Metal-ceramic crown, tooth and supporting structures stress distribution analysis using the 3DFEA.

Introduction: Metal-ceramic crown fracture presents a significant clinical problem. Understanding the stress distribution within the crown structure, regarding design and material properties, under occlusal loading is of outmost importance. The 3D finite element analysis has shown to be representative in investigating the biomechanics of complex structures. Aim of the study: The objective was to investigate aspects of the metal-ceramic crown biomechanics under different loading conditions using the 3D FEA model of an upper first premolar. Material and methods: Definitions of geometry and volume for all particular segments of tooth morphology were derived from digitalized upper right first premolar cross-sections. The metal-ceramic crown was designed on a shoulder type margin. The FEA was performed with NASTRAN (MacNeal-Schwendler Corp, USA). Materials’ mechanical properties were acquired from average values of the literature. The final model consisted of 1.684, 512 four-nodded tetrahedral elements, 246, 510 nodes with a total of 739, 530 degrees of freedom. Boundary conditions were fixed on the outermost layer of the alveolar bone. Single to tripodal contact accumulative static load values of 200N were applied occlusally. Results: The greatest stress concentration was observed within the palatal part of the ceramics (-30.00 MPa) and the metal core (-28.44 MPa). Significant compressive stress values were concentrated within ceramics at the palatal cervical crown margin (-23.75 MPa). Conclusions: Greatest stresses induced during occlusal load involve both metal and ceramics. The 3D FEA of stress distribution explains mechanics involved in typical clinical fractures of metal-ceramic crowns.