Influence of height discrepancy between pulp chamber floor and crestal bone in the mechanical fatigue performance of endodontically-treated teeth restored with resin composite endocrowns

To explore and characterize the effect of the discrepancy between crestal bone height (CB) and pulp chamber floor (PCF) in the fatigue performance of endodontically-treated teeth rehabilitated with an endocrown restoration. A total of 75 human molars free of defects, caries history or cracks were selected, then endodontically treated and randomly allocated into 5 groups (N = 15) according to the difference between PCF and CB, as follows: PCF 2 mm above, PCF 1 mm above, PCF leveled, PCF 1 mm below and PCF 2 mm below. Endocrown restorations were made with composite resin (Tetric N-Ceram, shade B3, Ivoclar) in 1.5 mm thickness and luted with a resin cement (Multilink N, Ivoclar) onto the dental elements. Monotonic testing was performed to define the fatigue parameters, and a cyclic fatigue test was used until failure of the assembly. The collected data were submitted to statistical survival analysis (Kaplan-Meier followed by Mantel-Cox and Weibull), fractographic analysis and finite element analysis (FEA) were performed as complementary analyzes. The PCF 2 mm below and PCF 1 mm below groups presented the best results regarding fatigue failure load (FFL) and number of cycles for failure (CFF) (p 0.05). The PCF leveled and PCF 1 mm above groups presented no statistical difference between them (p > 0.05), but performed better than the PCF 2 mm above group (p