BACKGROUND
Custom cast posts were first described more than 100 years ago, and utilized the optimal impression techniques, casting, and cementation materials available at that time. In most of the world, cast posts (still taught in some dental schools) have been supplanted in clinical practice by prefabricated posts made either of metallic alloys or from fiberreinforced composite. In even a cursory review of the literature, the evidencebased support for a trend away from metal posts to fiber posts is abundant and conclusive:
• Fiber posts, regardless of brand, are anisotropic and have a modulus of elasticity similar to that of dentin (~20 GPa), which allows the post to flex slightly (microscopically) with the tooth and dissipate stress, thereby reducing the likelihood of damage to the root.14
• Fiber posts are not susceptible to galvanic or corrosion activity; the latter of which is responsible for a high percentage of failures with cast posts5 which, in turn, fail twice as often (clinically) as do prefabricated metal posts.6
• Fiber posts are available in translucent and toothcolored versions (the original black carbon posts are passé), which are aesthetically invisible under all ceramic crowns, veneers and resin restorations, and also mitigate the effects of the dark root syndrome (Figure 1).7,8

Figure 1. Typical gingival darkening created by metal post and core technique.	Figure 2. Cross section of a good quality post which is highly loaded with fibers with no voids.
Figure 3. Cross section of a poor quality post showing lower fiber loading with voids in the matrix.	Figure 4. Cross section of a fiber post with low-fiber and high-resin matrix content.

• Fiber posts (excepting a South American post design that has a metal wire running through its long axis) are more easily and safely removed "by hollowing them out from the inside," should retreatment ever become necessary.912 In fact, cemented metal posts may further limit or complicate endodontic treatment options if these become necessary.13
While all brands of fiber posts appear to have these commonalities, they are not all the same; they can vary considerably from brand to brand in terms of composition and microstructure. The difference in the manufacturing process of the posts can significantly influence their mechanical properties,14,15 and thus their clinical performance. Furthermore, a connection can be found between the data obtained with SEM observations of fiber posts and their clinical behavior. SEM photographs (Figures 2 to 4), taken at the same (700x) magnification, show the variations in size of fiber, orientation, number of fibers, amount of composite, and the relative percentages which varies from fiber post to fiber post. In fact, posts that have more imperfections in the matrix will have a less compact and even structure, and thus are weaker and less resistant to load stress.14
Increases in the mechanical properties (fracture strength) appear directly proportional to the density of fibers and to their interface/bond to the matrix.16 In addition to influencing flexural strength, the fiber type, density, and uniformity of microstructure also affect the radiopacity and fatigue resistance. Figure 5 shows the relative radiopacity of various fiber posts side by side, and Figures 6 to 8 demonstrate the same variation in an extracted tooth that is prepared for a 1.5 mm tapered fiber post. It is obvious that the MacroLock Illusion XRO (CLINICIAN’S CHOICE) is the most radiopaque in this sampling of fiber posts (Figure 7).

Figure 5. Radiograph of various shapes, designs, tapers of early radio-apparent fiber posts.	Figure 6. Radiograph of typical fiber post when prepared for a 1.5 mm taper.
Figure 7. The Macro-Lock Illusion X-RO (CLINICIAN’S CHOICE) shows excellent radiopacity at 1.5 mm post space preparation.	Figure 8. Same tooth radiographed with a popular radio-apparent fiber post.
Figure 9. Scanning electron microscope photograph of intimate adaptation of fiber post, dual cure resin cement and root dentin.	Figure 10. Parallel-sided fiber post of 1.5 mm does not seat in same tooth without more apical removal of dentin structurally weakening the tooth.
Figure 11. A 1.5 mm parallel post with lateral serrations and core bulk again requires more apical dentin removal to seat to same length as the tapered Macro-Lock Illusion X-RO (compare to Figure 7).	Figure 12. A conservative nonflared canal is ideal for a conservative flared fiber post preparation.

Quartz fibers are among the most radiopaque fibers being used,17,18 and the quartz fiber posts have proven superior in fatigue resistance to glass fiber posts15 and to metal posts.19 Fatigue tests can be considered as the most relevant methodological standard for evaluating and predicting the behavior in an oral environment.18 The in vitro studies that more than any other permit the fair prediction of yielding and, therefore, the longterm behavior of the restoration, are the fatigue tests.20,21
Into the 1970s, it was hoped that metal posts could help reinforce weakened endodonticallytreated teeth. In the 1980s, Sorensen, et al20 surmised otherwise. Today there is a growing body of in vitro evidence that if properly placed, low modulus restorations (quartz fiber posts with bonded composite cores) with varying amounts of remaining tooth structure can, in fact, provide some restrengthening of weakened teeth restored with MOD restorations, veneers, or fullcoverage techniques.2226 Figure 9 shows a highpower SEM of the adaptation possible with an appropriately sized bonded fiber post creating a "monoblock." A ferrule of 2 mm has to be provided for the reconstruction of endodontically treated teeth by post and core techniques. (Studies show that increasing the length of a ferrule from 1 to 1.5 mm in a quartz fiber post does not significantly increase fracture loads, but an increase to 2 mm results in higher fracture thresholds.)
Now the clinical observation of carbon2730 or glass and quartz fiber3134 post restorations offer admirable performances at 7 to 11 years’ conclusion,35 and the difference in failure rates—particularly catastrophic failure rates—between fiber posts and cast posts is no less compelling at 4 years’ service.36
The placement of a single fiber post in a relatively "round" and minimally tapered conservative root canal has been described in many articles and is now appearing in textbooks. There is evidence that (unlike metal predecessors) there is no difference in the performance between tapered and parallel fiber posts.37,38 However, it is selfevident to an experienced clinician that parallel posts may often require the removal of additional dentin and the creation of acute internal angles ("stress magnets"). Therefore, the tapered apical/parallel body shape is preferable3941 if only for the sake of dentin conservation. Figures 10 and 11 show the same tooth as above, prepared for a tapered 1.5 mm fiber post. It is obvious from the radiographs that more tooth structure at the apical end of the canal would need to be sacrificed to allow the parallel 1.5 mm posts to seat to the same length, needlessly weakening the remaining root structure.
So, then, what is the contemporary technology protocol, when faced with a flared, ovoid, or figure8 canal?
Circular parallel post systems are only effective in the most apical portion of the post space, because the majority of prepared post spaces demonstrate considerable flare in the coronal half. Similarly, when the root canal is elliptical, a parallelsided post will not be effective unless the canal is considerably enlarged,42 thereby needlessly removing extra dentin. From a clinical perspective, when assessing posts that have failed, many are in fact cemented or bonded to areas in the canal still occupied by guttapercha. One of the causes for the lack of resultant retention is due to this oversight, which is a direct result of preparing a round canal space with a rotary instrument in a canal which is never round. There are 2 prefabricated posts available (in limited market areas) that are designed with a rounded, tapered apical extremity, and an oval coronal section (PeerlessPost [SybronEndo] and ELLIPSON [RTD]).
The low modulus approach needs to be adaptable to the overflared canal, while addressing the inherent challenges, which include Cfactor stress and Sfactor stress,43 polymerization shrinkage and, presumably, microleakage.
Most fiber posts on the market come in cylindrical sizes that mimic their metallic ancestors, so that the practitioner may use the drills already purchased. However, as previously discussed, a tapered preparation is the most noninvasive. Unlike fiber posts, as the diameter of metal posts increases, so does the stress transfer to the tooth,44 and so, logically, does the likelihood of root splits.
There are some tapered quartz fiber posts that come in extra large sizes that range from 0.8 mm at the apical tip to 2.3 mm at the coronal extreme (DT LightPost [RTD, BISCO] and MacroLock Post [RTD]). These sizes exceed the diameters available in most brands, and are capable of fitting most root canal treatments without further instrumentation.
The authors will now describe and suggest an approach and technique for the inevitable variations presented by prepared and filled root canals which fall into 3 proposed treatment categories.

THE SIMPLE CANAL

Figure 13a. Clinical presentation of failed post and core crown on upper right central incisor.	Figure 13b. A small starter drill is used to initiate removal of the gutta-percha.
Figure 13c. The appropriate size tapered Macro-Lock drill is used to maximize size while minimizing dentin removal.	Figure 13d. The Macro-Lock Illusion X-RO post inserted and checked for fit. Notice the small space between the post and the walls of the post preparation. A diamond is then used to shorten the post to the desired length.
Figure 13e. An acid gel (Ultra-Etch [Ultradent Products]) is injected from the bottom of the post space up to the cavosurface margin by using a 20- or 22-gauge needle to avoid air entrapment.	Figure 13f. After water rinsing from the bottom of the canal up, and light drying, the canal is checked for excess moisture with a paper point; the bonding agent is placed in the canal and lightly agitated to increase the bond strength to the dentin.
Figure 13g. After air-thinning the bonding agent from the bottom up, the canal is checked for excess bonding agent with a paper point, and the bonding agent is cured with a high output curing light for 20 seconds.	Figure 13h. The bonding agent is applied to the post with a microbrush.
Figure 13i. After evaporating the solvent and air thinning, the bonding agent is light-cured.	Figure 13j. Using a lentulo-spiral to insert the dual cure resin cement will accelerate the set. It is best to inject using a 20- to 22-gauge needle (Endo-Eze [Ultradent Products]) from the bottom up to eliminate air entrapment.
Figure 13k. After insertion of the fiber post into the dual-cured resin cement and placed to length, the cement is cured with light down the long axis of the fiber post for 30 seconds.	Figure 13l. After injecting and hand sculpting the core material around the remainder of the fiber post, the composite resin is light-cured.
Figure 13m. The clinical preparation of the fiber post and core for full-coverage restoration is shown in this intraoral photograph.	Figure 13n. The final ceramic restorations (Zirconia [ZirconZahn]) on the 2 upper central incisors.

In a "simple" case, where the canal treatment results in the typical tapered conservative shape (less than 25% larger than the fiber post [Figure 12]), a single fiber post can be inserted and covered with a composite core build up in preparation for the prosthetic restoration. The clinical protocol for this type of case is as follows:
All procedures inside the root canal should focus on the bottomup approach; the canal is prepared with the matching sized post drills and posts, and all remnants of guttapercha must be removed from the walls of the post space to facilitate bonding. The fiber post is generally shortened to the height of the core with a diamond bur before the bonding procedure is started, but it can also be cut with a diamond bur after the core is cured. If using a selfcuring resin cement, the post should always be cut to length first, so as not to vibrate the post while the cement may be setting. Fiber posts can be cut to length after the core is placed, but color changing posts are unique. A color changing post should be cut 1.5 mm short of the anticipated coronal extent of the core, and thus be buried in the core composite. This is done to prevent reappearance of the color under translucent ceramics due to exposure to intraoral temperature changes when the patient ingests cold beverages or food. The clinical presentation and treatment of a case that is typical for the simple canal is shown in Figures 13a to 13n. The tooth is isolated and guttapercha is removed with a small starter drill (Figure 13b), and the post space is created with the appropriate size taper drill (Figure 13c). Care should be taken to match the post, as close as possible, to the size of the existing canal space rather than over preparing the canal for a large post. At this time, all remnants of guttapercha should be removed and verified visually with magnification. (Some practitioners use chloroform to dissolve any remaining guttapercha in the post space area.) The fiber post (MacroLock Illusion XRO is tried in the canal (Figure 13d). Then, it is trimmed to length with a diamond bur to prevent chatter and possible damage to the post. To decontaminate the post after tryin and length adjustment, it is cleaned with alcohol prior to bonding. The canal is acid etched by placing the acid gel from the bottom up using a 20 or 22gauge needle tip (Figure 13e). This is done to keep an air lock from forming below the etchant, which would prevent etching of the entire canal space. It has been shown that agitating the acid with a microbrush during this 15second procedure increases bond strength. The canal is rinsed with water, again from the bottom up, using a 20 or 22gauge needle adapted to either a Stropko Irrigator (CLINICIAN’S CHOICE) or TriAway Adaptor (Ultradent Products), to thoroughly wash and remove the acid gel out of the canal space. This cannot be achieved with a typical 3way syringe, which can leave some acid in the canal, interfering with the chemical setting reaction of a dual or selfcure cement. The canal is lightly dried using air from the bottom up and then double checked with a paper point. The adhesive bonding agent is placed with a microbrush and agitated into the opened tubules of the root canal (Figure 13f). Air is delivered from the bottom up and excess bonding agent and pooling is prevented by inserting a paper point to absorb any excess. The bonding agent is then lightcured with a highpower, broad spectrum LED curing light for at least 30 seconds (Figure 13g). It must be remembered that light intensity for some curing lights falls drastically with distance, so the cure must be adequate. There are only 3 possible solutions for this: (1) a dual (photo and chemical) activation adhesive, (2) conducting the light through the post and photoactivate it together with the resin cement, or (3) lightcuring adequately with a highpower light (such as the VALO [Ultradent Products]) in its plasma emulation mode, 3 seconds at over 3,000 mW/ cm2. The point here is that if lightcured adhesives are used, undercuring will lead to failure. Next, bonding agent is applied to the post (Figure 13h) and lightcured (Figure 13i). Then, after the dual cure resin cement is placed into the canal with Skini Syringe mated to an EndoEze tip (Ultradent) (Figure 13j), the post is inserted and the dual cure resin cement is lightcured for 30 seconds (Figure 13k). It is best to inject the dual cure resin cement from the bottom up rather than using the lentulo spiral. This prevents any possible air entrapment and prevents the acceleration of set caused by the lentulospiral drill. The core material is injected around the post, and then lightcured (Figure 13l). The final preparation of the core for the patient is shown in Figure 13m and the final Zirconia (ZirconZahn) (ceramic) restorations are shown in Figure 13n.
There are many recommendations being made for the selection of cementation media and placement technique. Standard bonding tests would support the use of a fourthor fifthgeneration adhesive system (ie, AllBond 2 [BISCO] or OneStep [BISCO], SealBond Ultima [RTD], MPa [CLINICIAN’S CHOICE] respectively) in conjunction with dual cure or chemical cure resin cement, as being superior to selfetching or selfadhesive cement formulas.45 Clinical success with these also assumes proven chemical compatibility between the adhesive and the resin cement, and meticulous isolation, good access, vision, and technique. This is easy in the in vitro laboratory, but not always so easy in vivo.
In cases where access and/or visibility and/or good moisture control are compromised, some post manufacturers and clinicians/researchers report good results using selfadhesive, selfetching cements4648 and resinreinforced glass ionomer cements,49 particularly when using macroretentive quartz fiber posts (MacroLock Illusion XRO). However, it should also be noted that some of the comparative in vitro bond strength studies (to dentin) show these newer generations of cements to be inferior to the "totaletch/moistbonding" dual cure cementation technique. Furthermore, a post inserted like this should also have high flexural strength (minimum 1,500 MPa) since it won’t have the mechanical reinforcement that the adhesive cementation provides.
Because larger, tapered, and even doubletapered fiber posts are now offered, and these are mechanically compatible with the remaining tooth structure, good close adaptation of the post to the post space can routinely be achieved, with a minimum of cement thickness,40,41 thus minimizing the Sfactor. It is the more flared spaces that are addressed now.

THE ANATOMICAL POST AND CORE
Polymerization shrinkage, and the stresses associated with that (the Cfactor and Sfactor), are a big consideration in all bonding/restorative procedures, and nowhere is the Cfactor higher than it is in post cementation,43 because of the high number of involved surfaces and unbounded surfaces. Even though composite resin core materials generally have more filler and, therefore, higher strength than resin cements, the polymerization shrinkage stress is higher with 70% filler than that with 10% filler.50 This may seem counterintuitive to most dentists, but the objective is to utilize a technique that compensates for the inherent deficiencies of some materials and, in fact, actually capitalizes on them without becoming clinically cumbersome, time consuming, or with the integration of outside laboratory fees.
In an earnest attempt to address these factors, Grande, et al51 and Plotino, et al52 have described chairside techniques for adapting prefabricated fiber posts to ribbonlike, oval, or ovoid canal spaces by remodeling; in essence, by whittling the post with a diamond bur to match an analog achieved through a separate procedure. The results suggest that the volume of cement is minimized, and the retentive surfaces of the post are not compromised. However, no information is offered regarding the effects that whittling a round (tapered or parallel) post brings to the other mechanical properties of the fiber post, such as structural integrity.

Figure 14. A typical cross section of a tooth with a mildly flared canal which results in some excess space around the proposed fiber post in the coronal area.

Figure 15a. In this type of canal, the tooth is isolated and prepared to a post size that will fit at the apical end without overly enlarging the prepared canal.	Figure 15b. The Macro-Lock Illusion X-RO post is verified for fit—notice how the canal flares and there is excess space at the coronal aspect.
Figure 15c. Using a brush, a water soluble separating medium is applied to the post space.	Figure 15d. A light-cured composite (such as Grandio [VOCO]) is adapted to the prebonded post.
Figure 15e. The post and hybrid composite are seated into the prepared post space creating a custom post.	Figure 15f. After light-curing, the custom fiber post and core is removed—this mitigates the S-factor by allowing the resin to shrink toward the post.
Figure 15g. The custom fiber post and core, the result of creating a core build-down into the canal.	Figure 15h. After a thorough rinsing of the prepared canal space and the custom fiber post and core, the core is reseated in the canal and the labial aspect marked with a pencil.
Figure 15i. The canal is etched and the etchant is agitated with a microbrush, rinsed from the bottom up, and a bonding agent is agitated into the dentin and light-cured.	Figure 15j. Labial view of Macro-Lock Illusion X-RO post inserted into the cement.
Figure 15k. The post is seated into the canal with the pencil marking placed labially. The custom posts allow for a minimal thickness of luting cement thus, minimizing the S-factor. Excess cement is removed before light polymerization.	Figure 15l. The margins of the tooth preparation are refreshed and etched prior to bonding the core.
Figure 15m. Bonding resin is placed on the dentin prior to hand sculpting the composite resin core, then the core build up is shaped/completed and light-cured.	Figure 15n. This photograph shows the hand-sculpted, custom-fabricated fiber post and core after hand sculpting and light-curing.
Figure 15o. The core is finalized with a coarse diamond bur to length and depth requirements for the ceramic crown.	Figure 15p. The final ceramic restoration e.maxPress (Ivoclar Vivadent) with feldspathic overlay over the custom fiber post and core is shown in this photograph.

In the mildly flared space (Figure 14), we can create a composite "core builddown" followed by the core buildup. In the flared canal with a coronal circumference 25% to 50% greater than that of the largest fiber post (by itself) available, the authors suggest the following protocol.
In this clinical case, the canal has a moderate flare with the above criteria. The tooth is isolated, and the canal is prepared as previously with a size appropriate drill (Figure 15a). After the canal is thoroughly cleaned, the fiber post is inserted and the fit verified (Figure 15b). A water soluble separating medium is applied to the post space (Figure 15c), a lightcurable hybrid composite core material (such as Grandio [VOCO]) is adapted to the prebonded post (Figure 15d), which is then inserted into the root canal space (Figure 15e). The composite is lightcured through the lightconductive fiber post, and the post is removed from the canal (Figures 15f and 15g). When performing this technique, the clinician must look for undercuts before creating the "core builddown." It won’t be possible to remove the post if cured in those undercuts, and the procedure will have to be repeated, possibly injuring the post. After verifying the position (Figure 15h) by marking the labial with a pencil for orientation, the canal is thoroughly rinsed and the build down is rinsed to remove the water soluble separating medium. As in the first clinical protocol, the canal is etched with a microbrush which is agitated in the canal (Figure 15i), rinsed from the bottom up, dried from the bottom up, and any excess water removed with a paper point. The lightcured bonding agent is applied and fully cured as in the previous protocol. The dual cure resin cement is placed in the canal, the core builddown is inserted (Figures 15j and 15k), and thoroughly lightcured. After cementation, the dentin is refreshed with a diamond, the surface etched (Figure 15l), rinsed and bonded (Figure 15m); then, the core material is adapted and lightcured. The resultant freehanded core is shown in Figure 15n, which is modified with a tapered coarse round ended diamond (Figure 15o), and the final ceramic crown (IPS e.max [Ivoclar Vivadent]) over the customfabricated fiber post and core is shown in Figure 15p.

Figure 16a. Photo of failed cast post and core with widely flared canal—note the thickness of the prior cement used.	Figure 16b. With the gutta-percha and cement removed, no other dentin was removed, and the largest diameter fiber post that fit at the apex was the starting point.
Figure 16c. The existing canal space was acid-etched with phosphoric acid for 15 seconds and rinsed from the bottom up with a 20- to 22-gauge needle tip. The bonding resin was agitated into the dentin, air-thinned from the bottom up, verified with a paper point.	Figure 16d. The bonding resin is thoroughly cured with a high output light-curing unit.
Figure 16e. The dual-cured resin cement (Rebilda DC [VOCO]) is then injected from the bottom of the preparation to the coronal aspect.	Figure 16f. The "master" prebonded post is inserted to length into the dual cure resin cement.
Figure 16g. Prebonded Fibercones (RTD) are inserted prior to light- curing to minimize the amount of dual cure resin and to strengthen the post.	Figure 16h. The core composite is injected between and around the Fibercones and central "master" fiber post and hand sculpted prior to light-curing.
Figure 16i. The occlusal view of the "reinforced" fiber post and core with rubber dam still in place.	Figure 16j. The intraoral clinical view of the "reinforced" fiber post as prepared for the full coverage ceramic restoration.

This way, any shrinkage in the "builddown" is now in free space, not between the tooth and the restoration, neutralizing the Sfactor effect. And it assures that the cement thickness will be minimal and uniform.48 In most cases, the airinhibited layer on the builddown can remain intact. If in doubt, the excess cement and remaining tooth structure can be refreshed before the bonding agent and core buildup composite is applied.
It is a directindirect technique, and has shown optimistic results.5355

THE POST WITH ACCESSORY POSTS
Now, in the case where the coronal circumference has a wide flare of more than 50% greater than that of the largest fiber post available, or the practitioner is working with a ribbon, ovoid, or triangular canal, the suggested technique is as follows:
As can be seen from Figure 16a, the existing canal in which a cast post and core failed, is over prepared and widely tapered at the coronal aspect. By following the previous methodology, the canal is prepared and the fit of the fiber post is assessed (Figure 16b). The large amount of resin cement will need to be minimized to decrease the shrinkage factor, and the cement and core material will need strengthening. The canal is etched, rinsed, and dried lightly; the compatible bonding agent is agitated into the canal (Figure 16c); and lightcured (Figure 16d). After direct injection of the dualcured resin cement (Figure 16e), the prebonded fiber post is inserted (Figure 16f), and prebonded Fibercones (RTD) are inserted (Figure 16g). Then, core composite is injected between and around the Fibercones and central "master" fiber post and hand sculpted prior to lightcuring (Figure 16h). Lastly, the core build up is shaped, lightcured, and prepared to final shape with diamonds (Figures 16i and 16j).
Figure 17a shows the typical triangular shape encountered when restoring anterior teeth. Figure 17b shows a MacroLock Illusion XRO with an accessory Fibercone placed in the lingual slot area. The final clinical photograph is shown in Figure 17c. This we will call the (direct) accessory post technique, in which the "master" fiber post—sizeselected for its fit at the apical end of the space—is accompanied by one or more slender, tapered accessory posts (eg, Fibercone). The clinician may draw an immediate parallel to their training with gutta percha cones. RTD translucent quartz fiber posts (DT LightPost and MacroLock Illusion XRO) have been shown to have limited but relatively superior transmission of the polymerization light energy5658 down into the postrestorative space, a property which is an important attribute and would necessarily disqualify the use of many other (less conductive) fiber posts for this technique.

Figure 17a. The typical triangular shape of anterior root canal space after endodontic preparation.	Figure 17b. This anatomic space is ideal for the placement of a Macro-Lock Illusion X-RO fiber post complemented with an auxiliary Fibercone to decrease the amount of dual cure resin used and fortify the restoration.

Figure 17c. Postoperative photograph of the Fibercone and auxiliary Fibercone in the triangular shaped canal.

In addition, the flexural and compressive strength of the factorymade composite (99.9% crosslinked) are higher than a composite handcured by light energy at chairside. In comparison, the crosslinked networks during polymerization and degree of conversion for most direct resin materials ranges from 45% to 70%.59
Published studies demonstrate the other benefits of this Accessory Post technique:
• Minimizes shrinkage in flared canals and, therefore, gap formation60
• Reduces the need for drilling in order to adapt posts to root cavity61 (minimizes dentin removal)
• Reduces the thickness of cement and increased fracture resistance.60
Fiber posts, associated with composite resin or with accessory fiber posts, seem to be more indicated as an alternative to cast post and core in flared roots, because of the lower risk of catastrophic failures and better stress distribution.62
It is possible to conclude that use of the fiber post, associated with accessory posts, is the method of choice for reinforcing structurally weakened roots, and provides an improvement in the load carrying ability of the restored root is validated, as opposed to the use of one single inadequately fitting post.63,64

SUMMARY
In contemporary dental practice, there is no remaining reason to use metallic posts, custom or prefabricated. Many cases that several years ago would have required a retentive post will not require that post today, because of the many improvements in bonding agents and composite resin restoratives. However, in cases where less than 50% of coronal tooth structure remains—or in other cases wherein the judgment of the clinician a post is indicated—there are now aesthetic, noncorrosive, fracture resistant and radiopaque alternatives for all varieties that save time and money without compromise. Their most compelling advantage, regardless of the geometry or amount of residual tooth structure, is the protection from root fracture that a low modulus restoration provides.
In selecting the materials (posts, resins) for these techniques, the dentist is advised not to cut corners, and to seek the strongest and most radiopaque products available.

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28. Schmitter M, Rammelsberg P, Gabbert O, et al. Influence of clinical baseline findings on the survival of 2 post systems: a randomized clinical trial. Int J Prosthodont. 2007;20:173178.
29. Ferrari M, Vichi A, Mannocci F, et al. Retrospective study of the clinical performance of fiber posts. Am J Dent. 2000;13(special issue):9B13B.
30. Fazekas A, Menyhárt K, Bódi K, et al. Restoration of root canal treated teeth using carbon fiber posts [in Hungarian]. Fogorv Sz. 1998;91:163170.
31. Cagidiaco MC, Radovic I, Simonetti M, et al. Clinical performance of fiber post restorations in endodontically treated teeth: 2year results. Int J Prosthodont. 2007;20:293298.
32. Ferrari M, Cagidiaco MC, Grandini S, et al. Post placement affects survival of endodontically treated premolars. J Dent Res. 2007;86:729734.
33. Grandini S, Goracci C, Tay FR, et al. Clinical evaluation of the use of fiber posts and direct resin restorations for endodontically treated teeth. Int J Prosthodont. 2005;18:399404.
34. Cagidiaco MC, Goracci C, GarcíaGodoy F, et al. Clinical studies of fiber posts: a literature review. Int J Prosthodont. 2008;21:328336.
35. Ferrari M, Cagidiaco MC, Goracci C, et al. Longterm retrospective study of the clinical performance of fiber posts. Am J Dent. 2007;20:287291.
36. Ferrari M, Vichi A, GarcíaGodoy F. Clinical evaluation of fiberreinforced epoxy resin posts and cast post and cores. Am J Dent. 2000;13(special issue):15B18B.
37. Naumann M, Blankenstein F, Dietrich T. Survival of glass fibre reinforced composite post restorations after 2 years—an observational clinical study. J Dent. 2005;33:305312.
38. Signore A, Benedicenti S, Kaitsas V, et al. Longterm survival of endodontically treated, maxillary anterior teeth restored with either tapered or parallelsided glassfiber posts and fullceramic crown coverage. J Dent. 2009;37:115121.
39. Dietschi D, Duc O, Krejci I, et al. Biomechanical considerations for the restoration of endodontically treated teeth: a systematic review of the literature—Part 1. Composition and micro and macrostructure alterations. Quintessence Int. 2007;38:733743.
40. Baldissara P, Zicari F, Ciocca L, et al. Effect of fiber post emerging diameter on composite core stabilization. J Dent Res. 2007;86(A, special issue). Abstract 2623.
41. Boudrias P, Sakkal S, Petrova Y, et al. Anatomical post design applied to quartz fiber/epoxy technology: a conservative approach. Oral Health. 2001;91:920.
42. Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics. 3rd ed. St. Louis, MO: Mosby; 2001:279.
43. Breschi L, Mazzoni A, De Stefano D, et al. Adhesion to intraradicular dentin: a review. Journal of Adhesion Science and Technology. 2009;23:10531083.
44. RodríguezCervantes PJ, SanchoBru JL, BarjauEscribano A, et al. Influence of prefabricated post dimensions on restored maxillary central incisors. J Oral Rehabil. 2007;34:141152.
45. Mazzoni A, Marchesi G, Cadenaro M., et al. Pushout stress for fibre posts luted using different adhesive strategies. Eur J Oral Sci. 2009;117:447453.
46. Kremeier K, Fasen L, Klaiber B, et al. Influence of endodontic post type (glass fiber, quartz fiber or gold) and luting material on pushout bond strength to dentin in vitro. Dent Mater. 2008;24:660666.
47. Akgungor G, Akkayan B. Influence of dentin bonding agents and polymerization modes on the bond strength between translucent fiber posts and three dentin regions within a post space. J Prosthet Dent. 2006;95:368378.
48. Radovic I, Monticelli F, Goracci C, et al. Selfadhesive resin cements: a literature review. J Adhes Dent. 2008;10:251258.
49. Baldissara P, Monaco C, Valandro LF, et al. Retention of quartz fiber posts using different luting cements. J Dent Res. 2009;88(A, special issue). Abstract 976.
50. Ferrari M, Carvalho CA, Goracci C, et al. Influence of luting material filler content on post cementation. J Dent Res. 2009;88:951956.
51. Grande NM, Butti A, Plotino G, et al. Adapting fiberreinforced composite root canal posts for use in noncircularshaped canals. Pract Proced Aesthet Dent. 2006;18:593599.
52. Plotino G. Grande NM, Pameijer CH, et al. Influence of surface remodelling using burs on the macro and micro surface morphology of anatomically formed fibre posts. Int Endod J. 2008;41:345355.
53. Ferrari M, Scotti R. Fiber Posts: Characteristics and Clinical Applications. Paris, France: Masson Publishing; 2002:9495.
54. IglesiaPuig MA, ArellanoCabornero A. Fiberreinforced post and core adapted to a previous metal ceramic crown. J Prosthet Dent. 2004;91:191194.
55. Grandini S, Sapio S, Simonetti M. Use of anatomic post and core for reconstructing an endodontically treated tooth: a case report. J Adhes Dent. 2003;5:243247.
56. Miller MB. Fiber posts. In: Reality Now. Houston, TX: Reality Publishing; 2006: 643660.
57. Christensen GJ. Posts a shift away from metal? CRA Newsletter. 2004;28(5):13.
58. Goracci C, Corciolani G, Vishi A, et al. Lighttransmitting ability of marketed fiber posts. J Dent Res. 2008;87:11221126.
59. Lambert D. A "recipe for success" with posterior composites utilizing preheated resins. Oral Health. 2009;99:67.
60. Porciani PF, Vano M, Radovic I, et al. Fracture resistance of fiber posts: combinations of several small posts vs. standardized single post. Am J Dent. 2008;21:373376.
61. Maceri F, Martignoni M, Vairo G. Mechanical behaviour of endodontic restorations with multiple prefabricated posts: a finiteelement approach. J Biomech. 2007;40:23862398.
62. Raposo LHA, Silva GR, SantosFilho PCF, et al. Effect of posts and materials on flared teeth’s mechanical behavior. J Dent Res. 2008;87(B, special issue). Abstract 1862.
63. Braz R, Conceição AAB, Conceição EN, et al. Evaluation of reinforcement materials used on filling of weakened roots. J Dent Res. 2005;84(A, special issue). Abstract 1733.
64. Porciani PF, Grandini S, Papacchini F, et al. The fit of two fiber posts into the root canal space enlarged with rotary NiTi files at four different levels. International Dentistry S Afr. 2007;9(1):4450.

Dr. Boksman is an adjunct clinical professor at the Schulich School of Medicine and Dentistry, and has a private practice in London, Ontario, Canada. He can be reached at lboksman@clinicalresearchdental.ca.

Disclosure: Dr. Boksman has a paid parttime consultancy position as the director of clinical affairs for Clinical Research Dental and CLINICIAN’S CHOICE.

Dr. Hepburn works as adjunct professor at the operative dentistry department of the University of Buenos Aires Dental School (Buenos Aires, Argentina), and at the Oral Rehabilitation Postgrade Career in the University del Desarrollo Dental School (Concepción, Chile). He has a private practice in Buenos Aires, Argentina. He can be reached at hepburn@speedy.com.ar.

Disclosure: Dr. Hepburn is a consultant for VOCO GmbH (Germany).

Dr. Kogan works as a professor of Restorative Dentistry Universidad Tecnológica de Mexico, visiting professor Nova Southeastern University College of Dental Medicine, Fort Lauderdale, Fla and has a private practice in Mexico City, Mexico. He can be reached at ekoganf@gmail.com.

Disclosure: Dr. Kogan is the designer and patent owner of the PeerlessPost (SybronEndo).

Dr. Friedman maintains a private practice limited to endodontics in London, Ontario, Canada, and is assistant adjunct professor in the division of restorative dentistry at the University of Western Ontario, London, Canada. He can be reached via email at ndofriedman@rogers.com.

Disclosure: Dr. Friedman reports no disclosures.

Dr. de Rijkwas formerly in the department of restorative dentistry at the University of Tennessee Health Science Center Memphis, Tenn. He is currently an associate professor of restorative dentistry and chief of the biomaterials Unit at the School of Dental Medicine East Carolina University. He can be reached at (252) 737-7020 or at derijkw@ecu.edu.

Disclosure: Dr. de Rijk reports no disclosures.

Indications for Endodontic Posts
The creation of reliable resistance and retention form for the definitive restoration, while preserving the maximum amount of healthy tooth structure possible, should be the aim when creating coronal buildups in endodontically treated teeth.⁵ With modern dental materials using adhesive techniques, the use of endodontic posts can now be avoided in many cases. In cases with an insufficient amount of remaining coronal tooth structure, composite resin adhesive bonding techniques offer the possibility of creating additional retention for the core buildup. The answer to the question of whether an endodontic post is necessary, thus, depends on the degree of destruction of the clinical crown:
• Teeth with a minimal amount of destruction can be prepared using an adhesively bonded direct composite resin buildup for the prosthetic restoration.
• With a medium amount of destruction, a buildup with post anchoring can likewise be avoided in many cases, thanks to the adhesive bonding technique.
• With an extensive amount of destruction of the clinical crown, an endodontic post should be used to create reliable retention of the core buildup.
Note: for those interested, more exact information on this topic can be taken from the shared scientific opinion of the German Scientific Association of Dentistry (DGZMK), German Association of Prosthodontics and Dental Materials (DGZPW), and the German Association of Conservative Dentistry (DGZ) in Aufbau endodontisch behandelter Zähne (“Buildup of Endodonically Treated Teeth”) (2003).

Requirements of Endodontic Posts
The fundamental requirements of endodontic posts include, among other things: high tensile strength, high fatigue resistance to occlusal and shear loading, and stress-free distribution of the forces affecting the tooth root; excellent accuracy of fit, biocompatibility, and electrochemical innocuity are also essential. Unnecessarily weakening the tooth root through increased substance loss should be avoided by selecting a suitable post form (shape).⁶
For therapy of aesthetically challenging situations these days, all-ceramic crowns and bridges fabricated from translucent ceramic are widely used, especially in the anterior and premolar regions. These are comparable to natural teeth with respect to their light-conducting properties. The expectations of the optical properties of endodontic posts are rising in response to the demand for aesthetic restorations in teeth that have undergone root canal therapy. Unaesthetic effects, originating from the endodontic post shining through and metal or black carbon fiber posts construction, cannot be reconciled with high expectations of aesthetic results.⁵
In addition to metal posts, which can be subdivided into active posts (with screw threads) and passive designs, up-to-date metal-free systems made from high-strength zirconium oxide ceramic and fiber-reinforced composites are now available.⁶ In addition to the unfavorable optical properties, the disadvantages of metal posts include: high rigidity (high E modulus) with resulting concomitant risk of arising hypercritical stress peaks (with active posts foremost from the thread outward) and the problem of corrosion. All-ceramic posts made from zirconium oxide are indeed almost tooth-colored; however, these represent an increased risk in the occurrence of stress peaks. This is due to extremely hard and inelastic materials (E modulus, ca. 200 GPa) that are not in harmony (from a biomechanical perspective) with the relatively elastic dentine (E modulus, ca. 18 to 20 GPa) of the tooth root, resulting in an increased risk for root fractures. In addition, in most cases involving postoperative complications, the zirconium oxide posts cannot be removed without considerable and irreparable damage to the tooth root due to their considerable hardness.

Fiber-Reinforced Composite Endodontic Posts
Fiber-reinforced composite posts consist of a resin matrix, in which structural reinforcing carbon fibers or quartz/glass fibers are embedded. Black carbon fiber-reinforced composite posts are, on the one hand, poorly suited for combination with translucent all-ceramic restorations due to their unaesthetic optical properties. On the other hand, carbon fiber posts also have unfavorable biomechanical properties (significantly higher E modulus, ca. 120 GPa) in comparison to the nearly tooth-colored quartz fiber and glass fiber posts.
The quality of fiber-reinforced composite posts, which are now offered by a large number of manufacturers, can vary greatly because the manufacturing process determines the quality. The highest quality is provided by ensuring for the most even distribution of the fiber in the organic matrix possible, optimally dense fibers, a high degree of polymerization of the organic components, and a homogeneous post structure absent of blisters and inclusions.⁷ After polymerization, the blanks are brought into their final form through a milling process. There are different post geometries, which also exhibit considerable differences in surface quality due to variations in the milling processes.
Endodontic posts fabricated from quartz fiber- or glass fiber-reinforced composite have favorable biomechanical properties. They feature high strength and, at the same time, exhibit elasticity characteristics that are similar to dentine.⁸ This minimizes the risk of root fractures caused by stress peaks induced by loading and shear forces through the most stress-free distribution possible of these arising forces in the tooth root. The even load distribution is supported through the friction-locked bond between post and tooth substance, due to adhesively bonding the fiber post in the root canal with composite cement. The adhesive bond, however, appears to be inferior to the radicular dentine due to the structural differences in comparison to coronal dentine sections.^9,10
The favorable optical properties of tooth-colored fiber posts (glass and quartz fiber), which are consistent with natural teeth in their ability to conduct light, facilitate the goal of high quality and aesthetic restorations when they are combined with all-ceramic materials. The posts can be processed in one time-saving surgery visit that eliminates the dental laboratory steps, due to the direct technique in combination with an adhesive composite buildup. This technique is also a procedure that is gentle to the tooth substance: thin dentine walls are stabilized by the plastic buildup composite and the composite resin cement. Moreover, the areas underneath can be saved and maintained as additional retentive areas for the plastic buildup composite restoration.¹¹
The rare failures of fiber posts are either due to loss of adhesion or a fracture of the post. Catastrophic post failure, which leads to a fracture in the tooth root, is less likely in contrast to posts made from rigid metal or zirconium oxide materials.¹² Contrary to tooth-colored posts made from zirconium oxide, posts made from fiber-reinforced composite can be removed from the root canal, if the need arises, without serious complications that often arise when excavation is done with a rotating instrument.
The following case report will demonstrate the clinical steps involved in the utilization of a fiber-reinforced composite endodontic post in a maxillary central incisor and the subsequent treatment with an all-ceramic crown.

CASE REPORT
Diagnosis and Treatment Plan

Figure 1. Preoperative photo: note the unsightly existing crown on tooth No. 8.	Figure 2. Periapical radiograph: an endodontically treated tooth with a metal post.

A 38-year-old patient presented with the desire to replace an unsightly crown on the right central incisor (tooth No. 8) and to have a veneer placed on the left central incisor (tooth No. 9) (Figure 1). The PFM crown on the No 8 was much too short and the dentin core was extremely discolored and dark. The tooth reacted unremarkably to percussion and did not display any irritation to the cryogenic spray in the sensitivity test. An endodontically treated tooth with a metal post in the root and a normal periapical region was exhibited in the periapical radiograph (Figure 2). Other than a large, mesial, provisional composite buildup, tooth No. 9 was clinically and radiographically unremarkable.
After presenting and explaining the treatment alternatives, a decision was reached to remove the crown on tooth No. 8 with an attempt to take out the metal post. Subsequent insertion of an adhesively bonded, fiber-reinforced composite endodontic post and fabrication of a zirconium oxide all-ceramic crown were planned. An all-ceramic veneer for tooth No. 9 was also planned.

Clinical Treatment Steps
After the crown was removed from tooth No. 8, the existing build-up material was carefully removed and the coronal portion of the metal endodontic post exposed (Figure 3). The post still exhibited good retention, so an attempt was made to destroy the integrity of the cement with ultrasonic energy (Figure 4), in order to remove the post without a bur and/or other instrumentation, which can often endanger the precious remaining root structure (caveat: longitudinal fracture). After a short time, the post loosened and was easily removed from the canal (Figure 5).

Figure 3. After removal of the existing PFM crown, the old build-up material was removed.	Figure 4. The integrity of the cement layer was broken with ultrasonic energy for an atraumatic removal of the old post.

A fiber-reinforced composite post (Rebilda Post [VOCO GmbH]) that would be adhesively bonded into place was chosen. After placing a retraction cord and selecting the appropriate post diameter, the post preparation was carried out with a depth-marked precision drill (Figure 6). The penetration depth was already preset by the length/ extent of the old metal post in this special case. The length of the post drilling should usually allow that a minimum of 4 mm of endodontic root filling material remains, in order to ensure an adequate apical seal.
Figure 7 shows the try-in of the fiber-reinforced post with the maximum coronal diameter (2.0 mm) possible. The fiber-reinforced post was inserted into the cavity and the fit verified. Rebilda Post glass fiber-reinforced composite posts are available in 3 sizes (coronal diameter: 1.2 mm, 1.5 mm, and 2.0 mm) and all have a cylindrical-conical design. The tapered anatomical shape of the tooth root in the apical region is reflected in the design (conical shape) of the post. This permits an anatomically influenced preparation design that is more conservative than those required for straight parallel-walled post systems.
To prepare for the adhesive cementation procedure, the dental assistant cleaned the post with alcohol, dried it with air and then applied silane (Ceramic Bond [VOCO GmbH]). The task of disinfecting the post preparation was carried out concurrently (according to the manufacturer’s instructions) with 3% NaOCl (Figure 8). Next, the prepared canal was flushed with water (Figure 9) and then dried with paper points (Figure 10).

Figure 5. The carefully removed metal post.	Figure 6. The post preparation was done with a length-marked standard post drill.
Figure 7. The fiberglass-reinforced composite post (Rebilda Post [VOCO GmbH]) was tried in the root preparation. The assistant then cleaned the post with alcohol, dried it, and applied silane to it (Ceramic Bond [VOCO GmbH]).	Figure 8. The root canal was flushed with NaOCI solution.
Figure 9. The post preparation was rinsed with water.	Figure 10. The prepared canal was dried with paper points.
Figure 11. A clear matrix was placed, followed by adhesive pretreatment of the post preparation and residual tooth structure with a self-etching dual-cured adhesive resin (Futurabond DC [VOCO GmbH]).	Figure 12. Excess adhesive was removed with a paper point.

A clear matrix band was placed on the tooth to help properly shape the buildup. A self-etching dual-cured adhesive, Futurabond DC (VOCO GmbH), was rubbed into remaining tooth substance and in the entire post canal for 20 seconds with a small endodontic microbrush (Figure 11). Then, the solvent was gently evaporated with oil-free air and excess adhesive was removed from the post preparation with the assistance of a paper point (Figure 12). Immediately after this, a low viscosity dual-cured composite resin core build-up material (Rebilda DC [VOCO GmbH]) was applied into the preparation with a QuickMix (VOCO GmbH) syringe using a slender application tip. The syringe tip was inserted to the deepest point in the prepared post canal and the build-up composite was continuously injected while slowly withdrawing the tip. The tip was watched carefully to be sure that the opening was always immersed in the luting composite. This type of “immersion filling” ensures that there are no air bubbles in the cement layer, which also results in maximum adhesion to the canal wall and increased post-to-tooth integrity. The excess cement that escaped from the coronal opening of the post preparation was simply left to incorporate into the buildup. The coronal composite buildup was created with the same application syringe after the post was inserted (Figure 13). The composite was subsequently polymerized with the curing light for 40 seconds (Figure 14). After removing the matrix, tooth No. 8 was immediately prepared for a zirconium oxide all-ceramic crown (Figure 15). A band of dentin edge was clearly discernable in the preparation cervical to the composite buildup. The dentine border serves as a ferrule, which should be a minimum of 2 mm wide circumferentially in the ideal case. When circularly surrounded by the definitive crown, this creates a ferrule effect that protects the integrity of the remaining root structure and increases the strength of the post-core assembly and the expected longevity for the definitive restoration. Tooth No. 9 was then prepared for a ceramic veneer (Figure 15). A temporary was fabricated from the preoperative impressions and placed with temporary cement (Figure 16). The adhesively cemented fiber-reinforced composite post was clearly discernible on a postoperative periapical radiograph (Figure 17).
Figure 18 shows the aesthetic results achieved for the patient.

Figure 13. The post was luted into place and the core buildup was created using a low viscosity dual-cured composite resin (Rebilda DC [VOCO GmbH]).	Figure 14. The composite resin was polymerized with light for 40 seconds.
Figure 15. The completed preparations for a zirconium oxide crown on tooth No. 8 and an all-ceramic veneer on tooth No. 9.	Figure 16. The provisional restorations were fabricated from a preoperative impression and cemented temporarily into place.
Figure 17. Postoperative periapical radiograph.	Figure 18. The completed case. Note the markedly improved aesthetics.

SUMMARY
Endodontic posts do not increase the strength of the remaining tooth structure in endodontically treated teeth. On the contrary, depending on the post design employed (tapered versus parallel-sided), the root can be weakened relative to the amount of tooth removed during preparation. In many cases, if there has been a high degree of damage to the clinical crown, conservative preparation for an anatomic tapered (biomimetic) post with the incorporation of a ferrule on solid tooth structure is necessary to protect the reaming root structure as well as for the long-term retention of the composite resin core and the definitive restoration. Adhesively luted endodontic posts reinforced with glass or quartz fiber lead to better homogeneous tension distribution when loaded than rigid metal or zirconium oxide ceramic posts. Fiber-reinforced posts also possess advantageous optical properties over metal or metal oxide post systems.
The clinician should realize that there are admittedly substantial differences in the mechanical loading capacity of the different fiber-reinforced endodontic posts and should be aware of such differences in order to research and select a suitable post system for use.

References

1. Lewinstein I, Grajower R. Root dentin hardness of endodontically treated teeth. J Endod. 1981;7:421-422.
2. Reeh ES, Messer HH, Douglas WH. Reduction in tooth stiffness as a result of endodontic and restorative procedures. J Endod. 1989;15:512-516.
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5. Nergiz I, Schmage P. Wurzelstifte im Wandel der Zeit. Endodontie Journal. 2004;4:10-17.
6. Edelhoff D, Spiekermann H. Alles über moderne Stiftsysteme. Zahnärztl Mitt. 2003;93:60-66.
7. Grandini S, Goracci C, Monticelli F, et al. Fatigue resistance and structural characteristics of fiber posts: three-point bending test and SEM evaluation. Dent Mater. 2005;21:75-82.
8. Pfeiffer P, Schulz A, Nergiz I, et al. Yield strength of zirconia and glass fibre-reinforced posts. J Oral Rehabil. 2006;33:70-74.
9. Kurtz JS, Perdigão J, Geraldeli S, et al. Bond strengths of tooth-colored posts, effect of sealer, dentin adhesive, and root region. Am J Dent. 2003;16(special issue):31A-36A.
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11. Monticelli F, Goracci C, Ferrari M. Micromorphology of the fiber post-resin core unit: a scanning electron microscopy evaluation. Dent Mater. 2004;20:176-183.
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Dr. Manhart attended dental school of the Ludwig-Maximilians-University (LMU), Munich, and is an internationally renowned lecturer in the fields of aesthetic and restorative dentistry (composites, ceramics, aesthetic post systems, treatment planning). After graduation in 1994, he started working as a clinical dentist and scientist in the department of restorative dentistry, LMU. After conferment of the title Doctor of Medical Dentistry (PhD) in 1997, he completed a postdoc program at the University of Texas, Houston, for dental biomaterials, aesthetic dentistry, and interdisciplinary treatment planning. Dr. Manhart currently holds the position of professor in the department of restorative dentistry at the LMU Dental School. The main focus of his extensive clinical work is related to aesthetic dentistry (composite, ceramics, veneers) and the management of large, complex prosthodontic full-mouth rehabilitations. Since 1994, Dr. Manhart studies and teaches adhesive and aesthetic dentistry. He has authored more than 140 articles, one book, and several book chapters. He is principal investigator in many clinical and in vitro studies and researches the clinical longevity of dental restorations. Dr. Manhart is lecturing extensively, delivering more than 300 continuing education presentations and hands-on courses all over the world. He can be reached at manhart@manhart.com.

Disclosure: Dr. Manhart reports no disclosures.