Cracked tooth syndrome. IN BRIEF • Includes a consideration of means available to provide acute care for a patient PRACTICE suffering from . Part 2: restorative options • Provides a comprehensive review of the available literature of both direct and indirect restorations/restorative materials for the management of to manage an incompletely fractured posterior tooth. • Introduces the concept of the direct cracked tooth syndrome coronal splint as a novel approach for the management of this distressing condition. S. Banerji,1 S. B. Mehta2 and B. J. Millar3

VERIFIABLE CPD PAPER

The second of this two part series on ‘cracked tooth syndrome’ will focus on the available methods for the immediate, intermediate and defi nitive management of patients affected by this condition. Included in this article is a comprehensive account of the relative merits/drawbacks of various restorative materials and their respective techniques of application for the treatment of symptomatic, incompletely fractured posterior teeth.

PRINCIPLES FOR THE propagation of the crack and reduce the Table 1 Immediate treatment options MANAGEMENT OF ingress of bacterial microorganisms into for CTS CRACKED TOOTH SYNDROME the dental pulp.2 Occlusal adjustment – destructive, short term It is apparent from the fi rst article of this Historically a plethora of different ‘forms’ Remove segment – highly destructive series that the diagnosis of cracked tooth of dental restorations have been advocated syndrome can pose a major challenge to to ‘splint teeth’ affected by incomplete Immobilisation of segment: the dental operator. It would also be fair to fractures. This paper will divide these into Copper ring diffi cult and state that the management of the condition four broad categories. Hence: periodontally damaging is by no means always a simple straight- • Immediate Orthodontic time consuming, forward matter. • Direct restorations placed intra- band possibly not available While it would appear that there is no coronally without cuspal coverage Temporary highly destructive, universally accepted restorative proto- • Direct restorations, which provide crown time consuming col, it is generally agreed that the aim cuspal coverage Direct quick, low cost, readily composite splint available and non-invasive of restorative therapy is to immobilise • Indirect restorations placed intra- the segments of the tooth that move on coronally without any cuspal support loading. The latter may be achieved in and indirect restorations which provide crack propagation but also relieve the a limited number of cases simply by the cuspal coverage (onlays and full associated symptoms.3 removal of the affected cusp and restoring coverage restorations). However, it has been argued that sim- the defect with an appropriate material, or ply grinding the tooth out of occlusion in the majority of cases by the placement The aim of this article is to review the is likely to be only of limited benefi t as of a restoration that prevents independent available literature on the above restora- the tooth may still be critically stressed movement of the tooth segments on either tions when used to treat cases of cracked by a food bolus to such an extent that side of the crack, thereby ‘splinting’ the cusp syndrome, with emphasis placed the process of fl exure will still continue tooth together.1 on the efficacy, efficiency, economic on loading.4 Furthermore, occlusal adjust- The process of splinting should minimise viability and biological cost of each of ment may not only involve the removal fl exure of the compromised cusp, therefore the above. of healthy sound tooth tissue, but when not only aiming to alleviate the symptoms undertaken without analysing the effects of pain on biting but also prevent further IMMEDIATE THERAPY OF CTS on the residual dentition may also lead to It is generally accepted that the more rap- unwanted occlusal interferences elsewhere idly a tooth with a crack is treated, the in the dental arch. 1, 2 Senior Clinical Teacher; General Dental Practitioner 5 and Clinical Teacher, 3*Professor and Consultant in easier it will be to avoid irreversible dam- Fox et al. have recommended that fol- Restorative , Department of Primary Dental age. Table 1 provides a list of the pos- lowing a positive diagnosis of a cracked Care, King’s College London Dental Institute, Bessemer Road, London, SE5 9RW sible immediate treatment options. As tooth where a pre-existing restoration is *Correspondence to: Professor B. J. Millar an ‘immediate’ or remedial approach a present, it should be removed to assess Email: [email protected] number of authors have advocated the the full extent of the fracture. Often dur- Refereed Paper undertaking of occlusal adjustments upon ing this process the affected cusp may Accepted 25 March 2010 DOI: 10.1038/sj.bdj.2010.496 affected teeth, to reduce the stress on the ‘splinter off’ and the remaining defect ©British Dental Journal 2010; 208: 503–514 tooth, so as to not only prevent further managed accordingly.

BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010 503

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

Where there has been no splintering off way. The placement of such restorations the affected portion of the tooth, immedi- while effective are however, time con- ate immobilisation by means of an ‘imme- suming, biologically invasive and costly. diate extra-coronal circumferential splint’ Furthermore, rarely in the opinion of the may be applied. The latter may take the authors is it possible to prepare a tooth to form of a copper ring or a stainless steel receive a full coverage provisional crown orthodontic band, both of which should when a patient fi rst presents with CTS on be tight fi tting, contoured to not interfere the same appointment. It is worthwhile with the occlusion and cemented using noting however that any delay in institut- a zinc-polycarboxylate cements.6 ing immediate therapy may lead to further It is generally agreed however that stain- progression of the fracture and in the worst less steel orthodontic bands are the pre- scenario culminate in tooth loss as well. ferred option, as they can be contoured A novel concept which has yet to be more effectively so as to infl ict less irrita- fully supported by a clinical trial is the tion/damage to the gingival/periodontal placement of bonded composite resin tissues. Upon review, following a period directly over the surface of the tooth to of two to four weeks after the application splint across the fracture and immobi- of the immediate splint, the absence of lise the segments (Fig. 1). The splinting pain has been described to indicate not method is used by all the authors and is b only a correct diagnosis but also success- referred to as a ‘direct composite splint’ ful immobilisation.7 Where symptoms of (DCS). It can be used with minimal tooth thermal sensitivity persist, endodontic reduction of the functional areas of the therapy may need to be considered.7 In occlusal surface but the authors now prefer such cases, the splint may remain in situ to use it as a non-invasive splint with no until the completion of root canal therapy tooth reduction, creating a fl at splint in a and the eventual application of the defi ni- supra-occlusal position. Resin composite is tive restoration. applied to a thickness of 1.0-1.5 mm over While the placement of copper rings and the occlusal surface of the affected tooth, stainless steel bands have been suggested and fi nished just beyond the external line c to be a clinically effective, minimally angles of the affected tooth. The restora- invasive and a cost effective immediate tion should be contoured to display the treatment modality for teeth affected by absence of occlusal contacts in either lat- cracked tooth syndrome,7 in the opinion of eral or protrusive mandibular movements the authors, the technique of placing the (which may require the addition of resin latter may be time consuming and techni- composite to guiding teeth). cally challenging. Furthermore, with the The above approach of placing a res- advent of adhesive dentistry, many dental toration in supra-occlusion follows the operators may not have acquired the tech- principles of the well documented Dahl d nical experience needed with the place- concept9-11 whereby it would be expected, ment of copper rings; indeed, copper rings in cases other than those with limited erup- Fig. 1 A tooth with amalgam restoration and a mesial crack (a). Air abrasion was may not always be readily available in the tive potential, that through the combined used to augment micro-mechanical modern general dental practice. Likewise, process of dento-alveolar segment intru- retention (b) and a direct composite many general dental practitioners may sion and extrusion respectively, occlusal splint was placed in supra-occlusion (c) not have the technical expertise or ready contacts would be re-established after a without any tooth preparation which is designated as an immediate option for the access to stainless steel orthodontic bands. suitable period of time. management of an incompletely fractured, Discomfort associated with the application A DCS has the potential, in theory, to be symptomatic lower right second molar of copper rings and their tolerance may used as both an immediate and intermedi- tooth. (d) demonstrates the importance of ensuring that the splinted tooth is free be other complicating factors. In addition ate restorative option. It has the potential of occlusal contact on mandibular lateral patients may object to the aesthetics where of being biologically conservative, aes- excursive movement the band is visible. thetic, effi cient to apply, reversible and an The preparation and placement of full inexpensive restorative modality, which coverage acrylic provisional crowns has also offers the potential to offer imme- literature review has been published by been described by Gutherie et al.8 as a diate pain relief and assist in diagnosis Poyser et al.12 documenting the principles predictable, ‘immediate splinting’ option (particularly where there may be doubt). of the Dahl concept. for the management of incompletely frac- However, careful case selection and the A DCS may also be used before the tured teeth. Preformed crowns of differing attainment of patient consent are very application of an adhesive onlay (Fig. 2), varieties may also be applied in a similar important factors to consider. A detailed where the desired inter-occlusal space for

504 BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

the defi nitive restoration may be accom- plished by the process of controlled intru- sion and extrusion of the dento-alveolar segments. The application of DCS restora- tions does however require considerable further research to validate its application in every day dental practice.

THE USE OF DIRECT/PLASTIC c INTRA-CORONAL RESTORATIONS (WITHOUT CUSPAL COVERAGE) TO TREAT CASES OF CTS Dental amalgam (conventional/bonded)

Dental amalgam, composite resin and glass-ionomer cements are among three a d of the most commonly used plastic, direct restorative materials in contemporary den- Fig. 2 An example of a case where a tal practice. In principle, their use intra- fractured tooth (a) is treated initially with a provisional direct supraocclusal splint coronally in the management of cases of shown in (b) before the defi nitive gold CTS (in the absence of any splintering) is adhesive onlay has been placed, initially in based on their ability to attach themselves supra-occlusion, and now shown at three to the areas of tooth tissue located either month review where the occlusal contacts have re-established (c, d) side of the fracture and thereby prevent independent movement of either fragment upon loading. In doing so, it would be hoped that these materials would restore the fracture strength of the tooth equiva- lent to that of a sound caries free tooth.13 Longitudinal studies on the performance of extensive amalgam restorations have confi rmed amalgam’s success as a direct, b plastic restorative material.14,15.However, the fact that dental amalgam lacks intrin- sic adhesive potential would infer that it would have little effect on ‘binding’ frac- suffering from CTS that had been managed examples of direct composite resin used tures or restoring fracture resistance unto by the application of bonded amalgam to restore fractured teeth. In Figure 3 con- teeth affected by CTS (without the need of restorations, bonded using Panavia EX ventional tooth reduction was carried out auxiliary retentive aids). (Kuraray, Japan).19 before composite placement. Figures 4 and It has been shown that fresh dental Panavia EX is a chemically active resin 5 show cases where only minimal reduc- amalgam can be bonded to etched enamel that bonds to both enamel and metal.20 tion was carried out and the composite and dentine with an ‘adhesive liner’,16 Bonds strengths of 8.8-14.2 MPa have was placed at the original vertical dimen- hence the concept of the ‘bonded amal- been reported to develop between etched sion. Figure 6 shows a similar case with gam restoration’. Two case reports have enamel and Panavia EX,19 versus that of no occlusal reduction where the composite been published involving the successful 18-20 MPa between composite resin and resin was placed in supra-occlusion. application of bonded amalgam restora- etched enamel. The results of in vitro studies regarding the tions for patients presenting with CTS. In vitro studies have reported the fracture ability of resin composite to restore cuspal The fi rst, a single clinical case involving strength of molar teeth containing bonded stiffness are confl icting in outcome; while the use of ‘Amalgabond’;17 the adhesive amalgam MOD restorations to be signifi - some have reported little marked improve- agent present in Amalgabond contains cantly higher than when compared to con- ment23 others have shown that the place- 4-META (4-methacryloxylethyl-trimelli- ventional MOD amalgam restorations.21,22 ment of composite resin restorations has the tate anhydride). 4-META has been shown potential to restore fracture strength, and in to have the capacity to bind with colla- Directly bonded resin composites some cases to a level superior to that of a gen fi brils present in the organic compo- Composite resin offers an aesthetic alterna- healthy, un-prepared tooth.24 nent of dentine and to metallic ions.18 The tive to silver amalgam for the restoration Opdam et al.25 investigated the short term second case report included four patients of posterior teeth. Figures 3-6 illustrate clinical effi cacy of bonded (direct) composite

BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010 505

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

a

a d

b

c

Fig. 3a Illustrates the same case as in Figure 1 and is an example of a tooth with CTS which has been managed by the means of a direct resin composite onlay and a conformative approach. (b) b e illustrates the case immediately post-op and (c) is three years post-operatively Fig. 4 Illustrates an example of a tooth with amalgam restoration and cusp fracture (a). Following the removal of the existing amalgam restoration (b) resin when placed intra-coronally for the the fracture line is visible (see arrows), treatment of 21 painful, cracked teeth. The the occlusal surface has been reduced authors concluded that direct composite resin by 0.5 mm and a bevelled fi nish applied circumferentially (c). Resin composite has restorations without cuspal coverage can be been applied using an incremental ‘build-up effective in treating cases of CTS (75% of technique’ (d). A pre-operative silicone cases reported alleviation of symptoms when matrix can also be used to fabricate the verbally questioned). Opdam et al.26 have occlusal anatomy of the restoration. A c direct placement supraocclusal restoration also published a report in 2008, document- (DCS) has been placed in supra-occlusion ing the results of a seven year evaluation of with minimal tooth preparation, which may the effi cacy of direct composite resin when be retained as an intermediate restoration in the short to medium term (e) used to restore painful cracked teeth (pre- viously containing amalgam restorations). The results of the latter study displayed an annual failure rate of 6%. It has been postulated that in the absence to effectively splint the tooth.26 The latter secondly due to the presence of a pre-exist- of cuspal coverage, repeated loading of the effect may be exaggerated in cases of CTS ing fracture, cuspal fl exibility would have restoration or residual tooth tissue may by two factors; fi rstly, CTS is often seem already been increased when compared to stress the ‘adhesive layer’ and ultimately among patients who display parafunctional a healthy un-fractured, sound tooth, plac- lead to its breakdown, with the concomi- grinding habits who would be more likely to ing further greater strain on a progressively tant failure of the ability of the restoration apply higher loads to the restored tooth, and weakening adhesive layer.

506 BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

It has been reported that resin bonded composites (and bonded amalgam restora- tions) are less effective in restoring fracture resistance where cavities are greater than half of the intercuspal width (without the use of cuspal coverage).23 The incremental application of composite resin to a cav- ity (versus bulk placement) also has a sig- nifi cant impact on improving the ultimate fracture resistance of a restored tooth.27 Polymerisation shrinkage is a factor commonly cited as an important cause for the higher reported failure rate associated with large composite resin restorations.28 Shrinkage may also cause the fl exion of the cusps towards the bulk of the material which may further accentuate the fracture, a c and also induce stresses in the material and the adhesive layer, which would in turn lead to the failure of the ability of the material to immobilise the crack. The feature of polymerisation shrink- age may, however, be vital to the suc- cess reported for direct resin composite onlays, as it may help to splint the crack by effectively embracing the cusps together, d as polymerisation shrinkage will cause the material to shrink towards the cen- Fig. 5 Amalgam removed (a) and tooth tre of the restoration and add up to the prepared with minimal cuspal reduction (b), then restored with direct composite bonded surface.29 resin (c) at correct occlusal height and at Other factors which should also be taken review (d) into consideration when considering the application of resin composite in poste- b rior teeth include, the risks of restoration bulk fracture and accelerated wear. The attainment of high quality proximal con- tact points and occlusal anatomical form (cermets), however, have been reported to complete a complex composite resin res- may also be a concern when using direct restore prepared teeth to a strength equiva- toration compared to similar amalgam res- composite. lent to that of sound teeth or those restored torations,33 it still takes less time than to with resin composite.31 The poor aesthetics complete an indirect restoration. All too Glass ionomer cements (GICs) associated with cermets is a concerning often, where a patient has had to return The role of glass ionomer cements (GICs) in factor. following a diagnosis of an incomplete the management of cases of incompletely GICs may have a role to play in the man- fracture for the preparation of an indirect fractured posterior teeth to the knowledge agement of cases of CTS as base materi- restoration, the fracture may have pro- of the authors has not been extensively als under extensive direct composite resin gressed to the pulp or culminated in the documented. It has been suggested that fi llings thereby reducing the volume of loss of an extensive amount of the tooth. while GICs have the capacity to increase resin required and the associated levels of According to a leading authority, tooth stability among teeth with class polymerisation shrinkage.32 cracked teeth should be considered to be II posterior cavities, they offer a lower In summary, direct plastic restoratives at an increased risk of pulpal complica- bond strength to both enamel and den- (bonded amalgam and resin composite tions (in particular, where there has been tine when compared to resin composite.30 restorations), when applied without cus- thermal sensitivity);26 the preparation of Furthermore, due to their inferior wear pal coverage to manage cases of cracked such teeth to receive indirect restorations and fatigue properties (compared to silver tooth syndrome, have the potential to would not only result in the loss of more amalgam and composite resin), they are provide a conservative, cost effective and sound tooth tissue but necessitate the use not the fi rst choice of material for applica- time effi cient option to the use of indirect of a provisional restoration. Both the lat- tion in stress bearing posterior cavities.30 alternatives. While it has been proposed ter factors will increase the risk of pulpal Silver reinforced glass ionomer cements that it takes 2.5 times longer to place and complications.

BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010 507

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

ab c Fig. 6 A cavity showing amalgam removed and crack visible (see arrow) on distal margin (a). The tooth was restored without cusp reduction and directly placed composite as a supraocclusal composite splint. (b) shows immediate post-op view and (c) is three years post op

It has been reported by Gutmann et al.34 in cold sensitivity was observed to occur in end of the observation period, a survival that approximately one fi fth of all teeth the group treated by the means of bonded rate of 100% was elucidated; all 21 cases diagnosed with cracked tooth syndrome amalgam overlays following a two week reported the elimination of symptoms of will eventually require endodontic ther- post-operative period (while the baseline thermal sensitivity and pain on biting apy; furthermore the prognosis of endo- levels for thermal sensitivity remained when asked verbally. Similar results were dontically treated, cracked teeth appears unchanged for the non-bonded group). The published by Homewood.37 to be relatively poor. A study by Tan et latter observation may be accounted for by The application of resin composite over al.35 reported a failure rate of 14.5% for the ability of the resin liner to seal patent the affected cusp in cases of CTS appears cracked, root fi lled teeth after a relatively dentinal tubules, but also by the fact that to reduce the stress on the weakened cusp, short evaluation period of just two years. the non-bonded group required 4 mm of possibly by a combination of factors such Caution does need to be exercised when tooth reduction of the involved cusp (to as composite resin itself having some level considering the use of either direct bonded accommodate the pin[s]) as opposed to 2 of ‘shock absorbing effect’25 by increas- amalgams or resin composites for cavities mm for the bonded group, which may have ing cuspal stiffness and by re-distribut- which are greater than half the intercuspal made a difference in the pulpal response ing occlusal loads away from the crack width in cases of CTS,23 and perhaps among to cold. towards the axial walls and down the long patients who display signs of . The results of both studies37,38 have indi- axis of the tooth. A reduction in the height cated a possible role for amalgam over- of the affected cusp may also reduce its DIRECT RESTORATIONS lays in the management of incomplete level of fl exion upon loading, which may WITH CUSPAL COVERAGE; fractures in posterior teeth (at least in the also help in the management of symptoms DIRECT OVERLAYS/ONLAYS short term), particularly where a bonded but also reduce the stress on the adhesive Direct amalgam overlays amalgam restoration is applied. layer, and thereby enhance the longevity (conventional/bonded) of the restoration. Directly bonded resin Figure 3 shows an example of a tooth Hood et al. in 199136 reported that teeth composite onlays with CTS, which has been managed by the restored with amalgam overlays had ‘frac- According to the results of an in vitro means of a direct resin composite onlay ture energies equivalent to that of intact study, where teeth were assessed and a conformative approach. Figure 3c teeth’. Accordingly, Homewood37 has advo- for fracture resistance where composite has been taken of the same restoration, cated the overlaying of the cusps of teeth resin restorations had been placed both three years post-operatively. affected by CTS as a primary mode of with and without cuspal coverage, cases A success rate of 72.7% has been treatment for such cases. The latter under- with cuspal coverage displayed a signifi - reported for teeth restored by means of took an analysis to assess the perform- cantly higher fracture resistance.39 direct composite resin inlays/onlays (over ance of conventional amalgam overlays The above was refl ected in two clinical a period of 11 years); fracture, occlusal for the management of cases with CTS, studies by Opdam et al.25,26 In both stud- wear and secondary caries were the prime and reported a very high success rate (in ies, following the removal of the existing causes of failure.28 However, Bartlett et al.40 excess of 93%).37 amalgam restoration, the cusps of affected have contraindicated the use of direct (or Davis et al.38 have also published the teeth (as opposed to the entire occlusal sur- indirect) composite resin for the treatment results of a clinical study to compare the face) were reduced by 0.5-1.0 mm coro- of worn posterior teeth. efficacy of conventional pin retained nally from the onset of the micro-crack In summary, it would appear that the complex amalgam fi llings versus bonded and the resulting cavity outline fi nished use of plastic materials (bonded amalgams amalgam restorations. A similarly high with a bevelled margin (before the applica- and bonded resin composite) when placed proportion of cases displayed resolution tion of direct composite resin). over the affected cusp in cases of cracked of symptoms as reported by Homewood.37 In the more recent of the two studies, tooth syndrome seems not only to be time Interestingly, the results of the study by cases that were included were evaluated and cost effective but also clinically suc- Davies et al.38 showed a further reduction for a period of six to seven years.26 At the cessful in the alleviation of associated

508 BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

symptoms. Further studies are however painful, cracked teeth. Their application invasive, indirect restoration that has been required to assess the long term effi cacy is time consuming, sometimes necessitat- used to treat cases of cracked tooth syn- of bonded amalgams in cases of CTS. ing the use of a provisional inlay (which drome’.46,47 Examples are illustrated in Pulpal involvement does not appear to be may further accentuate the crack) and Figures 2 and 7. a major issue either where direct overlays require the removal of healthy hard tissue Yap47 has presented a case report docu- have been applied to manage CTS, which undercuts, which is biologically invasive. menting the application of a resin bonded is a concern where indirect methods are Furthermore, a fi ve year study by Wassell (adhesive) metal onlay for the management used. Should endodontic therapy, however, et al.,43 when comparing the failure rates, of a patient presenting with CTS, involv- be required where a plastic direct mate- wear rates and other aspects of clinical ing the placement a cast cobalt chromium rial has been applied, the cost implications performance of direct composite inlays alloy (Degussa, Germany). The prepara- are minimal and access to the pulp would versus conventional composite resin res- tion involved the reduction of the occlu- be relatively straightforward, as opposed torations placed incrementally, revealed no sal surface by 1.0 mm over the functional to in the presence of an indirect casting, signifi cant statistical difference between cusps and 0.7 mm over the non-functional which may need to be re-fabricated fol- the two forms of dental restorations. cusps; a shoulder design fi nish line was lowing the completion of root canal ther- applied circumferentially, 1.2 mm beneath apy (while the direct restoration may be INDIRECT RESTORATIONS the prepared occlusal surface. The resto- readily repaired). WITH CUSPAL COVERAGE ration was reported to be in place for a (ONLAYS AND FULL/PARTIAL The prime concern with the applica- period of at least one year and the tooth COVERAGE CROWNS) tion of direct overlays is the level of tooth described to be asymptomatic. The use of reduction, the need for considerable opera- While direct restorations placed intra- cobalt-chromium alloys on account of tor skill and the longevity of these restora- coronally (without cuspal coverage) have a their extreme rigidity permits an ultra- tions, particularly among bruxists. role in the management of cracked painful conservative preparation. teeth, consensus opinion is that for wider The successful application of resin INDIRECT RESTORATIONS cavities in particular, there is a need for bonded alumina abraded type III cast Inlay restorations cuspal coverage to further protect and gold alloy onlays (luted with Panavia (conventional and adhesive) strengthen the residual tooth structure.23 EX, Kuraray, Japan) to treat six cases of The fabrication of direct restorations which CTS has also been described.46 In the lat- Conventional intra-coronal inlay restora- provide cuspal coverage is considerably ter study, all affected teeth were prepared tions utilise the concept of ‘wedge reten- demanding of operator skill; the longev- to accommodate metal to the thickness of tion’, which has the potential of exerting an ity of direct plastic restorative materials 1.5-1.0 mm and restorative margins were outward pressure on the tooth.41 Pressure may also be a concern. The remainder of fi nished on enamel tissue, with a ‘small may be exerted not only upon trial of the this article will focus on indirect restora- chamfer’ placed 1-2 mm circumferen- restoration (pre-cementation) but also dur- tions which provide cuspal coverage for tially below the prepared occlusal surface. ing its functional lifespan, where cyclical the treatment of CTS. Restorations were evaluated for a mean occlusal loads are applied. Consequently, service period of 48 months; no failures conventional inlays have absolutely no ONLAY RESTORATIONS were noted. role in the treatment of cases of CTS. Conventional/adhesive metal onlays Figure 7 shows an incompletely frac- With an increase in the demand by den- tured symptomatic lower molar tooth tal patients for more aesthetic, predict- The procedure for the preparation of a which has been restored by the application able posterior tooth restoratives, ceramic tooth to receive a conventional cusp cov- of a gold adhesive onlay. The tooth has inlays and indirect composite inlays have ered gold onlay has been meticulously been prepared to receive a cast type III gold become commonplace in contemporary described and has been advocated for the adhesive onlay; the occlusal surface has dental practice as an alternative to direct conservative management of damaged been reduced by 1.0-1.5 mm and a cham- composite resin. occlusal surfaces of posterior teeth.44 While fer margin applied circumferentially. This To the authors’ knowledge, to date there historically they have been widely used for cast gold overlay was conformative and have been no reports published document- the management of CTS, there appears to fi tted to the existing vertical dimension. ing the effi cacy of adhesive aesthetic (resin be little clinical data to document their The use of type III or type IV cast gold or ceramic inlays) for the treatment of CTS. effectiveness in this application. alloys offer the merits of favourable wear An in vitro analysis has shown that bonded The advent of newer generation dentine characteristics, ease of casting and fi nish- MOD ceramic (Cerec) inlays and laboratory bonding systems and the availability of ing, high corrosion resistance and ease of fabricated indirect resin bonded composite low viscosity chemically active cements burnishing.46 The formation of an oxide inlays have the potential to increase the to bond tooth structure to either metals, layer on the fi t surface of gold alloy adhe- fracture strength of human molar teeth ceramic or composite resin, has paved the sive onlays by heat treatment at 650°C for with wide cavities to values of similar way for restorations which may be used ten minutes or tin plating is thought to strength to that of sound, healthy teeth.42 to treat dental conditions in a very ‘mini- increase adhesion with the chemically The use of adhesive inlays may only mally invasive manner’.45 The adhesive active resin lutes.48 have a limited role in the management of metal onlay ‘is an example of a minimally The adhesive onlay restoration quite clearly

BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010 509

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

g

a d

h

b

e i

c f j

Fig. 7 (a) shows an incompletely fractured symptomatic lower molar tooth, (b) shows the presence of a canine guided occlusion despite marked canine wear. (c) shows that the tooth has been prepared to receive a cast type III gold adhesive onlay with the occlusal surface reduced by 1.0-1.5 mm and a chamfer margin applied circumferentially. (d) shows the bonded metal onlay restorations in situ. (e) shows the upper molar tooth with a leaking posterior composite restoration and this tooth has also been prepared (f) to receive an adhesive onlay restoration (g) with occlusal contacts shown in (h). Canine guidance is shown in (i) and this was modifed by the addition of resin composite to ensure posterior disclusion upon lateral excursive movements, to provide protection to the recently placed restorations (j)

offers the advantage of being biologically prognosis of endodontically treated, frac- onlay restorations is also economically conservative of tooth tissue. Additionally, tured teeth is relatively poor.35 costly and time consuming. The use of it would also be reasonable to presume that The application of provisional adhesive adhesive metal onlays is also contra-indi- trauma to the pulpal tissues (which would metal onlay restorations may, however, cated among patients who display signs result from the process of tooth preparation) be challenging, as may be the presence of poor motivation and plaque control would be less likely from the effects of less of close proximal contact points, where it respectively, where there are high aes- invasive tooth preparations (than would be may be necessary to extend the prepara- thetic demands and where there is the the case from more aggressive tooth reduc- tion beneath the contact area.47 The prepa- poor availability of at the tions). It has been well documented that the ration and placement of metal adhesive restorative margins.47

510 BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

The placement of metal adhesive onlays coverage restoration. The application of an value. However, their application is time in supra-occlusion may be a possible vari- indirect ceramic would also necessitate the consuming (even with single visit restora- ation on the approach adopted by Chana et use of a provisional restoration. The need tions) and costly. al.,46 permitting a possible ‘ultra-conserv- for a provisional restoration in cases of Of particular concern to the present ative approach’ to treat CTS (utilising the CTS has been postulated to increase the authors is the high biological cost in terms well documented Dahl concept), although risk of pulpal complications.25 of occlusal surface reduction, which may it is imperative that a positive diagnosis is However, with the advent of contem- be concomitantly associated with a higher derived, and careful case selection under- porary computer aided design/computer risk of irreversible pulpal damage (than taken where the placement of a restoration aided manufacturing (CAD/CAM) systems, may be the case with a metal adhesive in supra-occlusion has been planned. such as Cerec (Sirona, USA), it is possible onlay preparation). The need to undertake Figure 2 illustrates a case where a gold to complete a restoration in one visit. The endodontic treatment may not only com- adhesive onlay has been placed initially advantages of a CAD/CAM porcelain par- promise the longevity of the affected tooth, in supra-occlusion for a tooth which has tial onlay restorations in cases of CTS, in but also require re-making of the ceramic been affected by an incomplete fracture. particular where acute thermal symptoms onlay prosthesis. The latter is not only eco- The occlusal contacts have re-established are present according to Griffi n1 include, nomically costly, but will also involve the by the three month review. This is in agree- the absence of irritation from temporary further loss of healthy tooth tissue. ment with studies where crowns are inten- fabrication and cementation, reduced risk tionally fi tted high to avoid the need for of salivary and bacterial ingress from less Indirect bonded resin occlusal reduction.10 than ideal provisional restorations (which composite onlays may show signs of fracture, leakage or The bonded indirect composite onlay res- Ceramic onlays displacement) and the absence of pulpal toration offers an alternative treatment (conventional/CAD-CAM) stresses from a second visit which would option to the use of either direct composite The ability to etch and bond ceramic include restoration ‘try-in’, cementation, onlays or ceramic onlays in the treatment materials to tooth enamel offers a possi- further tooth desiccation and bacterial of CTS. Indirect composite onlay restora- ble aesthetic alternative to the use of metal exposure or possible hand-piece trauma. tions have been shown to be effective for onlays. With the advent of more recent A report has been published describing the treatment of painful, cracked teeth.49 leucite reinforced ceramics it has been two cases of CTS which were successfully Depicted by Figure 8 is an example of a possible to fabricate all porcelain resto- managed for a period of at least two years symptomatic fractured, vital posterior tooth rations with a higher fracture resistance post restoration by the application of CAD/ which has been restored by the means of and increased fl exural and compressive CAM generated partial coverage bonded an indirect resin composite onlay. Note the strengths respectively.2 porcelain onlays.1 It is important to note need for a more aggressive level of tooth Liebenberg2 has published a report that though that many practitioners may not reduction, when compared to the prepara- describes the protocol for the fabrication of have ready access to CAD/CAM facilities; tion for a tooth to receive a cast adhesive ‘partial coverage porcelain onlays’ to treat furthermore the inability to use ‘layer- gold onlay, as shown by Figure 7. cases of cracked, painful teeth. The use of ing techniques’ culminates in restorations Deliperi et al.50 state that in compari- such restorations is claimed to be very which may not carry optimal aesthetic son to direct composite resin onlays, the effective in the treatment of CTS based value. Technique sensitivity is a feature indirect technique allows for restorations on anecdotal evidence of treating several commonly seen as a drawback to the use which have more favourable anatomical cases over a period of at least fi ve years.2 of CAD/CAM manufacturing systems. form, a more accurate occlusal prescription Tooth preparation to receive the above While dental porcelains can be used to and more predictable proximal contact form of restoration essentially involves produce restorations of a high aesthetic anatomy. It has been well documented that the reduction of the weakened cup by 2.0 value, their property of low critical strain the feature of polymerisation shrinkage is mm, followed by the placement of a cham- in tension culminates in a relatively brit- a major drawback associated with the use fer/rounded shoulder of 2 mm in width tle material which may display signs of of direct composite restorations. The latter applied just beneath the prepared occlusal fracture with little or no plastic deforma- complication is largely negated with the surface(s).2 Emphasis has been placed on tion. Processing fl aws within the material use of indirect techniques (as much of this the presence of enamel around the entire substructure may also lead to eventual takes place extra-orally); however, polym- peripheral margin and accurate prepara- cracking. Occlusal adjustments of ceramic erisation shrinkage occurring at the level of tion/impression making. restorations may initiate micro-fractures, the resin lute may still feature. According The use of ceramic onlays clearly involves render the exposure of unglazed ceramic to Wendt,51 on account of a higher level a greater level of tooth reduction than that (which may cause wear of the opposing of polymerisation conversation attain- advocated for the placement of metal adhe- dentition) and repair of ceramic restora- able with indirect methods, such restora- sive onlays. As discussed above, this would tions may be challenging. tions can be expected to display improved culminate in a preparation approach that Porcelain bonded partial coverage mechanical and physical properties such is less biologically conservative than that onlays offer a more conservative alterna- as strength and wear resistance. for the preparation for an adhesive metal tive to full coverage restorations for the When compared to bonded porcelain onlay, yet less invasive than that for a full management of CTS, with high aesthetic onlays, both form of restoration require the

BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010 511

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

same level of tooth reduction. However, form of restoration may represent a suc- indirectly bonded resin composite onlay cessful method of treating incompletely restorations offer the merits of ease of fractured posterior teeth. repair (with direct materials) and adjust- Indirect resin composite onlays appear ment respectively. They are also less abra- to have a role in the management of sive towards opposing occlusal surfaces. CTS. They can provide an effective treat- The potential to add direct composite may ment option and can overcome many of be crucial in cases of CTS, where loss of the drawbacks associated with the use of a vitality may precede the cementation of directly bonded composite onlays. While the defi nitive restoration, as the latter their placement requires more tooth prepa- can be readily repaired post-endodontic ration, they are more conservative than therapy, without the need for a remake. full coverage restorations and offer the Furthermore, the indirect composite onlay potential for effective repair. Cost and will continue to serve its purpose as a time factors, together with the need for splint, while root canal therapy is being temporisation, are obvious disadvantages. undertaken (particularly in cases where Caution may need to be applied when con- b treatment may be more than one visit). sidering their placement among patients Indirect composite onlays have been who display signs of .40 Fig. 8 An example of a symptomatic fractured, vital posterior tooth (a) with a shown to display a greater capacity mesial fracture (see arrow) which has been to absorb compressive loading forces, Full coverage crowns restored by the means of an indirect resin thereby reducing the impact force on the Based on their observation that cracks on composite onlay (b) underlying tooth structure by 57%, when posterior teeth typically extend from the compared to dental porcelain. The latter occlusal incline to the cervical third of the property is thought to be accounted for clinical crown, Gutherie et al.8 have advo- The effi cacy of full coverage acrylic by the lower elastic modulus presented by cated the use of full coverage crowns to be provisional crowns in the management of composite resin. A reduction in the load the most appropriate form of restoration to cases suffering from CTS was evaluated transmitted to a fractured fl exible tooth manage cases of cracked tooth syndrome. by Gutherie et al.8 A failure rate of 11% is critical in preventing further progress It has been argued that the resistance form was reported; all of the failures required of the crack. Brunton et al.49 showed that provided by a full coverage restoration endodontic therapy. premolar teeth restored by the means of enables occlusal forces to be distributed In a more extensive study, where 127 composite onlays exhibited higher levels over the entire prepared tooth, thereby cases of posterior teeth with cracks with of fracture resistance than equivalent teeth minimising stresses which would otherwise concomitant symptoms of reversible restored with ceramic onlays. be relayed to the crack; while the reten- were restored with full cover- It would appear that the weak link tion form of the crown through the process age defi nitive crowns, a staggering 21% associated with the use of indirect of frictional contact and by the action of of cases were reported failed within the resin composite restorations is the resin the cement lute helps to splint the tooth fi rst six months of evaluation; all cases based lute.50 fragments, thereby minimising their inde- required subsequent root canal therapy.53 Signore et al.52 have published the results pendent movement when occlusal forces Cases with single marginal ridge fractures of a six year retrospective study describing are released.8 (either mesial or distal) were reported to the clinical performance of bonded indi- A modified preparation to the con- be more likely to be in need of endodontic rect composite onlays for the treatment of ventional full coverage preparation (for treatment. The proportion of teeth (with 43 cracked, painful teeth. For cases where either a full veneer preparation or that CTS) with the subsequent need of further cavity widths were less than half the dis- for a metallo-ceramic crown) has been endodontic therapy8,53 is significantly tance from the central fossa to the cusp described, which is thought to reduce the higher following the application of full tip, only the involved cusp was reduced; functional stresses applied to the fractured coverage crowns than among those cases for larger cavities, complete cuspal cover- segments.56 These modifi cations include: a which have been splinted by other restora- age was undertaken. All cavities were fi rst further reduction of the involved cusp with tive means as described above. pre-restored with a directly bonded resin the application of a subsequent bevel, the Various studies have reported the loss composite, followed by a reduction by 1.5- avoidance of the placement of boxes and of vitality following the application of full 2.0 mm of the occlusal surface; all margins grooves on or adjacent to the fractured coverage single unit crowns to be in the were placed on sound enamel and usu- aspects of the tooth, placement of margins range of 15 to 19%.54,55 Loss of pulpal vital- ally placed supra-ginigivally. Onlays were more apically (which will improve bracing ity is an obvious problem following the cemented using a 3-step total etch system of the crown by the surrounding tooth), the preparation of teeth to receive the latter with the use of a dual cured low viscos- use of adhesive core materials, the use of form of restoration; the problem appears ity composite cement (Variolink, Ivoclar, thicker die spacers to permit the fabrica- to be further compounded in cases of CTS, Vivadent). A favourable survival rate of tion of a passively fi tting restorations and where reversible pulpitis would generally 93.02% was reported, suggesting that this the use of low viscosity cements. be an already pre-existing condition. It has

512 BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

been reported by Tan et al.35 that endo- restorations, cost and time factors are also future. Br Dent J 2005; 198: 669-676. 13. Geurtsen W, Garcia-Godov F. Bonded restorations dontically treated, cracked teeth have a obvious drawbacks to the use of conven- for the prevention and treatment of the cracked relatively poor long term outlook. tional indirect restorations. tooth syndrome. Am J Dent 1999; 11: 266-270. 14. Plasmans P J, Breugers N H, Mulder J. Long term In cases where root canal treatment is Adhesive metal and indirect resin com- survival of extensive amalgam restorations. J Dent indicated following the application of a posite onlays may in time show some Res 1998; 77: 453-460. 15. Van Nieuwenhuysen J P, D’Hoore W, Carvahlo J, defi nitive crown, this may necessitate the level of considerable promise for improv- Quist V. Long term evaluation of extensive remaking of the crown which further adds ing the prognosis of teeth affected by CTS, restorations in permanent teeth. J Dent 2003; 131: 395-405. to the cost of the procedure. The prepa- and form excellent defi nitive, long term 16. Staninec M, Holt M. Bonding of amalgam to tooth ration of teeth to receive full coverage restorative options for the treatment of structure: tensile adhesion and microleakage tests. J Prosthet Dent 1988; 59: 397-402. crowns is also time consuming. teeth affected by this condition, in par- 17. Trushkowsky R. Restoration of a cracked tooth ticular where affected teeth may have been with a bonded amalgam. Quintessence Int 1991; SUMMARY 22: 397-400. intruded by ultra-conservative restorations 18. Ueno Y. A clinical evaluation of adhesive amalgam A number of defi nitive different restora- placed in supra-occlusion. A more biologi- lining with 4 META/MMA TBB adhesive resin without anaesthesia. J Jpn Soc Adhes Dent 1989; tions/restorative techniques have been cally conservative tooth preparation will 73: 181-189. described for their respective use to treat without doubt help to prolong the longev- 19. Bearn D, Saunders E, Saunders W. The bonded amalgam restoration – a review of the literature posterior teeth affected by CTS. However, ity of the tooth but also help to prevent and report of its use in the treatment of four cases there is only very limited clinical evidence irreversible pulpal damage. of cracked tooth syndrome. Quintessence Int 1994; 25: 321-326. available in the dental literature to sub- Of the limited data available, it would 20. Omura I, Yamauchi J, Harada I, Wada T. Adhesive stantiate the use of any of them. be fair to conclude that direct restora- and mechanical properties of a new dental adhe- sive. J Dent Res 1984; 62: 233. The prognosis of a tooth affected by tions with cuspal coverage, in particular 21. Eakle W S, Staininec M, Lacy A M. Effect of bonded CTS is determined by three principal fac- bonded composite restorations appear to amalgam on the fracture of teeth. J Prosthet Dent 1992; 68: 257-260. tors, hence: the extent and location of the be the most benefi cial when considering 22. Oliveira J P, Cochran M A, Moore B K. Infl uence fracture, the point in time when restora- prognostic outcome of teeth restored for of bonded amalgam restorations on the fracture strength of teeth. Oper Dent 1996; 21: 110-115. tive intervention is initiated and thirdly the purposes of incomplete posterior tooth 23. Geurtsen W, Orth M, Gartner A. Fracture resistance by the type of restoration applied to splint fractures.25,26 Furthermore, their application of human maxillary molars with MOD amalgam or composite fi llings. Dtsch Zahnarztl Z 1989; the fracture. is cost effective, effi cient and they also 44: 108-110. The prognosis of teeth involved by permit an aesthetic outcome with limited 24. Ausiello P, DeGee A S, Rengo S et al. Fracture 26 resistance of endodontically treated CTS, where the presenting cavity is not damage infl icted upon the dental pulp. adhesively restored. Am J Dent 1997; 10: 237-241. in excess of one half of the bucco-lini- However, the placement of direct composite 25. Opdam N J, Roeters J J. The effectiveness of bonded composite restorations in the treatment of painful, gual width when restored by the means of onlay restorations is very dependent upon racked teeth: six month evaluation. Oper Dent 2003; directly bonded plastic restorations with- operator skill, and furthermore, some level 28: 327-333. 26. Opdam N J, Roeters J J, Loomans R A, Bronkhorst out cuspal coverage, appears to be reason- of tooth preparation is still required. E. Seven year clinical evaluation of painful, cracked ably acceptable. The preparation of teeth teeth restored with a direct composite restoration. J Endod 2008; 34: 808-811. to receive such restorations is biologically 1. Griffi n J. Effi cient, conservative treatment of symptomatic cracked teeth. Compendium 2006; 27. Weiczkowski G, Joynt R B, Klockowski R et al. Effects conservative, with the subsequent loss 27: 93–102. of incremental versus bulk fi ll technique on resistance to cuspal fractures of teeth restored with posterior of pulp vitality not being an associated 2. Liebenberg W H. Partial coverage indirect tooth coloured restorations; steps to clinical success. composites. J Prosthet Dent 1988; 60: 283-288. primary concern. The prognosis of root Am J Dent 1999; 12: 201–209. 28. Van Dijken J W V. Direct resin composite inlays/ onlays: an 11 year follow up. J Dent 2000; fi lled cracked teeth in the longer term 3. Agar J R, Weller R N. Occlusal adjustments for initial treatment and prevention of cracked tooth 28: 299-300. appears poor.35 syndrome. J Prosthet Dent 1988; 60: 145-147. 29. Stavridakis M M, Kakaboura A I, Ardu S, Krejci I. Marginal and internal adaptation of bulk fi lled According to a leading authority, teeth 4. Hiatt W H. Incomplete crown-root fractures in pulpal . J Periodontol 1973; class I and cuspal coverage direct resin composite affected by CTS should be initially restored 44: 369-379. restorations. Oper Dent 2007; 32: 515-523. 30. Hoffman W, Just N, Haller B, Hugo B, Klaiber B. The by means of bonded direct restorations as a 5. Fox K, Youngson C C. Diagnosis and treatment of the cracked tooth. Prim Dental Care 1997; 4: 109-113. effect of glass ionomer cements or composite resin means of immediate/intermediate therapy; 6. Geurtsen W. The cracked tooth syndrome; clini- bases on restoration of cuspal stiffness of endodn- tically treated premolars in vitro. Clin Oral Investig where an indirect restoration is indicated cal features and case reports. Int J Periodontics Restorative Dent 1992; 12: 395-405. 1998; 2: 77-83. from the outset, such a restoration should 7. Ehrmann E H, Tyas M J. Cracked tooth syndrome: 31. McCullock A S, Smith B G N. In vitro studies of cuspal reinforcement with adhesive restorative only be placed after having managed the diagnosis, treatment and correlation between symptoms and post-extraction fi ndings. Aust Dent J materials. Br Dent J 1986; 161: 450-452. immediate symptoms.25,26 1990; 35: 105-112. 32. Krejci I, Lutz F, Krejci D. The infl uence of different base materials on marginal adaptation and wear of Conventional full coverage crowns and 8. Gutherie G C, Difi ore P M. Treating the cracked tooth with a full crown. J Am Dent Assoc 1991; conventional class II composite resin restorations. conventional onlays have been utilised as 122: 71-73. Quintessence Int 1988; 19: 191-198. 33. Roulet J F. Benefi ts and disadvantages of tooth a historical gold standard for the above 9. Dahl B, Krogstad O, Karlsen K. An alternative treat- ment of cases with localised . J Oral Rehabil coloured alternatives to amalgam. J Dent 1997; purpose.57 With the former, the copious 1975; 2: 209-214. 25: 459-473. 10. Hemmings K W, Darbar U R, Vaughan S. Tooth wear 34. Gutmann J L, Rakusin H. Endodontic and restorative loss of tooth tissue and high risks of loss treated with direct composite restorations at an management of incompletely fractured molar teeth. of pulp vitality respectively are major increased vertical dimension: results at 30 months. Int Endod J 1994; 27: 343-348. 35. Tan I, Chen N N, Poon C Y, Wong H B. Survival of concerns, which may impart a consid- J Prosthet Dent 2000; 83: 287-293. 11. Gerasimidou O. Tooth mobility, movement and root fi lled cracked teeth in a tertiary institution. Int erable negative effect on the prognostic symptoms caused by occlusal changes. PhD Thesis. Endod J 2006; 39: 886-889. King’s College London, 2009. 36. Hodd J A A. Biomechanics of the intact, prepared outcome of teeth affected when treated by 12. Poyser N J, Porter R W J, Briggs P F A, Channa H S, and restored tooth; some clinical implications. Int such an approach. The need for provisional Kelleher M G D. The Dahl concept: past, present and Dent J 1991; 41: 25-32.

BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010 513

© 2010 Macmillan Publishers Limited. All rights reserved PRACTICE

37. Homewood C I. Cracked tooth syndrome – inci- composite inlays versus conventional composite res- report. Oper Dent 2009; 30: 143-150. dence, clinical fi ndings and treatment. Aust Dent J torations: 5 year follow up. J Dent 2000; 28: 375-382. 51. Wendt S L Jr. The effect of heat used as secondary 1998; 43: 217-222. 44. Rosenstiel S F, Land M F, Fujimoto J. Contemporary cure upon the physical properties of three com- 38. Davis R, Overton J. Effi cacy of bonded and non- fi xed prosthodontics, 3rd ed. pp 230-261. posite resins. II. Wear, hardness and color stability. bonded amalgams in the treatment of teeth Mosby, 2001. Quintessence Int 1987; 18: 351-356. with incomplete fractures. J Am Dent Assoc 2000; 45. Behle C A. Conservative direct and indirect resin 52. Signore A, Benedicenti S, Covani U. Ravera G. A 4 131: 496-478. posterior restorative alternatives for racked denti- to 6 year retrospective clinical study of cracked 39. Fennis W M, Kuijs R H, Kreulen C M, Verdonschot N, tion. Pract Periodontics Aesthet Dent 1997; teeth restored with bonded indirect resin composite Creugers N H. Fatigue resistance of teeth restored 9: 405-413. onlays. Int J Prosthodont 2007; 20: 609-616. with cuspal coverage composite restorations. Int J 46. Chana H, Kelleher M, Briggs P, Hopper R. Clinical 53. Krell K, Rivera E. A six year evaluation of cracked Prosthodont 2004; 17: 313-317. evaluation of resin bonded gold alloys. J Prosthet teeth diagnosed with reversible pulptitis: treatment 40. Bartlett D, Sundaram G. An up to 3 year random- Dent 2000; 83: 294-300. and prognosis. J Endod 2007; 33: 1405-1407. ized clinical study comparing indirect and direct 47. Yap A U J. Cuspal coverage with resin bonded metal 54. Saunders W P, Saunders E M. Prevalence of resin composite used to restore worn posterior onlays. Dent Update 1995; 22: 403-406. periradicular periodontitis associated with crowned teeth. Int J Prosthodont 2006; 19: 613. 48. Tanaka T, Atusuta M, Nakabayashi M, Masuhara E. teeth in an adult Scottish subpopulation. Br Dent J 41. Shillingburg H T, Hobo S H, Lowell D W, Jacobi R, Surface treatment of gold alloys for adhesion. 1988; 185: 137-140. Brackett S. Fundamentals of fi xed prosthodontics, J Prosthet Dent 1988; 60: 271-279. 55. Cheung G S, Lia S C, Ng R P. Fate of vital pulps 3rd ed. pp 171–180. Quintessence Publishing, 1997. 49. Brunton P A, Cattell P, Burke F J T, Wilson N H F. beneath a metal ceramic crown or a bridge retainer. 42. Roznowski M, Bremer B, Geurtsen W. Fracture resis- Fracture resistance of teeth restored with onlays Int Endod J 2005; 38: 521-530. tance of human molars restored with various fi lling of three contemporary tooth-coloured resin- 56. Casciari B J. Altered preparation design for cracked materials. In Moermann W H. Proceedings of the bonded restorative materials. J Prosthet Dent 1999; teeth. J Am Dent Assoc 1991; 130: 571-572. international symposium on computer restorations. 82: 167-171. 57. Christensen G J. The cracked tooth syndrome: a pp 559–566. Chicago: Quintessence, 1991. 50. Deliperi S, Bardwell D N. Direct cuspal coverage pragmatic treatment approach. J Am Dent Assoc 43. Wassell R W, Walls A W G, McCabe J F. Direct posterior resin composite restorations: a case 1998; 124: 107-108.

514 BRITISH DENTAL JOURNAL VOLUME 208 NO. 11 JUN 12 2010

© 2010 Macmillan Publishers Limited. All rights reserved