Biomechanical Assessment of Restored Mandibular Molar by Endocrown in Comparison to a Glass Fiber Post-Retained Conventional Crown: 3D Finite Element Analysis

Purpose: To compare equivalent and contact stresses in a mandibular molar restored by all-ceramic crowns through twomethods: ceramic endocrowns and ceramic crowns supported by fiber-reinforced composite (FRC) posts and core, by using 3D finite element analysis during normal masticatory load. Materials and Methods: Three 3D models of a mandibular first molar were made and labeled as such: intact molar with no restoration (A); ceramic endocrown-restored molar (B); ceramic crown supported by FRC posts and core restored molar (C). By using 3D FE analysis with contact components, normal masticatory load was simulated. The mvM stresses in all models were calculated. Maximal mvM stresses in the ceramic of restorations, dentin, and luting cement were contrasted among models and to values of materials’ strength. Contact shear and tensile stresses in the restoration/tooth interface around restorations were also calculated. Results: The highest mvM stress levels in the enamel and dentin for the tooth restored by ceramic endocrown were lower in the crown ceramic than in tooth restored with FRC posts and all-ceramic crowns; however, in the resin adhesive cement interface it was lower for ceramic crown supported by FRC posts than the in ceramic endocrown restoration. Themaximum contact shear and tensile stress values along the restoration/tooth interface of ceramic endocrowns were lower than those with ceramic crowns supported by FRC posts. Conclusions: Ceramic endocrown restorations presented a lower mvM stress level in dentin than the conventional ceramic crowns supported by FRC posts and core. Ceramic endocrown restorations in molars are less susceptible to damage than those with conventional ceramic crowns retained by FRC posts. Ceramic endocrowns properly cemented in molars must not be fractured or loosen during normal masticatory load. Therefore, ceramic endocrowns are advised as practicable, minimally invasive, and esthetic restorations for root canal treated mandibular molars.The authors of this study thank Professor Chen Zhong Zhong and Mr. Zhang Jian Fei from the School of Mechanical Engineering, Zhengzhou University for their technical support rendered for the 3D FEA