Effect of post-retained composite restorations and amount of coronal residual structure on the fracture resistance of endodontically-treated teeth

Purpose: To compare the fracture resistance and failure patterns of endodontically-treated teeth with a progressively reduced number of residual walls restored using resin composites, with or without translucent glass fiber posts. Methods: Ninety extracted human single-rooted maxillary premolars were used. After endodontic treatment, the following groups were created: Group 1 (control group): endodontically-treated single-rooted maxillary premolars with four residual walls; Group 2: three residual walls; Group 3: two residual walls; Group 4: one residual wall, and Group 5: no residual wall. Groups 2-5 were each divided into two subgroups: subgroups "a" were restored with resin composites, while subgroups "b" were restored with translucent glass fiber posts and resin composites. Static fracture resistance tests and statistical analyses (P= 0.05) were performed. Results: The mean failure loads (N) were 502.4±152.5 (Group 1), 416.4±122.2 (Group 2a), 423.0±103.3 (Group 2b) 422.1±138.9 (Group 3a) 513.2±121.7 (Group 3b), 488.7±153.7 (Group 4a) 573.4±169.2 (Group 4b), 856.7±112.2 (Group 5a) and 649.5±163.5 (Group 5b), respectively. The samples restored with fiber posts exhibited predominantly restorable fractures. The number of residual cavity walls influenced the mechanical resistance of endodontically-treated teeth.