Direct Observation of Fracture process in bond system between all-ceramic restorations and adhesive resin cements

在IPS Empress 2全瓷系统中，通过在热压的顶盖上贴面瓷来制造贴面，然而，多次烧制贴面对IPS Empress 2核陶瓷与粘合树脂粘固剂之间的粘结强度的影响尚不清楚。在这项研究中，微拉伸粘结强度之间的核心陶瓷和树脂水门汀进行了评价。根据统计分析，未加热（41.5 Mpa）和加热4次（39.1 Mpa）的平均粘合强度无显著差异。还发现，多次烧制贴面显着影响的威布尔图的粘结强度。认为全瓷冠在脆性模式磨削加工下存在各种亚表面裂纹，这些裂纹降低了全瓷冠的强度。然而，在CAD/CAM系统加工的牙冠中实际发生的裂纹的种类、大小和位置并不清楚。在这项研究中，评价亚表面损伤的CAD/CAM加工全瓷冠使用粘结界面切片技术。通过扫描电镜观察，发现在牙冠的牙槽嵴、边缘、轴壁和内表面均存在磨痕，这些磨痕可能是牙冠在循环载荷作用下发生断裂的原因。

In IPS Empress 2 all-ceramic system, the restorations are fabricated by veneering porcelain on the copings hot-pressed, however, the effects of multiple firing for veneering on the bond strength between IPS Empress 2 core ceramics and a adhesive resin cement are not clarified. In this study, the micro-tensile bond strength between the core ceramics and a resin cement was evaluated. From the statistical analysis, the mean bond strength was not significantly different for unheated (41.5 Mpa) and for heated four times (39.1 Mpa). It was also found that the multiple firing for veneering significantly influenced the Weibull plots of the bond strength. It is thought that the all-ceramic crowns machined under brittle-mode grinding contain various subsurface cracks, and these cracks decrease the strength the crowns. However, the kind, the size and the location of the cracks actually occur in the crowns machined by CAD/CAM systems are not clarified. In this study, evaluation of the subsurface damages in CAD/CAM machined all-ceramic crowns were carried out using the bonded-interface sectioning technique. From the SEM observation, it is concluded that Median and Lateral cracks were generated by grinding at the ridge, the margin, the axial wall and the inner surface of the crowns, and these cracks can be the fracture origin of the crown under cyclic occlusal loadings.