. Following local anesthetic placement, a flapless surgical approach was utilized with the Guide Right surgical guide to follow the Guide Right sinus elevation protocol previously described. Upon creation of the osteotomy and identification of the sinus membrane, Puros (RTI Surgical) OsteoGen and 50 μg. Infuse bone graft (BMP-2) are placed into the osteotomy.

Figure 8. During virtual planning, it was determined an angle correction of 12° would be required based on the anatomy present (green line: long axis of Guide Right sleeve, blue line: long axis of the virtual implant, red line: angle correction required) to be incorporated into the surgical guide design.

Figure 9. Periapical radiograph following placement of the collagen plug strips of allograft prior to implant placement.

Figure 10. Periapical radiograph following immediate placement into the elevated sinus at site 3.

OsteoGen Plug 1020 (IMPLADENT LTD) was used to elevate the sinus membrane. The plug was sectioned into quarters lengthwise. Then 50 to 100 μg of BMP-2 in 0.40 ml sterile H₂O was applied to the plug pieces for 15 minutes prior to application. Minimal H₂O is recommended to avoid dilution of the BMP-2 once inserted into the sinus area.^7-9 Each piece of the plug is then cut into smaller pieces for the elevation of the sinus membrane. Pieces of the 50 to 100 μg of BMP-2 laced plug are introduced into the osteotomy with collage pliers and pressed apically with the plugger. The last Guide Right sinus drill was then utilized to gently move the graft apically while running counterclockwise to elevate the membrane. A periapical radiograph was then taken to verify sinus elevation and containment of the graft at the site (Figure 9). The osteotomy was widened utilizing the osteotomy final drill for the implant to be placed (Mega’Gen), and a 5- × 10-mm implant was placed (Mega’Gen). The implant length selected should not be greater than the height of the elevation. A periapical radiograph was taken to document implant placement and was within the limits of the sinus elevation (Figure 10). A 2.5-mm healing abutment was placed, the patient was dismissed, and healing would be allowed for osseointegration prior to initiation of the restorative phase.

Case 2

A 76-year-old male patient presented for implant placement at site 14 that had a missing tooth. A periapical radiograph noted 3 to 4 mm of residual crestal bone at the site. A diagnostic CBCT scan guide was created, and a CBCT scan was taken. The scan data was imported into virtual planning software, and a virtual implant was placed at the site (Figure 11).

Figure 11. CBCT views during the planning stage with Guide Right sleeves in the diagnostic stent illustrating the 3- to 4-mm crestal bone height available.

Figure 12. Periapical radiographs taken at various stages of the crestal elevation (left: following initial reverse drill osteotomy, middle: following sinus elevation, right: following implant placement).

Figure 13. CBCT views following crestal sinus elevation and implant placement illustrating the gain in crestal height to accommodate the implant at site 14.

The patient returned, and consent forms were reviewed and signed. A similar protocol as described for the prior case was followed. Following an initial reverse drill osteotomy with the Guide Right sinus elevation drills, a periapical radiograph was taken (Figure 12, left). Collagen plug pieces with BMP-2 were utilized to elevate the sinus, and a periapical radiograph was taken (Figure 12, middle). A 5- × 10-mm Mega’Gen tapered implant was placed, and a periapical radiograph was taken to document the implant and graft (Figure 12, right). A 2.5-mm healing abutment was placed, and a CBCT scan was taken documenting that the implant was encased in graft material, especially apically (Figure 13). The patient was dismissed, and healing would be allowed for osseointegration prior to initiation of the restorative phase.

Case 3

A 74-year-old female patient presented with a missing tooth 15 and tooth 16 present in a good position, requesting an implant to replace tooth 15 instead of a fixed bridge from 14 to 16. A periapical radiograph noted 3 to 4 mm of residual crestal bone at the site. Implant planning was done for maxillary left second molar that required sinus elevation. A diagnostic CBCT scan guide was created, and a CBCT scan was taken. The scan data was imported into virtual planning software, and a virtual implant was placed at the site (Figure 14).

Figure 14. CBCT views during planning stage with Guide Right sleeves in the diagnostic stent illustrating the 3- to 4-mm crestal bone height available at site 15.

Figure 15. Periapical radiograph taken following crestal sinus elevation (left) and after implant placement (right).

The patient returned, and consent forms were reviewed and signed. A similar protocol as described for the prior cases was followed. Following sinus elevation with the Guide Right sinus elevation drills, collagen plug pieces with BMP-2 were utilized to elevate the sinus, and a periapical radiograph was taken (Figure 15, left). A 5- × 10-mm Megagen tapered implant was placed, and a periapical radiograph was taken to document the implant and graft (Figure 15, right). A 2.5-mm healing abutment was placed, the patient was dismissed, and healing would be allowed for osseointegration prior to initiation of the restorative phase.

Case 4

A 69-year-old female patient presented 3 months after tooth No. 14 had been extracted for evaluation for implant placement at the site. Minimal bone was noted below the sinus after a CBCT scan was taken with a Guide Right diagnostic stent (Figure 16). Minimal crestal height was confirmed. A surgical guide was fabricated with Guide Right sleeves.

Figure 16. CBCT views during the planning stage with Guide Right sleeves in the diagnostic stent illustrating the minimal crestal bone height available.

Figure 17. CBCT after the initial reverse osteotomy pushed the crestal bone material to raise the sinus membrane.

Figure 18. CBCT following additional graft placement to further elevate the sinus membrane and implant placement.

The patient returned, and consent forms were reviewed and signed. A similar protocol as described for the prior cases was followed. Following initial elevation, a CBCT scan was taken to confirm the initial graft was contained and had not spread inside the sinus due to perforation of the membrane (Figure 17). Further graft placement and elevation were performed, and a 5- × 10-mm Mega’Gen implant was placed. A CBCT scan was taken to document the implant placement and amount of sinus elevation, confirming it was contained around the implant (Figure 18). A cover screw was placed and the patient was dismissed, and healing would be allowed for osseointegration prior to initiation of the restorative phase.

CONCLUSION

Loss of crestal height is a frequent occurrence in the posterior maxilla, complicated by periodontal bone loss that may be a causative factor for the loss of that tooth and pneumatization of the sinus. A crestal approach to increase crestal height to accommodate implant placement is a simpler, less traumatic approach than lateral sinus augmentation. The technique described using a diagnostic CBCT stent, virtual planning, and surgical guide allows a flapless approach to the procedure. Utilization of the Guide Right sinus elevation instrumentation decreases the potential for membrane perforation during elevation and osteotomy creation. This results in a simpler, more predictable approach to implant placement in the resorbed posterior maxilla.

REFERENCES

1. Summers RB. A new concept in maxillary implant surgery: the osteotome technique. Compendium. 1994.15(2):152, 154–6. 

2. Summers RB. The osteotome technique: Part 3—Less invasive methods of elevating the sinus floor. Compendium. 1994;15(6):698, 700, 702–4 passim. 

3. Boyne PJ, James RA. Grafting of the maxillary sinus floor with autogenous marrow and bone. J Oral Surg. 1980;38(8):613–6. https://pubmed.ncbi.nlm.nih.gov/6993637/   

4. Tatum H Jr. Maxillary and sinus implant reconstructions. Dent Clin North Am. 1986;30(2):207–29. 

5. Ercoli C, Funkenbusch PD, Lee HJ, et al. The influence of drill wear on cutting efficiency and heat production during osteotomy preparation for dental implants: a study of drill durability. Int J Oral Maxillofac Implants. 2004;19(3):335–49. 

6. Di Fiore A, Sivolella S, Stocco E, et al. Experimental analysis of temperature differences during implant site preparation: Continuous drilling technique versus intermittent drilling technique. J Oral Implantol. 2018;44(1):46-50. doi:10.1563/aaid-joi-D-17-00077 

7. Nevins M, Kirker-Head C, Nevins M, et al. Bone formation in the goat maxillary sinus induced by absorbable collagen sponge implants impregnated with recombinant human bone morphogenetic protein-2. Int J Periodontics Restorative Dent. 1996;16(1):8-19.    

8. Boyne PJ, Marx RE, Nevins M, et al. A feasibility study evaluating rhBMP-2/absorbable collagen sponge for maxillary sinus floor augmentation. Int J Periodontics Restorative Dent. 1997;17(1):11-25.  

9. Freitas RM, Spin-Neto R, Marcantonio Junior E, et al. Alveolar ridge and maxillary sinus augmentation using rhBMP-2: a systematic review. Clin Implant Dent Relat Res. 2015;17 Suppl 1:e192-201. doi:10.1111/cid.12156 

ABOUT THE AUTHORS

Dr. Meitner graduated from Marquette University in Milwaukee after completing a tour of duty in the US Navy, completed his certificate and board examinations in periodontics at the Eastman Institute for Oral Health at the University of Rochester in New York, and remains a part-time professor of clinical dentistry in the Department of Periodontology at the university. He has been in private practice in periodontics for more than 30 years in Pittsford, NY, and is the developer of the Guide Right protocol. He can be reached at swmeit4@gmail.com.

Dr. Kurtzman is in private general practice in Silver Spring, Md. A former assistant clinical professor at the University of Maryland, he has earned Fellowships in the AGD, the American Academy of Implant Prosthodontics, the American College of Dentists, the International Congress of Oral Implantologists (ICOI), the Pierre Fauchard Academy, and the Association of Dental Implantology; Masterships in the AGD and ICOI; and Diplomate status in the ICOI and the American Dental Implant Association. He has lectured internationally, and his articles have been published worldwide. He has been listed as one of Dentistry Today’s Leaders in Continuing Education since 2006. He can be reached via email at dr_kurtzman@maryland-implants.com.

Disclosure: Dr. Meitner is a product developer and non-paid consultant for DePlaque. Dr. Kurtzman reports no disclosures.

For anyone who has been involved with an All-on-4 procedure, the thought of going into surgery with no interim ready to convert may not only sound strange but quite scary. As prosthodontists, we have been involved in hundreds of these cases and had the teeth ready to convert hundreds of times. So why would we now intentionally begin a surgery without the teeth? Technology!

While we have had the technology and digital know-how for years to do this, we have resisted. We started immediately loading full arches when the only method available was converting a traditional denture. When stackable guides started becoming popular, we transitioned to this for the improved accuracy of implant placement and ease of conversions. With both of these methods, we had the problem of interims breaking weeks to months into the process. This would significantly impact the experience patients had and would put their implants at risk. So, when Smart Denture Conversion abutments came to market, we were early adopters. They ease conversions but also provide a prosthesis with more strength. This became our method of choice for conversions in our practice. We started using them with dentures and later began milling prosthetics supported by stackable guides. To this day, we still use stackable guides and Smart Denture Conversion abutments with great success and ease. So why try something new?

CASE REPORT

Allison presented to our dental implant center with a failing maxillary dentition. We discussed her options, and she elected to go with the All-on-4 option and replace all of her maxillary teeth with a prosthesis supported by at least 4 dental implants. Typically, this prosthesis ideally requires 15 mm of restorative space to make room for not only the teeth but the gingiva as well. Through our implant planning, it was found that if we wanted 15 mm of restorative space, we would not have enough bone for the implants. Allison had a short maxilla, so we changed the plan. We transitioned to a full-arch, implant-supported bridge—what Misch called an FP1 prosthesis. This prosthesis is just bridges replacing the teeth, with no gingiva. So, what was the challenge?

We have enjoyed years and years of not having patients return with their interim prosthetics broken while waiting for their implants to integrate. We feel much of our success was from drawing a line and not crossing it. Making an immediate load conversion of an FP1-type prosthesis comes with concern—we can’t make a thicker interim prosthesis since the prosthesis itself is replacing just the teeth. So what do we do?

We have had the software and 3D printers for years, capable of designing teeth and printing them all on the day of surgery. When doing this, we can design the interim to sit directly on the multi-unit abutments and be held in place with Rosen screws (Rosen Screws). This combination provides the added strength in a thinner prosthesis but isn’t possible without technology. I would like to walk you through the day of surgery.

Before Surgery

Regardless of the route we choose for getting our patients into their interim prostheses, it always begins with a records appointment. We discuss with patients their goals for their new smiles. Once we know where we are going, we evaluate where we are at now (midline, incisal edge position, vertical, occlusal plane, etc). We also take photos, intraoral scans (TRIOS [3Shape]) (Figure 1), and CBCT scans (OP 3D [DEXIS]).

Figure 1. Preoperative intraoral scan.

From everything we gathered at Allison’s first visit, we designed her teeth digitally with exocad (exocad America) (Figure 2). We referenced the list of changes and photos to ensure the design achieved her goals. Something to note here is that while we had designed the new teeth, we still had the old teeth aligned to them (transparent in the image)—this is important later.

Figure 2. Teeth designed in exocad (exocad America).

After the teeth are decided, they are brought into the implant planning software (Blue Sky Plan [BlueSkyBio]). When placing implants for an FP1 prosthesis, it is critical to position them directly beneath the teeth they are replacing. The last thing you want is an implant going into an embrasure space where a papilla is supposed to be. While it is possible to place a full-arch prosthesis directly to implants, it is very difficult. It is the reason multi-unit abutments were created. So, for Allison’s plan, the implants and abutments were planned below the planned teeth at Nos. 3, 5, 7, 10, 12, and 14 (Figure 3). After the implants and abutments were confirmed, this was exported out, finalized as a final prosthesis design (Figure 4), and later used in the guide fabrication (Figure 5).

Figure 3. Implants placed in Blue Sky Plan (BlueSkyBio) directly below the teeth.

Figure 4. The prosthestic design adapted to the planned implants.

Figure 5. The planned prosthetic was incorporated into the surgical guides.

All of the planning we completed was brought into 3D editing software (Meshmixer [Autodesk]) and used to fabricate the surgical guides used at the surgery. Allison’s guides started with a tooth-supported guide attached to a foundation guide. This foundation guide stayed attached to her maxilla for the duration of surgery, serving as a stable base for a variety of other guides.

To summarize the presurgical planning goals, we then had a variety of surgical guides designed and fabricated, as well as the interim prosthesis designed but not fabricated (milled or printed).

Surgery

After Allison was sedated, our surgery started. After administering local anesthetic to her maxilla, a facial flap was laid from left to right. When using a foundation guide with stackable pieces, this flap needs to be extended further apically than usual. The foundation guide starts attached with plastic pins to a tooth-supported guide. This allows us to use a stable starting point as a reference to ensure we’ve accurately transferred the digital plan to surgery. With the one guide securely fitted to the teeth, we secured the foundation guide to her bone.

Note that with this technique, we made Allison’s foundation guide in titanium (Titanium 98 mm Disc [Imagine USA]). As you will see, we needed the guide to stay exactly where we put it for the duration of the procedure. Our lab (Renew Full Arch Lab) designed a millable foundation guide just for this technique. We wanted something more stable than 3D printed resin guides. We sandblasted the titanium so that it scanned easier. Also note that, with her case, we opted to use screws (Pro-Fix [Osteogenics]) rather than pins to secure the guide. Again, this was for improved stability. The third design element to ensure stability was to have the guide touch the bone in those few places where the screws go in. We have pinned a lot of floating resin guides for All-on-4 surgeries and can assure you that these 3 changes make a significant difference in stability.

When the screws were in, the plastic pins were removed, and the tooth guide was taken out (Figure 6). The next step was important to this particular technique—making a scan of the patient’s teeth and the foundation guide (Figure 7). This was the first of 2 scans used to design her interim prosthesis.

Figure 6. After the foundation guide was screwed to the bone, the tooth guide was removed.

Figure 7. The teeth and foundation guide were scanned with TRIOS (3Shape).

Then it was time to extract the teeth. With an FP1 procedure, you aren’t removing the bone to make room for an All-on-4 prosthesis. Instead, you are trying to maintain as much bone as possible since only bone can support the gingiva you hope will form the papillae (Figure 8). But we needed to remove any bone that would prevent the future teeth from seating. To guide this very specific alveoplasty, we took the same design of the arch and added it to the stackable guide. This gave us a clear view of the bone that needed to be removed (Figure 9). The goal was to remove enough bone to make room for gingiva (1.5 to 2.0 mm).

Figure 8. Teeth were extracted with an effort to preserve as much bone as possible.

Figure 9. The designed prosthesis was printed and rested on the foundation guide.

Figure 10. The implant guide was used to accurately place the implants.

Figure 11. Multiple abutments were placed on the implants.

Adequate bone was removed, and the implant guide was used to place the dental implants (GM Drive [Neodent]) according to our plan (Figure 10). Then the multi-unit abutments were placed (Figure 11), ensuring no contact with bone (note that it will likely require further alveoplasty). The abutments were then torqued to place. The next step is the second most important part of this technique. Photogrammetry requires that we scan something that acts as a fiduciary to relate its highly accurate data to the intraoral scan. With our scanner, there are cylinders for this purpose. These were placed on Allison’s multi-unit abutments and scanned (Figure 12). This scan included the foundation guide and cylinders (Figure 13). These 2 scans (teeth with guide and guide with cylinders) were immediately given to the lab for alignment.

Figure 12. The iMetric cylinders were placed on the multi-unit abutments.

Figure 13. The foundation guide and iMetric cylinders were scanned with the TRIOS.

Figure 14. The iMetric scan bodies were placed on the multi-unit abutments.

The cylinders were removed and replaced with the photogrammetry scan bodies (Figure 14). These were used with the photogrammetry unit (iCam [iMetric 4D]) to scan the implant positions. It scans all of the scan bodies in less than a minute and provides better accuracy than most desktop scanners and traditional jigs. This data was also given to the lab. It is this technology that makes this technique possible.

Photogrammetry has been around for decades in a variety of industries but is relatively new to dentistry. Intraoral scanners are very accurate when scanning small objects like teeth. But they fail when asked to scan longer distances, such as, for example, one side of an arch to the other. Desktop scanners have traditionally been used to scan for full-arch, implant-supported prosthetics, but they require a model. Getting a verified abutment-level model is best achieved through taking preliminary impressions and then final impressions with the use of a jig. Photogrammetry gets better accuracy within minutes. It’s a beautiful thing and a must for clinicians doing a lot of full-arch implant dentistry.

When the scan is complete and sent to the lab, they can finalize the design. In the meantime, one must graft around implants, graft all sockets, and suture. After the teeth are ready, they are inserted, and Rosen screws are used to secure them. Rosen screws are designed to provide a wedging effect and are meant to be hand-tightened. Once the teeth were inserted, occlusion was dialed in, and then screw access holes were filled with PVS.

Lab Work

The key to designing quickly at the time of surgery is that the design is done before surgery but is just missing the implant connections. With 2 intraoral scans and a photogrammetry scan, the rest is easy. All 3 scans are aligned, and the design is adapted to the implant positions. I’ll walk you through the details.

When the 2 intraoral scans were sent to the lab during surgery, the lab started the sequence of alignments. Remember, the design of the interim was already aligned with the preoperative scans of her failing dentition. The first scan from surgery has 2 important things: the current teeth and the foundation guide. The teeth in the first new scan are used to align this scan to the pre-op scan (Figures 15 and 16). This relates the foundation guide to the interim design. The second new scan has 2 important things as well: the foundation guide and the cylinders. This scan is aligned with the first new scan using the foundation guide as the common reference between them (Figures 17 and 18). These 2 alignments achieve a very important goal: to align the interim design to those photogrammetry cylinders (Figure 19). We can then use those cylinders to align the highly accurate photogrammetry data to the scene (Figure 20), which means the implant positions are now where we need them. The final step is adapting the interim design to the implant positions (Figure 21).

Figure 15. Common points were selected between the first surgery scan and the preoperative scan.

Figure 16. The exocad software used its alignment algorithm to match the scans (dark blue is considered a perfect alignment).

Figure 17. It’s the same idea in the sec- ond scan: The common points on the 2 guide scans are selected.

Figure 18. The dark blue denotes great alignment between the guide in scan 1 and scan 2.

Figure 19. The iMetric cylinders were aligned to the presurgery interim design.

Figure 20. The scan of the cylinders was used to align the photogrammetry data.

Figure 21. The presurgery design was adapted to the newly scanned implant positions.

The next step in the lab is to 3D print the interim design. It is important to note certain requirements of a printer used for this purpose. Not all 3D printers have adequate accuracy to print a design meant to fit a multi-unit abutment and screw. Second, it’s also important to consider the speed of the printer since the patient is waiting. And lastly, the printer has to be able to print a tooth-colored material (Rodin Sculpture [Pac-Dent]) that can withstand occlusal forces.

The final lab step was to wash the print, cure it, and finish it. Allison’s interim prosthesis was washed twice in isopropyl alcohol and cured in a flash unit surrounded by nitrogen (Otoflash G171 [anax USA]). We then used pumice and acetyl polish to give the print a nice shine. It was then ready for insertion.

CONCLUSION

As you can see, this technique is a careful dance between the clinician and the lab. Each has very specific roles and must do them to the best of their ability to ensure success. We have the luxury in our practice to share a roof with the lab so that we can keep everything in-house. For our lab’s clients, we design the interim prostheses before surgery; they capture the scans; we align and adapt; and they print, finish, and deliver. This technique avoids traditional conversions and delivers more predictable, custom interims. This means we are more likely to hit our target goals and give our patients the smiles they are hoping for.

ABOUT THE AUTHOR

Dr. Farley is a surgical prosthodontist practicing in Mesa, Ariz. He and his business partner own and operate Revive Dental Implant Center and Renew Full Arch Lab (renewdigitaldesign.com), where they utilize the newest technologies to provide high-quality full-arch prosthetics. Dr. Farley also teaches live and online courses through their education center, DigitalDDS (digitaldds.com). He can be reached at nfarley@revivedental.com.  

Disclosure: Dr. Farley reports no disclosures. 

INTRODUCTION

In part 1 of this series, in the March 2023 issue, we discussed single and multi-unit restorations. This is part 2 of the series, which will focus on implant-retained and -supported full-arch removable treatment with ceramic dental implants.

Background

As the baby boomer population is entering into the senior phase of their lives, there are a large number of edentulous adults in the United States seeking treatment. According to the American College of Prosthodontics and the National Center for Health Statistics,¹ there are 36 million completely edentulous adults in the United States. With implant restorations being very common nowadays and highly successful, this population cohort is aware of and requesting implant treatment on a daily basis. In recent years, a unique phenomenon has occurred where patients are requesting less invasive procedures and materials. In the case of dental implants, the request for ceramic implants from patients has been on a rapid rise. Implant treatment modalities for complete edentulism can be divided into 2 categories: fixed and removable. The fixed option tends to be more appealing due to its similarities with native dentition; however, cost, stringent hygiene, and maintenance requirements become an obstacle for some patients.² The removable overdenture option is preferred in cases of financial limitations, oral hygiene limitations, and/or limited availability of bone. In addition to this, the removable option is more attractive when aesthetics are of concern, especially if the transition line cannot be hidden or additional lip support is required.³ The survival rates of implants supporting maxillary overdentures in one long-term study was shown to be 91.9% vs 98.6% in the mandible.⁴ Age, sex, and splinting do not influence survival rates.^4,5 A minimum number of 4 implants is recommended in the maxilla for the support of a maxillary overdenture.^6,7

Figure 1. The PUREloc abutments and components (Straumann).

Figure 2. Docklocs (Zeramex) abutments for XT ceramic implants.

There is very little literature on ceramic implants and overdentures. The authors were unable to find any research on 2-piece ceramic implants used for overdentures. The reason for this is twofold: First, ceramic implants have a shorter history of use in comparison to titanium implants. Second, the locator components for ceramic implants have been introduced recently and are only commercially available with a few ceramic implant systems, including PUREloc (Straumann) (Figure 1) and Docklocs (Zeramex) (Figure 2). With the advancement in ceramic implant manufacturing, composites of ceramics have emerged as reliable implant materials, thereby expanding the applications and prosthetic range of ceramic implants. The zirconia composites yttria-stabilized zirconia, zirconia-toughened alumina, and alumina-toughened zirconia have primarily emerged as the 3 forms of zirconia used in the manufacturing of load-bearing ceramics.⁸ Yttria has been used to increase the structural stability of zirconia by limiting aging and improving its optical properties and aesthetic value.⁹ Furthermore, there are 2 major methods of manufacturing ceramic implants: milling of a zirconia bloc or injection molding of a ceramic slurry. Implants produced by both methods have been tested for structural and mechanical stability, and no statistically significant difference was observed in their responses to artificial aging and mechanical stress tests.¹⁰ In light of these technical and manufacturing improvements, the range of ceramic implant applications is expanding, and more prosthetic components are becoming available. This allows the clinician and the lab to offer more metal-free solutions to address patients’ edentulism. Osman, Payne, et al¹¹ used one-piece ceramic implants in their pilot study with ball attachments for maxillary and mandibular overdentures. Out of 28 implants, 4 failed to integrate prior to loading and were replaced. At one-year followup, all remaining implants survived and were successful. In another study, Osman, Swain, et al¹² compared one-piece titanium implants to one-piece ceramic implants, both with ball-type attachments, and the success rates after one year in the maxilla were significantly low (71.9% for titanium and 55% for ceramic). Part of the reason for these low success rates can be attributed to the small sample size as well as the fracture of 2 ceramic implants in the maxilla. The implant literature has demonstrated a slightly higher failure rate of dental implants in the maxilla. It has been 10 years since that study, and thanks to material engineering and advanced manufacturing protocols, there have been significant changes and improvements in load-bearing ceramic implant material toughness, flexural strength, and overall composition. To the best of the authors’ knowledge, no studies are available on 2-piece ceramic implants with locator-type abutments. This is an area where more research is needed to validate the long-term success and indications for removable full-arch solutions on ceramic implants. 

CASE REPORT 

Complete Maxillary Edentulism

An 86-year-old female patient presented to our clinic for a tooth replacement consultation. She had been fully edentulous in the maxilla for the past decade and was not happy with her complete dentures. Her main complaints were dietary restrictions and the inability to taste her food since her palate was covered. The patient initially resisted implants because she did not want to have metals inside her body. She heard about ceramic dental implants and requested them as a solution due to lifestyle preferences.

Figure 3. Preoperative photo of the edentulous ridge, showing adequate bone volume and keratinized tissues.

Figure 4. Pre-op panoramic radiograph used to identify vital structures and virtually plan the implant placement.

Figure 5. Pure 2-piece ceramic implant (Straumann).

Figure 6. Intraoperative radiograph to confirm implant parallelism and also showing the use of drill stoppers for depth control.

Figure 7. Clinical photo immediately after implant placement showing the minimally invasive approach.

The clinical examination revealed a fully edentulous maxillary ridge with adequate keratinized tissue (Figure 3). A panoramic radiograph was taken to evaluate the location of maxillary sinuses and the available bone for adequate anteroposterior positioning of the implants (Figure 4). Available treatment options were discussed, and the patient chose the removable overdenture due to finances and less stringent hygiene requirements in comparison to a fixed implant bridge. The surgery was carried out freehand with local anesthesia. Since the patient had adequate keratinized tissue, a mucotome was used to access the bone instead of laying an extended cross-arch flap. Implant osteotomy was done using copious irrigation and manufacturer protocols, and 4 Straumann Pure 2-piece ceramic implants (Straumann) (Figure 5) were placed in the maxillary arch. Intraoperative radiographs were taken to confirm the positioning and angulation of the implants (Figure 6). Final insertion torque of the implants was 35 to 40 N/cm², and implant stability quotient (ISQ) values of 60 to 78 were measured using the Osstell Beacon device (W&H Dentalwerk). Cover screws were placed over 3 of the 4 implants, and a short healing abutment was placed on the right posterior implant (Figure 7). The implants were left to heal undisturbed. The postoperative panoramic radiograph shows adequate spacing and parallelism of the implants (Figure 8).

Figure 8. Final panoramic radiograph of all 4 implants after placement.

Figure 9. The PUREloc plan abutment was used to determine the correct height of the final locator-type abutments.

Figure 10. Intraoral photo of the locator- style PUREloc ceramic abutments.

Figure 11. Occlusal photo of the final palateless overdenture with shortened arch size.

Figure 12. Intaglio of the overdenture showing the PUREloc housings with white (light, 750-g retention) inserts.

Figure 13. Final photo of denture delivery showing lip and facial harmony and aesthetics.

The implants were uncovered 4 months after placement, and healing abutments were placed. The ISQ values showed an increase from 71 to 78 on all implants. The gingival tissue height was measured using the PUREloc plan abutment (Figure 9), which allows for the determination of the exact height of the locator abutment to be used. Two weeks after uncovering, the PUREloc abutments were positioned (Figure 10), and impressions were taken to initiate the prosthetic phase. A palateless maxillary implant-supported overdenture (Figures 11 and 12) was fabricated and delivered. The patient was happy with the newfound retention, stability, and aesthetics of her overdenture (Figure 13), as well as the ability to have an open palate and better taste food. 

DISCUSSION

Ceramic implants are being requested at an exponential pace by patients. The demand for ceramic implants is primarily driven by patients. After a decade and a half of presence in the United States and more than a dozen FDA-approved and commercially available systems, we are just now seeing a rise in the demand for ceramic implants from dentists themselves. The largest players in the dental implants industry, namely Straumann, Nobel Biocare, Neodent, and Keystone, have either added ceramic implants to their portfolios by means of licensing and distribution or, in the case of Straumann and Neodent, are manufacturing their own ceramic implants. The Straumann Pure portfolio of 2-piece ceramic implants is currently limited to implants 4.1 mm in diameter. The authors believe that having wider implants of 5 mm and greater diameters will allow for better strength, support, and favorable load distribution for edentulous solutions. That said, there are other commercially available 2-piece ceramic implants that are 5-plus millimeters in diameter and have locator-type solutions. 

CONCLUSION

The evolution of zirconia materials has allowed for a better prosthetic variety, including the fabrication of LOCATOR-type abutments that allow for full-arch solutions. This case demonstrates the successful use of ceramic implants in order to rehabilitate a fully edentulous maxillary arch. As material science advances, we also expect the production of multi-unit-type abutments that will allow for an abutment-level, fixed, full-arch solution (All-on-X) with ceramic implants. That said, since the majority of 2-piece ceramic implants currently available are tissue-level, a fixture-level All-on-X solution is also currently possible on ceramic implants.

REFERENCES

1. Fleming E, Afful J, Griffin SO. Prevalence of tooth loss among older adults: United States, 2015–2018. NCHS Data Brief. 2020;(368):1-8. https://www.cdc.gov/nchs/data/databriefs/db368-h.pdf

2. Yao CJ, Cao C, Bornstein MM, et al. Patient-reported outcome measures of edentulous patients restored with implant-supported removable and fixed prostheses: A systematic review. Clin Oral Implants Res. 2018;29(Suppl 16):241–54. doi:10.1111/clr.13286

3. Neves FD, Mendonça G, Fernandes Neto AJ. Analysis of influence of lip line and lip support in esthetics and selection of maxillary implant-supported prosthesis design. J Prosthet Dent. 2004;91(3):286-8. doi:10.1016/j.prosdent.2003.12.006 

4. Balaguer J, Ata-Ali J, Peñarrocha-Oltra D, et al. Long-term survival rates of implants supporting overdentures. J Oral Implantol. 2015;41(2):173–7. doi:10.1563/AAID-JOI-D-12-00178 

5. Di Francesco F, De Marco G, Sommella A, et al. Splinting vs not splinting four implants supporting a maxillary overdenture: A systematic review. Int J Prosthodont. 2019;32(6):509–18. doi:10.11607/ijp.6333 

6. Slot W, Raghoebar GM, Vissink A, et al. A systematic review of implant-supported maxillary overdentures after a mean observation period of at least 1 year. J Clin Periodontol. 2010;37(1):98-110. doi:10.1111/j.1600-051X.2009.01493.x 

7. Sadowsky SJ. Treatment considerations for maxillary implant overdentures: a systematic review. J Prosthet Dent. 2007;97(6):340–8. doi:10.1016/S0022-3913(07)60022-5 

8. Schierano G, Mussano F, Faga MG, et al. An alumina toughened zirconia composite for dental implant application: in vivo animal results. Biomed Res Int. 2015;2015:157360. doi:10.1155/2015/157360 

9. Kelly JR, Denry I. Stabilized zirconia as a structural ceramic: an overview. Dent Mater. 2008;24(3):289–98. doi:10.1016/j.dental.2007.05.005

10. Monzavi M, Zhang F, Meille S, et al. Influence of artificial aging on mechanical properties of commercially and non-commercially available zirconia dental implants. J Mech Behav Biomed Mater. 2020;101:103423. doi:10.1016/j.jmbbm.2019.103423 

11. Osman RB, Payne AG, Duncan W, et al. Zirconia implants supporting overdentures: a pilot study with novel prosthodontic designs. Int J Prosthodont. 2013;26(3):277–81. doi:10.11607/ijp.2903 

12. Osman RB, Swain MV, Atieh M, et al. Ceramic implants (Y-TZP): are they a viable alternative to titanium implants for the support of overdentures? A randomized clinical trial. Clin Oral Implants Res. 2014;25(12):1366–77. doi:10.1111/clr.12272 

ABOUT THE AUTHORS

Dr. Boyer graduated from the University of California, Los Angeles (UCLA) School of Dentistry in 2008. He completed 2 hospital-based GPR training programs at Cedars-Sinai Medical Center in Los Angeles and in the VA Healthcare system, where he received advanced training in oral and maxillofacial surgery, complex and comprehensive treatment planning, and the placement and restoration of dental implants. He has been in private practice in Los Angeles since 2010. Dr. Boyer is a faculty member at the UCLA School of Dentistry, where he teaches dental students as well as the residents in the Advanced Education in General Dentistry program. In 2020, he was invited to be one of 4 investigators in a 5-year, worldwide multicenter ceramic implant osseointegration and stability study led by the International Academy of Ceramic Implantology (IAOCI) and the Zirconia Implant Research Group. Dr. Boyer is active in multiple dental implant organizations and was recently appointed as a board member of the IAOCI. He can be reached at dentist@ucla.edu.

Dr. Noumbissi obtained his DDS degree from Howard University in Washington, DC. He attended the prestigious Loma Linda University full-time graduate program in implant dentistry. There, he received 3 years of formal training in dental implantology, which culminated with a certificate in implant dentistry and an MS degree in implant surgery. He is a clinical and experimental researcher and author and has published book chapters and articles in implant dentistry with a focus on ceramic implants in peer-reviewed dental journals. He is a visiting professor at the University of Milan, an adjunct professor the University of Chiety-Pescara in Italy, and a visiting researcher in the ceramic materials department at INSA Lyon in France. Dr. Noumbissi is the founder and current president of the International Academy of Ceramic Implantology and a Fellow and an ambassador of the Clean Implant Foundation. Dr. Noumbissi has extensive experience with ceramic implants, and his opinions and expertise are often sought both by clinicians and manufacturers. His practice is located in Silver Spring, Md. He can be reached at sammy@iaoci.com.

Disclosure: Dr. Boyer has lectured for Osstell. He did not receive any financial compensation for this article. Dr. Noumbissi reports no disclosures. 

Implant dentistry has become a prominent treatment modality in many of our dental practices. Advances in engineering, design, and manufacturing have created fixtures that are both predictable, functional, and aesthetic. To become proficient in diagnosing and treatment planning, the practitioner must understand vital anatomy and the limitations to these popular modes of therapies. CBCT diagnosing allows visualization in 3 dimensions, maximizing implant placement to maximize the final restorative results.^1,2 Modern implants are used to replace single teeth and multiple missing teeth and certainly aid in supporting partial or complete removable appliances. Full-arch, fixed prostheses require edentualism, or removal of non-restorable teeth. Candidacy for each of these potential implant patients is dictated by the quality and quantity of available bone and the individual’s overall health. Bone height and width are carefully considered. Proper and complete planning prior to any surgical intervention may improve the overall prognosis and meet patient satisfaction. CBCT scanning (PaX-i3D Green [Vatech America]) of the edentulous sites is done, and evaluations of vital anatomy, including nerve position and the sinuses, are made. Interocclusal spacing is measured. Interocclusal space per each arch is a critical review. With the All-on-X treatment modality, it is reported that 14 to 16 mm of available room is required for the final prosthesis per arch.^3,4 This often indicates a significant reduction in bone height. Maintaining valuable hard tissue should be a consideration in any dental therapy as the bone morphology may change over time due to several physiologic conditions, including health, medication use, periodontal/peri-implant health, and maintenance.

Osteotomies for the Hahn Tapered Implant System (Glidewell) are completed through the surgical guides. In the case report in this article, these guides were fabricated by 3DDX (3D Diagnostix). CBCT DICOM files were electronically sent along with a cast of the maxillary and mandibular arches to create a 3D reconstruction of the patient’s CT scan. Virtual planning software revealed the vital anatomy and the ideal positioning of the implants in the available bone. Specific guided surgical drills compensate for the implant, soft tissue, and thickness of the guide itself. The body of this implant is tapered with a buttress thread pattern, allowing for initial stability and minimization of resorption in all bone types. The coronal microthreads aid in the preservation of crestal bone. The surface of the Hahn Tapered Implant System is a resorbable blast media to promote osseointegration. A machined collar facilitates soft-tissue maintenance, while its conical, internal hex connection provides a secure, stable prosthetic seal.^5,6 Positioning of the implants is confirmed with conventional digital radiographs and a postoperative CBCT scan. Cover screws are threaded into the implants to allow for non-stressful, unerupted healing. After approximately 4 months of integration, the implants are uncovered, and prosthetic fabrication begins with an implant-level impression.

Although, with technology, visualizing implant position and the final prosthetic design becomes predictable, other factors need to be considered by the dentist. Bone anatomy and medical conditions are considered. Also, an often neglected part of this process is the desires of the patient. Meeting expectations helps in the overall satisfaction of any restoration. A tooth-up or tooth-down approach helps in diagnosing and explaining to the patient what the final prosthesis will be and how it will function. Bone loss is a natural, physiologic response to losing teeth.⁷ A major deterrent to the surgical placement of any implant by the dentist is the position of the mandibular nerve and the size of the maxillary sinuses. As root structure is removed, the maxillary sinuses collapse, and the hard tissue shrinks up and in the maxilla and down in the mandible.⁸ This compromises any ability for surgical placement. When a tooth root is removed, bone shrinkage physiologically occurs apically and palatally. Also, with the loss of support, the maxillary sinus will often collapse.

The limited bone availability may make implant placement challenging or unpredictable. Grafting procedures allow regeneration of bone at sites where deficiencies arise. Bone grafting techniques are an essential part of the implant dentist’s skill set. Autogenous grafts, or those harvested from another site in the patient’s mouth, may be the gold standard but require an invasive approach. Allograft materials, harvested from the bone of human donors, are popular since a secondary surgical site is not required. Cortico/cancellous particulates are processed to prevent disease transmission and antigenic responses.^9-11

Internet searches by our patients are creating a high awareness of the benefits of our treatment. There are many options available to those who experience edentulism or decayed or periodontally involved teeth. Conventional dentures and partial dentures are at one end of the spectrum, while the “All-on-X” concept of removing all teeth with the result of fabrication of fixed, implant-retained prostheses with immediate or delayed loading is clearly on the other end of the process. Following proper diagnosing and treatment planning, implants can be considered to support dentition. Often, teeth may appear unaesthetic but are otherwise periodontally sound. The question that the dental professional must answer is whether removing teeth and viable bone structure to place dental implants along an edentulous arch and immediately loading them with a composite restoration that will eventually be replaced with a zirconia prosthesis is the best mode of therapy. Here, we will describe a circumstance in which the patient presented with missing teeth in the maxillary right and left posterior area and missing teeth in the mandible. The remaining dentition, although unaesthetic, was sound. 

CASE REPORT

The patient presented in a severe Class III occlusal relationship and with a deep underbite (Figure 1). CBCT analysis demonstrated significant collapse of the right and left posterior sinuses and inadequate bone height and width to support dental implants (Figure 2). Because of the maxillary sinus collapse, in order to surgically place dental implants with a positive prognosis, the maxillary right and left sinuses were augmented using the Caldwel-Luc procedure, and the remaining maxillary dentition was temporized. The arch was opened, and the severe underbite was corrected to a more comfortable position for the patient. During the integration of the sinus grafts, the patient could evaluate TMJ setting, aesthetics, and function (Figure 3). 

Figure 1. The patient presents in a severe Class III occlusal relationship and with a deep underbite. Maxillary right and left posterior teeth were missing, and the anterior dentition was periodontally sound.

Figure 2. CBCT analysis demonstrated significant collapse of the right and left posterior sinuses.

Figure 3. Prior to any commitment to final prostheses, the maxillary right and left sinuses were augmented using the Caldwel-Luc procedure, and the remaining maxillary dentition was temporized. The severe underbite was corrected.

Proper positioning and spacing of the posterior implants were evaluated using a “tooth-first” approach. Conventional guided surgical protocols were followed, including virtual design and positioning of implants in the edentulous areas before any surgical intervention. The tooth design was determined prior to any surgical intervention, and osteotomies were performed to idealize dentition shape. For example, for a 6-mm-wide first bicuspid tooth, the pilot bur is positioned 3 mm from the adjacent tooth. The pilot osteotomy for the subsequent 7-mm second bicuspid replacement would thus be 6.5 mm from the primary pilot opening (Figure 4). The size width of the implant chosen is ideally one-half of the desired tooth width (Figure 5).⁶ Following 6 months of integration of the sinus grafting, a new CBCT analysis demonstrated adequate bone height and width to continue with implant placement (Figure 6). 

Figure 4. Proper positioning and spacing of the posterior implants was evaluated using a “tooth-first” approach. The tooth design is determined prior to any surgical intervention.

Figure 5. The size width of the implant chosen is ideally one-half of the desired tooth width.

Figure 6. Following 6 months of integration of the sinus grafting, a new CBCT analysis demonstrated adequate bone height and width to continue with implant placement.

Figure 7. Guided surgical protocols were followed with an understanding of “tooth-first” restorations. Virtual design allows for fabrication of a surgical guide that aids in better positioning of the dental implants to better support the required function and predetermined aesthetics.

Figure 8. The surgical guide was both tooth- and bone-supported to maximize stability. No rocking was allowed.

Figure 9. To ensure that the surgical guide rested on hard tissue, a complete reflection of gingiva was made, exposing the available bone.

Figure 10. Guided surgical protocol was used to make the osteotomies directly through the designed guides. This method provides for maximizing the predetermined implant position in the available bone.

Figure 11. The osteotomies were widened using the guided burs.

Figure 12. The Hahn Tapered Implant System (Glidewell) was torqued to position.

Figure 13. Digital radiographs ensured proper positioning to the crest of bone and were examined visually intraorally.

Figure 14. A final CBCT analysis was completed prior to suturing the reflections.

Figure 15. After integration of the implants, impression techniques were used, and the final zirconia crowns were seated to place along with the conventional splinted restorations in the anterior.

Figure 16. Full-arch restoration was completed in stages, resulting in improved aesthetics and function for the patient, meeting his expectations.

Figure 17. Images of preoperative dental relationships to transitional appliances to the final zirconia prosthetics with increased form and function.

Figure 18. Pre-op vs final smile.

Guided surgical protocols were followed with an understanding of “tooth-first” restorations. Virtual design allowed for the fabrication of a surgical guide that aided in better positioning of the dental implants to better support the required function and predetermined aesthetics (Figure 7). The surgical guide was both tooth- and bone-supported to maximize stability. No rocking was allowed. To ensure that the surgical guide rested on hard tissue, a complete reflection of the gingiva was made, exposing the available bone (Figures 8 and 9). Guided surgical protocol was used to make the osteotomies directly through the designed guides. This method provided for maximizing the predetermined implant position in the available bone. The osteotomies were widened using the guided burs (Figures 10 and 11). Figure 12 illustrates the Hahn implants torqued to position at 45 Ncm. Digital radiographs ensured proper positioning to the crest of bone and were examined visually intraorally. A final CBCT analysis was completed prior to suturing the reflections (Figures 13 and 14). After integration of the implants, impression techniques were used, and the final zirconia implant crowns were seated and placed. The splinted restorations in the anterior were also cemented (Figure 15). The full-arch restoration, screw-retained implant prostheses were completed in stages, resulting in improved aesthetics and function for the patient and meeting the patient’s expectations (Figure 16). Figures 17 and 18 illustrate the preoperative dental relationships to transitional appliances to the final zirconia prosthetics with increased form and function and the final smile design compared to the pre-op aesthetics. 

CONCLUSION

Fully or partially edentulous patients are often resigned to a minimized quality of life. Function is most critical in individuals missing teeth, but creating aesthetics, emergence profile, and smile design may be equally important in their eyes. Those with natural teeth often find it challenging to imagine wearing denture teeth or losing their teeth totally, regardless of their conditions. Tooth loss results in bone loss over time, as has been discussed here. Bone loss may also occur around dental implants depending on many factors, so maintaining available hard tissue intuitively results in some semblance of insurance for any future treatment or retreatment. Implant-retained crowns and bridges allow for replacement with fixed teeth. CBCT-diagnosed and treatment planned and digitally designed restorations using custom-milled zirconia offer the most viable alternative and dramatically improve both chewing efficiency and patient quality of life. Therefore, consideration should be made to maintaining natural dentition when possible. Not every situation requires full-mouth extraction and bone contouring to achieve acceptable form and function and a long-term positive prognosis.

REFERENCES

1. Haiderali  Z. The role of CBCT in implant dentistry: uses, benefits, and limitations. British Dent J. 2020;228:560–1. doi:10.1038/s41415-020-1522-x

2. Kosinski TF. Being proficient, efficient, and financially rewarded doing implant dentistry. The Profitable Dentist. 2018;4:50-67. 

3. Bissasu M, Bissasu S. An intraoral method of verifying interocclusal distance for completely edentulous patients. J Prosth Dent. 2022;128(3):245–7. doi:10.1016/j.prosdent.2020.07.027

4. Kosinski TF. Dental implant hybrids for maximum esthetics: a next generation option for implant-retained prostheses. Inside Dentistry. 2015;11(5):74-80. 

5. Chen P, Nikoyan L. Guided implant surgery: a technique whose time has come. Dent Clin North Am. 2021;65(1):67-80. doi:10.1016/j.cden.2020.09.005 

6. Kosinski TF, Tilley S. The implant screw retained fixed detachable bridge: improving quality of life for edentulous patients. Inside Dentistry Technology. 2020;11(2):31-44. 

7. Kaufman E. Maxillary sinus elevation surgery: an overview. J Esthet Restor Dent. 2003;15(5):272–82; discussion 283. doi:10.1111/j.1708-8240.2003.tb00298.x 

8. Kosinski TF. Improving our patients’ quality of life: creation of the bruxzir hybrid to increase form and function. The Profitable Dentist. 2018;3:56–9. 

9. Carpentieri J, Greenstein G, Cavallaro J. Hierarchy of restorative space required for different types of dental implant prostheses. J Am Dent Assoc. 2019;150(8):695-706. doi:10.1016/j.adaj.2019.04.015 

10. Kosinski TF. Bone grafting: Essential indications and techniques in implant dentistry. Chairside Magazine. 2017;12(2):67-74. 

11. Kosinski TF. Tooth extractions and bone grafting. Dent Today. 2018;37(9):70-75. 

ABOUT THE AUTHORS

Dr. Kosinski received his DDS degree from the University of Detroit Mercy School of Dentistry (Detroit Mercy Dental) and his mastership in biochemistry from the Wayne State University School of Medicine. He is an affiliated adjunct clinical professor at Detroit Mercy Dental; serves on the editorial review board of REALITY, the information source for aesthetic dentistry; and is the past editor of the Michigan Academy of General Dentistry Update. He is currently the editor of the AGD journals General Dentistry and AGD Impact and is the editor of Implants Today for Dentistry Today. He is a past president of the Michigan AGD. He is a Diplomate of the American Board of Oral Implantology/Implant Dentistry, the International Congress of Oral Implantologists, and the American Society of Osseointegration. He is a Fellow of the American Academy of Implant Dentistry and received his Mastership in the AGD. Dr. Kosinski has published more than 220 articles on the surgical and prosthetic phases of implant dentistry and was a contributor to the textbooks Principles and Practices of Implant Dentistry and 2010’s Dental Implantation and Technology. He can be reached at drkosin@aol.com or via the website smilecreator.net.

Dr. Tilley is a graduate of the University of Alabama School of Dentistry. She is a native of Pensacola, Fla, and has been practicing dentistry in her hometown since 1998. She has done extensive training at the Las Vegas Institute for Advanced Dental Studies and the Engel Institute with Drs. Timothy Kosinski and Todd Engel. Her lectures discuss bone grafting procedures and surgical and prosthetic aspects of implant dentistry. She is a Fellow of the International College of Dentists and most recently was inducted into the American College of Dentists and the Academy of Dentistry International. She is a member of the AGD, the ADA, the Florida Dental Association, the Alabama Dental Association, the Academy of Laser Dentistry, and the Academy of American Facial Esthetics. Dr. Tilley is also a Fellow with the International Congress of Oral Implantologists. She has published extensively on implant dentistry techniques, lasers, and Botox/fillers. She can be reached via email at stephflynntilley@cox.net.

Disclosure: The authors report no disclosures. 

Perforation of the maxillary sinus by a dental implant is a concern for many dental implant clinicians. Maxillary sinus floor elevation (SFE) is used to augment insufficient alveolar bone when placing dental implants in the maxillary posterior region and can be accomplished via a trans-alveolar approach¹ or a lateral approach.^2,3

The most common complication during SFE is the perforation of the Schneiderian membrane,^4,5 with a reported prevalence of 8% to 32%.^6,7 The risk factors include the presence of sinus septa, low residual bone height, and smoking.⁸ Some studies have found that membrane perforation increased the possibility of developing sinusitis.^8,9 It has been reported that survival rates do not differ significantly between implants placed under perforated or intact Schneiderian membranes⁸; however, there are studies reporting a relationship between membrane perforation and graft or implant failures.^9,10 It is thought that the displacement of a graft material into the sinus may be responsible for complications such as maxillary sinusitis after sinus perforation.⁸ Therefore, various methods aimed at repairing the perforated membrane have been developed, including suturing and the use of fibrin adhesives and absorbable collagen membranes.^11,12 However, most of these studies presented repair procedures via a lateral approach for SFE.

Membrane perforation is the most common complication of the SFE procedure⁹ and is usually repaired via a lateral approach.¹³ However, when perforation occurs during SFE, the lateral approach requires a second operation site and increases patient discomfort.

The prevalence of maxillary sinusitis after SFE has been reported to be 8.4% to 9.8%,^14,15 with the incidence rate of sinusitis being lower for a crestal approach than for a lateral approach.¹⁶ Membrane perforation is a risk factor for postoperative sinusitis,¹⁴ which decreases the survival rates of implants.¹⁶ 

With regard to sinus membrane elevation surgery, some complications are inevitable, even though prevention is the best method. Once complications occur, the clinician should acquaint himself or herself with the cause, explain the issue to the patient, and treat the complications accordingly. Cases of serious complications should be promptly referred to a related specialist.¹⁵ During surgery, the most common complication is sinus membrane perforation, which could increase the risk of post-op infection and failure of the graft and/or implant. Therefore, it is necessary to be aware of the various methods for closing perforations. After surgery, an infection is the most common complication; early diagnosis and treatment (antibiotics and incision drainage) are very important for the prevention of severe complications.^15,16 

To minimize complications such as bleeding and sinus membrane perforation, the normal anatomical structures and pathological findings should be identified and diagnosed before surgery. Cooperation with an otorhinolaryngologist should be considered in cases of asymptomatic maxillary sinus lesions, nasomental patency, chronic maxillary sinusitis, mucous retention cysts, and nasal septum deviations.¹⁶ To prevent arterial bleeding, the clinician should evaluate the vertical resorption of alveolar bone and the position of the posterior superior alveolar artery.¹¹ Sinus lateral wall thickness is very different for each individual. If the wall thickness is too thin or thick, there is a high possibility of perforation of the sinus membrane during formation of the bony window.^11,12 Asymptomatic mucous retention cysts and antral pseudocysts are not a contraindication. However, mucoceles with extensive and destructive aspects are a contraindication for sinus membrane elevation. Sinus elevation is often difficult in cases with mucous retention cysts or pseudocysts where aspiration with a 21-gauge needle could be effective for sinus elevation, bone grafting, and implant placement.¹⁴ Sinus septums have been reported in 16% to 58% of patients and could increase the risk of membrane perforation.^2,3 Normal sinus membrane thickness is 0.3 to 0.8 mm, and cilia cells remove various secretions and foreign substances formed in the maxillary sinus. If there is a lesion causing maxillary sinusitis or a history of sinus-related surgery, the risk of post-op complications, such as maxillary sinusitis, greatly increases because the cilia cells cannot function normally.¹¹ The most important factor to identify before surgery is maxillary ostium patency (osteomeatal patency), the lack of which could cause post-op maxillary sinusitis due to an issue with the maxillary sinus drainage system. In addition, the risk of post-op complications also increases in cases of nasal septum deviation and nasal mucosa inflammation or injury.¹²

CASE REPORTS

Case 1 

An ASA II, 45-year-old, male patient was missing tooth No. 14 (upper left first molar) for a long time. The patient expressed dissatisfaction with his missing teeth before this appointment. He had previously consulted with many other dentists and was not completely satisfied with the treatment options presented to him. The patient was skeptical about sinus lift surgery. However, he was unwilling to choose other alternative treatments, such as a bridge.

After an initial conversation and discussion with the patient regarding the right approach and treatment plans, he was reassured and decided to proceed with a crestal sinus lift using the Crestal Approach Sinus Kit (CAS Kit) (Hiossen) followed by an implant placement.

To begin, topical anesthetic was placed at the surgical site, and 4% Septocaine with epinephrine 1:100,000 (Septodont) was given via infiltration. An incision was made using a 15c blade. A periosteal elevator was used to retract the flap, followed by initiation of the osteotomy using a 2-mm guide drill with a 3-mm stopper (Figure 1), keeping it 2 mm away from the sinus cavity. Next, the osteotomy was drilled using a 3.1-mm drill with a 4-mm stopper, followed by a 4.1-mm drill with a 5-mm stopper (Figures 2 and 3). One of the unique features of the CAS Kit bur is that it has an inverted cone design that creates a bone lid, which prevents the Schneiderian membrane from being perforated (Figure 3). After the sinus was lifted, a depth gauge that had an atraumatic tip was used to confirm the membrane lift with a stopper at 5 mm. After confirmation of the membrane lift, a tube attached to a hydraulic lifter containing 1 cm³ or 3 cm³ of saline was used to safely raise the membrane in gradual increments so as to not perforate the membrane (Figure 4). 

Figure 1. A guide drill marked the osteotomy site.

Figure 2. A 3.1-mm CAS Drill (Hiossen) with a 4-mm stopper.

Figure 3. A 4.1-mm CAS Drill with a 4-mm stopper.

Figure 4. A hydraulic lifter with saline solution used to safely lift the sinus membrane.

Figure 5. A bone carrier head with a bone condenser was used to fill the sinus cavity with bone graft material.

Figure 6. Implant placement in the sinus cavity post sinus lift and bone graft insertion.

Figure 7. Drilling the implant into the osteotomy site.

Figure 8. Implant placement in the sinus cavity with bone graft materials.

A bone carrier head with bone condenser was used to fill bone graft materials inside the sinus cavity (Figure 5). An x-ray was taken to confirm the sinus lift. The 5- × 8.5-mm implant was placed with 40 Ncm torque value, and sutures were placed (Figures 6 and 7). The patient came back after 4 months for restorations, and the screw-retained crown was delivered. Residual bone height was close to 5 mm; hence, we were successfully able to achieve vertical sinus lift followed by a bone graft without any trauma to the sinus membrane (Figure 8). It was a minimally invasive procedure. 

Case 2  

An ASA I, 20-year-old girl with a congenitally missing upper right back molar (No. 2) had pain around wisdom tooth No. 1. During the examination, it was discovered that she had an opposing second molar No. 31, and it was slightly supra-erupted due to missing tooth No. 2. The patient expressed concerns with wanting to remove wisdom tooth No. 1 due to pain resulting from pericoronitis (Figure 9).

Figure 9. Wisdom tooth placement and condition.

All treatment options were presented, including the extraction of the wisdom tooth and no treatment due to possible further complications. The patient wanted another molar in the back for better chewing and to prevent supra-eruption of the lower second molar. After discussing with the patient, we devised a plan to extract tooth No. 1 and to place an implant with a sinus lift for tooth No. 2 to increase chewing efficiency and improve overall self-confidence. The sinus was pneumatized, and the residual bone height was approximately 4 mm.

Anesthesia was performed with 2% lidocaine with 1:100,000 epinephrine via infiltration. A subcrestal horizontal incision was made around the area of the first molar to the second molar, and a vertical incision was made on the distal of the first molar. The flap was reflected with the sharp end of the Molt 9 periosteal elevator using a push stroke. After adequate reflection, retraction was much easier with the Seldin elevator. The extraction of tooth No. 1 was done atraumatically. Osteotomy was initiated with a guide drill with a 2-mm stopper for site No. 2, followed by a 2.8-mm drill with a 3-mm stopper. An x-ray was taken to confirm the orientation (Figure 10). Then the final size of drill (3.3 mm) with a 5-mm stopper was used to lift the Schneiderian membrane under copious irrigation. A depth gauge was used with the final size of the stopper to confirm the separation of the membrane without any perforation. The membrane lifter was then used to lift the sinus with saline using a 3-cm³ syringe. OsteOss, a mixture of cortico-cancellous bone, was used to graft the sinus cavity in order to lift the membrane using a bone condenser. A 6- × 8.5-mm implant (ET III NH Implant [Hiossen]) was placed at 35 ncm, and the implant stability quotient was measured at a value of 67 (Figure 11). Finally, a healing cap was placed.

Figure 10. Implantation path and orientation.

Figure 11. Implant placement within the sinus cavity after the sinus lift.

Figure 12. Placement of a healing abutment to support healing of the gingiva and to create emergence profile.

Figure 13. Restoration blending with adjacent tissue.

Four months after the implant placement, the patient returned for the restorative phase. A clinical examination showed healthy soft tissue around the implant with an abundance of keratinized tissue. A closed-tray impression coping was used for the final impression. The tooth was restored with a screw-retained solid zirconia abutment, which was chosen over a customized titanium abutment (Figure 12). The radiography showed that the crown and abutment had an adequate fit. The final photo shows natural aesthetics and the harmony of the restoration blending with adjacent tissue (Figure 13).

CONCLUSION 

The sinus lift procedure poses many threats to the patient’s health due to the high possibility of perforating the Schneiderian membrane. New and more advanced equipment, such as the CAS Kit, helps to alleviate concerns by facilitating a surgical procedure that is safer in placing implants in the posterior atrophic maxilla while significantly mitigating the chances of perforating the sinus membrane and maintaining sufficient bone generation, providing stable implantation with minimal marginal bone loss. The placement of an implant with equipment such as the CAS Kit provides a better alternative to performing an osteotome procedure, which has proved to be much more time-consuming and has a higher risk of membrane perforation and large amounts of bone loss in the patient.¹⁶

REFERENCES

1. Shihab O. Intentional penetration of dental implants into the maxillary sinus: a retrospective study. Zanco J Med Sci. 2017;21:1536–9. doi:10.15218/zjms.2017.001. 

2. Summers RB. A new concept in maxillary implant surgery: the osteotome technique. Compendium. 1994;15(2):152, 154–6, 158 passim; quiz 162. 

3. Boyne PJ, James RA. Grafting of the maxillary sinus floor with autogenous marrow and bone. J Oral Surg. 1980;38(8):613–6. https://pubmed.ncbi.nlm.nih.gov/6993637

4. Călin C, Petre A, Drafta S. Osteotome-mediated sinus floor elevation: a systematic review and meta-analysis. Int J Oral Maxillofac Implants. 2014;29(3):558–76. doi:10.11607/jomi.3206 

5. Stacchi C, Andolsek F, Berton F, et al. Intraoperative complications during sinus floor elevation with lateral approach: a systematic review. Int J Oral Maxillofac Implants. 2017;32(3):e107–18. doi:10.11607/jomi.4884

6. Hernández-Alfaro F, Torradeflot MM, Marti C. Prevalence and management of Schneiderian membrane perforations during sinus-lift procedures. Clin Oral Implants Res. 2008;19(1):91–8. doi:10.1111/j.1600-0501.2007.01372.x

7. Ardekian L, Oved-Peleg E, Mactei EE, et al. The clinical significance of sinus membrane perforation during augmentation of the maxillary sinus. J Oral Maxillofac Surg. 2006;64(2):277–82. doi:10.1016/j.joms.2005.10.031 

8. Schwarz L, Schiebel V, Hof M, et al. Risk factors of membrane perforation and postoperative complications in sinus floor elevation surgery: Review of 407 augmentation procedures. J Oral Maxillofac Surg. 2015;73(7):1275–82. doi:10.1016/j.joms.2015.01.039

9. Nolan PJ, Freeman K, Kraut RA. Correlation between Schneiderian membrane perforation and sinus lift graft outcome: a retrospective evaluation of 359 augmented sinus. J Oral Maxillofac Surg. 2014;72(1):47-52. doi:10.1016/j.joms.2013.07.020 

10. Al-Moraissi E, Elsharkawy A, Abotaleb B, et al. Does intraoperative perforation of Schneiderian membrane during sinus lift surgery causes an increased the risk of implants failure?: A systematic review and meta regression analysis. Clin Implant Dent Relat Res. 2018;20(5):882–9. doi:10.1111/cid.12660

11. Schwartz-Arad D, Herzberg R, Dolev E. The prevalence of surgical complications of the sinus graft procedure and their impact on implant survival. J Periodontol. 2004;75(4):511-6. doi:10.1902/jop.2004.75.4.511

12. Vlassis JM, Fugazzotto PA. A classification system for sinus membrane perforations during augmentation procedures with options for repair. J Periodontol. 1999;70(6):692–9. doi:10.1902/jop.1999.70.6.692

13. Shende H, Mundada B, Bhola N. Comparative efficacy of osteotome vs CAS kit assisted indirect maxillary sinus lift and immediate implant placement in posterior atrophic maxilla—a study protocol. J Pharm Res Int. 2021;33(63A):183–8. doi:10.9734/jpri/2021/v33i63A35232

14. Kim YK, Ku JK. Sinus membrane elevation and implant placement. J Korean Assoc Oral Maxillofac Surg. 2020;46(4):292–8. doi:10.5125/jkaoms.2020.46.4.292

15. Timmenga NM, Raghoebar GM, van Weissenbruch R, et al. Maxillary sinus floor elevation surgery. A clinical, radiographic and endoscopic evaluation. Clin Oral Implants Res. 2003;14(3):322–8. doi:10.1034/j.1600-0501.2003.140310.x

16. Kim YW, Keum YS, Son HJ, et al. Predictability of simultaneous implant placement with sinus floor elevation in the severely atrophic posterior maxillae; comparison of lateral and trans-crestal approaches. J Korean Dent Assoc. 2010;48:205–17.

ABOUT THE AUTHOR

Dr. Patel graduated from Temple University’s prestigious oral surgery host program as an honors student and earned an excellence award in the field of cosmetic dentistry over the course of his successful practice in general dentistry. He is an active member of the Chicago Dental Society, the ADA, and the International Congress of Oral Implantologists (ICOI). Dr. Patel is a Fellow and a Diplomate in Oral Implantology of the ICOI and the American Association of Implant Prosthetics. He is also a world-renowned faculty member and course director for Hiossen. He can be reached at connectbrijesh87@gmail.com.

Disclosure: Dr. Patel is a course director for AIC, Hiossen Implant’s research and education center, and receives compensation for lectures. 

Dental implants have long been used to replace missing single teeth, multiple teeth, and full arches. The success rate of dental implants can approach 94.6% at 10 years.¹ The failure of dental implants can occur for a variety of reasons, leading to the explanation of the failed implant fixture. Although residual excess cement from luting or bonding implant crowns to the stock or custom abutment intraorally is a common complication, the technique is still widely used.^2-7 In 2018, Goodacre et al⁸ said that the most common complication reported with single implant crowns was abutment screw loosening. This screw loosening occurs on 4% of screw-retained crown-abutment complexes and 3% of cement-retained implant crowns. However, this is a vast improvement over previous abutment screw loosening data from 2003 of 25% with early screw designs.⁹ 

When the clinician or the patient discovers the crown-abutment complex is loose, it is critical to remove it immediately. Failure to do so will result in damage to the abutment screw, the abutment hexagon, or the dental implant. Fabrication of a new crown-abutment complex is relatively easy but adds cost for the patient. Conversely, if the loose crown-abutment complex is ignored, damage can occur to the dental implant. This damage may require an explanation of the implant fixture, adding potential morbidity and significant cost to the patient. 

This technique article outlines the steps to remove, evaluate, and recommission the crown-abutment complex when the implant screw loosens, thereby lacking the appropriate torque to clamp the crown-abutment complex securely to the implant. Critical to the successful removal of a cement-retained crown is proper instrumentation. Dental burs specifically designed for ceramics are an absolute must to minimize the potential for chipping, fracture, or introducing microcracks in the ceramic layer that will later exhibit catastrophic failure. Komet USA manufactures burs specifically designed to grind ceramics, including zirconia (ZR6801 018). These feature a “white stripe” along with another colored stripe to indicate whether the bur is coarse (151-µm “green stripe”), medium (80-µm “blue stripe”), or fine (46-µm “red stripe”). Komet USA also manufactures metal-cutting burs, such as the H34 012 and H34L 012, which work extremely efficiently to penetrate metal crowns or cut metal crowns off. With our Tucker gold castings,^10,11 we use the H34L 012 to smooth the sprue bump efficiently during laboratory fabrication.

Another point that needs to be emphasized is the need for dental handpieces that rotate true; eliminate bur chatter; and have good torque, adequate illumination, and good air/water spray to keep the field cool and clean.¹² The Swiss-manufactured EVO.15 Micro-series CoolTouch+ electric handpieces (Bien-Air Dental) meet this criterion with extreme precision of rpm and torque by utilizing an iPod controller. The PM 1:1 straight nose cone (Bien-Air Dental) is excellent for making chairside adjustments to lithium disilicate (IPS e.max [Ivoclar]) or zirconia crowns using Komet USA’s yellow DCB diamond abrasives, ZR Flash polishers, and the “Footsie” polisher shape (94019C and 94019F).

The technique to recommission the crown-abutment complex is essentially an endodontic access, and the burs and handpieces utilized would be the same for creating access through a ceramic or porcelain-fused-to-metal crown. Essentially, when we are finished, we have turned a cement-retained implant crown into a screw-retained crown-abutment complex often referred to as a “screwmentable” or, as described by McGlumphy et al¹³ in 1992, “a combination implant crown.” 

The technique for recommissioning a cement-retained crown with a loose abutment screw is as follows:

1. A No. 19 crown-abutment complex was noted to be “loose” by the patient (Figure 1).

Figure 1. Tooth No. 19 implant crown.

2. A radiograph was taken, and the implant was identified as an AstraTech Implant System/OsseoSpeed TX 3.5/4.0 implant (Dentsply Sirona Implants) using whatimplantisthat.com. The torque value was noted as 20 Ncm for the abutment screw (Figure 2).

Figure 2. Tooth No. 19 implant crown radiograph.

3. Penetration of the porcelain layer of the implant crown was done with a ZR6801 018 round bur (Komet USA). The white stripe indicates that the bur is engineered for grinding all types of ceramics, including zirconia. The green stripe indicates that the “grit size” is coarse. An EVO.15 1:5L Micro-Series CoolTouch+ electric handpiece was utilized at 200,000 rpm with copious amounts of water spray to minimize potential chipping and microcracks in ceramic (Figure 3).

Figure 3. Penetration of the porcelain layer of the implant crown with a ZR6801 018 round bur (Komet USA).

4. Penetration of the metal substructure was done using an H34 012 bur (Komet USA) that is designed for cutting metal and is very good at removing metal crowns. It was used at 200,000 rpm (Figure 4).

Figure 4. Penetration of the metal substructure of the implant crown with an H34 012 metal crown remover bur (Komet USA).

5. The screw access chimney appeared to have Cavit internally. Cavit was received with a 6SE latch grip (Komet) with an electric slow-speed contra-angle EVO.15 1:1L Micro-Series handpiece utilized at 20,000 rpm. The cotton pellet below the Cavit was removed to expose the head of the abutment screw (Figure 5).

Figure 5. Removal of Cavit over a cotton pellet with an 6SE slow speed round bur (Komet USA).

6. An AstraTech hexagonal screwdriver was used to loosen the abutment screw and remove the crown-abutment complex. The AstraTech Implant System/OsseoSpeed TX implant was inspected internally to verify that there was no fracture of the implant or stripping of the internal hexagon (Figure 6).

Figure 6. Inspection of the implant fixture and internal hexagon.

7. Initially in this case, the screw was unable to be removed from the crown-abutment complex. The chimney of the crown-abutment complex was reamed with an 851 016 round end bur (Komet USA) tapered with a safety tip to avoid damage to the head of the abutment screw. The key point is to hold the crown-abutment complex such that the abutment screw is held down and will not contact the 851 016 bur. Clinicians may elect to attach the crown-abutment complex to a laboratory analog at this step to act as a “handle” and prevent the abutment screw from being damaged (Figure 7).

Figure 7. Reaming of the screw access chimney of the implant crown and abutment with an 851 016 round end tapered bur with a safety tip (Komet USA).

8. Inspect the screw and abutment hexagon for damage. If either is stripped or worn, replacement is necessary (Figure 8).

Figure 8. Inspection of the abutment screw and abutment hexagon.

9. The abutment screw was tightened to 20 Ncm of torque. The seating of the crown-abutment complex was verified with a radiograph. The prosthetic screw was covered with polytetrafluorethylene tape, commonly known as Teflon tape, plumber’s tape, or TFE (tetrafluoroethylene) threaded seal tape (Oatey Co). The access was sealed with composite (Filtek Z250 Universal Restorative [3M]) and cured for 20 seconds using a curing light (Parkell curing light [Parkell]). Occlusion was confirmed, and the patient was dismissed (Figure 9).

Figure 9. The tooth No. 19 recommissioned crown-abutment complex with the screw access sealed with PTFE tape and composite.

CONCLUSION

As mentioned, the most common complication for single implant crowns is screw loosening, which occurs at a frequency of 3%. It is important that a loose abutment screw not be ignored but dealt with immediately to prevent irreversible damage to the crown-abutment complex or the implant. The use of appropriate instrumentation, including burs and handpieces, is necessary to prevent damaging the crown-abutment complex so it can be recommissioned into a screw-retained restoration.

REFERENCES

1. Moraschini V, Poubel LA, Ferreira VF, et al. Evaluation of survival and success rates of dental implants reported in longitudinal studies with a follow-up period of at least 10 years: a systematic review. Int J Oral Maxillofac Surg. 2015;44(3):377–88. doi:10.1016/j.ijom.2014.10.023 

2. Wilson TG Jr. The positive relationship between excess cement and peri-implant disease: a prospective clinical endoscopic study. J Periodontol. 2009;80(9):1388–92. doi:10.1902/jop.2009.090115

3. Hess TA. A technique to eliminate subgingival cement adhesion to implant abutments by using polytetrafluoroethylene tape. J Prosthet Dent. 2014;112(2):365–8. doi:10.1016/j.prosdent.2013.06.026 

4. Wadhwani C, Rapoport D, La Rosa S, et al. Radiographic detection and characteristic patterns of residual excess cement associated with cement-retained implant restorations: a clinical report. J Prosthet Dent. 2012;107(3):151–7. doi:10.1016/S0022-3913(12)60046-8 

5. Wadhwani C, Hess T, Piñeyro A, et al. Cement application techniques in luting implant-supported crowns: a quantitative and qualitative survey. Int J Oral Maxillofac Implants. 2012;27(4):859–64. 

6. Wadhwani C, Piñeyro A, Hess T, et al. Effect of implant abutment modification on the extrusion of excess cement at the crown-abutment margin for cement-retained implant restorations. Int J Oral Maxillofac Implants. 2011;26(6):1241–6. 

7. Wadhwani C, Hess T, Faber T, et al. A descriptive study of the radiographic density of implant restorative cements. J Prosthet Dent. 2010;103(5):295-302. doi:10.1016/S0022-3913(10)60062-5 

8. Goodacre BJ, Goodacre SE, Goodacre CJ. Prosthetic complications with implant prostheses (2001-2017). Eur J Oral Implantol. 2018;11(Suppl 1):S27-S36.  

9. Goodacre CJ, Bernal G, Rungcharassaeng K, et al. Clinical complications in fixed prosthodontics. J Prosthet Dent. 2003;90(1):31-41. doi:10.1016/s0022-3913(03)00214-2 

10. Hess TA. The Tucker technique: the proximal hollow grind to address a root concavity. Oper Dent. 2014;39(5):454–9. doi:10.2341/13-158-T 

11. Hess TA, Wadhwani CP. The Tucker technique: conservative molar inlays preserving the transverse ridge. Oper Dent. 2012;37(1):93–7. doi:10.2341/11-048-T 

12. Pereira GKR, Fraga S, Montagner AF, et al. The effect of grinding on the mechanical behavior of Y-TZP ceramics: A systematic review and meta-analyses. J Mech Behav Biomed Mater. 2016;63:417–42. doi:10.1016/j.jmbbm.2016.06.028 

13. McGlumphy EA, Papazoglou E, Riley RL. The combination implant crown: a cement- and screw-retained restoration. Compendium. 1992;13(1):34, 36, 38 passim. 

ABOUT THE AUTHOR

Dr. Hess is a graduate of the University of Alberta and completed his DDS degree from the University of Washington (UW) in 1994. He is an affiliate assistant professor of restorative dentistry, an affiliate assistant professor of oral medicine, and the director of the Tucker Institute at the UW School of Dentistry. He is director of education at the Washington Academy of General Dentistry Global Learning Center. Dr. Hess lectures nationally and internationally and has published articles in numerous peer-reviewed journals. He is a member of the International Academy of Gnathology and an active member of the American Academy of Restorative Dentistry. He can be reached at drhess@tahessdds.com. 

Disclosure: Dr. Hess reports no disclosures. 

As dental implants continue to be the treatment of choice for many dentists and patients alike, and newer implant systems continue to emerge on the market, the importance of understanding the different implant connections available is imperative for a higher standard of care. 

To better understand implant connections, first we have to visualize the timeline of dental implants to see why there is a large variety of connections. Initially, Dr. Gustav Dahl designed subperiosteal implants as a framework placed over the residual ridge with projections resembling abutments as part of the framework for the definitive prosthesis. Later, Dr. Leonard Linkow introduced blade implants that were the first intraosseous implants but similar to a subperiosteal, with the abutment and implant as a unibody. Modern day implants designed by Professor Brånemark were installed for the first patient in 1965, and that was the birth of 2-piece implants and, by extension, implant connections.¹ 

The role of implant connections is to separate the abutment from the implant, thereby allowing us to modify and tailor our treatment methodology in reflection to each clinical presentation with the highest chances of success and survivability. Two-piece implants allow us to modify the design of the prosthesis over time and execute 2-stage surgeries when primary stability is insufficient, achieve primary closure for bone augmentation, and offer an opportunity for further soft tissue manipulation at second-stage surgery. Ultimately, every feature comes with a price; by design, the connection is an interface “microgap” that can be colonized by bacteria, causing bacterial leakage (Figure 1). The interface suffers from micromovements of the abutment under loading, acting as a micro pump for the bacteria into the surrounding tissue. In response, the bone remodels to establish a zone of defense, ie, biologic width. Different interface designs can significantly influence the remodeling of the muco-alveolar complex.² In response, clinicians and manufacturers poised and developed different designs of implant connections to minimize the drawbacks from a biologic, mechanical, and aesthetic perspective. While the landscape is vast in terms of shapes and sizes, the ideologies and concepts behind the connections are very simple (Table 1).

Figure 1. Microgap at the abutment-implant interface.

The first endosseous-design implants had an external connection. That is the first classification of implant connections: external and internal connections. It is important to note that some scientific papers refer to them as external and internal hex. In this context, “hex” means connection and does not refer to a hexagonal shape (Figure 2). 

Figure 2. (a) External hex: Brånemark External hex implant (Nobel Biocare). (b) Internal hex: Bone Level Tapered Implant (Straumann).

At that time, implants were used exclusively for full-arch prostheses to restore form and function for completely edentulous patients. The implant installation was followed by a period of 6 months of undisturbed healing; a second-stage surgery for insertion of a transmucosal healing abutment; and, finally, a definitive prosthesis. External connection implants functioned properly without limitations for that purpose, but as their success rates increased, clinicians began expanding their use to off-label indications: partially edentulous and single, missing teeth. Without the rigid fixation and splinting afforded by a full-arch prosthesis, we began experiencing the deficiencies of external connections for single crowns and FPDs: screw loosening (most common), screw fractures, and micromovement at the abutment-implant interface.³ By design, external connections lacked anti-rotation features, had low torquing levels of their prosthetic screws, and a looser fit at the connection level. There are different forms of external hex connections: hexagon, octagon, and spline, and over the years, they have been machined to respond to their inherent problems by adding/increasing friction grips to the hex, deeper screw engagement, wider screw diameters, higher screw torquing levels, and the number of threads. 

To overcome the inherent deficiencies of external connections, in 1998, internal connection implants were introduced to assist clinicians in replacing single teeth without external connection implants’ mechanical complications. Internal connections, by design, offered a larger surface area of contact between the abutment and implant as the connection moved inside the implant, improving the fit and minimizing rotational misfit (Figure 3). The longer engagement also created a stiffer, unified interface to resist joint opening, thereby reducing the pumping effect of microleakage and its biological consequences. Additionally, as the connection is bound by the body of the implant, it is able to dissipate the lateral forces within the body of the implants and the investing alveolar bone rather than in the abutment screw.^4-7

Figure 3. External and internal hex.

The second classification of implant connections derives from the geometric shape of the platform. Many designs exist on the market, most commonly hexagonal, octagonal, conical, trilobe, or a combination of these.^8,9 The variety of shapes affords different advantages in terms of passivity, anti-rotation, and microgap size. For example, the mean microgap was significantly larger for flat-to-flat (hexagonal or trilobe) connection systems when compared to conical (ie, Morse taper) connections.¹⁰ In true Morse taper connections, the abutment and implant are machined with a specific taper that is press fit together. Oftentimes, the abutments are tapped in rather than held with a screw. While Morse taper fosters the smallest microgap due to the profile and structural design of these connections, the abutments often fracture at the neck of the abutment and are much more difficult to remove when compared to conventional, non-Morse taper connections due to cold welding.^11,12 In response, implant manufacturers use a combination of designs to reap the benefits and minimize the drawbacks of different designs with a combination of connection geometry and position. Implants can be categorized as bone-level and tissue-level. Tissue-level implant platforms extend beyond the crest of bone, usually 1.8 to 2.8 mm above the crest with an internal connection. Bone-level implant platforms terminate at the crest of bone and may have an internal or external connection. 

The third classification of connections is engaging and non-engaging (Figure 4). Engaging connections, as the term implies, means the abutment has an anti-rotation feature, and the timing of the abutment is important as the definitive final crown can only fit in one specific orientation. With non-engaging abutments, the connection is free to rotate without a specific timing. Engaging abutments have a longer vertical height in the connection and are most commonly used for single crowns. Non-engaging abutments have a shorter vertical height connection and, therefore, are used for multiple-unit and full-arch restorations as it’s easier to have a passive fit of the definitive prosthesis when the implants are not fully parallel.

Figure 4. (a) Engaging and (b) non-engaging abutments.

Figure 5. Multi-unit abutments.

The final classification of connections is conventional abutments and multi-unit abutments (MUAs). Conventional abutments have a single screw holding the prosthesis, whether it is screw-retained or cement-retained. MUAs have 2 screws: one screw that holds the MUA onto the implant and another occlusal screw that retains the prosthesis to the MUA (Figure 5). MUAs are used for restorations involving more than one implant and can assist the clinician in correcting for variability in implant angulation and creating a more passive definitive prosthesis. 

SUMMARY

As the implant industry continues to evolve, it is essential to recognize that the fundamental principles of implant connections remain unchanged. While this article provides an overview of implant connections, it is not an exhaustive review. Its purpose is to equip readers with a basic understanding that enables them to ask pertinent questions and conduct further research in the field.

REFERENCES

1. Abraham CM. A brief historical perspective on dental implants, their surface coatings and treatments. Open Dent J. 2014;8:50–5. doi:10.2174/1874210601408010050 

2. Herrero-Climent M, Romero Ruiz MM, Díaz-Castro CM, et al. Influence of two different machined-collar heights on crestal bone loss. Int J Oral Maxillofac Implants. 2014;29(6):1374–9. doi:10.11607/jomi.3583 

3. Meng JC, Everts JE, Qian F, et al. Influence of connection geometry on dynamic micromotion at the implant-abutment interface. Int J Prosthodont. 2007;20(6):623–5. 

4. Binon PP. Implants and components: entering the new millennium. Int J Oral Maxillofac Implants. 2000;15(1):76-94.

5. Finger IM, Castellon P, Block M, et al. The evolution of external and internal implant/abutment connections. Pract Proced Aesthet Dent. 2003;15(8):625–32; quiz 634.  

6. Sailer I, Sailer T, Stawarczyk B, et al. In vitro study of the influence of the type of connection on the fracture load of zirconia abutments with internal and external implant-abutment connections. Int J Oral Maxillofac Implants. 2009;24(5):850–8. 

7. Da Silva EF, Pellizzer EP, Quinelli Mazaro JV, et al. Influence of the connector and implant design on the implant-tooth-connected prostheses. Clin Implant Dent Relat Res. 2010;12(3):254–62. doi:10.1111/j.1708-8208.2009.00161.x 

8. Coppedê AR, Bersani E, de Mattos Mda G, et al. Fracture resistance of the implant-abutment connection in implants with internal hex and internal conical connections under oblique compressive loading: an in vitro study. Int J Prosthodont. 2009;22(3):283–6. 

9. Delgado-Ruiz R, Silvente AN, Romanos G. Deformation of the internal connection of narrow implants after insertion in dense bone: an in vitro study. Materials (Basel). 2019;12(11):1833. doi:10.3390/ma12111833 

10. Akça K, Cehreli MC, Iplikçioğlu H. Evaluation of the mechanical characteristics of the implant-abutment complex of a reduced-diameter morse-taper implant. A nonlinear finite element stress analysis. Clin Oral Implants Res. 2003;14(4):444–54. doi:10.1034/j.1600-0501.2003.00828.x 

11. Baixe S, Fauxpoint G, Arntz Y, et al. Microgap between zirconia abutments and titanium implants. Int J Oral Maxillofac Implants. 2010;25(3):455–60. 

12. Ricciardi Coppedê A, de Mattos Mda G, Rodrigues RC, et al. Effect of repeated torque/mechanical loading cycles on two different abutment types in implants with internal tapered connections: an in vitro study. Clin Oral Implants Res. 2009;20(6):624–32. doi:10.1111/j.1600-0501.2008.01690.x

ABOUT THE AUTHOR

Dr. Barsoum completed his bachelor’s of dental medicine in 2012 at Misr International University in Cairo. He then graduated magna cum laude from Boston University, where he earned his DMD degree and later completed a 3-year residency and fellowship at New York University in the Ashman Department of Periodontics and Implant Dentistry, where he is also an adjunct assistant professor. Dr. Barsoum’s practice in New York City focuses on dental implants, prosthetics, and full-mouth rehabilitation. He can be reached at adam@barsoum.com or at his practice’s website, nyc.barsoum.com.

Disclosure: Dr. Barsoum reports no disclosures.