Q U I N T E S S E N C E I N T E R N AT I O N A L
RESTORATIVE DENTISTRY
Manja Kölpin
Composite filling or single crown? The clinical dilemma of how to restore endodontically treated teeth Manja Kölpin, DDS1/Guido Sterzenbach, Dr med dent, DDS1/Michael Naumann, Prof Dr med dent2 The restoration of endodontically treated teeth involves a difficult decision-making process, especially when it comes to more complex prosthetic rehabilitations. Regarding singletooth restoration, there are high-level requirements for the restorative components and the application of all necessary treatment steps to achieve the final restoration. So when is there a need for a single-crown restoration or when might a composite resin restoration also be sufficient? For the assess-
ment of endodontically treated teeth as abutment teeth for prosthetic restorations, there are no clear guidelines beyond single-tooth restorations. The aim of this article is to compile important aspects of the restoration of endodontically treated single teeth, including more complex prosthetic reconstructions, based on the scientific literature. (Quintessence Int 2014;45:457–466; doi: 10.3290/j.qi.a31802. Originally published in Quintessenz 2013;64(11):1359–1371)
Key words: core build-up, crown, postendodontic restoration, prosthodontic restoration, survival
Various possibilities for postendodontic restoration have been described in the literature. In general, there is often a lack of information regarding how to consider the prospective function of a tooth before starting endodontic treatment. The function of the respective tooth should be clear, for example as an abutment for a fixed partial denture or a combined fixed-removable partial denture, or only for a single-tooth restoration. Furthermore, after finishing the pretreatment, its success and function should be evaluated again, and thus confirmed if the treatment concept can be realized. The type of prosthetic reconstruction may affect the success of the (post)endodontic restoration, the sur1
Clinician, Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Charité – Universitätsmedizin Berlin, Berlin, Germany.
2
Professor, Department of Prosthetic Dentistry, Center of Dentistry, University of Ulm, Ulm, Germany.
Correspondence: Dr Manja Kölpin, Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Charité – Universitätsmedizin Berlin, Aßmannshauser Straße 4-6, 14197 Berlin, Germany. Email: [email protected]
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vival of the respective tooth, and – depending on the number of involved abutment teeth – the success of the complete prosthetic restoration. It is for good reason that the paper by Ray and Trope1 is one of the most cited publications in endodontology, and it states that the quality of the final restoration (in this case singlecrown restoration) co-determines the success of the endodontic treatment. The key to success is the treatment planning and detailed gathering of information, since not all of what is possible from a dentist’s perspective is favored by the patient. Input and effort have to be balanced. The question is, what restoration one can “dare” and which aspects are key to success in practice? There are several clinical constellations, some complex and others more straightforward, and not every aspect can be discussed in this article. Rules of thumb can be used to reduce the complexity of prosthetic treatment planning. One condition is that endodontic treatment and the core build-up are performed well.
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The endodontist should evaluate – in collaboration with the referring dentist – the prospective suitability of the tooth in question for a particular final restoration. The aim is to avoid the situation of a perfectly endodontically treated tooth being extracted since it has no value for a planned prosthetic restoration. The foundation for success is the (post)endodontic treatment. There are four stages of endodontic treatment: 1. Chemical and mechanical cleaning of the root canal 2. Shaping of the root canal 3. Root canal filling 4. Definitive coronal restoration.2 To avoid reinfection of the root canal and mechanical failures such as fractures, thus enhancing treatment success, endodontically treated teeth should be finally restored as soon as possible.3-5 The aims of postendodontic treatment are: • Sealing of the filled root canal system • Recreation of function and prevention of mechanical failures, eg fracture under functional load.6 The significance of fracture prophylaxis becomes apparent with the observation that endodontically treated teeth have a higher risk of fracture compared to vital teeth.7 However, brittleness of tooth structure is not a consequence of endodontic treatment.8-10 The biomechanical properties of premolars compared to contralateral vital premolars has been analyzed.10 It was shown that with the exception of microhardness, tensile and compressive strength do not differ when compared to vital teeth. In addition, there is no difference in moisture content between endodontically treated and contralateral vital teeth.11 Previous research has shown that collagen-associated water content is reduced by up to 10% in endodontically treated teeth,11,12 but there are no consequences in terms of physical properties.10,13 The fracture risk depends less on the change in mechanical properties than on consequences due to the loss of tooth structure during endodontic treatment. As a result of loss of coronal and radicular tooth structure, the intake of force on the tooth is changed, and this in turn results in destabilization or overload.
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This was shown by one study on extracted endodontically treated premolars, which analyzed the impact of stepwise loss of tooth structure during endodontic treatment.14 Preparation of the access cavity, removal of the roof of the pulp chamber, and preparation of the root canal itself caused a loss of tooth stability of 4% to 6%. Preparation of a dihedral cavity caused a 50% loss of stability. With trihedral (mesial-occlusal-distal) cavities, there were gains of up to 65%. The so-called “cherry stone effect”, which postulates a reduced regulation of bite force as a result of loss of mechanical receptors in the periodontium due to endodontic treatment,15 should be questioned in the light of current knowledge. One recent publication described the missing difference between vital and non-vital teeth.16
TREATMENT OPTIONS FOR THE SINGLE TOOTH A prospective endodontically treated tooth can be classified according to the defect and type of tooth. It is practicable to differentiate between five classes of defect dimensions. An essential criterion for the type of restoration is the number of remaining cavity walls. A cavity wall of a remaining thickness less than 1 mm is defined as missing, since inadequate mechanical stability is likely.17 • Class I: A tooth of Class I has an access cavity with four intact cavity walls. An adhesive core build-up is recommended and can be applied as a definitive filling using hybrid composite resin. • Class II: An access cavity and three remaining cavity walls result in an adhesive core build-up, which can be applied as a definitive filling. • Class III: When an access cavity and two remaining cavity walls are present, an adhesive core build-up is recommended. The restoration can be applied in directly or indirectly, eg laboratory restoration. Therefore, an adhesive treatment concept is recommended. • Class IV: The access cavity and one remaining cavity wall indicate a need for supporting retention for the core build-up by an assembled endodontic post or
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Figs 1a to 1I
Orthodontic extrusion with magnet attachments as a pretreatment before crown placement.
Fig 1a Initial clinical situation of the right maxillary canine (oral view).
Fig 1b
Initial radiograph.
Fig 1c
Fig 1d Second magnet luted in soft vacuum-formed splint.
Fig 1e
Splint with luted magnet in situ.
Fig 1f Right maxillary first premolar after luting of the magnet before extrusion; the coronal third of the lateral root has visible radiologic translucency, with suspicion of external root resorption.
Fig 1g sion.
Fig 1h Clinical situation after orthodontic extrusion. For exposing the root compromised by a lateral resorption process, additional surgical crown lengthening was required.
Fig 1i Right maxillary first premolar after insertion of a single crown.
•
Three weeks after starting extru-
the fabrication of a cast post and core build-up. For anterior teeth, a solely directly adhesive core buildup can be an option. Preparation for a crown may optimize the esthetic appearance, but results in excessive loss of tooth structure. Class V: This describes an access cavity and four missing cavity walls, ie the tooth is decoronated. An adhe-
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First magnet adhesively luted.
sive core build-up in combination with an assembled endodontic post is indicated. Alternatively, a cast post and core can be an option. The latter needs undercuts eliminated before manufacture, as these result in additional hard tissue loss. For definitive restoration, a single crown restoration is recommended.
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The postendodontic complex Different systems are available for the insertion of endodontic posts. With increasing demand, passive assembled posts are usually used in practice. These are composed of metallic (titanium) or nonmetallic materials (eg, glass or quartz fiber-reinforced composite posts [see Fig 5c], or zirconia posts18). Passive insertion requires specific luting materials.19 With the development of self-adhesive resin cements, a feasible way for luting posts was introduced, reducing the technical sensitivity of the adhesive endodontic post insertion protocol.19 There is no need for additional bonding components, thus direct application in the hard-toaccess root canal is possible. When post insertion is necessary, the “ferrule design” is key to absorb bite forces. The height of the prepared dentin collar should be at least 1.5 mm to 2 mm, so that the “ferrule effect” can be established. There are several clinical situations, such as extensive cervical caries lesions, when the ferrule design cannot be ensured.20 To manage the problem of insufficient ferrule, two techniques are available.21 One method is the orthodontic extrusion of the tooth, eg by the use of a magnetic attachment (Fig 1).22 Another possibility to enable ferrule design is surgical crown lengthening. Both techniques have their limitations in posterior teeth. On one hand, magnetic extrusion of a multi-rooted tooth is complicated due to limited magnetic strength. On the other hand, there is – according to the height of the root trunk – a risk for exposure of the furcation area, which causes periodontal complications. It is predictable that the technique of magnetic extrusion would be preferable for anterior teeth, considering esthetic aspects. In addition, a negatively changed crown-toroot ratio as a consequence of surgical crown lengthening in the anterior region would be a disadvantage. Scientific studies regarding these aspects are rare.
Direct or indirect restoration in limited cases Indirect restorations are feasible by manufacturing partial or full crowns consisting of metal and nonmetal materials, depending on the defect extension. Adhe-
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sively luted partial ceramic crowns allow preparation in a more defect-orientated way, with good esthetic results (Figs 2 and 3). In particular, a defect of Class III with two remaining cavity walls is a limited case in which both a direct and an indirect approach are possible. However, a metallic or nonmetallic crown might also be an option. The chosen restoration is further influenced by the practitioner’s skill and experience, as well as by patient-based factors, eg socioeconomic background.23 Another case (Fig 4) demonstrates how the margin elevation technique24-26 as the therapeutic option enables treatment of an endodontically treated tooth using an adhesive approach with a partial ceramic crown. A prosthetic restoration with a full crown in this case would necessitate surgical crown lengthening and insertion of a endodontic post. The “elevation” of the mesial box using a composite filling and an adequate preparation design allows straightforward adhesively luted indirect restoration. Figure 5 shows an example of a postendodontic restoration with adhesively luted posts and full ceramic crowns for two maxillary anterior teeth.
SURVIVAL OF POSTENDODONTIC RESTORATIONS There follows an overview of current clinical performance of postendodontic restorations, which includes aspects of survival and its influencing factors, as well as studies comparing crowns and direct composite fillings.
Status of clinical trials: long-term results of postendodontic restorations A literature search by our working group showed that there are only a few long-term studies on the survival of postendodontic restorations. In the coming years more results are to be expected.27-29 However, the studies include different materials and recording of baseline and outcome parameters, which complicates adequate assessment. In one prospective clinical trial with an observation time of 10 years, 149 teeth with postendodontic restor-
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Figs 2a to 2d
Restoration of an endodontically treated tooth with a ceramic partial crown.
Fig 2a Radiograph of left mandibular second molar before prosthetic treatment.
Fig 2b Preparation design for ceramic partial crown.
Fig 2d
Fig 2c Partial crown in lithium disilicate ceramic.
Partial crown after adhesive luting in situ.
Figs 3a to 3c Postendodontic restoration of maxillary left first molar with adhesively luted partial crown of lithium disilicate ceramic.
Fig 3a Clinical situation of maxillary left first molar after endodontic treatment; adhesive core build-up mesiocclusally.
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Fig 3b
Preparation design.
Fig 3c Clinical situation after luting of restoration.
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Figs 4a to 4g
Pretreatment of a tooth using the margin elevation technique.
Fig 4a Radiograph of the initial situation of the left maxillary second premolar: insufficient core build-up mesially.
Fig 4b Clinical situation after orienting preparation. Mesial box is separated with retraction cord; a dry working field for adhesive luting is not possible.
Fig 4c Application of rubber dam was not possible; application of a matrix system.
Fig 4d Placement of a light-curing composite resin in a multi-layer technique.
Fig 4e Applied rubber dam before insertion of indirect restoration.
Fig 4f Clinical situation after adhesive luting of ceramic partial crown.
Fig 4g Radiographic control after incorporation.
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Figs 5a to 5f
Restoration of two maxillary teeth with adhesively luted posts and full ceramic crowns.
Initial clinical situation (frontal
Fig 5b view).
Initial clinical situation (incisal
Fig 5c
Situation of luted posts.
Fig 5d Right maxillary central and lateral incisors prepared for a full ceramic crown.
Fig 5e sion.
Retraction cords before impres-
Fig 5f ation.
After incorporation of the restor-
Fig 5a view).
ations including glass-fiber-reinforced posts and several prosthetic restorations were examined.30 Factors influencing tooth survival were evaluated. An annual failure rate of 4.6% was calculated. Correct interpretation of this, relatively high, failure rate needs to include the preparation design. When the study was started, the crown margin was prepared in the cervical dentin under the core build-up. A ferrule design, the current standard, was not realized at that time. This may be one essential factor concerning the high failure rate. Regarding the influence of prosthetic restorations on survival, the 5-year evaluation showed a significantly higher failure risk for teeth restored with single crowns or teeth that were part of a combined fixed-removable partial denture. Interestingly, after 10 years the type of restoration could not be confirmed as a significant risk factor. Also, the influence of remaining tooth structure was shown to have an impact on tooth survival; in particular, teeth without any cavity wall showed a higher failure risk. A further parameter for survival is the position of the tooth in the dental arch. The study quoted above30
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showed that anterior teeth have twice the risk of failure compared with posterior teeth. An explanation for this is the occurrence of non-axial shear forces in the anterior region, which can be deemed unfavorable biomechanical stress.31 A randomized controlled clinical pilot study evaluated the survival of 91 teeth that were reconstructed with adhesively luted fiber-reinforced and titanium posts.32 Prosthetic restorations were single crowns and fixed partial dentures of metal ceramic, and combined fixed-removable partial dentures. The results showed that, when ferrule design is ensured (in 13 cases by the procedure of surgical crown lengthening), a survival of 92% is possible, irrespective of the post material. The type of prosthetic restoration was not a statistically relevant factor.
Restorations for single teeth: composite filling or crowns? Direct restoration with composite resin results in minor loss of tooth structure, and reduced treatment time and costs.2 A working group compared endodontically
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treated teeth to vital teeth, when treated with composite fillings.7 It was shown that survival of restorations for the group of endodontically treated teeth was 86% after 6 years, a lower survival rate than for vital teeth (93%). Besides the wish to realize a durable restoration, saving costs is increasingly important for many patients. In the case of an endodontically treated tooth with defect Class III (access cavity and two remaining cavity walls), there are two possibilities for treatment: either treatment with an adhesive multi-layered composite resin filling, which in Germany would incur additional private costs for a patient with compulsory sickness insurance; or to prepare the tooth for a single crown restoration, which when cast of base metal can be covered by the insurance up to 100% of the value. More esthetic solutions incur higher costs. As early as 1984, it was asked whether the clinical success of endodontically treated teeth depends on the position in the dental arch, insertion of an endodontic post, and if there is a dependent relation to overlaying restorations.33 The authors showed, in a retrospective design, that clinical success is not gradable in anterior teeth by capping a tooth. In contrast, it was concluded that crowning posterior teeth had a significant effect. In a literature review, Goodacre and Spolnik34 found a positive influence on long-term survival of indirect partial crowns overlaying restorations in the posterior region. In a retrospective study, 400 endodontically treated teeth were examined regarding the effect of coronal restorations over a 2-year period.35 The authors identified statistically higher survival rates of teeth restored with crowns compared to amalgam and composite resin restored teeth. In this publication there was no information about defect extensions, so there were teeth included that had a cast post and core build-up without cavity walls and also teeth with undocumented remaining tooth structure. Another of the few prospective clinical trials evaluated direct composite resin and glass-fiber post-supported restorations for endodontically treated premolars in comparison to restorations with metal-ceramic crowns.36 After 3 years, there was no
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statistically significant difference concerning clinical success rates. To date, no long-term follow up of this study has been published. Thus, no particular therapy approach can be recommended. The same study group evaluated endodontically treated premolars with Class II defects with amalgam fillings.37 After 5 years, teeth with amalgam restorations showed more root fractures than adhesively restored teeth, but fewer secondary caries lesions. The authors recommended avoiding crowns for endodontically treated premolars due to greater protection of tooth structure (5-year survival for premolars restored with amalgam fillings was 91%, and for teeth restored with posts and crowns this was 90%). Regarding the limitations of the presented studies, one systematic review concludes: “There is insufficient evidence to determine whether a conventional filling such as composite material is more effective than full coronal coverage for the restoration of root filled premolar teeth with sufficient coronal tooth structure.”2
Fixed partial dentures and cantilever fixed partial dentures One literature review reported that endodontically treated teeth are suitable anchors for fixed partial dentures.38 In relation to vital teeth, survival is decreased; Walton39,40 reported failure rates of 21% for endodontically treated teeth and 5% for vital teeth. Another investigation demonstrated lower failure risks for teeth restored with endodontic posts after root canal filling as anchors of fixed partial dentures than for single crowns and removable partial dentures.30 A literature review also showed that the distal anchor of a cantilever fixed partial denture should be a vital tooth, because survival decreases for endodontically treated teeth due to mechanical failure.38 One in-vitro study analyzed two-unit cantilever fixed partial dentures on maxillary anterior teeth after a chewing simulation of 10 years.41 It was shown that the amount of remaining tooth structure and insertion of a post had no statistically significant influence on survival. The inclusion of a ferrule design within the study is important in explaining the results. Another in-vitro investigation of canti-
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lever fixed partial dentures on endodontically treated premolars showed that teeth with cast post and core reconstructions exhibited unfavorable biomechanical properties for a prosthetic restoration as the cantilever fixed partial denture.42 A systematic review calculated the survival rate for cantilever fixed partial dentures as 81% after 10 years,43 although it should be noted that the results included both vital teeth and endodontically treated teeth.
Fixed-removable partial dentures and telescopic crowns A clinical study concluded that 154 endodontically treated teeth observed over 3 years had a higher risk of failure if included in a fixed-removable partial denture.21,44 It is difficult to combine prosthetic restoration with endodontically compromised teeth.5 One literature review suggested that care should be taken when planning a fixed-removable partial denture with endodontically treated abutment teeth.38 The authors noted several contributing factors, such as the degree of coronal destruction of the tooth and the possible insertion of an endodontic post, with the related effects on forces. They also advised keeping recall intervals short. A retrospective study showed that endodonically treated teeth as anchors for double crown-retained partial dentures have a higher risk (odds ratio 3.298) of tooth loss and increased fracture rates.45 A prospective clinical study supported the results for this type of restoration. In comparison to vital teeth, there was a higher risk of failure for endodontically treated teeth.46
CONCLUSION When there is a need for the application of a core buildup before endodontic therapy, the number of remaining cavity walls, ie the degree of destruction, should be carefully evaluated. At this time, the type of prosthetic restoration should be determined, and thus the benefit-risk ratio can be assessed. Clinical success of a postendodontic restoration based on a single tooth, and also of more complex restorations, depends on the
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degree of destruction of the respective abutment tooth. It should be remembered that there is no therapy that is absolutely “safe”. The fewer abutment teeth remaining, the more important every single tooth for restoration stability, in particular in cases when fixed partial dentures are no longer a treatment option. Creation of a ferrule design is mandatory in cases of excessively destroyed teeth with two or fewer cavity walls. This applies in particular for maxillary anterior teeth, which have a higher risk of failure under the impact of non-axial shear forces.
REFERENCES 1. Ray HA, Trope M. Periapical status of endodontically treated teeth in relation to the technical quality of the root filling and the coronal restoration. Int Endod J 1995;28:12–18. 2. Fedorowicz Z, Carter B, de Souza RF, et al. Single crowns versus conventional fillings for the restoration of root filled teeth. Cochrane Database Syst Rev 2012;5:CD009109. 3. Fox K, Gutteridge DL. An in vitro study of coronal microleakage in root-canaltreated teeth restored by the post and core technique. Int Endod J 1997;30:361–368. 4. Lynch CD, Burke FM, Ni Riordain R, et al. The influence of coronal restoration type on the survival of endodontically treated teeth. Eur J Prosthodont Restorative Dent 2004;12:171–176. 5. Tang W, Wu Y, Smales RJ. Identifying and reducing risks for potential fractures in endodontically treated teeth. J Endod 2010;36:609–617. 6. Schmage P, Nergiz I. Konventionelle postendodontische Versorgung. In: Baumann MA, Beer R (eds). Farbatlanten der Zahnmedizin Endodontologie 2. Auflage. Stuttgart: Georg Thieme, 2007:260–263. 7. Adolphi G, Zehnder M, Bachmann LM, et al. Direct resin composite restorations in vital versus root-filled posterior teeth: a controlled comparative long-term follow-up. Oper Dent 2007;32:437–442. 8. Consensus report of the European Society of Endodontology on quality guidelines for endodontic treatment. Int Endod J 1994;27:115–124. 9. Edelhoff D, Kern M, Weigl P. Aufbau endodontisch behandelter Zähne. Dtsch Zahnärztl Z 2003;58:199–201. 10. Sedgley CM, Messer HH. Are endodontically treated teeth more brittle? J Endod 1992;18:332–335. 11. Papa J, Cain C, Messer HH. Moisture content of vital vs endodontically treated teeth. Endod Dent Traumatol 1994;10:91–93. 12. Helfer AR, Melnick S, Schilder H. Determination of the moisture content of vital and pulpless teeth. Oral Surg Oral Med Oral Pathol 1972;34:661–670. 13. Fusayama T, Maeda T. Effect of pulpectomy on dentin hardness. J Dent Res 1969;48:452–460. 14. Reeh ES, Messer HH, Douglas WH. Reduction in tooth stiffness as a result of endodontic and restorative procedures. J Endod 1989;15:512–516. 15. Randow K, Glantz PO. On cantilever loading of vital and non-vital teeth. An experimental clinical study. Acta Odont Scand 1986;44:271–277. 16. Stenger B, Harder S, Kern M. Responsiveness of vital and endodontically treated teeth to loading. J Dent Res 2011;90(Spec Iss A):Abstr 492. 17. Naumann M, Preuss A, Frankenberger R. Load capability of excessively flared teeth restored with fiber-reinforced composite posts and all-ceramic crowns. Oper Dent 2006;31:699–704.
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18. Bateli M, Kern M, Wolkewitz M, et al. A retrospective evaluation of teeth restored with zirconia ceramic posts: 10-year results. Clin Oral Investig 2013 Jul 31 [Epub ahead of print]. 19. Goracci C, Ferrari M. Current perspectives on post systems: a literature review. Aust Dent J 2011;56(Suppl 1):77–83. 20. Juloski J, Radovic I, Goracci C, et al. Ferrule effect: a literature review. J Endod 2012;38:11–19. 21. Hatzikyriakos AH, Reisis GI, Tsingos N. A 3-year postoperative clinical evaluation of posts and cores beneath existing crowns. J Prosthet Dent 1992;67:454–458. 22. Mehl C, Wolfart S, Kern M. Orthodontic extrusion with magnets: a case report. Quintessence Int 2008;39:371–379. 23. Levin R. Dealing with dental insurance. J Am Dent Assoc 2006;137:99–100. 24. Dietschi D, Spreafico R. Current clinical concepts for adhesive cementation of tooth-colored posterior restorations. Pract Periodontics Aesth Dent 1998;10:47–54;quiz 56. 25. Veneziani M. Adhesive restorations in the posterior area with subgingival cervical margins: new classification and differentiated treatment approach. Eur J Esthet Dent 2010;5:50–76. 26. Zaruba M, Gohring TN, Wegehaupt FJ, et al. Influence of a proximal margin elevation technique on marginal adaptation of ceramic inlays. Acta Odont Scand 2013;71:317–324. 27. Bitter K, Noetzel J, Stamm O, et al. Randomized clinical trial comparing the effects of post placement on failure rate of postendodontic restorations: preliminary results of a mean period of 32 months. J Endod 2009;35:1477–1482. 28. Cagidiaco MC, Garcia-Godoy F, Vichi A, et al. Placement of fiber prefabricated or custom made posts affects the 3-year survival of endodontically treated premolars. Am J Dent 2008;21:179–184. 29. Ferrari M, Vichi A, Fadda GM, et al. A randomized controlled trial of endodontically treated and restored premolars. J Dent Res 2012;91:72S–78S. 30. Naumann M, Koelpin M, Beuer F, et al. 10-year survival evaluation for glassfiber-supported postendodontic restoration: a prospective observational clinical study. J Endod 2012;38:432–435. 31. Torbjorner A, Karlsson S, Odman PA. Survival rate and failure characteristics for two post designs. J Prosthet Dent 1995;73:439–444. 32. Sterzenbach G, Franke A, Naumann M. Rigid versus flexible dentine-like endodontic posts-clinical testing of a biomechanical concept: seven-year results of a randomized controlled clinical pilot trial on endodontically treated abutment teeth with severe hard tissue loss. J Endod 2012;38:1557–1563.
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33. Sorensen JA, Martinoff JT. Intracoronal reinforcement and coronal coverage: a study of endodontically treated teeth. J Prosthet Dent 1984;51:780–784. 34. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically treated teeth: a literature review. Part I. Success and failure data, treatment concepts. J Prosthodont 1994;3:243–250. 35. Aquilino SA, Caplan DJ. Relationship between crown placement and the survival of endodontically treated teeth. J Prosthet Dent 2002;87:256–263. 36. Mannocci F, Bertelli E, Sherriff M, et al. Three-year clinical comparison of survival of endodontically treated teeth restored with either full cast coverage or with direct composite restoration. J Prosthet Dent 2002;88:297–301. 37. Mannocci F, Qualtrough AJ, Worthington HV, et al. Randomized clinical comparison of endodontically treated teeth restored with amalgam or with fiber posts and resin composite: five-year results. Oper Dent 2005;30:9–15. 38. Goga R, Purton DG. The use of endodontically treated teeth as abutments for crowns, fixed partial dentures, or removable partial dentures: A literature review. Quintessence Int 2007;38:e106–e111. 39. Walton TR. An up to 15-year longitudinal study of 515 metal-ceramic FPDs: Part 1. Outcome. Int J Prosthodont 2002;15:439–445. 40. Walton TR. An up to 15-year longitudinal study of 515 metal-ceramic FPDs: Part 2. Modes of failure and influence of various clinical characteristics. Int J Prosthodont 2003;16:177–182. 41. Tunjan R, Rosentritt M, Sterzenbach G, et al. Are endodontically treated incisors reliable abutments for zirconia-based fixed partial dentures in the esthetic zone? J Endod 2012;38:519–522. 42. Manda M, Galanis C, Venetsanos D, et al. The effect of select pulp cavity conditions on stress field development in distal abutments in two types of fixed dental prostheses. Int J Prosthodont 2011;24:118–126. 43. Tan K, Pjetursson BE, Lang NP, et al. A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years. Clin Oral Implants Res 2004;15:654–666. 44. Wegner PK, Freitag S, Kern M. Survival rate of endodontically treated teeth with posts after prosthetic restoration. J Endod 2006;32:928–931. 45. Dittmann B, Rammelsberg P. Survival of abutment teeth used for telescopic abutment retainers in removable partial dentures. Int J Prosthodont 2008;21:319–321. 46. Szentpetery V, Lautenschlager C, Setz JM. Frictional telescopic crowns in severely reduced dentitions: a 5-year clinical outcome study. Int J Prosthodont 2012;25:217–220.
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RESTORATIVE DENTISTRY
Manja Kölpin
Composite filling or single crown? The clinical dilemma of how to restore endodontically treated teeth Manja Kölpin, DDS1/Guido Sterzenbach, Dr med dent, DDS1/Michael Naumann, Prof Dr med dent2 The restoration of endodontically treated teeth involves a difficult decision-making process, especially when it comes to more complex prosthetic rehabilitations. Regarding singletooth restoration, there are high-level requirements for the restorative components and the application of all necessary treatment steps to achieve the final restoration. So when is there a need for a single-crown restoration or when might a composite resin restoration also be sufficient? For the assess-
ment of endodontically treated teeth as abutment teeth for prosthetic restorations, there are no clear guidelines beyond single-tooth restorations. The aim of this article is to compile important aspects of the restoration of endodontically treated single teeth, including more complex prosthetic reconstructions, based on the scientific literature. (Quintessence Int 2014;45:457–466; doi: 10.3290/j.qi.a31802. Originally published in Quintessenz 2013;64(11):1359–1371)
Key words: core build-up, crown, postendodontic restoration, prosthodontic restoration, survival
Various possibilities for postendodontic restoration have been described in the literature. In general, there is often a lack of information regarding how to consider the prospective function of a tooth before starting endodontic treatment. The function of the respective tooth should be clear, for example as an abutment for a fixed partial denture or a combined fixed-removable partial denture, or only for a single-tooth restoration. Furthermore, after finishing the pretreatment, its success and function should be evaluated again, and thus confirmed if the treatment concept can be realized. The type of prosthetic reconstruction may affect the success of the (post)endodontic restoration, the sur1
Clinician, Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Charité – Universitätsmedizin Berlin, Berlin, Germany.
2
Professor, Department of Prosthetic Dentistry, Center of Dentistry, University of Ulm, Ulm, Germany.
Correspondence: Dr Manja Kölpin, Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Charité – Universitätsmedizin Berlin, Aßmannshauser Straße 4-6, 14197 Berlin, Germany. Email: [email protected]
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vival of the respective tooth, and – depending on the number of involved abutment teeth – the success of the complete prosthetic restoration. It is for good reason that the paper by Ray and Trope1 is one of the most cited publications in endodontology, and it states that the quality of the final restoration (in this case singlecrown restoration) co-determines the success of the endodontic treatment. The key to success is the treatment planning and detailed gathering of information, since not all of what is possible from a dentist’s perspective is favored by the patient. Input and effort have to be balanced. The question is, what restoration one can “dare” and which aspects are key to success in practice? There are several clinical constellations, some complex and others more straightforward, and not every aspect can be discussed in this article. Rules of thumb can be used to reduce the complexity of prosthetic treatment planning. One condition is that endodontic treatment and the core build-up are performed well.
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The endodontist should evaluate – in collaboration with the referring dentist – the prospective suitability of the tooth in question for a particular final restoration. The aim is to avoid the situation of a perfectly endodontically treated tooth being extracted since it has no value for a planned prosthetic restoration. The foundation for success is the (post)endodontic treatment. There are four stages of endodontic treatment: 1. Chemical and mechanical cleaning of the root canal 2. Shaping of the root canal 3. Root canal filling 4. Definitive coronal restoration.2 To avoid reinfection of the root canal and mechanical failures such as fractures, thus enhancing treatment success, endodontically treated teeth should be finally restored as soon as possible.3-5 The aims of postendodontic treatment are: • Sealing of the filled root canal system • Recreation of function and prevention of mechanical failures, eg fracture under functional load.6 The significance of fracture prophylaxis becomes apparent with the observation that endodontically treated teeth have a higher risk of fracture compared to vital teeth.7 However, brittleness of tooth structure is not a consequence of endodontic treatment.8-10 The biomechanical properties of premolars compared to contralateral vital premolars has been analyzed.10 It was shown that with the exception of microhardness, tensile and compressive strength do not differ when compared to vital teeth. In addition, there is no difference in moisture content between endodontically treated and contralateral vital teeth.11 Previous research has shown that collagen-associated water content is reduced by up to 10% in endodontically treated teeth,11,12 but there are no consequences in terms of physical properties.10,13 The fracture risk depends less on the change in mechanical properties than on consequences due to the loss of tooth structure during endodontic treatment. As a result of loss of coronal and radicular tooth structure, the intake of force on the tooth is changed, and this in turn results in destabilization or overload.
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This was shown by one study on extracted endodontically treated premolars, which analyzed the impact of stepwise loss of tooth structure during endodontic treatment.14 Preparation of the access cavity, removal of the roof of the pulp chamber, and preparation of the root canal itself caused a loss of tooth stability of 4% to 6%. Preparation of a dihedral cavity caused a 50% loss of stability. With trihedral (mesial-occlusal-distal) cavities, there were gains of up to 65%. The so-called “cherry stone effect”, which postulates a reduced regulation of bite force as a result of loss of mechanical receptors in the periodontium due to endodontic treatment,15 should be questioned in the light of current knowledge. One recent publication described the missing difference between vital and non-vital teeth.16
TREATMENT OPTIONS FOR THE SINGLE TOOTH A prospective endodontically treated tooth can be classified according to the defect and type of tooth. It is practicable to differentiate between five classes of defect dimensions. An essential criterion for the type of restoration is the number of remaining cavity walls. A cavity wall of a remaining thickness less than 1 mm is defined as missing, since inadequate mechanical stability is likely.17 • Class I: A tooth of Class I has an access cavity with four intact cavity walls. An adhesive core build-up is recommended and can be applied as a definitive filling using hybrid composite resin. • Class II: An access cavity and three remaining cavity walls result in an adhesive core build-up, which can be applied as a definitive filling. • Class III: When an access cavity and two remaining cavity walls are present, an adhesive core build-up is recommended. The restoration can be applied in directly or indirectly, eg laboratory restoration. Therefore, an adhesive treatment concept is recommended. • Class IV: The access cavity and one remaining cavity wall indicate a need for supporting retention for the core build-up by an assembled endodontic post or
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Figs 1a to 1I
Orthodontic extrusion with magnet attachments as a pretreatment before crown placement.
Fig 1a Initial clinical situation of the right maxillary canine (oral view).
Fig 1b
Initial radiograph.
Fig 1c
Fig 1d Second magnet luted in soft vacuum-formed splint.
Fig 1e
Splint with luted magnet in situ.
Fig 1f Right maxillary first premolar after luting of the magnet before extrusion; the coronal third of the lateral root has visible radiologic translucency, with suspicion of external root resorption.
Fig 1g sion.
Fig 1h Clinical situation after orthodontic extrusion. For exposing the root compromised by a lateral resorption process, additional surgical crown lengthening was required.
Fig 1i Right maxillary first premolar after insertion of a single crown.
•
Three weeks after starting extru-
the fabrication of a cast post and core build-up. For anterior teeth, a solely directly adhesive core buildup can be an option. Preparation for a crown may optimize the esthetic appearance, but results in excessive loss of tooth structure. Class V: This describes an access cavity and four missing cavity walls, ie the tooth is decoronated. An adhe-
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First magnet adhesively luted.
sive core build-up in combination with an assembled endodontic post is indicated. Alternatively, a cast post and core can be an option. The latter needs undercuts eliminated before manufacture, as these result in additional hard tissue loss. For definitive restoration, a single crown restoration is recommended.
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The postendodontic complex Different systems are available for the insertion of endodontic posts. With increasing demand, passive assembled posts are usually used in practice. These are composed of metallic (titanium) or nonmetallic materials (eg, glass or quartz fiber-reinforced composite posts [see Fig 5c], or zirconia posts18). Passive insertion requires specific luting materials.19 With the development of self-adhesive resin cements, a feasible way for luting posts was introduced, reducing the technical sensitivity of the adhesive endodontic post insertion protocol.19 There is no need for additional bonding components, thus direct application in the hard-toaccess root canal is possible. When post insertion is necessary, the “ferrule design” is key to absorb bite forces. The height of the prepared dentin collar should be at least 1.5 mm to 2 mm, so that the “ferrule effect” can be established. There are several clinical situations, such as extensive cervical caries lesions, when the ferrule design cannot be ensured.20 To manage the problem of insufficient ferrule, two techniques are available.21 One method is the orthodontic extrusion of the tooth, eg by the use of a magnetic attachment (Fig 1).22 Another possibility to enable ferrule design is surgical crown lengthening. Both techniques have their limitations in posterior teeth. On one hand, magnetic extrusion of a multi-rooted tooth is complicated due to limited magnetic strength. On the other hand, there is – according to the height of the root trunk – a risk for exposure of the furcation area, which causes periodontal complications. It is predictable that the technique of magnetic extrusion would be preferable for anterior teeth, considering esthetic aspects. In addition, a negatively changed crown-toroot ratio as a consequence of surgical crown lengthening in the anterior region would be a disadvantage. Scientific studies regarding these aspects are rare.
Direct or indirect restoration in limited cases Indirect restorations are feasible by manufacturing partial or full crowns consisting of metal and nonmetal materials, depending on the defect extension. Adhe-
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sively luted partial ceramic crowns allow preparation in a more defect-orientated way, with good esthetic results (Figs 2 and 3). In particular, a defect of Class III with two remaining cavity walls is a limited case in which both a direct and an indirect approach are possible. However, a metallic or nonmetallic crown might also be an option. The chosen restoration is further influenced by the practitioner’s skill and experience, as well as by patient-based factors, eg socioeconomic background.23 Another case (Fig 4) demonstrates how the margin elevation technique24-26 as the therapeutic option enables treatment of an endodontically treated tooth using an adhesive approach with a partial ceramic crown. A prosthetic restoration with a full crown in this case would necessitate surgical crown lengthening and insertion of a endodontic post. The “elevation” of the mesial box using a composite filling and an adequate preparation design allows straightforward adhesively luted indirect restoration. Figure 5 shows an example of a postendodontic restoration with adhesively luted posts and full ceramic crowns for two maxillary anterior teeth.
SURVIVAL OF POSTENDODONTIC RESTORATIONS There follows an overview of current clinical performance of postendodontic restorations, which includes aspects of survival and its influencing factors, as well as studies comparing crowns and direct composite fillings.
Status of clinical trials: long-term results of postendodontic restorations A literature search by our working group showed that there are only a few long-term studies on the survival of postendodontic restorations. In the coming years more results are to be expected.27-29 However, the studies include different materials and recording of baseline and outcome parameters, which complicates adequate assessment. In one prospective clinical trial with an observation time of 10 years, 149 teeth with postendodontic restor-
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Figs 2a to 2d
Restoration of an endodontically treated tooth with a ceramic partial crown.
Fig 2a Radiograph of left mandibular second molar before prosthetic treatment.
Fig 2b Preparation design for ceramic partial crown.
Fig 2d
Fig 2c Partial crown in lithium disilicate ceramic.
Partial crown after adhesive luting in situ.
Figs 3a to 3c Postendodontic restoration of maxillary left first molar with adhesively luted partial crown of lithium disilicate ceramic.
Fig 3a Clinical situation of maxillary left first molar after endodontic treatment; adhesive core build-up mesiocclusally.
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Fig 3b
Preparation design.
Fig 3c Clinical situation after luting of restoration.
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Figs 4a to 4g
Pretreatment of a tooth using the margin elevation technique.
Fig 4a Radiograph of the initial situation of the left maxillary second premolar: insufficient core build-up mesially.
Fig 4b Clinical situation after orienting preparation. Mesial box is separated with retraction cord; a dry working field for adhesive luting is not possible.
Fig 4c Application of rubber dam was not possible; application of a matrix system.
Fig 4d Placement of a light-curing composite resin in a multi-layer technique.
Fig 4e Applied rubber dam before insertion of indirect restoration.
Fig 4f Clinical situation after adhesive luting of ceramic partial crown.
Fig 4g Radiographic control after incorporation.
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Figs 5a to 5f
Restoration of two maxillary teeth with adhesively luted posts and full ceramic crowns.
Initial clinical situation (frontal
Fig 5b view).
Initial clinical situation (incisal
Fig 5c
Situation of luted posts.
Fig 5d Right maxillary central and lateral incisors prepared for a full ceramic crown.
Fig 5e sion.
Retraction cords before impres-
Fig 5f ation.
After incorporation of the restor-
Fig 5a view).
ations including glass-fiber-reinforced posts and several prosthetic restorations were examined.30 Factors influencing tooth survival were evaluated. An annual failure rate of 4.6% was calculated. Correct interpretation of this, relatively high, failure rate needs to include the preparation design. When the study was started, the crown margin was prepared in the cervical dentin under the core build-up. A ferrule design, the current standard, was not realized at that time. This may be one essential factor concerning the high failure rate. Regarding the influence of prosthetic restorations on survival, the 5-year evaluation showed a significantly higher failure risk for teeth restored with single crowns or teeth that were part of a combined fixed-removable partial denture. Interestingly, after 10 years the type of restoration could not be confirmed as a significant risk factor. Also, the influence of remaining tooth structure was shown to have an impact on tooth survival; in particular, teeth without any cavity wall showed a higher failure risk. A further parameter for survival is the position of the tooth in the dental arch. The study quoted above30
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showed that anterior teeth have twice the risk of failure compared with posterior teeth. An explanation for this is the occurrence of non-axial shear forces in the anterior region, which can be deemed unfavorable biomechanical stress.31 A randomized controlled clinical pilot study evaluated the survival of 91 teeth that were reconstructed with adhesively luted fiber-reinforced and titanium posts.32 Prosthetic restorations were single crowns and fixed partial dentures of metal ceramic, and combined fixed-removable partial dentures. The results showed that, when ferrule design is ensured (in 13 cases by the procedure of surgical crown lengthening), a survival of 92% is possible, irrespective of the post material. The type of prosthetic restoration was not a statistically relevant factor.
Restorations for single teeth: composite filling or crowns? Direct restoration with composite resin results in minor loss of tooth structure, and reduced treatment time and costs.2 A working group compared endodontically
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treated teeth to vital teeth, when treated with composite fillings.7 It was shown that survival of restorations for the group of endodontically treated teeth was 86% after 6 years, a lower survival rate than for vital teeth (93%). Besides the wish to realize a durable restoration, saving costs is increasingly important for many patients. In the case of an endodontically treated tooth with defect Class III (access cavity and two remaining cavity walls), there are two possibilities for treatment: either treatment with an adhesive multi-layered composite resin filling, which in Germany would incur additional private costs for a patient with compulsory sickness insurance; or to prepare the tooth for a single crown restoration, which when cast of base metal can be covered by the insurance up to 100% of the value. More esthetic solutions incur higher costs. As early as 1984, it was asked whether the clinical success of endodontically treated teeth depends on the position in the dental arch, insertion of an endodontic post, and if there is a dependent relation to overlaying restorations.33 The authors showed, in a retrospective design, that clinical success is not gradable in anterior teeth by capping a tooth. In contrast, it was concluded that crowning posterior teeth had a significant effect. In a literature review, Goodacre and Spolnik34 found a positive influence on long-term survival of indirect partial crowns overlaying restorations in the posterior region. In a retrospective study, 400 endodontically treated teeth were examined regarding the effect of coronal restorations over a 2-year period.35 The authors identified statistically higher survival rates of teeth restored with crowns compared to amalgam and composite resin restored teeth. In this publication there was no information about defect extensions, so there were teeth included that had a cast post and core build-up without cavity walls and also teeth with undocumented remaining tooth structure. Another of the few prospective clinical trials evaluated direct composite resin and glass-fiber post-supported restorations for endodontically treated premolars in comparison to restorations with metal-ceramic crowns.36 After 3 years, there was no
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statistically significant difference concerning clinical success rates. To date, no long-term follow up of this study has been published. Thus, no particular therapy approach can be recommended. The same study group evaluated endodontically treated premolars with Class II defects with amalgam fillings.37 After 5 years, teeth with amalgam restorations showed more root fractures than adhesively restored teeth, but fewer secondary caries lesions. The authors recommended avoiding crowns for endodontically treated premolars due to greater protection of tooth structure (5-year survival for premolars restored with amalgam fillings was 91%, and for teeth restored with posts and crowns this was 90%). Regarding the limitations of the presented studies, one systematic review concludes: “There is insufficient evidence to determine whether a conventional filling such as composite material is more effective than full coronal coverage for the restoration of root filled premolar teeth with sufficient coronal tooth structure.”2
Fixed partial dentures and cantilever fixed partial dentures One literature review reported that endodontically treated teeth are suitable anchors for fixed partial dentures.38 In relation to vital teeth, survival is decreased; Walton39,40 reported failure rates of 21% for endodontically treated teeth and 5% for vital teeth. Another investigation demonstrated lower failure risks for teeth restored with endodontic posts after root canal filling as anchors of fixed partial dentures than for single crowns and removable partial dentures.30 A literature review also showed that the distal anchor of a cantilever fixed partial denture should be a vital tooth, because survival decreases for endodontically treated teeth due to mechanical failure.38 One in-vitro study analyzed two-unit cantilever fixed partial dentures on maxillary anterior teeth after a chewing simulation of 10 years.41 It was shown that the amount of remaining tooth structure and insertion of a post had no statistically significant influence on survival. The inclusion of a ferrule design within the study is important in explaining the results. Another in-vitro investigation of canti-
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lever fixed partial dentures on endodontically treated premolars showed that teeth with cast post and core reconstructions exhibited unfavorable biomechanical properties for a prosthetic restoration as the cantilever fixed partial denture.42 A systematic review calculated the survival rate for cantilever fixed partial dentures as 81% after 10 years,43 although it should be noted that the results included both vital teeth and endodontically treated teeth.
Fixed-removable partial dentures and telescopic crowns A clinical study concluded that 154 endodontically treated teeth observed over 3 years had a higher risk of failure if included in a fixed-removable partial denture.21,44 It is difficult to combine prosthetic restoration with endodontically compromised teeth.5 One literature review suggested that care should be taken when planning a fixed-removable partial denture with endodontically treated abutment teeth.38 The authors noted several contributing factors, such as the degree of coronal destruction of the tooth and the possible insertion of an endodontic post, with the related effects on forces. They also advised keeping recall intervals short. A retrospective study showed that endodonically treated teeth as anchors for double crown-retained partial dentures have a higher risk (odds ratio 3.298) of tooth loss and increased fracture rates.45 A prospective clinical study supported the results for this type of restoration. In comparison to vital teeth, there was a higher risk of failure for endodontically treated teeth.46
CONCLUSION When there is a need for the application of a core buildup before endodontic therapy, the number of remaining cavity walls, ie the degree of destruction, should be carefully evaluated. At this time, the type of prosthetic restoration should be determined, and thus the benefit-risk ratio can be assessed. Clinical success of a postendodontic restoration based on a single tooth, and also of more complex restorations, depends on the
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degree of destruction of the respective abutment tooth. It should be remembered that there is no therapy that is absolutely “safe”. The fewer abutment teeth remaining, the more important every single tooth for restoration stability, in particular in cases when fixed partial dentures are no longer a treatment option. Creation of a ferrule design is mandatory in cases of excessively destroyed teeth with two or fewer cavity walls. This applies in particular for maxillary anterior teeth, which have a higher risk of failure under the impact of non-axial shear forces.
REFERENCES 1. Ray HA, Trope M. Periapical status of endodontically treated teeth in relation to the technical quality of the root filling and the coronal restoration. Int Endod J 1995;28:12–18. 2. Fedorowicz Z, Carter B, de Souza RF, et al. Single crowns versus conventional fillings for the restoration of root filled teeth. Cochrane Database Syst Rev 2012;5:CD009109. 3. Fox K, Gutteridge DL. An in vitro study of coronal microleakage in root-canaltreated teeth restored by the post and core technique. Int Endod J 1997;30:361–368. 4. Lynch CD, Burke FM, Ni Riordain R, et al. The influence of coronal restoration type on the survival of endodontically treated teeth. Eur J Prosthodont Restorative Dent 2004;12:171–176. 5. Tang W, Wu Y, Smales RJ. Identifying and reducing risks for potential fractures in endodontically treated teeth. J Endod 2010;36:609–617. 6. Schmage P, Nergiz I. Konventionelle postendodontische Versorgung. In: Baumann MA, Beer R (eds). Farbatlanten der Zahnmedizin Endodontologie 2. Auflage. Stuttgart: Georg Thieme, 2007:260–263. 7. Adolphi G, Zehnder M, Bachmann LM, et al. Direct resin composite restorations in vital versus root-filled posterior teeth: a controlled comparative long-term follow-up. Oper Dent 2007;32:437–442. 8. Consensus report of the European Society of Endodontology on quality guidelines for endodontic treatment. Int Endod J 1994;27:115–124. 9. Edelhoff D, Kern M, Weigl P. Aufbau endodontisch behandelter Zähne. Dtsch Zahnärztl Z 2003;58:199–201. 10. Sedgley CM, Messer HH. Are endodontically treated teeth more brittle? J Endod 1992;18:332–335. 11. Papa J, Cain C, Messer HH. Moisture content of vital vs endodontically treated teeth. Endod Dent Traumatol 1994;10:91–93. 12. Helfer AR, Melnick S, Schilder H. Determination of the moisture content of vital and pulpless teeth. Oral Surg Oral Med Oral Pathol 1972;34:661–670. 13. Fusayama T, Maeda T. Effect of pulpectomy on dentin hardness. J Dent Res 1969;48:452–460. 14. Reeh ES, Messer HH, Douglas WH. Reduction in tooth stiffness as a result of endodontic and restorative procedures. J Endod 1989;15:512–516. 15. Randow K, Glantz PO. On cantilever loading of vital and non-vital teeth. An experimental clinical study. Acta Odont Scand 1986;44:271–277. 16. Stenger B, Harder S, Kern M. Responsiveness of vital and endodontically treated teeth to loading. J Dent Res 2011;90(Spec Iss A):Abstr 492. 17. Naumann M, Preuss A, Frankenberger R. Load capability of excessively flared teeth restored with fiber-reinforced composite posts and all-ceramic crowns. Oper Dent 2006;31:699–704.
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18. Bateli M, Kern M, Wolkewitz M, et al. A retrospective evaluation of teeth restored with zirconia ceramic posts: 10-year results. Clin Oral Investig 2013 Jul 31 [Epub ahead of print]. 19. Goracci C, Ferrari M. Current perspectives on post systems: a literature review. Aust Dent J 2011;56(Suppl 1):77–83. 20. Juloski J, Radovic I, Goracci C, et al. Ferrule effect: a literature review. J Endod 2012;38:11–19. 21. Hatzikyriakos AH, Reisis GI, Tsingos N. A 3-year postoperative clinical evaluation of posts and cores beneath existing crowns. J Prosthet Dent 1992;67:454–458. 22. Mehl C, Wolfart S, Kern M. Orthodontic extrusion with magnets: a case report. Quintessence Int 2008;39:371–379. 23. Levin R. Dealing with dental insurance. J Am Dent Assoc 2006;137:99–100. 24. Dietschi D, Spreafico R. Current clinical concepts for adhesive cementation of tooth-colored posterior restorations. Pract Periodontics Aesth Dent 1998;10:47–54;quiz 56. 25. Veneziani M. Adhesive restorations in the posterior area with subgingival cervical margins: new classification and differentiated treatment approach. Eur J Esthet Dent 2010;5:50–76. 26. Zaruba M, Gohring TN, Wegehaupt FJ, et al. Influence of a proximal margin elevation technique on marginal adaptation of ceramic inlays. Acta Odont Scand 2013;71:317–324. 27. Bitter K, Noetzel J, Stamm O, et al. Randomized clinical trial comparing the effects of post placement on failure rate of postendodontic restorations: preliminary results of a mean period of 32 months. J Endod 2009;35:1477–1482. 28. Cagidiaco MC, Garcia-Godoy F, Vichi A, et al. Placement of fiber prefabricated or custom made posts affects the 3-year survival of endodontically treated premolars. Am J Dent 2008;21:179–184. 29. Ferrari M, Vichi A, Fadda GM, et al. A randomized controlled trial of endodontically treated and restored premolars. J Dent Res 2012;91:72S–78S. 30. Naumann M, Koelpin M, Beuer F, et al. 10-year survival evaluation for glassfiber-supported postendodontic restoration: a prospective observational clinical study. J Endod 2012;38:432–435. 31. Torbjorner A, Karlsson S, Odman PA. Survival rate and failure characteristics for two post designs. J Prosthet Dent 1995;73:439–444. 32. Sterzenbach G, Franke A, Naumann M. Rigid versus flexible dentine-like endodontic posts-clinical testing of a biomechanical concept: seven-year results of a randomized controlled clinical pilot trial on endodontically treated abutment teeth with severe hard tissue loss. J Endod 2012;38:1557–1563.
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33. Sorensen JA, Martinoff JT. Intracoronal reinforcement and coronal coverage: a study of endodontically treated teeth. J Prosthet Dent 1984;51:780–784. 34. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically treated teeth: a literature review. Part I. Success and failure data, treatment concepts. J Prosthodont 1994;3:243–250. 35. Aquilino SA, Caplan DJ. Relationship between crown placement and the survival of endodontically treated teeth. J Prosthet Dent 2002;87:256–263. 36. Mannocci F, Bertelli E, Sherriff M, et al. Three-year clinical comparison of survival of endodontically treated teeth restored with either full cast coverage or with direct composite restoration. J Prosthet Dent 2002;88:297–301. 37. Mannocci F, Qualtrough AJ, Worthington HV, et al. Randomized clinical comparison of endodontically treated teeth restored with amalgam or with fiber posts and resin composite: five-year results. Oper Dent 2005;30:9–15. 38. Goga R, Purton DG. The use of endodontically treated teeth as abutments for crowns, fixed partial dentures, or removable partial dentures: A literature review. Quintessence Int 2007;38:e106–e111. 39. Walton TR. An up to 15-year longitudinal study of 515 metal-ceramic FPDs: Part 1. Outcome. Int J Prosthodont 2002;15:439–445. 40. Walton TR. An up to 15-year longitudinal study of 515 metal-ceramic FPDs: Part 2. Modes of failure and influence of various clinical characteristics. Int J Prosthodont 2003;16:177–182. 41. Tunjan R, Rosentritt M, Sterzenbach G, et al. Are endodontically treated incisors reliable abutments for zirconia-based fixed partial dentures in the esthetic zone? J Endod 2012;38:519–522. 42. Manda M, Galanis C, Venetsanos D, et al. The effect of select pulp cavity conditions on stress field development in distal abutments in two types of fixed dental prostheses. Int J Prosthodont 2011;24:118–126. 43. Tan K, Pjetursson BE, Lang NP, et al. A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years. Clin Oral Implants Res 2004;15:654–666. 44. Wegner PK, Freitag S, Kern M. Survival rate of endodontically treated teeth with posts after prosthetic restoration. J Endod 2006;32:928–931. 45. Dittmann B, Rammelsberg P. Survival of abutment teeth used for telescopic abutment retainers in removable partial dentures. Int J Prosthodont 2008;21:319–321. 46. Szentpetery V, Lautenschlager C, Setz JM. Frictional telescopic crowns in severely reduced dentitions: a 5-year clinical outcome study. Int J Prosthodont 2012;25:217–220.
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