Abstract:
The aim of this study was to evaluate fracture resistance and failure pattern of endodontically treated premolars with simulated abfraction in various restorations. Thirty-two extracted two-rooted maxillary first premolars with same sizes and shapes were randomly divided into 4 groups (n=8) for different restorations types. The control group was endodontically treated without simulated abfraction and restored with resin composite at access opening. Groups 1 - 3 were simulated with abfraction, filled with resin composite, endodontically treated and then restored with different methods. Group 1 (RF) was restored with resin composite at access opening, group 2 (P/RF) was restored with fiber post and resin composite and group 3 (P/ZC) was restored with fiber post, resin composite and zirconium crown. The teeth then were placed into acrylic blocks with simulated PDL. The specimens were loaded at central fossae, 30° to long axis of the teeth until failure. The data were analyzed by one-way ANOVA and Scheffe test at a 95% level of confidence. The results showed that the fracture resistance of control group, groups RF and P/RF had not statistically significant difference (p>0.05), while the fracture resistance of group P/ZC was significantly higher than those of groups RF and P/RF (p<0.05) with no significant difference from control group. For failure patterns, 80% of specimens in control group, groups RF and P/RF failed with palatal cusp fractures, while all specimens in group P/ZC cracked and fractured along crown margins and posts retained crowns to roots. The study concluded that resin composite filling at simulated abfraction could present the fracture resistance close to the teeth without abfraction. The fiber posts did not affect fracture resistance of the teeth with simulated abfraction, however, they retained the crowns to the roots which prevented sudden coronal crown lost. The zirconium crowns and fiber posts could significantly increase fracture resistance of teeth with simulated abfraction. In addition, the coronal remaining walls at the cervical areas are the main factors for proper restorations.
