OBJECTIVETo investigate the stress distributions under load in an all-ceramic crown of the upper central incisor in differential thickness.

METHODSThe 3-dimensional finite element model of all-ceramic crown of the upper central incisor in differential thickness was applied with differential loads (100, 150, 200 N). The stress values and distributions of all-ceramic crown were calculated and expressed.

RESULTSThe tendency of stress distributions in all-ceramic crown of differential thickness and loads was similar. The maximal stress intensity value was located in the loading site and the cervical region. As the thickness of all-ceramic crown increased, the stress concentration reduced. When the load increased, the stress values increased, especially in the loading site and the cervical region.

CONCLUSIONThe increasing of the thickness of all-ceramic crown will decrease stress concentration. Because stress concentration is mainly in cervical region and loading site, these regions should be cared in fabrication of all-ceramic crown.

Ceramics ; Crowns ; Dental Porcelain ; Dental Stress Analysis ; Finite Element Analysis ; Humans ; Incisor ; Tensile Strength

Objective: To investigate the failure reasons of all-ceramic restorations fabricated with chair-side CAD-CAM technology (CEREC®) and to improve the clinical survival of all-ceramic restorations. Methods : All-ceramic single-tooth restorations of CEREC® in stomatology hospital of Jiangsu province between 2013 and 2016 were summarized. By clinical examination and CEREC Biogeneric surveying, the failure reasons and related restoration types were evaluated. These results were analyzed with Chi-square test and Spearman correlation analysis. Results: A total of 61 cases with restoration types of 11 inlays, 38 onlays, 2 endocrowns, and 11 all-crowns, resulted in a failure rate of 5.4% in all-ceramic single-tooth restorations in 1-4 years follow-up. The reasons for failure included ceramic fracture (n=33), debonding (n=13), tooth fracture (n=15), which attributed to thin ceramic thickness (n=27), acute line angle (n=6), insufficient enamel bulk (n=3), insufficient retention type (n=10), insufficient resistance type (n=15). Conclusion The most common reason for failure in CEREC® restorations was insufficient preparation space in occlusal surface.