Increasing the filler load in a composite material improves its overall physical properties as well as resistance to the functional wear placed on the restorative material. The material’s viscosity is directly affected, as the increase in filler loading will result in a higher viscosity material, while less filler material will result in a low-viscosity-based material. In many clinical situations, there is a need to have a less viscous composite resin instead of a putty-like consistency in order for it to better adapt to the cavity walls.³ This led to the advent of new flowable composite resins that were introduced in late 1996.

In their early configurations, flowable, resin-based composites were conventional composites with filler loads ranging from 37% to 53% (volume); compare that to the range of 60% to 72% (volume) for most of today’s conventional hybrid materials.⁴ By altering the percentage of filler, the viscosity of the material becomes modified. This allows manufacturers to package their materials in small syringes with small-gauge needles, allowing for easy dispensing, especially into smaller preparations, which would otherwise be challenging to fill without voids.

Figure 1. A carious lesion on the facial of the mandibular canine.	Figure 2. A retraction cord was placed to help with isolation.
Figure 3. Phosphoric acid was placed on the enamel of the preparation only (selective-etching).	Figure 4. Application of the universal adhesive to the prepared cavity.
Figure 5. Application of the first layer of flowable composite.	Figure 6. The second layer of flowable composite was placed along the gingival portion of the restoration.
Figure 7. The final layer of the lighter shade flowable was applied to blend with the middle third of the restoration.	Figure 8. The slightly overfilled restoration prior to contouring with the finishing diamond.
Figure 9. A one-step polisher was used to place the final polish.	Figure 10. The final restoration immediately after polishing and cord removal.

Fast-forward to the year 2020, and you will see that flowable composites have evolved into much more of a widely based restorative option than ever before. The challenges flowable composites faced were in the areas of strength and fracture toughness, wear-resistance, and polymerization shrinkage as well as in modulus of elasticity. Manufacturers’ technological advancements have seen increased percentages of filler materials now in the range of 70% to 80% by volume.⁵ The ability of manufacturers to insert submicron particles and join them into nanoclusters has dramatically changed the physical properties of flowables.⁶ The changes can be seen in the literature supporting their overall increase in flexural strength as well as compressive strength.⁷ The concern of polymerization shrinkage is still certainly in the mindset of many practitioners, and rightfully so, as flowables still have greater shrinkage than conventional composites.⁸ With the argument still clear, one must turn to how to best handle the flowable composite in relation to polymerization shrinkage. In regard to the placement of flowable composite, one must look at 2 very important factors related to cavity configuration and depth of material. Cavity design is dictated by the phenomenon we all call the C-factor. What we have come to learn about this, in relation to flowables, is that a horizontal placement, rather than the traditional layering protocol of incremental layering, helps to decrease the C-factor and thus decreases the shrinkage stress.⁹ Secondly, by placing the layers of flowable in no more than 1-mm increments, you will receive the most favorable outcome in regard to the shortcomings of flowable composites.¹⁰ The improved filler component has also improved the aesthetic and optical qualities of flowables by allowing the passage of light through the materials, much like that of natural tooth structure, to create a restoration that merges effortlessly with the surrounding natural dentition.¹¹ The smaller particle size also leads to a much faster and easier polishing due to the lack of “plucking” that one would experience with more dated materials containing large-particle-size fillers. Utilizing various shades of flowable layered over each other for subtle color combinations gives practitioners unparalleled freedom in developing natural-looking restorations.¹² The following case will highlight the use of a flowable composite to restore an undetectable Class V lesion on a mandibular canine.¹³

CASE REPORT
A 57-year-old female presented with an area of concern along her lower left gumline. Upon further evaluation, it was determined that she had a carious lesion along the facial surface of tooth No. 22 (Figure 1). Additionally, it was noted that she had numerous non-cervical carious lesions in other areas of her mouth, such as the one that can be seen on tooth No. 21 in the other images. Due to a lack of symptoms in tooth No. 21, an occlusal evaluation, as well as other factors, were evaluated prior to giving any restorative options to the patient at a later date.

After verifying the patient’s medical history, a mental block was used to anesthetize her, utilizing 1 carpule of 4% Articaine with epinephrine 1:100,000 (Septodont). Isolation would have been preferable under a rubber dam setting; however, due to the patient’s intolerance, we utilized a DynaFlex Cheek Retractor (DynaFlex) to help achieve an optimal working environment. A #00 Ultrapak Cord (Ultradent Products) was then placed to allow easier access to the carious lesion (Figure 2). Decay removal was then underway. Utilizing an electric handpiece (Bien-Air Dental), rotation adjustment settings can be made to incorporate high speeds for mass removal and then slow it down for more precise decay removal. The selective-etch technique was incorporated into this procedure in order to take advantage of the benefits phosphoric acid can provide by increasing the bond strength to enamel. A 35% phosphoric acid (Ultra-Etch [Ultradent Products]) was placed on the enamel for 15 seconds (Figure 3). CLEARFIL Universal Bond Quick (Kuraray Noritake) was then applied in an agitating fashion with vigorous scrubbing for 3 to 5 seconds (Figure 4). This was then air-thinned, followed by light-curing for 10 seconds using the VALO curing light (Ultradent Products). The first layer of CLEARFIL MAJESTY ES Flow (Kuraray Noritake) shade A-3 was applied evenly in a very thin layer of approximately 0.5 mm across the entire floor of the preparation (Figure 5).

The second layer followed the same rule previously mentioned by maintaining a very thin layer of 0.5 mm to no more than 1 mm, directing the CLEARFIL MAJESTY ES Flow shade only to the gingival portion of the restoration (Figure 6). By doing this, we were taking advantage of the shade options to help produce a seamless restoration.

The third and final layer, in this case, involved placing the same flowable, but this time, shade A-2 was used to help blend the restoration with the middle third of the tooth (Figure 7).

The final restoration was slightly overfilled (as shown in Figure 8) to allow finishing with either a fine diamond or a fluted carbide bur. The finishing protocol goes rather quickly when utilizing a highly filled nanoparticle flowable like CLEARFIL MAJESTY ES Flow, as the smaller particle size equates to a smoother finish. The final polishing step was accomplished using a one-step diamond-impregnated polisher (Jazz Polisher [SS White Dental]) running at approximately 10,000 rpm (an advantage of using an electric handpiece) with light pressure (Figure 9). The final restoration, immediately after cord removal, shows a wonderful balance of shade match, marginal integrity, and high polish to mimic that of natural tooth structure (Figure 10).

CONCLUSION
Earlier generations of flowable composites had some mechanical shortcomings by today’s standards, restricting their clinical applications. With the use of nanotechnology, newer generations of flowable composites have enhanced properties like those of the newer conventional resin composites. This means better adaptation, more elasticity, and better polymerization, along with minimized polymerization shrinkage. These enhanced physical and mechanical properties of the newer flowable composites have enabled clinicians to incorporate them in all aspects of restorative care with less concern than ever.

References

1. Bayne SC, Thompson JY, Swift EJ, et al. A characterization of first-generation flowable composites. J Am Dent Assoc. 1998;129:567-577.
2. Hervás-García A, Martínez-Lozano MA, Carbanes-Vila JC, et al. Composite resins. A review of the materials and clinical indications. Med Oral Patol Oral Cir Bucal. 2006;11:E215-E220.
3. Attar N, Tam LE, McComb D. Flow, strength, stiffness and radiopacity of flowable resin composites. J Can Dent Assoc. 2003;69:516-521.
4. Murchison DF, Charlton DG, Moore WS. Comparative radiopacity of flowable resin composites. Quintessence Int. 1999;30:179-184.
5. Strassler HE. Clinical update: flowable composite resins. Incisal Edge. 2007;1:61-68.
6. Balos S, Pilić B, Petronijević B, et al. Improving mechanical properties of flowable dental composite resin by adding silica nanoparticles. Vojnosanit Pregl. 2013;70:477-483.
7. Braga RR, Hilton TJ, Ferracane JL. Contraction stress of flowable composite materials and their efficacy as stress-relieving layers. J Am Dent Assoc. 2003;134:721-728.
8. Karthick K, Kailasam SK. Polymerization shrinkage of composites—a review. Journal of Indian Academy of Dental Specialists. 2011;2:32-36.
9. Nikolaenko SA, Lohbauer U, Roggendorf M, et al. Influence of c-factor and layering technique on microtensile bond strength to dentin. Dent Mater. 2004;20:579-585.
10. Malmström HS, Schlueter M, Roach T, et al. Effect of thickness of flowable resins on marginal leakage in class II composite restorations. Oper Dent. 2002;27:373-380.
11. Yu B, Lee YK. Differences in color, translucency and fluorescence between flowable and universal resin composites. J Dent. 2008;36:840-846.
12. Ceyhan YK, Ontiveros JC, Powers JM, et al. Accelerated aging effects on color and translucency of flowable composites. J Esthet Restor Dent. 2014;26:272-278.
13. Shaalan OO, Abou-Auf E, El Zoghby AF. Clinical evaluation of flowable resin composite versus conventional resin composite in carious and noncarious lesions: systematic review and meta-analysis. J Conserv Dent. 2017;20:380-385.

Dr. Schmedding has been a practicing cosmetic and restorative dentist for the last 25 years. He is a 1993 honors graduate from the University of the Pacific, Arthur A. Dugoni School of Dentistry. He currently maintains a private practice in Walnut Creek, Calif. Dr. Schmedding works with numerous manufacturers on the implementation and testing of various restorative products being brought to market. He speaks and teaches nationally and internationally on both aesthetic and restorative dentistry. He can be reached at troy.schmedding.dds@gmail.com.

Disclosure: Dr. Schmedding reports no disclosures.

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Q&A: Today’s Restorative Dentistry With Dr. Troy Schmedding

A dental restorative material called ACTIVA BioACTIVE-RESTORATIVE (Pulpdent) (hereafter referred to as ACTIVA in this article) is a proprietary formulation incorporating components of both glass ionomer systems and resin-based composites. After observations of 300 dental restorations, Croll, Berg, and Donly³ called this tooth-repair material “a resin-modified glass-ionomer bioactive ionic resin-based composite” and described methods for its use. With 12 examples, Croll and Lawson⁴ documented the diversity of the material after almost 4 years of use. Research regarding strength, wear resistance, adhesion dynamics, ion release, and other properties have supported 5 years of clinical observations in the senior author’s pediatric dentistry practice (3,761 tooth restorations from February 2014 to November 2019) concluding that ACTIVA functions well as a Class I and II dental restorative material for both primary and permanent teeth.^5-14

Figure 1. A 16-year-old with Class I and II caries lesions.	Figure 2. After local anesthesia and “split” rubber dam placement,15 mesial caries lesions were revealed.
Figure 3. The carious substance was debrided, and 2 occlusal preparations and mesio-occlusal preparations were completed. There was no evidence of distal surface caries lesions on the second premolar.	Figure 4. Preparations were disinfected with 2 glutaraldehyde/HEMA 60-second washes.16
Figure 5. After TheraCal LC (BISCO Dental Products) resin containing calcium silicate/MTA liner was placed and light-hardened in regions of deep dentinal penetration,17,18 a custom-contoured, 0.0015-in (0.0381-mm) stainless steel matrix strip (Strip-T [DENOVO Dental]) was placed and stabilized with a wooden wedge.	Figure 6. Enamel surfaces peripheral to cavosurface margins were roughened with a slow-speed diamond bur.
Figure 7. Self-etching bonding agent (Prompt L-Pop [3M]) was applied and agitated for 20 to 30 seconds (standard phosphoric acid etch/rinse/dry and resin bonding agent can also be used for this bonding step).	Figure 8. The bonding agent was light cured.
Figure 9. ACTIVA BioACTIVE-RESTORATIVE (Pulpdent) was injected carefully to overfill, avoiding air incorporation, using an AccuDose Syringe (Centrix). (An ACTIVA SPENSER [Pulpdent] mixer/dispenser can also be used for this step). Two layers, each light-hardened separately, can be used in very deep preparations.	Figure 10. Uncured ACTIVA was spread and extended over roughened, etched, and coated cavosurface margins.

This report serves as a step-by-step pictorial essay documenting Class I and II restorations of a maxillary permanent first molar and subsequent Class II repair of the adjacent premolar using this unique repair material in a teenager. We consider these restorations typical of ACTIVA tooth repair of permanent posterior teeth.

CASE REPORT
Figures 1 to 25 document Class I and II restorations of a maxillary first molar and subsequent repair of the adjacent second premolar using ACTIVA RESTORATIVE material. The initial caries lesions in the molar were diagnosed in November 2016. Twenty-six months later, with continued flossing neglect and regardless of efforts to educate and encourage routine flossing, the adjacent second premolar had also developed a disto-occlusal caries lesion. Repair of that tooth is also documented. The 2 repair procedures and followup in the 31-month time frame are shown and described.

DISCUSSION
We recommend that standard enamel-roughening, phosphoric acid etching (whether it be with a self-etching bonding agent or the etch/rinse/dry/apply method) be done when placing ACTIVA. However, when restoring primary teeth, the lead author does not use a bonding agent; the material is syringed into the tooth preparation, followed by a 20- to 30-second hiatus until the light beam is applied. Retention is gained by mechanical undercutting in preparation design. The acid component of the material might have some role in retention and also influences bonding. In permanent tooth ACTIVA repair, etching and bonding agents are always used, along with any mechanical undercutting that occurs in typical preparation design. The excess material that is peripherally spread over the enamel to the cavosurface margins serves as a marginal sealant in both primary and permanent tooth restorations. We recommend a calcium silicate/mineral trioxide aggregate liner in deeper regions of a preparation (Figures 5 and 22). The liner not only supplies calcium for pulpal healing but also virtually eliminates postoperative tooth sensitivity in our experience.^17,18

Figure 11. After 20 seconds of light application, the overfilled restoration was ready for finishing steps. Note that ACTIVA has a chemical resin polymerization reaction along with its light-curing feature, so deep hardening of the material is ensured.	Figure 12. A large round diamond bur was used to sculpt the occlusal surface.
Figure 13. Excess ACTIVA remains over the cavosurface margins, serving as marginal sealant.	Figure 14. The marginal ridge was sculpted with a Fissurotomy Bur (SS White Dental).
Figure 15. A finishing/polishing disc (Sof-Lex [3M]) was used to shape and smooth the marginal ridge.	Figure 16. A resin-based adhesive (Prompt L-Pop) was applied as finishing glaze.
Figure 17. The resin glaze was light cured for 10 seconds for full polymerization.	Figure 18. The occlusion was then evaluated, and adjustments made as needed.
Figure 19. August 2017, 7-months postoperatively.	Figure 20. In January 2018, the adjacent second premolar had developed a distal caries lesion.

A recent research report showed how ACTIVA restorations can perform poorly when placed using minimal acid etching with no bonding agent, as compared to a resin-based composite placed with both acid etching and an adhesive bonding agent.²¹ For complete comparisons, we do not understand why that study did not include ACTIVA being placed with acid etching and a bonding agent and why the resin-based composite was placed with only acid etching (ie, no bonding agent). In addition, there was no glutaraldehyde/HEMA disinfection of the cavity preparations and no calcium-containing liner (such as TheraCal LC [BISCO Dental Products]) placed in deep regions of either the ACTIVA or the comparison resin-based composite restoration preparations. Predictably, when bonding procedures and usual restorative protocols are not accomplished ideally, any resin adhesive restorative system will be compromised. We agree strongly with the researchers’ last statement, “Further studies should be conducted using a bonding agent,”²¹ but would add “and a restructured clinical technique.” Some new laboratory research from Dr. Lawson (submitted as an abstract for the IADR in March 2020) suggests that ion release from ACTIVA has some protective effect on the surrounding tooth structure, even when an adhesive is used.

Figure 21. The premolar required disto-occlusal ACTIVA repair in the same manner as the first molar.	Figure 22. TheraCal LC liner was placed and light cured in the deep area of the preparation. (This view gave an ideal opportunity to visualize the mesial aspect of the mesio-occlusal ACTIVA restoration of the first molar.)
Figure 23. Premolar repair was completed.	Figure 24. The restored first molar and the premolar are shown at 31-months and 16-months post-op, respectively.

Figure 25. This bite-wing radiograph was recorded when Figure 24 was photographed. A beginning distal-surface caries lesion on the mandibular second premolar was treated with silver diamine fluoride (SDF) and inserted using a soft dental pick.19 Other posterior proximal surfaces were similarly treated with SDF as a preventive measure.20

IN SUMMARY
Although there has been no clinical study on this subject, we consider these 2 dental restorations typical of what is achieved when using ACTIVA BioACTIVE-RESTORATIVE for Class I and II restorations of permanent posterior teeth. Having characteristics of both resin-based composites and glass ionomers may allow ACTIVA to benefit from advantageous properties of both restorative systems. Continuing experiences will tell how stratified adhesively bonded posterior tooth repair^1,2 compares with the durability and reliability of ACTIVA when facing the same clinical challenges in the long term.

References

1. Croll TP, Cavanaugh RR. Posterior resin-based composite restorations: a second opinion. J Esthet Restor Dent. 2002;14:303-312.
2. Croll TP, Cavanaugh RR. Tissue-specific, direct-application class II tooth repair: a case report. Compend Contin Educ Dent. 2009;30:608-614.
3. Croll TP, Berg JH, Donly KJ. Dental repair material: a resin-modified glass-ionomer bioactive ionic resin-based composite. Compend Contin Educ Dent. 2015;36:60-65.
4. Croll TP, Lawson NC. Activa bioactive restorative material in children and teens [white paper]. Inside Dentistry. 2018;14:1-8.
5. Garcia-Godoy F, Morrow BR, Pameijer CH. Flexural strength and fatigue of new Activa RMGICs. J Dent Res. 2014;93(special issue A). Abstract 254.
6. Girn VS, Chao W, Harsono M, et al. Comparison of mechanical properties of dental restorative material. J Dent Res. 2014;93(special issue A). Abstract 1163.
7. Pameijer CH, Garcia-Godoy F, Morrow BR, et al. Flexural strength and flexural fatigue properties of resin-modified glass ionomers. J Clin Dent. 2015;26:23-27.
8. Garcia-Godoy F, Morrow BR. Wear resistance of new Activa compared to other restorative materials. J Dent Res. 2015;94(special issue A). Abstract 3522.
9. Bansal R, Burgess J, Lawson NC. Wear of an enhanced resin-modified glass-ionomer restorative material. Am J Dent. 2016;29:171-174.
10. Chao W, Girn V, Harsono M, et al. Deflection at break of restorative materials. J Dent Res. 2015;94(special issue A). Abstract 2375.
11. Daddona J, Pagni S, Kugel G. Compressive strength and deflection at break of four cements. J Dent Res. 2016;95(special issue A). Abstract 0658.
12. Alrahlah A. Diametral tensile strength, flexural strength, and surface microhardness of bioactive bulk fill restorative. J Contemp Dent Pract. 2018;19:13-19.
13. Roulet JF, Hussein H, Abdulhameed NF, et al. In vitro wear of two bioactive composites and a glass ionomer cement. DZZ International. 2019;1:24-30.
14. Bhadra D, Shah NC, Rao AS, et al. A 1-year comparative evaluation of clinical performance of nanohybrid composite with Activa bioactive composite in class II carious lesion: a randomized control study. J Conserv Dent. 2019;22:92-96.
15. Croll TP. Alternative methods for use of the rubber dam. Quintessence Int.1985;16:387-392.
16. Christensen GJ. Disinfection of tooth preparations—why and how? Clinicians Report. 2009;2:1-2.
17. Gandolfi MG, Siboni F, Taddei P, et al. Apatite-forming ability of TheraCal pulp-capping material. J Dent Res. 2011;90(special issue A). Abstract 2520.
18. Gandolfi MG, Siboni F, Prati C. Chemical-physical properties of TheraCal, a novel light-curable MTA-like material for pulp capping. Int Endod J. 2012;45:571-579.
19. Croll TP, Berg JH. Delivery methods of silver diamine fluoride to proximal tooth surfaces for attenuation and prevention of dental caries lesions. Compend Contin Educ Dent. Feb 2020. In press.
20. Horst JA, Heima M. Prevention of dental caries by silver diamine fluoride.Compend Contin Educ Dent. 2019;40:158-164.
21. van Dijken JWV, Pallesen U, Benetti A. A randomized controlled evaluation of posterior resin restorations of an altered resin modified glass-ionomer cement with claimed bioactivity. Dent Mater. 2019;35:335-343.

Dr. Croll received his degree from the Temple University School of Dentistry and completed pediatric dentistry specialty training at the University of Connecticut. He is in private practice, specializing in pediatric dentistry in Doylestown, Pa. He is an adjunct professor of pediatric dentistry at the University of Texas Health Science Center at San Antonio Dental School and a clinical professor of pediatric dentistry at the Case Western Reserve School of Dental Medicine. He can be reached via email at willipus@comcast.net.

Dr. Lawson received his DMD degree from the University of Alabama at Birmingham (UAB) School of Dentistry and his PhD in biomedical engineering from UAB. He is currently an assistant professor and division director of biomaterials at UAB. Dr. Lawson has published more than 150 articles, abstracts, book chapters, and periodicals related to dental materials. He can be reached via email at nlawson@uab.edu.

Disclosures: Dr. Croll receives royalties for sales of Strip T Matrices by virtue of a business agreement with DENOVO Dental. Dr. Lawson has received grants from Pulpdent for research involving their products. Neither author received compensation for this article.

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There were a number of hurdles to overcome with resin-based restoratives, including issues related to polymerization shrinkage; excessive heat from exothermic curing; poor flexural, tensile, and compressive strengths; and poor wear resistance. Each of these critical factors has been overcome with the incredible advancements in composite resin material science over the past 30 years. With an increasingly high emphasis on aesthetics, the desire to exactly match the surrounding enamel at the cavosurface margin has always been one of the most challenging and important tasks in achieving aesthetic success. To accomplish appropriate color matching, most dentists are required to keep a large inventory of composite systems with an extensive range of shades. There are a number of disadvantages to this restorative model:

• The monetary cost of carrying multiple systems is a financial burden with poor returns.
• Multiple composite systems with multiple shades and dispensing methods take up significant physical space.
• A variety of adhesives may be required to accommodate the above composite systems.
• There is a high likelihood that many infrequently used or obscure shades will expire before the materials are ever even taken out of their packages.
• The use of many of these technique-sensitive materials requires training and an advanced skill set for placement, often involving a number of shades and specific layering procedures.
• All this effort requires extra time for both the patient and the restorative team.

A Single-Shade Composite Restorative Solution
When I first heard that a new, genuinely universal composite was being introduced, the famous saying from President Ronald Reagan came immediately to mind: “There you go again!” He would say it as a way of disarming his opponent, implying that they spoke with hyperbole or even falsehood. Over more than 3 decades of practice, I’ve read of the single-shade composite claim a number of times, without any of them ever truly achieving the goal. Hope was always followed by disappointment. So, it was with a healthy degree of skepticism that we beta tested OMNICHROMA (Tokuyama Dental America) composite resin restorative material. However, we were pleasantly surprised!

Figure 1. OMNICHROMA (Tokuyama Dental America) is available for delivery in both syringes and individual compules.

To begin with, the physics of composite resin and color were completely rethought. All other current composite materials rely on the chemical color of the resin to emulate certain shades of human teeth. Traditional composites are limited in their ability to shade match, meaning the doctor must pick a shade that is the same as the substrate being restored. For example, a tooth with VITA B1 enamel will require a B1 composite, while a C4 tooth will clearly not match that same B1 material. And teeth, of course, do not represent a single shade! A simple Class I cavity preparation may have an A4 cavity prep floor, dentin walls that appear as D3, and enamel that is B2 at the proximal ends but B1 near the cuspal inclines. Proper use of the current chemical color-based composites may require as many as 4 or 5 different shades to achieve a true match.

OMNICHROMA (Figure 1) utilizes Smart Chromatic Technology to leverage structural color as a way of matching the surrounding substrate. It relies on the material transmitting the color of adjacent tooth structure to provide a restoration that matches. This technology is not the same as using a translucent material that allows color to reflect through it. Structural color can be best appreciated when looking at a soap bubble, or the grooves on a compact disc, and seeing the rainbow reflection off of the surface. This myriad of colors is the result of microscopic structures physically interacting with light.

So, how is the structural color of Smart Chromatic Technology different than ordinary chemical color in composite restorative chemistry? Starting with the size and shape of the filled resin particles, OMNICHROMA utilizes supra-nano spherical SiO₂-ZrO₂ particles that are uniformly 260 nm in size. When compared on SEM with all other composites on the market, 2 obvious characteristics jump out—the consistent shape and the small particle size (Figures 2 and 3).

This unique filler size and shape allows for the natural color of the surrounding tooth to reflect through and with the OMNICHROMA material, which, by design, is created to be most effective in the red-to-yellow range of the spectrum. Human teeth have a natural chroma in the red-to-yellow range.

Let’s now look at a clinical example using this innovative composite resin.

Figure 2. SEM image comparison of OMNICHROMA and other typical composite resins.

Figure 3. Note the irregular shape and size of other composite fillers.

CASE REPORT
Diagnosis and Treatment Planning
A 60-year-old male patient with dental anxiety presented with a number of restorative issues (Figures 4 and 5). A recent root canal treatment had been done on a zirconia-crowned No. 4 with the pulp chamber sealed using an orange core material, and it was in need of an access-fill restoration. A loose screw-retained zirconia implant crown No. 5 in need of having its abutment screw replaced and access hole restored was noted. And, finally, a buccal Class V composite restoration on tooth No. 20 with recurrent decay was in need of replacement.

Clinical Protocol
The following is a description of the clinical steps taken to maximize efficiency and reduce chair time for our anxious patient.

1. Local anesthetic was administered for the restoration of tooth No. 20.

2. During the latent period, while the anesthetic was taking effect on No. 20, the access hole on the screw-retained implant crown No. 5 was opened, and the old abutment screw was removed. The implant crown and implant table were evaluated and determined to be healthy, and a new abutment screw was placed and torqued to the proper value. Yellow Teflon tape, impregnated with silver nitrate to reduce bacterial presence, was placed in the implant access chamber. The occlusion was evaluated using Madame Butterfly Blue Silk (Pankey Institute) articulation ribbon. A periapical radiograph was taken to determine a full seating of the screw-retained implant crown. A small cotton pledget was placed over the Teflon tape for step 3 (below) and then removed for step 4 (below).

Figure 4. Preoperative photo of the access openings of teeth Nos. 4 and 5.	Figure 5. Pre-op photo of tooth No. 20 with a failing Class V buccal composite with recurrent decay.
Figure 6. OMNICHROMA was placed in the endodontic access opening of prepared tooth No. 4.	Figure 7. OMNICHROMA was placed in the implant access channel of tooth No. 5. Note that both composites have not been polymerized and the significant color difference with the adjacent crown structure.
Figure 8. Light cure of both teeth Nos. 4 and 5.	Figure 9. Final restorations of teeth Nos. 4 and 5.
Figure 10. Removal of failing old composite restoration on tooth No. 20.	Figure 11. Recurrent decay was observed at the gingival level of tooth No. 20.
Figure 12. OMNICHROMA placement in the prepared Class V cavity on the buccal wall of tooth No. 20.	Figure 13. Immediate postoperative photo of the final restoration of tooth No. 20.

Figure 14. Note the color difference between the incrementally placed and cured OMNICHROMA material adjacent to the uncured material in this restoration.

3. Both the zirconia implant crown No. 5 and the recently endodontically treated tooth No. 4 (done through an existing zirconia crown) were micro-air abraded (PrepStart [Zest Dental Solutions]) with 27.5 µm AlO₂ at 40 psi to clean the ceramic surfaces. A 9% hydrofluoric acid (HF) porcelain etchant (Porcelain Etch [Ultradent Products]) was placed and allowed to set for 30 seconds to improve micromechanical retention. The HF etchant was thoroughly rinsed away, being careful to avoid contact with oral tissues. A 35% phosphoric acid gel (Ultra-Etch [Ultradent Products]) was then utilized for 10 seconds to remove any remaining salts. After rinsing, to remove phospholipids, Ivoclean (Ivoclar Vivadent) was placed, allowed to set for 20 seconds, and then thoroughly rinsed away. The access openings were rinsed and dried. Finally, a 2-part silane system (Bis-Silane [BISCO Dental Products]) was applied to maximize bond strength. These 5 steps take less than 2 minutes and ensure that a long-term, impenetrable seal of the composite material to the ceramic is achieved.

Figure 15. OMNICHROMA BLOCKER (Tokuyama Dental America) was used to provide proper substructure for the restorative material.

4. Both access openings were treated with an eighth-generation bonding agent (Tokuyama Universal Bond [Tokuyama Dental America]) used due to its very high and reliable adhesive strength and the time it saves because of its simple placement technique. Tokuyama Universal Bond is a simple system: Mix a drop of bond A and B, place it on the prepared surface, air dry for a total of 10 seconds (5 seconds weak air, 5 seconds mild air), and proceed to composite placement. No agitation or light curing is necessary, allowing for worry-free polymerization in areas a curing light can’t reach while bonding to any substrate.

5. Both access holes were bulk filled with the universal one-shade OMNICHROMA composite to a depth of 3.0 mm (curing depth varies with curing light intensity). The composite was then contoured and light cured (VALO LED [Ultradent Products]) for 10 seconds at the Xtra Power setting (3,200 mW/cm²) (Figures 6 to 8).

6. The occlusion was evaluated and adjusted. Then both crowns were polished back to a high luster (CeraGlaze [Kavo Kerr]). In the 14 minutes spent to complete steps 1 through 6, the patient achieved profound anesthesia for decay removal on tooth No. 20 (Figure 9).

7. The original 10-year-old composite material was removed from the buccal aspect of tooth No. 20, with recurrent decay noted on both the mesial and cervical aspects of the preparation. Careful slow-speed rotary excavation allowed for no hard- or soft-tissue damage. A Zekrya Gingival protector (DMG America) was used to protect the sulcus during micro-air abrasion (PrepStart). A 35% phosphoric acid (Ultra-Etch) was applied to the full preparation for 30 seconds and copiously rinsed with water. MicroPrime G (Zest Dental Solutions) was placed, followed by light air drying (Figures 10 and 11).

8. The restoration of tooth No. 20 was accomplished by first placing Tokuyama Universal Bond, followed by the placement of OMNICHROMA composite in 2.0-mm increments. Each 2.0-mm increment was light cured with the VALO LED light for 10 seconds at high power (1,400 mW/cm2). The excellent sculptability of this composite material enabled a minimal need for post-cure contouring and adjustment. Simple polishing was accomplished (Enhance PoGo Polishing System [Dentsply Sirona]) with no need for the use of carbide finishing burs (Figures 12 and 13).

DISCUSSION
Over the past few decades, claims by manufacturers to have developed a universal, single-shade composite have fallen short of expectations. Smart Chromatic Technology has truly revolutionized composite restorative materials for cosmetic dentistry. The unique use of structural color to mimic adjacent tooth shades has provided numerous benefits to our profession and patient population. OMNICHROMA is easy to use and works with almost any shade while reducing inventory, cost, decision making, and time.

As with any material, there is a learning curve; however, it is minimal and easy to master. The first startling clinical observation will be the significant color difference between the uncured and final restorations. It takes a small leap of faith to know that the white-opaque uncured material will match the bordering structures after polymerization. The composite, once cured, does blend with its surroundings, unlike all other materials that rely on chemical colors for shade matching (Figure 14).

A second part of the learning curve is the use of OMNICHROMA BLOCKER (Tokuyama Dental America), a supplementary product that is necessary if no natural tooth structure matrix exists for the structural color to mimic. A full Class IV fracture can be restored utilizing a thin shelf of OMNICHROMA BLOCKER on the palatal surface (Figure 14), followed by a layer of OMNICHROMA. I have also found the blocking agent to be useful when filling endodontic access holes with dark pulp chamber floors or through porcelain-fused-to-metal crowns. Oftentimes, a multi-step opaquing process is necessary to blend the composite with the crown and not end up with a “manhole cover.” A small increment of OMNICHROMA BLOCKER, followed by a layer of OMNICHROMA, will result in a seamless repair. If the core material is lighter (or even orange, as seen in tooth No. 4), OMNICHROMA BLOCKER is not necessary (Figure 15).

CLOSING COMMENTS
The concept of structural color over chemical color restorative material is a proven technology that will simplify shade matching and revolutionize cosmetic dentistry. The introduction of this new single-shade, universal composite restorative material is a giant leap forward by providing excellent shade matching that requires minimal investment in time and by eliminating the need for keeping and maintaining an extensive inventory of differently shaded composites.

Dr. Gray is a 1986 graduate of the Georgetown University School of Dentistry. He is a Master and LLSR in The AGD and a Fellow in the International Congress of Oral Implantologists, International College of Dentists, and Academy of Dentistry International. He is an instructor at the LD Pankey Institute and at 9 universities. Dr. Gray has spoken on new dental technologies in more than 200 US cities and 10 countries since 1994. Dentistry Today has honored Dr. Gray as one of its Leaders in Continuing Education. Dr. Gray is an Invisalign Premier Provider and maintains a full-time, fee-for-service private practice in Washington, DC. He can be reached at bg@smiledc.com.

Disclosure: Dr. Gray is an unpaid consultant for Tokuyama Dental America.

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CASE REPORT
Diagnosis and Treatment Planning
A patient presented with the desire to enhance her smile with porcelain restorations (Figures 1 and 2). She wished to brighten and widen her smile. There were pre-existing direct composite veneers on her maxillary central incisors and some Class V restorations on several premolars. There were also some Class II composites that had been placed in her premolar teeth. Her overall dental health was good, with no active caries or periodontal disease.

The patient decided to have the maxillary teeth treated now with the goal to have restorations on the mandibular teeth done at a later date. After discussing the options, she chose ceramic restorations for her maxillary 10 teeth. Her color choice was OM2 (VITA 3D shade guide), and after discussing the possible aesthetic details that could be built into the restorations, she stated that she desired no incisal translucency and minimal surface texture.

Preoperative Appointment
At the next appointment, to establish records and for communication with the dental laboratory team, a full series of photos was taken using a Canon D60 camera with a 100-mm macro lens. Preliminary maxillary and mandibular impressions were taken using a medium-viscosity A-silicone impression material (Silginat [Kettenbach LP]). This material combines the benefits of A-silicones with those of alginates, pairing low tear resistance with high dimensional stability. A face-bow record (Denar [Whip Mix]) was also taken. On the face-bow jig that would be sent to the lab team to use in mounting the hard model of the maxillary teeth on the semi-adjustable Denar articulator, a hard-setting, non-slumping A-silicone (Futar Fast [Kettenbach LP]) was used to quickly record the patient’s incisal edges and occlusal surfaces. A centric occlusal registration was made using hard-setting A-silicone bite registration material (Futar [Kettenbach LP]) for use in mounting the lower model on the articulator.

The impressions, occlusal registrations, and face-bow jig were sent to the dental laboratory, and the lab poured and mounted the preoperative models. Two pours were made, and 2 sets of models were mounted. On the second set of models, the lab team waxed up the maxillary arch, creating new contours on the 10 most anterior teeth (teeth Nos. 4 to 13). The wax-up goals included creating similar contours to the natural teeth, but in a wider arch form to achieve more fullness while decreasing the negative curve of the maxillary incisal edges.

The wax-up was duplicated in stone, and then a vacuum-formed clear plastic shim was made over the model to use as a prep guide. The lab team also made a stint over the wax-up using Lab Putty (Kettenbach LP) for the chairside fabrication of the provisional restorations after the preparations were complete.

Clinical Protocol
Teeth Nos. 6 to 11 were prepared for 360° laminates. The premolar teeth were prepared for onlay with facial veneer restorations to replace the composite restorations. This prep design was done to allow the fabrication of restorations that would widen the buccal corridor. All margins were prepared at or above the height of the tissue. The prepared teeth can be seen from the retracted facial view in Figure 3.

Figure 1. The preoperative smile.	Figure 2. The preoperative, retracted view of the maxillary teeth.
Figure 3. Teeth Nos. 6 to 11, after preparation.	Figure 4. Light body impression material (Panasil initial contact Light [Kettenbach LP]) was injected around the margins.
Figure 5. A photo taken after completing injection of the light body impression material.	Figure 6. The tray material (Panasil Putty Soft [Kettenbach LP]) was mixed by the chairside assistant.
Figure 7. The tray material (Panasil Putty Soft) was then inserted into the impression tray.	Figure 8. The final impression.
Figure 9. The bite registration (Futar Fast [Kettenbach LP]) in place.	Figure 10. The opposing side of the bite registration.
Figure 11. The patient’s smile, with provisional restorations in place.	Figure 12. Lithium disilicate (IPS e.max Press [Ivoclar Vivadent]) aesthetic restorations, shown on a mirror surface.
Figure 13. The retracted view, with high-strength all-ceramic restorations in place.	Figure 14. The patient’s new smile.

Because of the patient’s excellent periodontal health, no retraction cord or paste was needed. A putty-wash impression technique was done in this case using Panasil Putty Soft (Kettenbach LP) and a light-bodied impression material. According to the manufacturer, Panasil Putty Soft is “a kneadable, addition-curing, elastomeric impression material based on vinyl polysiloxane (VPS) with low final hardness.” In addition to its intraoral setting time of only 2 minutes, this highly efficient impression material provides maximal precision and optimal convenience. Panasil initial contact Light (Kettenbach LP) is a light-body impression material used in conjunction with the tray material.

First, the light-body material, which readily flows in the sulci, was injected around the margins and all the prepared tooth surfaces (Figures 4 and 5). In this technique, while the clinician injects the light-body material, the chairside assistant mixes the putty tray material (Figure 6) and places it in the impression tray (with tray adhesive having been previously placed and properly dried) (Figure 7). The assistant then hands it to the clinician to place it in the mouth. The putty consistency of the heavy body actually causes pressure on the light body, further pressing it into the sulcus.

After complete setting, the tray was removed. The final impression can be seen in Figure 8. Note the precise capture of the prepared teeth and margins. An occlusal registration was made using Futar bite registration material (Figure 9). The untrimmed registration can be seen immediately after removal in Figure 10.

Next, provisional restorations were fabricated using Visalys (Kettenbach LP). Visalys is a temporary crown and bridge material based on a multi-functional acrylic composite with outstanding mechanical properties. The material was injected into the stint (made previously over the duplicate model of the diagnostic wax-up) and placed on the prepared teeth. When the material was set, the shim was removed, excess provisional material was cleaned up, and the margins were refined using a small carbide finishing bur. The provisional restorations made from a copy of the wax-up gave the patient a prototype and preview of the final result. The completed provisionals can be seen in Figure 11.

Dental Laboratory Protocol
At the dental laboratory, the impression was poured and dies were trimmed. The prepared model was mounted onto the articulator using the new occlusal registration. Ten high-strength and aesthetic lithium disilicate (IPS e.max Press [Ivoclar Vivadent]) restorations were fabricated using the lost-wax and molten ceramic (pressed) technique. The surfaces were cut back and micro-layered to create the desired aesthetics. The intaglio surfaces of the restorations were etched using a phosphoric acid etching gel. The final restorations were photographed on a mirror surface (Figure 12), and then the case was prepared for delivery to the dental office.

Delivery of the Final Restorations
At the placement appointment, the provisional restorations were removed and the lithium disilicate restorations were tried-in using a drop of water as a try-in medium. After the verifying fit and aesthetics of the restorations were approved by the patient, each restoration was removed and thoroughly cleaned with water and then dried with oil and water-free air. Next, BIS-SILANE (BISCO Dental Products) was applied to the internal etched surfaces of the restorations and dried. Etchant gel (UNI-ETCH [BISCO Dental Products]) was applied to the enamel surfaces for 10 seconds and then thoroughly rinsed with water. The teeth were lightly air-dried, and a universal bonding agent (ALL-BOND UNIVERSAL [BISCO Dental Products]) was liberally applied to the prepared tooth surfaces and thinned with air. The bonding agent was light cured for 10 seconds using an LED curing light (S.P.E.C. 3 [COLTENE]). A dual-cure resin cement (DUO-LINK [BISCO Dental Products]) was applied to the internal surfaces of the restorations, and then the restorations were seated. At the gel state, the excess luting composite was teased away from the margins using a scaler. Dental floss was eased between the restorations to remove any further excess cement in the interproximal areas. After cleanup, the LED curing light was used to completely set the material so finishing could begin. Occlusal adjustments were done using fine finishing diamonds and porcelain polishing points (Brasseler USA).

The restorations can be seen in place from the retracted facial view in Figure 13. The patient’s new smile can be seen in Figure 14. She was happy with the result and plans to continue treatment in the future. 

CLOSING COMMENTS
While a good number of dental professionals have made the switch from physical to digital impression techniques, this article has demonstrated that clinicians can still provide patients with the smiles that they desire using high-quality, modern impression materials and proven clinical techniques.

Acknowledgment:
Dr. Nash would like to thank Boris Zukovski, master ceramist, Masters of Dental Aesthetics, Inc. (West Hills, Calif) for the excellent lab work for this case.

Dr. Nash maintains a private general practice in Huntersville, NC, where he focuses on cosmetic, aesthetic, and full-mouth rehabilitative treatments. He presents workshops and lectures nationally and internationally on these types of procedures and has authored chapters in 2 clinical textbooks. Dr. Nash is the cofounder of the Nash Institute for Dental Learning in Huntersville. He is a member and an accredited Fellow in the American Academy of Cosmetic Dentistry. He can be reached at rosswnashdds@aol.com.

Disclosure: Dr. Nash reports no disclosures.

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Direct Composite Resin Veneers

Porcelain veneers often require a reduction of tooth structure, whereas aesthetically improving a smile with composite resin can be much more conservative since tooth preparation is often not required. Composite resin restorations can be beautiful, conservative, and durable, and, when done in a timely manner, these restorations can also be highly profitable. When the cost of the material is compared to the net income earned for each restoration, the return on investment is impressive. Being able to accomplish them in a time-efficient manner seems to be the hiccup that is thwarting the popularity of direct placed restorations in the aesthetic zone. However, with the recent introduction of a template system (Uveneer [Ultradent Products]) for direct composite resin veneers, the clinician can more easily and predictably shape, contour, and polish these restorations (Figure 1).

The Uveneer template system offers large and medium sizes for upper and lower arches (from first premolar to first premolar) in each kit. The templates have a mark in the center that coincides with the handle to help with proper alignment. After using a template, it can be wiped with an alcohol gauze, autoclaved, and then placed back in the kit for the next patient needing this treatment option.

CASE REPORT
Diagnosis and Treatment Planning
A 34-year-old female presented with an upper left central incisor (tooth No. 9) that was darker than the adjacent teeth (Figure 2). A radiograph indicated there was no pulpal pathology. Although tooth No. 9 was her chief complaint, the slight mesial lingual rotation of tooth No. 8 was also discussed, as well as the irregular incisal edges of teeth Nos. 7 and 10. After discussing the treatment options, the patient was comfortable with veneering all 4 teeth using composite resin. The only tooth that needed to be reduced was No. 9, in order to mask the discoloration with composite resin.

Figure 1. The Uveneer Template System (Ultradent Products]).	Figure 2. The preoperative smile.
Figure 3. The discolored right central incisor (tooth No. 9), ready for bonding, had been reduced and isolated using Teflon tape and cheek retractors (KleerView [Ultradent Products]).	Figure 4. Excess composite was removed from the periphery of the Uveneer prior to curing.
Figure 5. A serrated strip and an ultrafine metal strip (VISIONFLEX UF [Brasseler USA]) were used.	Figure 6. EPITEX (GC America) polishing strips were used.

Clinical Protocol
The teeth were cleaned with pumice prior to the adhesive bonding steps. The reduction of tooth No. 9 was accomplished using a diamond bur (Brasseler 012506U0 [Brasseler USA]). To help isolate the area and to make the work proceed more efficiently, cheek retractors (KleerView [Ultradent Products]) were inserted to keep the lips and cheeks away from the operative area. Teeth Nos. 8 and 10 were wrapped with Teflon tape (Figure 3). The author prefers Teflon tape over other matrices because it intimately adapts to the tooth and is thin enough that it does not interfere with the establishment of proximal contacts, no wedges required.

The upper left central incisor was etched for 15 seconds (Ultra-Etch [Ultradent Products]), then thoroughly rinsed, and excess moisture was removed. The total-etch technique is preferred over the self-etch option when bonding to enamel. A universal adhesive (Peak Universal Bond [Ultradent Products]) was applied, air-thinned, and then cured using Velo LED Curing Light (Ultradent Products) for 10 seconds. Next, a nanohybrid composite (Shade B 0.5, Mosaic [Ultradent Products]) was placed on the tooth from a unidose compule, investing very little time in providing a rudimentary shape. The large-sized veneer template was then pressed into the uncured composite. As the template was pressed into the uncured composite, excess composite extruded from the periphery of the template, indicating that the template was in full contact with the composite. While stabilizing the template by holding onto the handle, the excess composite was removed with an instrument (Figure 4). The firm viscosity of the nanohybrid composite made removal of the excess much easier than if a creamy composite with lower viscosity had been used. The composite resin was then light-cured through the template for 10 seconds. The template was then removed from the cured composite. Next, a serrated strip (Jiffy Proximal Saw [Ultradent Products]) was used to ensure a clean contact, followed by an ultrafine metal strip (VISIONFLEX UF [Brasseler USA]) to smooth any tags of resin or bonding agent that may have still been adhering to the proximal wall (Figure 5). (Note: Using a strip more aggressive than ultra-fine may open the contact.) The final polish of the proximal walls was achieved using EPITEX (GC America) polishing strips; these are fine polishing strips that shine the proximal surface without opening the contact (Figure 6). The incisal edge of the veneer was adjusted using polishing discs (EP Esthetic Polishing System [Brasseler USA]) (Figure 7). The facial surface did not need to be adjusted or polished since the template left a beautiful glossy surface to the veneer.

Figure 7. A polishing disc (EP Esthetic Polishing System [Brasseler USA]) was used.	Figure 8. The large-size Uveneer template was placed on the uncured composite.
Figure 9. Excess composite was cleaned from the periphery of the template.	Figure 10. The template was removed from tooth No. 8. (Note the faint outline of the veneer in the cured composite.)
Figure 11. A mosquito diamond bur (004969U0 [Brasseler USA]) was used.	Figure 12. The postoperative smile of the completed direct composite resin veneers on teeth Nos. 7 to 10 (Mosaic [Ultradent Products]).

After completing the left central incisor, the upper right central incisor was addressed. No reduction of tooth No. 8 was necessary. The cheek retractors remained in place until all bonding was completed. Tooth No. 8 was acid-etched and rinsed following the same protocol as for tooth No. 9. Excess moisture was removed. The universal adhesive was then applied to tooth No. 8, and it was then air-thinned and light-cured. The Mosaic nanohybrid composite was applied to the tooth and quickly given a rudimentary shape. The large-sized template was placed on the uncured composite (Figure 8). The excess composite was cleaned from the periphery of the template (Figure 9). Once the composite was cured through the template, the template was removed using its handle (Figure 10). There was a slight outline of the template in the cured composite that was removed using a fine diamond mosquito bur (Jiffy Interproximal Diamond #4248, [Ultradent Products, Inc.] or Brasseler bur 004969U0 [Brasseler USA]) after removal of the Teflon tape (Figure 11). The mesial lingual rotation of tooth No. 8 was successfully camouflaged by using the large-veneer template to give it ideal shape and contour. The same finishing/polishing protocol as described for tooth No. 9 was then carried out. After tooth No. 8 was completed, the right and left laterals were addressed (Figure 12).

CLOSING COMMENTS
Historically, clinicians have hesitated to use composite resins for anterior aesthetics due to the materials’ poor optical properties, lack of shine, poor handling, and questionable longevity. The introduction of nanohybrid composite resins have helped to overcome many of the challenges once faced by clinicians and have brought with them a predictability and ease of placement that instills confidence in the practitioners who choose this material option. Knowing lifelike results can be achieved, along with strong and long-lasting results, conservative dentistry is now possible in many cases without the fears of the past.

Another important reason that has historically existed for not providing resin veneers has also been resolved. The profitability of composite veneers can only be realized if they can be done in a time-efficient manner. With the introduction of a veneer template system that allows a placement protocol with greater predictability and ease of application, the use of direct composite resin veneers is expected to increase in popularity among clinicians and patients.

Dr. Morgan graduated from the University of Texas Health Science Center at San Antonio. While beginning her practice in San Antonio, she was a founding officer in the South Texas Chapter of the American Academy of Cosmetic Dentistry. She relocated to Salt Lake City and helped develop seminars that included workshop/hands-on components for Ultradent Products, Inc. She has lectured worldwide on cosmetic dentistry. She is also a co-founder of The American Academy of Esthetic Orthodontics. She maintains Morgan and Presley Dental in Midvale, Utah, while continuing to teach resin bonding, tooth whitening, and orthodontic therapy under the name of Prestige Seminars. She can be reached at (801) 561-9999 or via email at morganjaimee@hotmail.com.

Disclosure: Dr. Morgan is a consultant for Ultradent Products, Inc.

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Indirect restorations have taken on an interesting and dynamic edge in recent years, resulting in a consumer-driven evolution of dental prosthetics. Patients demanded a more aesthetic restorative material with a metal-free substructure, and the market has delivered. But the introduction of new substrate materials, bonding agents, and cements has complicated the application of the indirect-restoration process. The aim of this article is to clarify the available luting and adhesive options and to provide insight into how one might best utilize those options.

Cementation or Adhesion: Which Is It?
While most clinicians use the terms “cementation” and “adhesion” interchangeably when referring to placing indirect restorations, the difference between these 2 approaches could not be more different. Cementation refers to the process in which a substance that hardens is used to bind 2 bodies together, purely on a mechanical basis. On the other hand, adhesion is defined as a force of attraction between unlike bodies that acts to hold them together chemically and mechanically. Bonding is the technique that adheres the bodies. This distinction is made only to clarify that adhesion is superior to cementation in terms of force of attraction between unlike bodies (eg, tooth and crown substrate).

For many years, metal was the only substrate available in the dental market, and only one cement type and one technique were required for the successful placement of crowns. With the introduction and wide acceptance of zirconia-based restorations (Lava [3M]) and lithium disilicate (IPS e.max [Ivoclar Vivadent]) in 2001 and 2005, respectively, different luting materials and techniques were required. Soon, it became apparent that, while dentists adopted both substrates, conventional cementation techniques were often inappropriately used during their placement. The chemical compositions of lithium disilicate and zirconia are so unlike metal and metal-based crowns that they necessitate the use of different adhesive steps and materials. For example, lithium disilicate and zirconia inherently possess high-energy and hydrophilic surfaces that are not conducive to adhesion. A priming step is needed to create a lower-energy, hydrophobic surface that can then reliably adhere to a cement.¹ This is accomplished by coating the inside of the crown with its intended primer and allowing it to dry before final placement. Typically, lithium disilicate crowns are primed with silane, while zirconia crowns are treated with zirconia-specific primers (such as Z-PRIME Plus [BISCO Dental Products]) available from a variety of manufacturers. In recent years, a universal primer (Monobond Plus [Ivoclar Vivadent]) was introduced that can be used on metal, metal-based (PFM), and all-ceramic substrates, including leucite-reinforced porcelains (such as IPS Empress Esthetic [Ivoclar Vivadent]) and other high-strength ceramics, like lithium disilicate (such as IPS e.max or Initial LiSi Press [GC America]) and high-strength polycrystalline all-ceramics, such as zirconia.

Current adhesive protocol for an indirect all-porcelain restoration requires the tooth to be prepared, etched, and treated with a suitable adhesive. Regardless of the cement used, the substrate must be treated separately with its own primer, and a cement can then act to hold the tooth and substrate together. While this is a seemingly simple concept, final tooth resistance/retention form, multiple substrate options, and a variety of luting materials can obscure the process for even the most astute clinicians.

Figure 2. A prepared short-nonretentive tooth. The crown was ready to be cemented using a total-etch technique with a dual-cure resin cement (Calibra Ceram [Dentsply Sirona]).	Figure 3. Uni-Etch W/BAC 32% Phosphoric Acid etch (BISCO Dental Products).
Figure 4. Bonding adhesive was applied (Prime & Bond [Dentsply Sirona]).	Figure 5. Primer was applied to the all-ceramic (BruxZir Zirconia [Glidewell Laboratories]) crown.
Figure 6. Placing Calibra Ceram in the crown.	Figure 7. The crown was seated on the tooth.

Other Factors Important to Restorative Longevity
The clinician should also keep in mind that, when adhering modern crown substrates to tooth structure, the design and execution of tooth preparation is an equally important part of the restoration process. The long-term success of a restorative material depends as much upon attaining proper resistance and retention form in the preparation as on the luting cement used in the placement. The height and taper of the prepared tooth will govern how the cement resists oblique forces for the lifetime of the restoration.

Proper isolation of the operative field using a rubber dam or other appropriate isolation techniques (such as Isolite [Isolite Systems]) plays a key role in long-term restorative success because moisture compromises the physical properties of both adhesives and cements.

Choosing a Cement
After the tooth and substrate have been properly prepared, the final step in the process is to apply an appropriate cement to the restoration. The primary purpose of the cement is to fill the micro-gap between the tooth and substrate.2 The secondary role of a cement is to assist in retention of the restoration. From mechanically retentive luting cements to adhesive cements, which are both mechanically and chemically retentive, there are many selections available to clinicians today. This can understandably cause confusion regarding which cement will be best suited for a given clinical situation and how best to proceed once a decision has been made. The choice ultimately depends on the resistance and retention of the crown preparation (Figure 1), the clinical situation, and the operators’ preferences. It should be noted that despite the numerous options, no cement can compensate for poor tooth preparation.

Let’s now review some of the available luting options.

Glass Ionomer Cements
Glass ionomer cements (GICs) were first introduced to the dental market in the 1970s. Classified as conventional luting cements, GICs boast thin film thickness, moisture tolerance, and anticariogenic properties via their ability to release fluoride. They are self-curing and are indicated for metallic, PFM, and all-porcelain restorations, provided that both the retention and resistance forms of the tooth are suitable. Because GICs have been around so long, they are well understood and can be an exemplary and reliable cement choice if used properly.

Resin-Modified Glass Ionomer Luting Cements
Resin-modified glass ionomer (RMGI) luting cements made their market debut in the 1990s as a hybrid between GICs and resin cements (RCs). An RMGI retains many of the benefits of a GIC but features improved strength and handling due to its resin-reinforced matrix. RMGIs are insoluble in oral fluids and able to be light-cured. They are indicated for metal and metal-based (PFM) restorations, as well as lithium disilicate and zirconia restorations where moisture control is difficult. However, in practice, they are only recommended for retentive preparations because even the newer RMGIs cannot match the strength of a resin cement.

Figure 8. Excess cement was cleaned after tack curing with the light-curing unit.	Figure 9. The prepared retentive tooth. The crown was ready for cementing with a self-etch, dual-cure resin cement (Calibra Universal [Dentsply Sirona]).
Figure 10. A primer (Z-PRIME Plus [BISCO Dental Products]) had been applied to the zirconia (BruxZir) crown.	Figure 11. The crown was filled with a self-adhesive resin cement (Calibra Universal).
Figure 12. The seated crown was tack cured using the light-curing unit for 3 seconds from the buccal direction and 3 seconds from the lingual direction.	Figure 13. Note the easy cleanup carried out at the margin after the tack curing.

Resin Cements
Resin cements were commercially launched in the 1980s, but a torrent of advancements has broadened the category in recent years. Classified as adhesive cements, their versatility and high-bond strength make them among the best cement options available in today’s market. However, the clinician must be exacting in the utilization of an RC in a given clinical situation or else their effectiveness can be limited. RCs can be grouped into 3 general subtypes: self-cure, light-cure, and dual-cure formulations. Note that many RCs are touted as being “universal,” but this term is little more than an affectation. Each manufacturer prescribes its own meaning to the word “universal,” so it is always best to scrutinize the indications of any product before use.

Total-Etch Light-Cure RCs
Total-etch light-cure RCs require the clinician to independently etch, rinse, and apply a bonding agent to the tooth before proceeding with the cementation of the crown. They are available in a variety of shades and are generally sold as 2-part systems: one syringe contains the catalyst, and a second syringe contains the base. The base can be used independently and can only be cured by light when used in this fashion. When mixed together with the catalyst, the 2 will react to create a dual-cure material. This RC type should be used only when adequate light energy can be attained. The placement of anterior veneers is a typical clinical situation where the total-etch light-cure RC is used in conjunction with the more translucent glassy ceramics (such as lithium disilicate).

Total-Etch Dual-Cure RCs
Total-etch dual-cure RCs are administered from a dual-barrel syringe. With these systems, the base and catalyst components combine as they are expressed from the syringe. They are available in a range of shades and are made by many manufacturers. The total-etch dual-cure RC shown as an example in this article is Calibra Ceram (Dentsply Sirona) (Figures 2 to 8). These cements still require independent etching, rinsing, and adhesive steps on the tooth side because of their total-etch formulation. Total-etch dual-cure RC luting cements are excellent options when the crown is less than retentive and in areas of the mouth where light is restricted.

Self-Etch RCs
The most recent category of RCs is self-etching RCs (Figures 9 to 13). This type incorporates the etchant and bonding agent into the cement itself. This classification is sometimes referred to as self-adhesive RCs. A built-in adhesive primer that penetrates the smear layer of the tooth differentiates this cement from other RCs. They are dual-cured, and the excess material can be easily cleaned up after seating the crown, pending an initial 5- to 10-second tack cure at the margins. Self-etch RCs are viable candidates for all retentive and some non-retentive preparations and can be paired with lithium disilicate and zirconia all-ceramic materials.

Generally, the clinician should consider using a total-etch approach when (a) little dentin is present, (b) the tooth can be properly isolated to allow for a dry bonding field, and (c) the preparation is retentive or mostly retentive. A self-etch approach may be considered when (a) little enamel is present, and (b) the tooth preparation is mostly retentive. When dealing with cut enamel, a short 3- to 5-second phosphoric acid etching followed by a self-etch RC is ideal. It is important to remember that over-etching or under-etching may reduce the strength of the final bonded restoration, so a precise balance must be emphasized during etching in any bonding situation.³

Closing Comments
The last decade has yielded much advancement in the area of indirect restoration materials, giving way to the more efficient final delivery of lab-fabricated restorations with increased longevity. With so many beneficial cement options available in today’s market, it is prudent for clinicians to remain aware of the specifications of each crown preparation and recognize how that ultimately dictates the choice of cement. The retentive or nonretentive nature of the preparation and each individual clinical scenario are the determining factors that must guide the path forward. Gone are the days when a singular cement system could serve all indirect restoration applications. Wise clinicians will stock multiple cements in their practices and maintain clear decision trees regarding when to use a specific restorative material and how to tackle any clinical situation that presents.

References

1. Kim BK, Bae HE, Shim JS, et al. The influence of ceramic surface treatments on the tensile bond strength of composite resin to all-ceramic coping materials. J Prosthet Dent. 2005;94:357-362.
2. Infodentis. Dental cement. Permanent and temporary cementation. http://www.infodentis.com/
   fixed-prosthodontics/dental-cement.php. Accessed January 17, 2018.
3. Alex G. Preparing porcelain surfaces for optimal bonding. Compend Contin Educ Dent. 2008;29:324-335.

Dr. Simos maintains private practices in Bolingbrook and Ottawa, Ill. He received his DDS degree from Chicago’s Loyola University and is the founder and president of the Allstar Smiles Learning Center and client facility in Bolingbrook, where he teaches postgraduate courses to practicing dentists on cosmetic dentistry, occlusion, and comprehensive restorative dentistry. He is an internationally recognized lecturer and leader in cosmetic and restorative dentistry. He can be reached via the website allstarsmiles.com, via the email address cmesmile50@gmail.com, or via the Twitter handle @allstarlc1.

Disclosure: Dr. Simos reports no disclosures.

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Dental practitioners are encouraged to use a composite material for the first time by an advertisement, a review, or word of mouth. Continued use of that restorative product is determined by the comfort zone the dentist attains with that material. Smoothness, a shade-blending effect for optimal aesthetics, nonstick handling, and an ability to polish easily are among the properties that clinicians look for in determining their go-to materials.

The Importance of Filler Particle Design
The size and shape of composite filler particles are vital to creating optimal success with the material. Most brands of composites contain irregularly shaped and sized fillers. This makes polishing and shade-blending a difficult challenge. In this article, a pair of clinical case examples will showcase the use of a recently introduced composite (Estelite Sigma Quick [Tokuyama Dental America]) that has 100% spherical fillers with an average particle size of 0.2 μm.

In Figure 1, one can note the sand-like spheres instead of particles with irregular edges.¹ This particle design leads to smooth and more easily polished restorations. It also contributes to longevity and excellent physical properties. The 100% spherical fillers allow blending within several shades to create an excellent transition between tooth structure and composite. Particle diameters of 0.2 μm are known to produce the best balance of material properties and aesthetics.² Well controlled equivalent particle size allows these composites to absorb and blend in with light reflected off surrounding teeth, creating a true chameleon effect.

Wear resistance is also enhanced with a smaller, spherically shaped particle design. Wear from the opposing arch is virtually zero compared to similar composites. In addition, wear to opposing teeth is truly minimal. Laboratory tests have shown that gloss is retained, even after 5,000 cycles of abrasion on the surface of the composite.³

Abrasive forces can “pluck out” the chunks of nonspherical fillers, leaving behind craters that are not as polishable as a smooth surface. Due to their shape, spherical fillers can rotate and move during polymerization. Therefore, there is less polymerization shrinkage and less marginal leakage between the restoration and cavity walls. Polishing nonspherical fillers can lead to voids in polished surfaces that may cause staining and leakage in the future.

Aesthetic Characteristics
Opalescence that is similar to natural tooth structure is easier to attain with spherically filled composites. High gloss retention is observed as well due to tooth-like diffusion and refraction. The spherical particle structure leads to a higher glossiness and enamel-like reflection/refraction compared to composites with an irregular particle structure.⁴ Higher diffusion and light refraction results in a material that will offer the ability for excellent aesthetic blending with adjacent tooth structure. Spherically filled composites reached 90% glossiness after only one minute of polishing, compared to a prominent composite material with irregular filler size that achieved 70% glossiness in the same period of time.^5,6

CASE 1
A patient presented with failing amalgam restorations on teeth Nos. 28 to 31 (Figure 2). She requested replacements for all 4 amalgam restorations. The patient was told that tooth No. 30 was quite undermined and that a crown would be the restoration of choice. However, she still opted for replacement of the amalgam with a direct composite filling. All 4 teeth presented with areas of decalcification. She was told that color match could be difficult due to the multiple shades observed in the surrounding tooth structure.

The patient was given infiltration anesthesia buccal to tooth No. 30 (Articaine 4% [Septodont]) and a mandibular block injection (Lidocaine 1.8%). Prior to the injection, the anesthetic used for the mandibular block was buffered (Onset [OraPharma]), carefully following the manufacturer’s instructions. The author’s clinical experiences with this added step have demonstrated that buffering the anesthetic provides more rapid and effective anesthesia, particularly for mandibular blocks.

The amalgam restorations were removed using a No. 556 carbide bur in an electric high-speed handpiece (COMFORTdrive System [KaVo]) (Figure 3), and all of the remaining decay was removed using a No. 4 round bur in a slow-speed handpiece. Caries removal was then verified using a caries indicator paste (VistaRed Caries Indicator [Vista Dental Products]). The deepest decay area was covered with a thin layer of TheraCal LC (BISCO Dental Products) as an indirect pulp cap/barrier prior to composite placement. Prepared areas were cleaned with a chlorhexidine gluconate disinfecting scrub (Consepsis [Ultradent Products]) that also reduces potential post-op sensitivity.

The enamel was selectively etched with 35% phosphoric acid gel (Ultra-Etch [Ultradent Products]) for 15 seconds. Next, a single component fluoride-releasing bonding adhesive (Bond Force [Tokuyama Dental America]) was scrubbed onto exposed dentin and enamel surfaces for 20 seconds. The wetted areas were then gently dried with oil-free air for 5 seconds and then dried for an additional 5 seconds with a moderate and stronger stream of air. The bonding agent was light cured for 10 seconds (Bluephase [Ivoclar Vivadent]).

The restorations were placed incrementally to allow for optimal interproximal contacts. Composi-Tight 3D Fusion (Garrison Dental Solutions) wedges and sectional matrices were placed and adapted (Figures 4 to 6). Tooth No. 31 was restored first, followed by tooth No. 30 and then teeth Nos. 28 and 29. In each case, a flowable composite (Surefil SDR flow+ [Dentsply Sirona Restorative]) was added to the proximal box areas, and a small layer was placed on the occlusal floor. Estelite Sigma Quick composite was then placed in 2 shades due to the decalcification and tooth discoloration. Initially, OA2 opaque shade was placed, followed by enamel shade A1. Estelite Sigma Quick has an extended working time (90 seconds or more under ambient light) and it is nonsticky with good packability.

Finishing and polishing was easily accomplished using Rally Mini Polishers (Garrison Dental Solutions) and Sof-Lex Spiral polishers (3M) (Figure 7).

CASE 2
A patient appeared with a broken composite filling on tooth No. 9, which had been initially restored following an accident 10 years earlier. Tooth No. 8 presented with a chipped and stained composite restoration as well, but the patient refused treatment on this tooth (Figures 8 and 9). Further treatment was suggested, including, but not limited to, orthodontic care, but the patient refused this as well. The patient was advised that his bite-related issues could lead to a shortened lifetime of any restoration and that a nighttime appliance would be essential to protect any restoration if orthodontic treatment was not initiated.

At the patient’s initial appointment, maxillary and mandibular alginate impressions were taken. After these models were poured, composite resin was added to recreate the broken incisal and proximal edges of tooth No. 9 on the maxillary model. A palatal matrix was then created using a fast-set putty impression material (Virtual Putty [Ivoclar Vivadent]). This matrix is an indispensable aide in restoring Class IV incisal edge damage (Figures 10 and 11).

The remainder of the old restoration was removed with a No. 556 high-speed carbide bur. The labial margin was established with an irregular long bevel to hide the marginal area using a course diamond (No. 1516.8 [Microcopy]). Labial and palatal areas were then sandblasted (MicroEtcher II [Zest Dental Solutions]), and the cavosurface margins were etched using a 35% phosphoric acid gel (Ultra-Etch [Ultradent Products]). This was followed by application of the self-etching bonding adhesive Bond Force.

The supra-nano spherical particle structure of Estelite Sigma Quick makes it an excellent option for anterior as well as posterior restorations. It was determined that 2 or 3 shades would work best for this restoration. Estelite Sigma Quick’s excellent ability to blend in allows for treatment success in one shade or with multiple shades and tints. It should be noted that it also stays in position with no obvious slumping, making it easy to handle for restorations involving anterior teeth.

The palatal matrix was then placed behind the upper incisors. The lingual shelf was placed on the matrix, using Estelite Sigma Quick shade WE with a carver (Hollenback 6 [Premier Dental Products]) (Figure 12). Shade OA1 was placed over the beveled labial margin in an extremely thin layer to conceal the labial fracture line. Next, Shade B1 was also placed in a thin layer to form the final contours of the restoration (Figure 13). A composite instrument (Microfil composite instrument Gold [Almore International]) was used to create a smooth and continuous layer. This was followed by a thin natural bristle paint brush to achieve prepolish contours. All the surfaces were light cured for 10 seconds using the Bluephase curing light.

The restoration was initially smoothed using a flame-shaped extra fine diamond polishing bur (Microcopy). Line angles and further anatomy were created using Super-Snap Rainbow Polishers (Shofu Dental). The final polish was accomplished by a silicone polishing brush and felt discs with Enamelize Polishing Paste (Cosmedent) (Figure 14). The creaminess and excellent handling properties of Estelite Sigma Quick made these restorations simple to create and easy to polish.

CLOSING COMMENTS
The author has been using Tokuyama’s Estelite Sigma Quick, a supra-nano scale composite, for the past 6 years and has been extremely happy with its properties and long-term success. Working with a 100% spherical filler composite has been a most pleasant experience. It possesses the aesthetic qualities and handling characteristics that clinicians are looking for in a composite restorative material.

Furthermore, in the rapidly changing world of dentistry, it is rare to find a material that stands the test of time. Newer materials aren’t necessarily better. It is up to the practitioner to learn about the properties, benefits, and drawbacks of the material options available. The ideal composite handles well, is creamy and easy to manipulate, blends well, and lasts a long time without volumetric or marginal change. Spherical supra-nano composites fall into this category.

This class of composite resin materials deserves to be tested by the astute clinician as a versatile and quality material option for both posterior and anterior direct composite restorations. The only way to truly judge a dental product is to try it!

References

1. Source: Tokuyama Research and Development Center, Japan.
2. Yuasa S. Composite oxide spherical particle filler. DE: The Journal of Dental Engineering. 1999;89:33-36.
3. Inoue G, et al. Wear resistance of new composite resin (first report). Journal of the Japanese Society for Dental Materials and Devices. 2007;26:116.
4. Kurokawa H, et al. Temporal change of polished surface of composite resin. Japanese Journal of Conservative Dentistry. 2007;50(special issue):17.
5. Inokoshi S. Pursuing color matching of crown-color fillers. Dental Outlook. 1996;88:785-821.
6. Inokoshi S. Color of composite resin filling—opacity and light diffusion properties. DE: The Journal of Dental Engineering. 2007:5-8.

Dr. Auster, a graduate of the University of Pennsylvania School of Dental Medicine, has 30 years of experience in cosmetic and reconstructive dentistry at his private practice in Pomona, NY. In 2016, he completed 2 terms on the board of directors of the American Academy of Cosmetic Dentistry (AACD). He also is a member of the leadership committee and was named the AACD Humanitarian of the Year in 2015. Dr. Auster is founder and past-president of the New York Affiliate of the AACD, the Greater New York Academy of Cosmetic Dentistry. He is a Dawson Scholar and received a Concept of Complete Dentistry Award from the Dawson Academy. Dr. Auster’s volunteer work includes 9 years of volunteer dentistry in Jamaica with Give Back a Smile, Donated Dental Services, and Smiles for Life. His office has contributed more than $40,000 to children’s charities in the past 3 years. He has received a Certificate for International Voluntary Service from the ADA. He is listed as one of Dentistry Today’s Leaders in Continuing Education and is a member of the Catapult Education Speakers Bureau. He conducts hand-on workshops, webinars, and full-day seminars focusing on comprehensive dentistry and discovering renewed passion in dentistry. He can be reached at (845) 364-0400 or via email at drpauster@gmail.com.

Disclosure: Dr. Auster has received compensation from Tokuyama Dental Corporation for writing this article.

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This clinical case report will outline materials and clinical steps to do just that. Furthermore, the latest use of adhesive cements, glass fiber-reinforced posts, core materials, and all-ceramic crowns needed to accomplish this task, will be showcased.

CASE REPORT
Diagnosis and Treatment Planning
Recently, a 50-year-old male was referred to me after the fracture of tooth No. 10 and subsequent endodontic therapy. He was asymptomatic, negative to percussion, and showed no oral signs of inflammation and/or infection. The radiograph indicated a normal periodontal ligament, and surrounding osseous tissue appeared normal (Figure 1). The patient had some missing teeth, and the remaining teeth displayed large amalgams and some composite bonded restorations. There was an end-to-end anterior incisal relationship (Figure 2). An overall treatment was established with the area of No. 10 needing immediate therapy. The specific therapy would include building up the tooth with a post-core followed by the fabrication and placement of an all-ceramic crown as the definitive restoration.

All the necessary materials were assembled to accomplish this task. This included drills, adhesives, cements, post, and core materials (3M) (Figure 3).

Clinical Protocol
Before any dehydration of the teeth took place from our clinical procedures, an accurate shade was taken utilizing a spectrophotometer (VITA Easy Shade V [VITA North America]) (Figure 4). A photo was taken (Nikon 3300 DSLR camera) and printed out (Lester Dine).

Figure 1. Pre-op radiograph, tooth No. 10.

Figure 2. Pre-op labial view, endo tooth No. 10.	Figure 3. Dental materials (3M) utilized for post-core.

The first step in the placement of a post was to analyze the radiograph to gain a sense of length and width of the canal for proper post selection. There are many recommendations regarding this matter. The clinician should remove as little intraradicular dentin as possible so as not to weaken the root; this is dependent on the endodontic preparation and calcification level. For long-term success, it is important to leave at least 5.0 mm of apical gutta-percha to act as a seal, with placement of the post approximately two thirds down the root. The initial access opening had a temporary filling which was removed using an electric handpiece (Forza ELM [Brasseler USA]). The access area was then enlarged somewhat to follow tooth morphology and to act as an anti-rotation component (Figure 5). The author prefers an electric handpiece due to controlled torque, RPM reduction, and the quieter nature of the procedure.

The process of canal preparation was initiated using a flexible Gates Glidden end-cutting drill to remove the desired amount of gutta-percha (Figure 6). Once the gutta-percha was removed, the appropriate size post was selected. The size selection was done through measurements of the canal and careful review of the radiograph.

The kit to be utilized in this case was the very latest 3-D Fiber Post from 3M. This clinical product represents a true advancement in post design. The key enduring feature of the 3-D fiber-reinforced glass post is that the inherent flexural modulus is similar to that of dentin. The post has a knurled coronal portion to engage the core material. It is 60% parallel glass fibers in a resin matrix that has been presilanated to enhance chemical bonding. The microstructure creates an ideal surface for mechanical interlock. The components of this system include the 3-D post, 35% phosphoric acid gel (Scotchbond Etchant [3M]), bonding adhesive (Scotchbond Universal [3M]), self-etching dual-cured resin cement (RelyX Unicem 2 [3M]), bulk-fill core material (Filtek Bulk Fill [3M]), and reamers.

Figure 4. Taking proper shade with VITA Easy Shade V (VITA North America).	Figure 5. The access opening was enlarged slightly.
Figure 6. Initial removal of gutta-percha with Gates Glidden drill.	Figure 7. Preparation of canal with reamer.
Figure 8. Try-in of red 3-D Fiber Post (3M).	Figure 9. Try-in of stock core over adjusted post.
Figure 10. Injection of RelyX Unicem 2 (3M) into the canal.	Figure 11. Using a bonding adhesive (Scotchbond Universal [3M]) to coat the 3-D Fiber Post.
Figure 12. Compression of the composite (Filtek Bulk Fill [3M]) (shade A3) onto the post.	Figure 13. Light curing the core material (Elipar Deep Cure LED [3M]).
Figure 14. Performing gingivoplasty with a soft-tissue diode laser (Picasso Lite Laser [AMD LASERS]).	Figure 15. Completed IPS e.max (Ivoclar Vivadent]) lithium disilicate crown.

Once the gutta-percha was removed, the appropriate size reamer (corresponding to the post size) was utilized to extend to the desired length (based upon the initial depth). This reaming portion was done slowly, with consistent torque and an up-and-down motion, to gently enlarge the canal. The taper of the reamer used was the exact taper and dimension of the post (Figure 7).

Once the canal was flushed with water and dried out, the preselected post size was tried in to determine the proper length (Figure 8). The post should extend coronally close to the anticipated length of the final crown. A silicone ring was used to mark the post length at the point where it would be cut. Then, the post was cut in about one second using a thin diamond disk with a straight laboratory handpiece. The advantage of this post system is that, once bonded into the canal, the functional load will be dissipated throughout the entire root to prevent buildup of peak forces (unlike that which can take place with a stiff modulus post that could lead to root fracture). These posts are very strong with a flexural modulus of 1,600 MPS.

Once the adjusted post was tried in, a stock polycarbonate crown form of appropriate dimensions was tried in over the post (Figure 9). Another method is to have a 0.020” polypropylene stent made from a prepared preoperative model. The key to success with this system is that all the components are tied logically and consecutively together. To debride, clean, and etch the canal, the 35% phosphoric etch (Scotchbond Etchant) was placed on the coronal structure and in the canal for 20 seconds. Once rinsed and dried thoroughly, a paper point was placed in the canal to absorb any residual water present. The next step was to place the Scotchbond Universal adhesive on the coronal aspects of the root. It was scrubbed in for 20 seconds, dried, and light cured (Elipar Deep Cure LED [3M]) for 10 seconds.

In my office, all the clinical work is done with the aid of magnification and LED illumination using an eyewear system fabricated by Designs for Vision. This is important in the next step, in which an orange filter was utilized to prevent premature polymerization of the cement. Under the orange filter, the post was covered with the luting agent (RelyX Unicem 2) first, and then, using a very small endo tip, the cannula was extended to the deepest apical location and injected as it was withdrawn. This protocol completely engulfed the canal with the resin cement. The self-etch, dual-cured cement bonds tenaciously to the intraradicular canal walls and to the post (Figure 10). Once the position was verified, the post was stabilized by transillumination through the post via use of the LED curing light. Scotchbond Universal was also placed on the post extension and light cured for 10 seconds (Figure 11).

After post placement, an appropriately shaded core material (Filtek Bulk Fill, shade A3) was compressed onto the post to engage the undercuts (Figure 12). Before curing the compressed core material, the core form was filled completely with the composite resin core material, making certain to eliminate any voids. The core was positioned properly according to tooth position, angulation, and occlusal scheme. Once satisfied with that, the entire mass was light-cured with the Elipar Deep Cure LED placed as close as possible to the core. It was light cured from the labial, lingual, and incisal for 10 seconds each (Figure 13). The curing light would cure the core material completely, up to a depth of 5.0 mm.

After the initial preparation of the tooth for a full-coverage lithium disilicate crown (IPS e.max [Ivoclar Vivadent]), a soft-tissue diode laser (Picasso Lite [AMD LASERS]) was utilized to perform a gingivoplasty. This was also done to more easily allow the placement of a ferrule of at least 2.0 mm onto natural tooth structure to support and strengthen the entire tooth-root-restoration complex (Figure 14). After taking the final vinyl polysiloxane impression (Extrude [Kerr]), a provisional was constructed from an impression matrix of the core and an opposing impression was secured.

The dental laboratory team pressed the crown using a shade darker ingot (IPS e.max Press Multi [Ivoclar Vivadent]) than the central incisors to match tooth No. 7.

The restoration was returned from the dental lab and the usual cementation protocol was carried out. The intaglio surfaces were silanated for 60 seconds and dried. Then, the crown was adhesively cemented using a self-etching self-adhesive resin cement (RelyX Unicem 2) (Figure 15).

CLOSING COMMENTS
There are many advantages found in the clinical protocol featured in this case report article. The clinician can take a decimated endo tooth, build it up, place an aesthetic crown, and reinforce the entire tooth-restoration complex. All components act as one, being that mechanical and chemical bonding take place on every level with every material. Certainly, the clinical outcome is a very durable and aesthetic restoration that is physiologically integrated within the natural dentition. Furthermore, by observing sound clinical principles related to the biological width, minimally invasive preparation techniques, and proper use of the diode laser, the soft-tissue response is very favorable.

Using the clinical protocol described herein, dentists can offer premier services, done efficiently and predictably, and resulting in patients who will be ever grateful for their restored smiles.

Dr. Braun received his master’s degree in prosthodontics and his DDS degree at the University of Michigan. In Saginaw, Mich, he has maintained a full-time private practice specializing in prosthodontics for more than 30 years. His staff appointments have included the University of Michigan School of Dentistry and hospitals in Ann Arbor and Saginaw. For 15-plus years, Dr. Braun has lectured internationally, including presentations at more than 20 ADA-affiliated state dental associations. He has lectured at the ADA, Hinman, Greater New York, and Chicago Midwinter meetings. He also conducts hands-on workshops, webinars, and has published a variety of articles on aesthetic restorative dentistry for journals. Several major dental manufacturing companies utilize his professional skills on a consultant basis for the development of new products. Dr. Braun continues to be selected by Dentistry Today as a Leader in Continuing Education. He can be reached at (989) 793-5551, or via email at jbraundds@sbcglobal.net.

Disclosure: Dr. Braun reports no disclosures.

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High-translucency (HT) ingots have improved the aesthetic quality but cannot always mask the color of a dark preparation. Zirconium oxide restorative materials got their start as tooth-colored replacements for traditional full-gold crowns on posterior teeth. Conservative posterior tooth preparations, similar to prep designs for gold, could be done because of the high strength of the material. However, early zirconia materials were very opaque and only indicated for first or second molars. Because zirconia is a metallic oxide (zirconium oxide), it can be used like a PFM crown to cover dark tooth preparations, and it can also be cemented with a conventional (nonadhesive) cement. Lithium disilicate and zirconia blocks can be designed and milled by the lab team to full contour, making them less labor intensive and less costly to the doctor. Since there are certain clinical indications where zirconia might be a desirable choice for use in the aesthetic zone, the challenge has been to provide the necessary aesthetic characteristics that are required for anterior restorations.

The following case report looks at an anterior case replacing previously placed feldspathic full-coverage restorations, while comparing lithium disilicate to a new aesthetic zirconia material (ArgenZ Anterior [Argen]).

CASE REPORT
A patient presented with a cohesive porcelain fracture on the facial surface of her right central incisor (tooth No. 8) that had been temporarily repaired with composite resin (Figure 1). Since it would be very difficult to match the old feldspathic material, it was decided to replace both the right (No. 8) and left (No. 9) central incisors with new all-ceramic restorations. The fracture in No. 8 was a longitudinal cohesive fracture in the facial ceramic (from the incisal edge to mid-tooth), so a high-strength material was considered for the replacement. In many dental practices, milled ceramic restorations, whether made by the lab team or at the chair, are becoming more commonplace because of reduced costs. In order to compare the aesthetic qualities of lithium disilicate (IPS e.max [Ivoclar Vivadent]) versus the anterior zirconia (ArgenZ Anterior), 2 separate cases would be fabricated by the lab team.

Figure 1. A preoperative view of feldspathic restorations on the right and left central incisors (teeth Nos. 8 and 9), prior to replacement for a facial fracture on No. 8.	Figure 2. The lithium disilicate restorations tried in on Nos. 8 and 9.
Figure 3. The anterior zirconia restorations, in place on Nos. 8 and 9.	Figure 4. An ArgenZ Anterior (Argen Corporation) restoration on tooth No. 8 and an IPS e.max (Ivoclar Vivadent) restoration on tooth No. 9.
Figure 5. An IPS e.max restoration on tooth No. 8 and an ArgenZ Anterior restoration on tooth No. 9.	Figure 6. Both ArgenZ Anterior restorations were tried in on teeth Nos. 8 and 9.
Figure 7. A digital photo in isolate shade mode (EyeSpecial II [Shofu Dental]) was used to communicate the shade and characterization to the dental technician.	Figure 8. A milled polymethyl methacrylate (PMMA) prototype restoration was made and tried in to evaluate tooth contours, reflective line angles, incisal length, and emergence profiles.
Figure 9. The facial contours and disto-facial line angle of the PMMA prototype were adjusted using an 8-fluted carbide composite finishing bur (Komet), making minor corrections as desired by the patient and doctor.	Figure 10. The patient approved the PMMA prototypes after adjustments, then it was sent to the lab team to be scanned for the milling of the definitive restorations. The patient wore the original provisional restoration in the interim.

Material Comparison and Selection
Figure 2 shows the lithium disilicate replacement restorations for teeth Nos. 8 and 9 tried in. The aesthetic match of the IPS e.max crowns was very good, with no problem observed in the value of the restorations.

Figure 3 shows the anterior zirconia replacement restorations for teeth Nos. 8 and 9 tried in. The aesthetics of the ArgenZ monolithic restorations was excellent when compared to the lithium disilicate restorations, with no decrease in the aesthetic quality observed.

To further compare the 2 materials, they were then placed side by side on adjacent preparations. Figure 4 shows an ArgenZ Anterior restoration on tooth No. 8 and a lithium disilicate restoration (IPS e.max) on tooth No. 9. Figure 5 is showing the opposite with a lithium disilicate restoration (IPS e.max) on tooth No. 8 and an ArgenZ Anterior restoration on tooth No. 9. Looking at both possibilities clinically in the patient’s mouth, it was impossible to discern any visible differences. The 2 anterior zirconia crowns, tried in on both teeth Nos. 8 and 9, can be seen in Figure 6.

Although any of these completed pair of restorations would have been a satisfactory end result for many patients, this case provided some challenges that typically can occur in the aesthetic zone. One problem with monolithic restorative materials is that if any characterization (such as stain and glaze) is done to the milled restoration, any adjustment to make even the most minor changes in the facial contour will adversely affect the aesthetic outcome. While in posterior restorations this may not be an issue, it can be a major problem for anterior restorations, requiring extra laboratory steps.

After comparison of these 2 materials, and since the aesthetic quality and value of the zirconia restorations was excellent, it was decided that the final case would be made using the ArgenZ Anterior material.

Aesthetic Zirconia for Anterior Teeth
ArgenZ Anterior was designed to give the clinician an aesthetic alternative for anterior full-coverage restorations when aesthetics and flexural strength are primary concerns. According to the manufacturer, there are several advantages with this new material: ArgenZ Anterior achieves 25% more translucency over HT zirconia, including ArgenZ Esthetic. This increased translucency comes from its unique composition that contains cubic zirconia. The crystalline structure of the cubic zirconia refracts light differently, increasing translucency and closely mimicking the appearance of a tooth’s natural dentin. In addition, ArgenZ Anterior has a flexural strength of 765 MPa, whereas the industry average for super translucent zirconia is around 650 MPa.

Milled PMMA Prototype to Customize the Definitive Restoration
In this case, the patient failed to approve the contours of either pair of completed restorations, so an attempt was made to make minor alterations in facial contour and embrasure shape to please the patient. Since this alteration of the crowns ruined the surface aesthetics, it was sent back to the laboratory to have a polymethyl methacrylate (PMMA) provisional made to verify that the corrections made to the original restorations would be acceptable before milling a second set of restorations. In hindsight, had this step been done first, it may have prevented the need to remake the ceramic restorations.

Prior to sending back the restora­tions for the remake, the shade was verified using a digital camera (EyeSpecial II [Shofu Dental]) in isolate shade mode so that the true colors of the teeth could be better visualized by the dental technician (Figure 7).

The recontoured ceramic restorations were then sent back to the laboratory where they were digitally scanned and a PMMA provisional restoration milled. The importance of this step should now be very clear. The facial position of the crowns relative to the lateral incisors, surface texture (or lack thereof), incisal length, prominence of the facial proximal (reflective) line angles, angle and depth of the facial embrasures, and sharpness or roundness of the mesial and distal incisal angles, are but a few nuances that need to be verified visually by the patient with a very exact prototype restoration (Figure 8). Any further modifications of the PMMA, if needed, can be easily accomplished at the try-in appointment (Figure 9). In this case, the patient originally had a diastema between teeth Nos. 8 and 9, so any black triangles in the gingival embrasure area needed to be compensated for in the mesial contours of the restorations to avoid negative space.

Final acceptance of the restoration contours by the patient, as done in the PMMA provisional restoration, were then scanned by the lab team into a digital file. Once that step was accomplished, an exact replica was then milled using the selected zirconia block and delivered to the patient (Figure 10).

Delivery of the Completed Case
The milled restorations are shown in Figure 11 on the master model. A cutaway view of an ArgenZ Anterior crown shows how precise the fit was to the master model (Figure 12). Final contouring, polishing, and glazing were then accomplished by the dental technician to complete the restorations (Figure 13).

The completed ArgenZ Anterior case was tried in and approved by the patient. Having satisfied the aesthetic desires of the patient, the case was ready to be cemented in. One clinical advantage of zirconia is that it can be conventionally cemented using a chemically bonded bioceramic luting cement (such as Ceramir Crown and Bridge [Doxa]), or adhesively cemented using a resin cement. For this case, a resin cement was chosen because of the aesthetics at the facial margin, should the patient experience gingival recession in the future as happened with her older restorations.

When using resin cement (such as Maxcem Elite Chroma [Kerr]) (Figure 14), a zirconia primer (such as Z-PRIME Plus [BISCO Dental Products]) or a universal primer (such as Monobond Plus [Ivoclar Vivadent]) is recommended to enhance the bond of the resin cement to the surface of the zirconia.

A universal bonding agent primer and adhesive (OptiBond XTR [Kerr]) was applied to the preparations in consecutive steps, air-thinned to evaporate the solvent, then light-cured according to manufacturer’s specifications. The internal surfaces of the zirconia crowns were treated with 2 coats of Z-PRIME Plus, then air-dried (Figure 15). The resin cement (Maxcem Elite Chroma) was placed into the restorations, and they were seated to place (Figure 16). A unique feature about this cement is that there is a color change from pink to tooth color to indicate when the gel set phase is complete. This gives the clinician a precise indication when to begin the clean-up process, preventing cleanup that can often be initiated too early in the setting process, possibly compromising the bond strength of the cement to the tooth. When the color change was complete (approximately 2 minutes), the marginal excess was cleaned up (Figure 17), then the restorations were light-cured (Demi Ultra [Kerr]). Figures 18 to 20 show the completed ArgenZ Anterior restorations. (Note: Zirconia restorative materials often display a slightly higher value than natural teeth when photographed due to less light absorption from the flash.)

Figure 11. A facial view of the milled ArgenZ Anterior restorations immediately after milling prior to the finishing and glazing by the dental technician.	Figure 12. This sectional view shows the intimate fit of the definitive restoration on the master die.
Figure 13. After some minor characterization and glazing, the completed restorations are shown on the master dies.	Figure 14. A zirconia primer (Z-PRIME Plus [BISCO Dental Products]) and resin cement (Maxcem Elite Chroma [Kerr]) were used in this case.
Figure 15. The zirconia primer (Z-PRIME Plus) was applied to the internal surface of the restorations prior to cementation.	Figure 16. The restorations, shown after filling with the self-etching resin cement and placement on the teeth. Note the pink color of the cement indicating that the gel set has yet to be reached; cleanup should not be initiated at this time.
Figure 17. Once the resin cement reached a gel set and turned to a tooth color, it was safe to remove marginal excess and floss the contacts without compromising the bond strength of the cement to the tooth or restoration.	Figure 18. Close-up retracted view immediately after cementation of the completed the ArgenZ Anterior restorations on teeth Nos. 8 and 9.
Figure 19. A smile view of the definitive restorations after cementation. (Note: The patient plans on replacing the maxillary lateral incisors and possibly the canines and premolars at a later time.)	Figure 20. A postoperative view (at one month) of the patient’s smile.

DISCUSSION
This case was particularly challenging, since previously placed monochromatic feldspathic veneers with gingival recession and root exposure were present on the rest of the teeth. This is an example of real world dentistry! The patient could not afford to replace all the restorations at once; however, she did not want to necessarily match the color and root characterization of the remaining teeth. The challenge for both the dentist and the ceramist was to meet the expectations of the patient, whose desire was to eventually replace the old restorations with slightly higher value restorations to cover the exposed root surfaces and to fill the negative spaces of the gingival embrasures. The high lip-line also contributed to a compromised aesthetic result during this transition time for the patient. Future treatment will include the replacement of the remaining restorations in the aesthetic zone to better match these new central incisors when the patient is ready.

Technical Perspectives
Here are some recommendations to help the clinician maximize the aesthetic result when using anterior zirconia restorations. Although this material is used in the posterior areas much like metal, as far as tooth reduction is concerned for aesthetic areas, it is best to reduce the tooth as one would for a pressed ceramic restoration. This added reduction will give better depth and translucency to the material, also enabling an increase in value when a restoration is being placed over darker tooth structure, to create a more pleasing aesthetic result.

Take digital photos prior to preparation to avoid an increase in value due to tooth desiccation and to capture subtle tooth characterizations, incisal translucency, and surface texture of the tooth to be matched. After shade selection that is first based upon value, then hue and chroma, photograph several shade guides close to the target shade next to adjacent teeth. This will allow the ceramist to more accurately determine the desired shade of the restoration.

As previously stated, it is important to use an indirect digital PMMA provisional restoration for aesthetic acceptance from the patient prior milling the zirconia restorations so that the contours will not need adjustment at the delivery appointment. Finished zirconia restorations that are glazed and/or polished should not be subject to facial postoperative changes chairside by the dentist.

For postoperative care, use a nonabrasive, small-particle size prophy paste that is proven to kind to ceramic surfaces (such as Proxyt Fine [Ivoclar Vivadent]) for all hygiene appointments. This will provide longevity to the surface of the definitive restorations, particularly ones that are glazed.

CLOSING COMMENTS
In the author’s opinion, the results seen in this clinical case report demonstrate that the new zirconia material (ArgenZ Anterior) is a viable aesthetic and high-strength option for anterior full-coverage restorations, when indicated.

Acknowledgment
The author would like to acknowledge the technical excellence of Mr. Vincent Devaud, CFC, MDT, Digital Smile Design Instructor and Consulting Services, Beverly Hills, Calif, for the restorations created and shown here.

Dr. Lowe received his DDS magna cum laude from Loyola University School of Dentistry (1982). Following graduation, he completed a general practice residency program at Edward Hines Veteran’s Administration Hospital. After completion of dental school, he taught restorative and rehabilitative dentistry on a part-time basis and an additional 5 years on a full-time basis at Loyola University School of Dentistry as well as building a private practice in Chicago, where he currently practices part time in addition to his full-time practice in Charlotte, NC. He is a member of Catapult Elite Speakers’ Bureau and has Fellowships in the AGD, International and American Colleges of Dentists, Academy of Dentistry International, Pierre Fauchard Academy, the International Academy of Dento-Facial Aesthetics, and the American Society for Dental Aesthetics. In 2004, he received the Gordon Christensen Outstanding Lecturer Award for his contributions in the area of dental education. In 2005, he was nominated to receive Diplomate status on the American Board of Aesthetic Dentistry, an honor shared by fewer than 50 dentists in the entire United States. Throughout his career, he has authored and published several hundred articles in many phases of cosmetic and rehabilitative dentistry. He can be reached at (704) 450-3321 or at boblowedds@aol.com.

Disclosure: Dr. Lowe reports no disclosures.

Also By Dr. Lowe

A One-Visit Option: An Alternative to Traditional Ceramic Restorations

Putting Material Science to Work: Use of a Self-Polishing, Universal Nanohybrid Composite

A New and Economical Concept for No-Prep Veneers

One major problem is that most dentists rely on only one impression material to address all clinical needs. Clinicians may be better served to stock more than one type of impression material to accommodate a variety of clinical situations.

This article will discuss the 3 most common classifications of impression materials: polyether (PE), vinyl polysiloxane (VPS), and a hybrid material called vinyl polyether siloxane (VPES). In addition, 3 mini case reports will be presented, focusing on the impression to give the clinician an understanding of the rationale that may be used when choosing the best impression material from different types of materials in various clinical situations. This article will assist the clinician in making optimal impression material choices.

Figure 1. Impression technique: Expressing light-body wash material around prep and teeth.	Figure 2. Impression technique: Filling the dual-arch tray with a heavy-body impression material.
Figure 3. Impression technique: Placing the loaded dual-arch tray into the mouth.	Figure 4. Impression technique: Final impression.

Impression Technique
The impression technique utilized in all cases presented in this article is the heavy-body/light-body wash technique where the light-body or wash material is placed directly around the prep and adjacent teeth (Figure 1). Simultaneously, the impression tray is filled with a heavy-body material (Figure 2), and the heavy-body material is then immediately inserted into the mouth so that both materials polymerize together (Figure 3). (It should be noted that the working times of each category of material and set time of each category of material vary greatly. Manufacturer suggested working times and set times were, and always should be, closely followed.) Once the set time elapses, the impression was taken out of the mouth and evaluated under 3.5x loupe magnification (Figure 4).

CASE 1
A new patient presented without an anterior fixed partial denture (FPD) from teeth Nos. 7 to 11 (Figure 5), stating that it had fallen out some time ago. Going without teeth did not bother him personally; his real motivation for replacement was his wife’s unhappiness with his appearance. This patient wanted a solution to help mend his domestic disharmony.

CASE 1 Figure 5. Anterior preparation. Figure 6. Polyether (Impregum [3M]) impression showing excellent detail of the captured margins.

The patient was on blood thinners and, while examining his teeth, it was noted that he produced a tremendous amount of saliva and gingival bleeding.

The existing margin of the old bridge was subgingival. The desired preparation design required us to keep the margins of the preparations at the same depth. Care was taken in the impression phase to minimize bleeding (Astringedent [Ultradent Products]) and saliva flow (controlled with cotton rolls) around the preparations.

Polyether
The biggest challenge this case posed was that of moisture control. A PE impression material (Impregum [3M]) was selected for use because of the inherent hydrophilic nature of this material. From a practical standpoint, the PE’s ability to perform in situations where moisture (water, saliva, blood, gingival fluids) is a challenge has set it apart from the other impression materials.¹ As a hydrophilic material, PE has exceptional flow and wettability, both of which allow for a high degree of detail in the impression and the resulting working model. The international standard for detail reproduction requires impression materials to possess the ability to reproduce a line that is 0.02 mm in width or less (a human hair is 0.04 to 0.06 mm), a measurement that PE consistently surpasses in both wet and dry conditions.²

PE was the first of the 3 impression materials to be introduced commercially during the 1960s. The base generally consists of PE macromonomers along with glycol-based plasticizers and silica fillers. The accelerator supplies the cross-linking sulfonate, which is the catalyst for the reaction. Because there is no by-product resulting from polymerization, dimensional stability of the material is retained as the reaction occurs.^1,2

While these traits are certainly laudable, PE impression materials exhibit high rigidity, a drawback that essentially can result in trouble removing the material from a patient’s mouth. Additives in the material, namely plasticizers, have been introduced to combat this rigidity issue, allowing for easier removal from the mouth after polymerization. PE impression materials have also historically been observed to have a bitter taste, causing more than a few complaints from patients throughout the years. However, advancements in the chemical makeup have effectively masked the taste with a minty flavor. Leading brands of PEs include Impregum Penta and Impregum Soft (3M) and Polyjel NF (Dentsply Sirona).

The outcome in this case was an excellent PE impression (Figure 6) that served as the foundation for the creation of a long-lasting FPD that this patient’s wife would appreciate for years to come.

CASE 2
A male patient fractured his molar in the upper left quadrant while eating breakfast (Figure 7). He was a very active and healthy patient and wanted his positive lifestyle reflected in his smile. He was worried that the tooth would need root canal therapy, or even removal. When he heard that the tooth could be returned to normal function with a crown, he expressed relief and wanted to get the restorative work started right away.

Because of the location and prep design (Figure 8) of the tooth, a more advanced VPS impression material would be used in this case.

CASE 2 Figure 7. Pre-op photo of a fractured maxillary left molar. Figure 8. Preparation was done and then the soft tissue was troughed circumferentially (prior to taking the impression) with a diode laser (Picasso Lite [AMD LASERS]). Figure 9. Final vinyl polysiloxane impression (Aquasil Ultra+ Smart Wetting [Dentsply Sirona]).

Vinyl Polysiloxane
VPS impression materials were introduced commercially in the 1970s, about a decade after PEs. The base consists of a siloxane co-polymer with silane terminal groups along with coloring agents and silica fillers. The accelerator supplies a siloxane co-polymer with vinyl terminal groups along with chloroplatinic acid, which is the catalyst for the reaction.³ The chemical process is designated as an addition reaction; this is distinctive from other silicone materials because there are no by-products associated with the polymerization of these molecules.^1,2,4 Similar to PEs, this clean reaction accounts for impressive dimensional stability of the material.

Some studies have indicated the presence of hydrogen gas during polymerization as a result of side reactions taking place within the base; however, the incorporation of palladium as a hydrogen absorber/scavenger, along with improved purification techniques and better proportioning of the materials, has negated this potential problem.²

VPS is naturally hydrophobic, which given the moist environment in which these materials are used, would seemingly qualify as a severe limitation when compared with PEs. However, the simple addition of an intrinsic surfactant has helped to overcome the hydrophobic nature of this material category, providing suitable wettability characteristics. Extrinsic surfactants may also be used on the patient’s tooth to accomplish the same end.^2,4 An example of a direct tooth surfactant is B4 Surface Optimizer (Dentsply Sirona Restorative). It is a credit to the long list of strengths for VPS that deter any negative feedback regarding the proclaimed hydrophobic nature of the material.

The detail reproduction measurements match or exceed the international standard, and flow conditions are excellent, if not ideal.² VPS materials have a desirable rigidity that provides a trouble-free removal process from the patient’s mouth. In addition, and unlike PE materials, VPS materials are naturally tasteless and odorless, though most on the market have been enhanced to contain some form of an artificial flavoring for the comfort of patients. Some leading brands of VPS materials include Imprint 4 (3M), EXAFAST (GC America), Take 1 Advanced (Kerr), Virtual XD (Ivoclar Vivadent), Honigum and StatusBlue (DMG America), AFFINITY VPS (CLINICIAN’S CHOICE Dental Products), SplashMax (DenMat), and many more.

Recent Advances in VPS Impression Materials
As a recent advancement in the VPS category, Dentsply Sirona has introduced Aquasil Ultra+ Smart Wetting impression material, which was used in case 2.

The tooth preparation was carried out with a subgingival margin. A diode laser (Picasso Lite [AMD LASERS]) was used to trough the soft-tissue circumferentially around the preparation. Then, a beautiful and detailed impression was taken of the final preparation (Figure 9).

The idea behind Aquasil Ultra+ Smart Wetting impression material is this: keep the framework of a high-functioning VPS and make it even better, without transitioning to the category of VPES hybrid. Aquasil Ultra was reformulated to produce a VPS impression material that does not compromise in any one area of performance. Specifically, the chemistry was altered so that the polymerization process would yield polyfunctional bonding between molecules, instead of the standard bifunctional, or linear, bonding presented with other silicone reactions. The end result is a matrix of “branched” macromolecules that offer stability in 2 key applications. First and most obviously, the newly reinforced structural design allows for outstanding dimensional stability, inherent material strength, and intraoral tear strength. Second, this improved molecular fortification makes possible the addition of more surfactants to the material without compromising strength. More surfactants equal better hydrophilicity.

The resulting material selection proved to be an excellent one for the patient presented in case 2. A worry-free impression for a worry-free restoration.

CASE 3
A female patient fractured her lower incisor at the gumline and wanted to save the tooth. Endodontic treatment was done and a post-and-core was then placed in the tooth. A circumferential subgingival margin was placed at a depth that provided a minimum of 2.0 mm of tooth structure (ferrule effect) to retain and support the crown (Figures 10 and 11). Because of the depth of the margin, the presence of crevicular fluid presented one of the challenges in capturing an accurate and detailed impression. In addition, bleeding, although minimal, was another factor that could have potentially compromised the outcome and therefore played a role in final impression material selection as well. A VPES was selected for the impression material of choice in case 3.

CASE 3 Figure 10. Buccal view of the preparation. Figure 11. Occlusal view of the preparation. Note the deep subgingival margin placed circumferentially to achieve an adequate ferrule effect. Figure 12. Final vinyl polyether siloxane impression (EXA’lence [GC America]). Note the clear and detailed impression of the subgingival margin.

Hybrid (VPES)
VPES impression materials are the most recent subset of dental impression materials available on the market, having made their commercial debut in the last few years. The developmental aim is very direct: combine the desired attributes of both leading categories of impression materials. Simply put, why settle for a PE or VPS when you can reap the benefits of both?

The chemical composition of a VPES is highlighted by a PE co-polymer that is cross-linked with an organo-hydrogen polysiloxane and a VPS co-polymer. A platinum catalyst is then employed to yield the final molecule, a vinyl siloxanether.³ The resulting material is professed to have the premium qualities of a VPS (stability, tear strength, elastic recovery) coupled with the natural hydrophilicity and flowability of a PE.^1,4 Theoretically, the hybrid material represents the ultimate optimization of traits from 2 well-established and reliable impression materials. In reality, the proposed synergistic effect of combining the PE and VPS has not been as readily apparent as expected. While studies can confirm that the final material is adequate to provide dentists with a third comparable option in today’s market, such a hybrid creation has not yet been shown to be greater than the regular sum of its 2 parts. However, this is not entirely surprising, since the era of the VPES is still in its infancy; more clinical studies are required to make a true comparison of the VPES to its predecessors. For now, the hybrid’s performance with respect to detail reproduction, wettability, tear strength, etc, is very much in line with what has been observed in PE and VPS products. The leading brand in this category of impression materials is EXA’lence (GC America) and was the material of choice for this case.

While this is an impression for which more could go wrong than right, the material selection for the impression was a major part of the successful outcome of the impression itself (Figure 12).

IN SUMMARY
Currently, the 3 most common impression materials are PE, VPS, and VPES hybrid. Each of these material categories exhibits slight advantages over the others, but all 3 are dependable candidates in terms of overall quality. The ever-present competitive streak in the field of dentistry seems to have ensured that no one product outstrips its competitor. What once may have been glaring disadvantages of one material have been more or less mitigated by the need for manufacturers to stay relevant. And so, while the PE, VPS, and hybrid categories differ in their chemical makeup, the manufacturers have provided clinicians with 3 comparable options to choose from, depending upon individual clinician preference and the clinical situation at hand.

Clinicians face daily challenges when preparing for dentures, partials, crowns, bridges, and implant prostheses that, because of the limitations of the impression materials in the past, were often insurmountable. Advancement in the chemical makeup of each impression material category now give the dentist options that can work well in cases that are routine or in the most challenging of clinical situations. It is up to the clinician to understand the different characteristics of the various impression materials and to choose one that is best matched to the specific clinical situation at hand. When this is accomplished, the most accurate reproduction of the dentition and surrounding oral landmarks can be achieved, and the outcome will be the creation of the best possible final prosthesis.

References

1. Burgess JO. Impression material basics. Inside Dentistry. October 2005. dentalaegis.com/id/2005/10/impression-material-basics. Accessed December 6, 2016.
2. Mandikos MN. Polyvinyl siloxane impression materials: an update on clinical use. Aust Dent J. 1998;43:428-434.
3. Sun M. A Laboratory Evaluation of Detail Reproduction, Contact Angle, and Tear Strength of Three Elastomeric Impression Materials [master’s thesis]. Bloomington, IN: Indiana University School of Dentistry; 2011.
4. Re D, De Angelis F, Augusti G, et al. Mechanical properties of elastomeric impression materials: an in vitro comparison. Int J Dent. 2015;2015:428286.

Dr. Simos maintains private practices in Bolingbrook and Ottawa, Ill. He received his DDS degree at Chicago’s Loyola University and is the founder and president of the Allstar Smiles Learning Center and client facility (Bolingbrook), where he teaches postgraduate courses to practicing dentists on cosmetic dentistry, occlusion, and comprehensive restorative dentistry. He is an internationally recognized lecturer and leader in cosmetic and restorative dentistry. He can be reached at cmesmile50@gmail.com, via the website allstarsmiles.com, and on Twitter @allstarlc1.

Disclosure: Dr. Simos reports no disclosures.

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