[Stress analysis of the all-ceramic crown with a numerical approach].

OBJECTIVE: To analyze the stress distribution in all-ceramic crowns when it was subjected to load. METHODS: A 3D numerical model of the all-ceramic crown of the right mandibular first molar was generated from scanned CT images. Finite element analysis (FEA) was used to evaluate the stress distribution in the all-ceramic crown when it was subjected to 5 load conditions. RESULTS: Stress distributions under 5 loading conditions were obtained. Stress concentrations were generally found near the loading areas at the veneer and at the lower surface of the core beneath the loading areas. In the 5 loading conditions, it was found that when the crown was loaded with vertical concentrated load, the tensile stresses around the shoulder areas were uniform, while stress concentration with maximum of 32.25 MPa was found at the shoulder areas in lingual-buccal direction when loads were applied at an angle of 10 degrees with the tooth axis on the buccal side. The masticatory load which was applied at 20 degrees with the tooth axis on the buccal side would cause stress concentration at the shoulder in mesial-distal direction. The maximum value could reach 11.29 MPa. CONCLUSIONS: The occlusal surface of the all-ceramic crown must be trimmed to increase multiple contact zones with the opposite surfaces in antagonist teeth to avoid excessive concentrated stress that may cause crown failure.