Should adhesive debonding be simulated for intra-radicular post stress analyses?

Objective. Elucidate the influence of debonding on stress distribution and maximum stresses for intra-radicular restorations. Methods. Five intra-radicular restorations were analyzed by finite element analysis (FEA): MP = metallic cast post core; GP = glass fiber post core; PP = pre-fabricated metallic post core; RE = resin endocrowns; CE = single piece ceramic endocrown. Two cervical preparations were considered: no ferule (f(0)) and 2 mm ferule (f(1)). The simulation was conducted in three steps: (1) intact bonds at all contacts; (2) bond failure between crown and tooth; (3) bond failure among tooth, post and crown interfaces. Contact friction and separation between interfaces was modeled where bond failure occurred. Mohr-Coulomb stress ratios (sigma(MC ratio)) and fatigue safety factors (SF) for dentin structure were compared with published strength values, fatigue life, and fracture patterns of teeth with intra-radicular restorations. Results. The sigma(MC ratio) showed no differences among models at first step. The second step increased sigma(MC ratio) at the ferule compared to step 1. At the third step, the sigma(MC ratio) and SF for f(0) models were highly influenced by post material. CE and RE models had the highest values for sigma(MC ratio) and lower SF. MP had the lowest sigma(MC ratio) and higher SF. The f(1) models showed no relevant differences among them at the third step. Significance. FEA most closely predicted failure performance of intra-radicular posts when frictional contact was modeled. Results of analyses where all interfaces are assumed to be perfectly bonded should be considered with caution. (C) 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.