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RO0211

30 I I trends _ tooth and restoration survival _Restoring endodontically treated teeth and retaining them throughout life remains a challenge. Several factors play a key role in the long-term sur- vival of endodontically treated teeth and associated restorations. The purpose of this article is to identify the key principles that affect tooth and restoration survival. _Principle #I Mostendodonticallytreatedposteriorteethshouldbe restoredwithcrownstoenhancetheirlongevity. Clinicians have observed a difference between endodontically treated teeth and vital teeth. Endo- dontically treated teeth fracture more often than vital teeth: they tend to break during extraction and pulpless molars without crowns can fracture.1,2 Multiple studies have shown that endodontically treated teeth benefit from the placement of crowns. One study determined that endodontically treated teethwithoutcrownswerelostatsixtimestherateof those with crowns.3 Another study demonstrated that endodontically treated teeth without crowns werelostafteranaveragetimeof50months,whereas endodontically treated teeth with crowns were lost after an average time of 87 months.4 Fixed partial dentures have increased clinical failure when sup- ported by endodontically treated abutment teeth compared with vital abutment teeth.1, 5–8 However, while crowns significantly improved the success of endodontically treated posterior teeth it has not beenshownthattheyimprovethesuccessofanterior teeth.9 Therefore, intact or minimally restored endo- dontically treated anterior teeth do not need com- plete coverage by a crown. They only need a crown when they are weakened by large and/or multiple coronal restorations or when they require significant colour/form changes that cannot be managed by a more conservative treatment.10 In contrast with the above studies, a group of researchers11 found similar success rates when they evaluated endodontically treated premolars restored with a post and direct composite resin restorations both with and without complete coverage. Similarly, a retrospective cohort study12 indicated that endo- dontically treated molars that are intact, except for the access opening, could be restored successfully using composite resin restorations. After considering the available data, we recognise the potential benefits of using composite resin to restore posterior teeth that are intact except for a conservative access opening. However, more clinical data is needed that identifies the long-term success of these teeth when occlusal wear and heavy forces orpara-functionalhabitsarepresent.Forthisreason, we recommend that endodontically treated teeth that have been previously restored receive crowns that encompass the cusps because of the occlusal forces that will be applied to cusps that have been weakened by previous tooth structure removal. Con- versely, it may be possible to avoid crowns on some previously restored posterior teeth with only conser- vative access openings and little to no wear visible that would indicate the presence of detrimental occlusal forces. Another example of a tooth that may not need a crown is a mandibular first premolar, which typically has a small, poorly developed lingual cusp and a lack of occlusal interdigitation that might spread the cusps apart and induce fracture.13 _Principle #II Posts do not reinforce endodontically treated teeth. Theironlypurposeistoretainthecore. Historically, the use of posts was based on the concept that they reinforce teeth. Virtually every laboratory study has shown that either posts do not reinforceteethortheydecreasethefracturestrength roots2_2011 Key principles that enhance success when restoring endodontically treated teeth Authors_ Dr Nadim Z. Baba & Dr Charles J. Goodacre, USA