Ferrule Design Does Not Affect the Biomechanical Behavior of Anterior Teeth Under Mechanical Fatigue: An In Vitro Evaluation.

OBJECTIVES: To investigate the survival and failure mode of fiber-post resin restorations over preparations with different ferrule designs when submitted to a fatigue load test.

METHODS AND MATERIALS: Fifty bovine incisors were selected and divided into five groups (n=10) according to ferrule design: a no-ferrule group, a 2-mm circumferential ferrule group, a 2-mm buccal ferrule group, a 2-mm lingual ferrule group, and a 2-mm buccal and lingual ferrule group. The fiberglass post was cemented and the composite core was built up and prepared, followed by cementation of a full composite crown. The samples were subjected to a cyclic fatigue test with loading applicator at 135°; a staircase approach was used until fracture. Survival (cycles to fracture) and failure modes were recorded. Survival data were analyzed with the log-rank test, while Kruskal-Wallis and Fisher exact tests were used to analyze failure mode data (α=0.05).

RESULTS: The median number of cycles to fracture ranged from 215,000 to 236,153. The log-rank test showed no statistically significant difference in survival rates among the groups ( p =0.82). Regarding failure mode, three types were observed: I, post and/or core fracture; II, root fracture in the cervical third; and III, root fracture in the middle third. No statistical difference was observed among the groups (Kruskal-Wallis test, p =0.147).

CONCLUSION: The ferrule design had no effect on fatigue resistance or failure mode of endodontically treated incisor teeth restored with a fiber post, composite core buildup, and composite crown.