The Effects of Adhesive Type and Thickness on Stress Distribution in Molars Restored with All-Ceramic Crowns

Purpose: This study investigated the effects of luting cement type and thickness on the stress distribution within all-ceramic crowns using finite element analysis. Materials and Methods: An all-ceramic crown restoration of the mandibular right first molar was prepared according to standard dental processes and scanned using micro-computed tomography. Eight 3D FE models were then developed that accounted for two adhesive systems, each with cement thickness of 60 mu m, 90 mu m, 120 mu m, and 150 mu m. The models were subjected to four loading conditions, and stresses in the veneer and core layers were evaluated. Results: The stress distribution and maximum stresses in the veneer, core, and cement are presented in corresponding loading conditions. The cement with higher elastic modulus resulted in lower tensile stresses in the veneer and core layers, and the shear strength of the cement was critical to the intactness of the all-ceramic crown. Conclusion: The cement thickness acts as a cushion between the crown and dentin substrate. Although there is an optimal thickness (approximately 90 mu m) that can reduce the stress level in ceramic crowns, cement thickness is not very important to stresses in the core or veneer in most cases when compared to the influence of loading conditions or cement moduli.