Distribuição de tensões, análise de fadiga e falha de molares com coroas clínicas curtas restaurados com coroas de resina impressas em 3D associadas a retenção por núcleo de reconstrução, pino de fibra de vidro, ou endocrown

Abstract

How 3D-printed resin crown associated with different root canal retention protocols influence the biomechanical performance of endodontically treated molars with short clinical crowns is unclear. The purpose of this in vitro study was to evaluate the influence of root canal retention combined with core build-up, fiberglass post or endocrown retention on the fatigue survival rate, fracture resistance, and stress distribution of 3D-printed resin crowns in endodontically treated molars with short clinical crowns. Sixty human molars were randomly assigned into 4 groups: CP, fiberglass post, cemented and reconstructed using dual-polymerizing resin core cement, and 3D-printed resin crown; C, dual-polymerizing resin core cement reconstruction without FGP, and 3D-printed resin crown; EC, 3D-printed resin endocrown restoration; and SD, sound teeth (control). The specimens were submitted to accelerated fatigue testing until failure or up to a maximum load of 2800 N (161 000 cycles). The surviving specimens were subjected to a static load to failure test. Fracture modes were classified. Three-dimensional finite element analysis was performed and the stress recorded using modified von Mises criterion. Groups were compared by using the Kaplan-Meier survival analysis (log rank test at α=.05 and pairwise post hoc comparisons) and life table analysis for load-at-failure (followed by Wilcoxon pairwise comparison α=.05). No significant difference was observed among the tested groups in terms of the number of fatigue cycles or fracture load (p > 0.05). High survival rates were observed in the accelerated fatigue test and most failures were classified as repairable, with similar rates of catastrophic failure across all groups. Stress concentration was verified mainly in the cervical root region, particularly on the lingual surface. The EC group exhibited a more uniform stress distribution at the interface between the restoration, cement layer, and tooth structure. 3D-printed resin crowns demonstrated high fracture resistance and predominantly repairable failure modes, irrespective of the root canal retention. The stress distribution and failure patterns were similar for endodontically treated molars with short clinical crowns restored with the different protocols investigated.