Restoration of Teeth Following Root Canal Treatment

Subject: Dentistry
Pages: 18
Words: 4993
Reading time:
22 min
Study level: College

Literature Review

Teeth with pulp disease, with or without superficial manifestation, or subjected to trauma require endodontic treatment at the hands of General Practice dentists or endodontists themselves. So do those subjected to less-than-optimal endodontic restoration. Beyond root canal treatment (RCT), returning the treated tooth to normal function has traditionally required restoration: filling the root canal by recreating a post in place of the excavated pulp and final sealing by prosthetic replacement of the crown. These twin structures markedly improve the prognosis for treated teeth. Beyond the obvious necessity for shortening the interval to final sealing in order to forestall re-entry of oral fluids and bacteria, there is considerable debate about appropriate materials and methods.

Among the few principles that professional societies and published researchers agree on is that practitioners should make a plan for restoring teeth even before subjecting these to root canal treatment (RCT). Keeping in mind the objective of restoring the tooth to full functionality, general dental practitioners and endodontists must assess viability for RCT and restoration. This may mean clearing out caries and remnants of previous restorations to enable better all-round examination for periodontal vitality, occluding faults, the ratio of the crown to root, biological width, fractures, and overall potential for restorability. Also central to preliminary assessment is the integrity of the remaining tooth structure. Excessive deterioration may require a lengthened crown or orthodontic eruption before proceeding with the main endodontic treatment. (1) Otherwise, there is little consensus in the profession about restoration ‘best practice’.

That said, retreatment is also called for in about half of restorations post-RCT owing chiefly to insufficient infection control. Clearly, every step of RCT and restoration can be a contributory factor: inadequate access cavity preparation leading to missed roots, deficient canal preparation and scaling, and defective provisional or permanent crown restoration itself. (53)

Traditional Restoration Practice

Preventive Steps

An important aim in all restoration procedures is to prevent seepage of saliva and microorganisms into the periradicular area (immediately outside or around the root) lest new abscesses form. (7)

The Rationale for Creating a Post

A post is purely utilitarian since, as Cheung argues, it is necessary only when there is not enough of the root and crown on which to create a restoration crown. (6) If this is the case, then the abiding considerations should be durability, minimal or no compression and low abrasion on surrounding tissue. Traditional post materials and techniques consisted of base metals, either custom- or prefabricated.

The traditional fabricated-to-suit gold post and core (and the gold-plated brass variant) has endured owing to a success rate reportedly as high as 91 percent, since the fine metal is inert, boasts enough compressive strength to resist normal occluding force, and hews close to enamel in point of coefficient of thermal expansion (≈15 [C–1] X 106) and elasticity (stiffness rating of 14.5 X 106 psi). (6)

By comparison, the hardness of other base metals, such as the stainless steel that has also been much-used, presents problems for clinicians in fabrication and coping with the possibility of root fracture. Along with brass (plated with gold to make posts), stainless steel is corrosion-prone. Even more worrisome are findings that the nickel content of stainless steel puts female dentists and patients themselves at risk for, among others: contact dermatitis, allergic reactions within the oral cavity, general malaise, fibromyalgia, metallic aftertaste, burning sensations, numbness, gingival tenderness, erythema, mucosal sloughing, facial swelling, hyper- or hyposialorrhea, cheilitis, erosions and glossitis, and chronic fatigue syndrome. (17-18, 20) Allergic contact hypersensitivity (ACH) to nickel has historically presented as the most frequent contact allergy, even reported raising the odds ratio for spontaneous abortions. However, Van Hoogstraten et al. have suggested that it is possible to obviate ACH with orally-administered T-dependent antigens prior to having stainless steel dental appliances installed. (19)

The benefit served by inserting a post is itself inconclusive. It has been argued that leaving the excavated space empty reduces the structural integrity of the tooth owing to both drying out within the cavity and collagen cross-linking. Structural infirmity means dentin becomes more brittle and the tooth itself more fracture-prone. (2-4) More recently, Miguez, Pereira, Atsawasuwan and Yamauchi validated these assumptions and hypotheses by quantifying collagen biochemistry and ultimate tensile strength. Using human third molars as specimens (n not specified), the research team discovered that demineralized teeth evinced greater tensile strength in the roots than the crown; that resistance to perpendicular force was greater than when pressure was exerted parallel to tubular direction; that these measures of relative strength held for both undemineralized crowns or roots vis-à-vis demineralized counterparts; and that collagen content was not statistically different across both crown and root but that the two important collagen cross-links dehydrodihydroxylysinonorleucine and pyridinoline were at least 30 percent more extensively present in the roots. (5) Precisely how collagen cross-links account for differential tensile strength at crown or root was not addressed.

Despite this showing of differential tensile strength, there seems to be no clear consensus about the necessity or benefit of a post. There are clinicians who adhere to the belief that a post is mandatory to provide support for the root. Other researchers point out that the very actions are taken to prepare the canal and embed the post firmly in place merely weaken the remaining root structure and predispose it to fracture. Hence, the latter clinician-researchers elect to place a post only when there is no longer enough of the tooth structure to provide a durable core for coronal restoration. (9-11)

Reviewing the literature circa 2005, Naumann, Kiessling and Seemann arrived at much the same conclusion: the decision to use a post requires judgment and is called for principally when a crown restoration is unlikely to resist occlusal pressure resting solely on an inadequate vestige of the treated tooth. To the researchers’ dismay, a majority of fully 6,029 German dentists responding to a postal survey opt to install a post nearly every time they did a post endodontic restoration. (54) This is based on the widespread belief (among no less than 54% of German dentists) that a post always strengthens endodontically treated teeth.

The prognosis for restoration is critically a function of the length of the post as this affects the crown-to-root ratio and extends sufficiently into the bone surrounding the root. Since root dimensions vary by type and even within the same type for a given patient, the rule of thumb seems to be that a post should descend from one-half to two-thirds down the length of the canal, half the root length surrounded by bone, and should at least equalling crown height. Moreover, post length is limited by the necessity for leaving enough of the temporary, inert filling (e.g. gutta percha) to seal the apical 3 to 6 mm. of the root canal from microleakage and new contamination by microbes. Otherwise, the patient runs the risk of endodontic failure. (39-42)

Post diameter may have little effect on retention success. The aggressive removal of dentin that is so prevalent may be counterproductive when it extends to thinning out the remaining sound dentin, notably in the apical segment, as to risk fracture and therefore requiring ET retreatment. Hence, it is recommended that post diameter be limited to one-third of root width at its narrowest and that at least 1 mm. of healthy dentin remains after drilling for post space, all the while paying attention to the anatomical fact that roots are never perfectly round. (10, 36, 43-44)

Reviewing the clinical evidence, however, Cheung realized that posts did not conclusively strengthen endodontically treated teeth. Emplacing posts is not a matter of unthinkingly habitual application. It would be a different matter if new materials could be found that universally applied to bonding posts to root dentin, the post and the core, and the final crown restoration to both core and remaining tooth structure. Being made up of the same material or composite, it stands to reason that such a post would truly strengthen the treated tooth. (6)

On the whole, the decision to use a post rests substantially on three criteria: the type of tooth being treated, the extent of tooth substance left after endodontic treatment that will support a restorative crown, and the sheer prevalence of “crown-down” in clinical practice.

For its part, the ‘crown-down’ technique employs either manually-operated stainless-steel Gates-Glidden drills or the newer nickel-titanium rotary devices to enlarge canal orifices and extraction of pulp all the way down to the apical segments. The clinician gains the convenience of straight-line access into the canal space (notably the apical region of curved roots), a more capacious irrigation reservoir and improved precision for molding the length and apical size needed. (12) The result is ‘more efficient cleaning and shaping of the root canal system’ (6) traded off against reducing sound crown and root dentin, and this after material damaged by caries, trauma, etc. has been cleared out.

By tooth type, a post may not be needed in the case of endodontically-treated molars. Owing to sheer size, these possess large pulp chambers and retain a great deal of material even after treatment (13). But when extensive damage has already eroded the molar, a clinician can avoid perforating the root or otherwise weakening it too much in the course of preparing the cavity by opting to site the post down the straightest canal, usually the distal for mandibular molars and palatal in the case of maxillaries. Even so, a single post may not provide adequate core retention; in which case, Kane and Burgess advise placing pins. (13)

A second tooth class, the premolars, presents other challenges. These include tooth substance being substantially less (than the molars), thinner mesiodistal roots, shorter pulp chambers for building up a core, more distinct root curvature, and a clinical crown frequently slanted lingually vis-à-vis its root. All of these not only contribute to the need for a post but also make shaping a more intricate task to avoid inadvertently perforating the root.

Lastly, there are the anterior teeth, in particular the incisors. Their overall shape and thin roots mesiodistally combine to make the preparation of space for any post fairly difficult. Given minimal structural damage, treated teeth may not require a post (11) and restoration employing bonding in the access cavity might suffice (9). Cosmetic concerns can be taken care of by utilizing veneers over the direct composite restoration. When loss of tooth structure is more extensive, a post could well supply the core that will help resist the functional force of mastication. One study suggested, however, that posts did not materially raise fracture resistance of incisors (14).

Post Cementation

Other than the core requirement of proper bonding to dentin (and therefore post retention), dental cement must satisfy other criteria, including compatibility with canal sealers, ease of removal in case of retreatment, and ability to withstand microleakage or thermocycling.

Zinc phosphate is the most established of the dental cement – other options being resin-based composites and polycarboxylate – in large part for forming more durable bonds and compatibility with the zinc oxide eugenol (ZOE) component of most root canal sealers. (6) Thirdly, a metal post originally bonded with zinc phosphate in the canal space is easier to remove than when bonded with resin-based cement. Ease of dissolving the bond means that retreatment due to endodontic failure is less likely to engender a root fracture.

In the case of the aforementioned survey of German dentists, it was found that the incidence of using zinc phosphate cement was considerably higher (51%), compared to glass ionomer cement (38%). (54)

Crown Considerations

The first consideration one finds is the thickness of the ferrule. Slutzky-Goldberg et al. hold that the thickness of the ferrule –the cast crown meant to stabilize treated teeth – is ultimately more critical to restoration success than any combination of materials for the post and crown. Such a cast crown needs to be a minimum of 1 to 2 mm. when measured “coronal to the finish line of the crown” (7) in order to optimize fracture resistance.

Three years earlier, Ma et al. had investigated precisely this phenomenon by cycling a 6-kg. test load 135 degrees to the long axis of 15 restored maxillary central incisors. The designated independent variable, therefore, was the number of load cycles required before the crown cement visibly failed. In turn, the dependent variable was ferrule thickness: three groups of five incisors each at 0 mm. (no ferrule), 0.5 mm. and 1.0 mm. Otherwise, the incisors had been restored uniformly: a ceramic crown, resin cement, a one-twentieth-inch ParaPost FiberWhite glass-filled composite post, ParaCore composite resin core set in place with ParaPost resin cement and bonded to dentin with ParaPost Cement Conditioner A & B. The crowns themselves bore a total preparation height of 7 mm., a lingual axial wall of 1.5 mm., and a shoulder of 1.0 mm around the incisor. (8) Crown material was IPS Empress 2 pressable ceramic material cemented with Variolink II resin cement. The clearest evidence of crown integrity is provided by the fact that the no-ferrule restorations failed after an average of 213 load cycles whereas none of the 1.0-mm. crowns failed even after being subjected to a quarter-million load cycles. Despite the comparatively minuscule sample, statistical analyses employing the nonparametric Kruskal-Wallis and Mann-Whitney U tests with Bonferroni corrections found significant differences between 1.0-mm. thick ferrules and no-ferrule incisors (p < 0.17). Such a result suggests that the superior performance of 1-mm. thick ferrules cannot possibly have occurred due to random variation alone. Moreover, the authors aver that these results on ferrule length also apply to cast metal and metal/ceramic crowns since no evidence has been adduced so far that all three crown types differ markedly in point of sheer durability.

Recent Innovations

The search continues for post space procedures, as well as post and core materials, that meet more fully the demanding criteria of restorative endodontics. Among the requirements for a new post and core materials are heat resistance, modulus of elasticity, and resistance to occlusion forces, withstanding oxidation and the resultant corrosion well, and excellent cohesion with the aid of the proper cement to the remaining dentin. (6) In general, fiber-reinforced posts are optimal for approaching most closely the properties of dentin.

Preparing the Post Space

The convenience of getting post drills with virtually any prefabricated post does not preclude the need to review variable root geometry and mechanical preparation before employing bespoke drills. The primary consideration is to avoid perforating roots. To this end, Guttman reminds clinicians engaged in restorations that due attention to anatomical and biological factors should include taper, proximal invaginations, crown angle vis-à-vis the root, the curvature of the latter, and the fact that mesiodistal diameter is apt to differ from that of facial/lingual roots. (37)

Minimizing the risk of perforating roots can also fall back on the recommendations of Gordon, nearly three decades old now, to follow a three-stage procedure. It is safer to remove the temporary gutta-percha filling with heat pluggers first as this also helps preserve the apical seal. Next, the clinician desiring the speed advantage of mechanical preparation had best choose Gates-Glidden drills and P-type reamers at low-speed settings. The safe best practice then finishes up with the drill that came with the prefabricated post. (38)

Ceramic Posts

The recent innovations in all-ceramic restorations are clearly superior in stiffness (i.e. resistance to fracture), high flexural strength, and long-term dependability, besides boasting satisfactory biocompatibility. In addition, the prefabricated variety is available in a variety of shapes and designs, offering flexibility, and one-visit adjustment and insertion. An all-ceramic crown is also aesthetically pleasing for looking more natural. But when a gold post is preferred for its modulus of elasticity, heat tolerance and good compressive strength, ceramic anterior teeth restorations prove translucent to the precious metal. For aesthetic purposes, clinicians may resort to a metal-ceramic alloy for custom-fabricating a porcelain-fused-to-metal post and core. More critically, there are no early reports of poor resin bonding to dentin, at least in the course of in vitro fatigue testing. (6, 22-24)

Other Metals

A much-used industrial metal, titanium brings to restorative dentistry the advantages of unmatched biocompatibility and corrosion resistance. (21) The drawback, however, is that titanium is more difficult to remove when retreatment becomes necessary because it fractures more easily than stainless steel posts. Being of about the same density as gutta-percha, posts constructed from popular titanium alloys are also hard to discriminate from the sealant in radiography.

Updates on Post Biomechanics

There are numerous prefabricated post types. By surface, posts are either smooth and retained with cement or prefabricated with screws to optimize retention, self-threading or requiring threading with taps. Caputo and Standlee arrived at three main classes (36):

  • ‘Parallel-sided, serrated or smooth, cemented into matched cylindrical channels prepared by a post drill;
  • Parallel-sided threaded and inserted into pre-tapped channels;
  • Tapered, serrated or smooth-sided, cemented into a post space prepared with a matched-size post drill.’ (36)

Subjected to photoelastic stress analysis, some of the screw types turned out to exert such pressure on root walls as to make fractures inevitable. (15) As well, there is the trade-off of requiring more dentin removal, notably when the clinician decides on parallel placement. The obvious compromise is to employ screw posts only when absolutely necessary, mainly where the crown-to-root ratio is borderline.

For what it is worth, the aforementioned survey of German dentists suggested that more than half rely on cast posts and cores and about a third have completely shifted to the prefabricated type. Despite the clear risk of fractures owing to the pressure exerted on root walls, nearly half of those preferring prefabricated posts opt for the screw type. (54)

The longitudinal shape defines a fourth post type, tapered toward the apical end. This variant has the virtue of requiring less dentin removal at the price of trading off retention.

Aside from the aforementioned retention advantage of parallel-sided posts, the active or passive installation comprises the final distinction in restoration procedures. Active posts are in contact with treated tooth dentin and consequently transfer all mastication pressures to the surrounding root canal space. The potential for fractures is then moderated solely by the density of the post material used, with metal putting the restoration at gravest risk and fiber-reinforced posts about as elastic as dentin and therefore minimizing the risk.

Post Cementation

This section discusses the newer dental cement and the intricate requirements for bonding posts to dentin generally. These cements are glass ionomer and resin-ionomer hybrid cement.

Owing to their potential for bonding to dentin, resin-based composites have made inroads. The evidence about effectiveness is mixed, however. Positive findings include better post retention (45-46), greater resistance to fracturing (47), diminished microleakage (48-49), and a modulus of elasticity that approximates that for dentin. Cheung was also of the opinion that resin cement thermocycling was a minor concern when applied in thin-film thickness (6) although others found significant drawbacks for the material in respect of both thermocycling and microleakage. (50-51)

In order to curtail microleakage and optimize bonding to the dentin wall, Cheung recommends a three-step procedure (6):

  1. Assuming a case of endodontic repair, the first stage calls for thorough cleaning with the objective of eliminating remaining inert filler and canal sealant else the new resin film will not bond properly to dentin. Removing gutta percha itself is a multi-step process of extraction with mechanical and thermal methods, cleaning the root canal walls with a Peeso brush and pumice slurry, and rinsing with 3-in-1 and irrigation syringes. Thorough cleaning also paves the way for satisfactory polymerization of resin cement, thus ensuring seal and post retention even when the sealant contains eugenol. (49, 52)
  2. The demineralized collagen layer must be removed with proteolytic agents such as sodium hypochlorite, shown by Varela et al. to enhance bonding by permitting resin tags to dentinal tubules. (45)
  3. Finally, an acid treatment (applied with a lentulo spiral) neutralizes the smear layer, after which aseptic wet bonding of the resin-based composite to dentin (employing a micro applicator with a fine-point tip) can take place.

The aforementioned advantage of zinc phosphate in ease of withdrawal when retreatment is needed contrasts sharply with the intractability of resin when used to cement metal posts. The problem does not arise when resin cement is used alongside fiber-reinforced posts since such posts are distinctly easy to remove.

The polycarboxylate and glass ionomer cement (GIC) bear drawbacks in respect of microleakage risk and deficient modulus of elasticity compared to zinc phosphate and dentin. (6)

In practice nonetheless, as exemplified by a German survey, the preference rate for composite resin (51%) to emplace core foundation is about twice that for GICs (26%). Amalgam has only marginal usage (0.5%). (54)

Fiber-reinforced Posts

There is a great deal of interest in the adaptation of ‘space-age’ composite materials, formally termed ‘fiber-reinforced polymer’ material for posts, for most closely resembling the physical properties of dentin. In composition, these are silica or, more commonly, carbon fibers usually coated with a matrix of epoxy resin. Being just seven to ten micrometers in diameter, carbon fiber can be heat-treated in longitudinal/parallel, woven or braided like any synthetic fiber. (6)

The early evidence on the physical properties of fiber post restorations suggests that they are less fracture-prone, boast superior aesthetics, reduce the amount of dentine that must be removed to make way for a post, do not corrode as metals/alloys do, bond better, and are more easily removed should retreatment be necessary. (32)

Being less rigid than any metalcore or post-casting and boasting a low flexural modulus approximating that of dentin (≈ 2 × 106 psi), fiber posts (from 1 and 4 × 106 psi) effectively dampen lateral forces before these are transferred to the surrounding dentin. Hence, there is a lower risk of root fracture occurring. And when failure does occur, there is a greater probability of successful restoration compared to metal posts. (25-28)

Secondly, fiber posts bond better to dentinal walls of the root canal than do alloy/metal, employing widely-used resin cement and resin composite cores. Assessment of bond properties with electron microscopes reveals the establishment of a hybrid layer, resin tags and an adhesive lateral branch. (16, 29-30) That being the case, there is less need to prepare an extensive post space and correspondingly lower probability of fracture. As well, a shorter parallel post can be considered in place of long tapered ones. (31)

While fiber-reinforced posts have not been in use long enough to yield extensive longitudinal or prospective study clinical data, the early evidence points to very high success rates. A review by Ferrari et al. that compared three types over an installed-restoration life of from one to six years obtained an overall success rate of 96.8 percent. (33) Two more retrospective studies of patient records going back four years yielded an almost-equivalent result of 95 percent. (34-35).

Glass and Mineral Trioxide Aggregate

Once the root canal has been filled and the cavity for the post adequately prepared, Slutzky-Goldberg et al. advocate the use of either glass ionomers and mineral trioxide aggregate (MTA) for hermetic sealing against the possibility of bacterial leakage. (7)

Differing Emphases by Specialty and Other Personal or Practice Variables

Clearly, as in most other professions, endodontists confront increased demand for ETT. To optimize their chances of success and reduce the known risks, the profession can take advantage of a continuous stream of innovations in materials, methods, and tools for restoring ETT. But adoption of innovation is slow, not least because published studies have been based on non-comparable research designs. As in many other fields of health and oral care, the usage of rigorous randomized cluster trials is more the exception than the rule.

Instead, Naumann, Kiessling and Seemann report from their nationwide survey of German dentists that innovation adoption is heavily influenced by age and its autocorrelation, length of time in the profession or a sub-specialty. There is also a kind of geographic clustering (54), which suggests the influence of region-specific continuous medical education (CME) and symposia such as might be conveniently attended by a cluster of dentists and endodontists in, say, Bavaria. Were it not for the significant minorities of dentists that do adopt innovations, one would have to conclude as these researchers in Germany and other countries do, that the profession is apt to go by what succeeds in the practice of each individual.

Summary and Conclusion

Thus far, this concededly brief review of the professional literature reveals growing demand for post-RCT restoration, particularly because as much as half of treated teeth become re-infected and thus require retreatment. On the whole, there is agreement about the goals of restoration, i.e. returning the treated tooth to normal function, filling the root canal by creating a post in place of the excavated pulp, final sealing by prosthetic replacement of the crown, and minimizing the interval from RCT to final sealing in order to avoid recontamination of the ETT. Restoration involves a diversity of materials, methods and ‘best practice’.

Improving the prognosis for treated teeth requires, first of all, assessment and improving viability for restoration. Planning for restoration even before carrying out RCT means clearing out caries and remnants of prior ETT. Both general dental practitioners and endodontists are called on to examine periodontal vitality, attend to occluding faults, crown-root ratios, tooth width, and existing and potential fractures. Assessing the integrity of the remaining tooth structure is also fundamental to restoration options, since excessive deterioration may require a lengthened crown or orthodontic eruption. Otherwise, there is considerable debate about appropriate materials and methods.

Even the matter of creating a post remains open to discussion. Certainly, a post is a sine qua non when there is not enough of the root and crown on which to create a restoration crown. A post is needed principally when a crown restoration is unlikely to resist occlusal pressure if it were to rest solely on the little that remains of a treated tooth. Otherwise, some researchers maintain, actions taken to prepare the canal and embed the post firmly merely weaken the remaining root structure and predispose the tooth to fracture.

When a post and core is justified, the traditional materials are base metals: gold or gold-plated brass post-and-core and stainless steel. The choice criteria include durability (both by virtue of being inert and resisting occluding force), minimal or no compression, low thermal expansion, and low abrasion on surrounding tissue. Stainless steel has a number of drawbacks, including being corrosion-prone, exposing both female dentists and patients to allergic contact hypersensitivity because of the nickel in the alloy, and a degree of hardness that makes fabrication and restoration inordinately difficult. As well, stainless steel raises the probability of root fractures, notably when screw-type posts are installed. Hence, the profession has veered towards fabricated-to-suit gold posts and cores.

Newer materials are now available for both post and crown. Such product development has been greater for posts because this is the more demanding and intricate stage in restoration. ‘Space age’ metals and composites like titanium, and carbon fiber.

Still, in the area of materials, a survey should cover dentists’ considerations post length and diameter. Restoration success rests on the length of the post as this affects the crown-to-root ratio and extends sufficiently into the bone surrounding the root. Obviously, root dimensions vary according to tooth type and even within the same type for a given patient. Hence, the criteria for post length include extending at least halfway down the length of the canal, half the root length surrounded by bone, at least equal to crown height, and leaving around 3 to 6 mm. for the apical seal. Post width seems secondary to restoration prognosis, although thinning out the remaining sound dentin, notably in the apical segment, increases the risk of fracture and ET retreatment in the future. Hence, it is recommended that post diameter be limited to one-third of root width at its narrowest and that at least 1 mm. of healthy dentin remain after drilling for post space, all the while paying attention to the anatomical fact that roots are never perfectly round

The reportedly popular ‘crown-down’ technique exemplifies method and equipment choices available to endodontists. One may opt for either manually-operated stainless-steel Gates-Glidden drills or the newer nickel-titanium rotary devices to enlarge canal orifices and extract pulp all the way down to the apical segments. By gaining the convenience of straight-line access into the canal space (notably the apical region of curved roots), a more capacious irrigation reservoir and improved precision for molding the length and apical size needed, clinicians, are able to more efficiently clean and shape the root canal. Once again, however, survey instrument formulation had the best address the drawbacks of either mechanical approach, reducing sound crown and root dentin residual to caries, trauma, etc. that required RCT in the first place.

Despite such gratifying advances in materials and methods, a diversity of findings in the literature has rather unsurprisingly ensued from employing a variety of research methods (e.g. retrospective, prospective, virtually no randomized cluster trials), statistically inadequate sample sizes, and the lack of a uniform method for, say, testing occlusal stress in vitro. Accordingly, even the theoretically sound advantages and drawbacks of a given material or restoration method are not predictive of a consensus in professional practice. As the example of a nationwide survey in Germany has shown, at least half of dentists are prone to stay with established crown and post materials. As few as one in four report adoption of an eminently superior alternative like carbon fiber composite. At that, cooperating dentists may not even be representative of the country universe if one presumes that tradition-minded dentists are reluctant to reveal how ‘backward’ they remain for staying with what has worked in their individual practices. This is the implication of findings that present restoration practices are inversely correlated with age and directly related with length of time in practice. Some professional ‘consensus” is evident on a regional basis, suggesting the effect of easily-convened provincial meetings and periodic interaction among individual dentists.


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