Stress Distribution in Cad/Cam Endocrowns Produced Via Different Materials and Techniques: a Numerical Simulation

Abstract

Computer-aided design/manufacturing (CAD/CAM) endocrowns are commonly applied for the strengthening of endodontically treated teeth with excessive tissue loss. Monolithic or multilayer structures may be used for this purpose. Restorations made with multilayering techniques may better mimic natural teeth. This study assessed the impact of different materials and application methods on the stress state of CAD/CAM endocrowns. To this end, a 3D FEM model simulating an endodontically treated mandibular first molar was elaborated. The sample was then modified to imitate the ceramic endocrown-applied molar tooth. Three FEM models were then developed from this main model to simulate the following endocrown structures: (1) lithium disilicate reinforced glass ceramic, (2) monolithic zirconia, and (3) multilayered glass ceramic and glass-fiber endocrown (i.e., a glass-fiber core structure and glass ceramic crown). The SolidWorks/Cosmosworks software packages were used for structural analysis. The materials used in the study were treated as homogeneous and isotropic. A 300 N load was applied to the occlusal surfaces of the restored teeth. The von Mises stresses were calculated at the cavity base, ranging from 0.417-0.700 MPa, 0.600-0.850 MPa, and 0.083-0.250 MPa, respectively. The multilayering technique provided the lowest stresses and stress distributions comparable with the natural tooth model. Models of teeth restored with zirconia endocrowns showed the highest stresses and were the least applicable in dental pracice.