金属烤瓷全冠面中央及边缘耐压强度分析

Investigation of Fracture Strength of the Centre and the Margin of the Porcelain on the Occlusional Surfaces of Metal-ceramic Crowns.

目的 :分析金属烤瓷全冠面中央及边缘的瓷耐压强度 ,探讨临床常见崩瓷现象。材料与方法 :利用离体左上第一磨牙常规制作无尖金属烤瓷全冠 2 0枚 ,随机分 2组 ,一组置 5mm直径球形压头于面中央 ,另一组同样压头置于面近颊尖处 ,于LJ5 0 0型拉力机上匀速 (10mm/min)加压 ,记录瓷崩裂时的载荷值并作统计分析。结果 :面中央受力组瓷层全部碎裂 ,平均载荷 3.0 5 2KN ,面近颊尖处受力组其瓷层呈片块状剥脱 ,与临床崩瓷现象相似 ,平均载荷 1.335KN ,仅为前组的44 %。两组最大载荷比较差异有显著性 (p <0 .0 1)。结论 :面边缘的瓷层为金属烤瓷全冠的结构薄弱区 ,是崩瓷现象最易发生处。临床上应采取必要措施重点防范。

Aim:[WT5”BZ]Investigate the fracture strength of the centre and the margin of the porcelain on the occlusional surfaces of metal ceramic crowns and study the porcelain fracture phenominon. Materials and Methods: Twenty metal-ceramic crowns, with which the occlusional surfaces were prepared to planes, were fabricated according to the left upper first molar and luted with 3M special cement. The specimens were mounted in acrylic resin blocks and then, divided into two groups randomly and tested for fracure strength in a LJ 500 tension test machine using 5mm steel ball contacting the centre or the margin of the porcelain on the occlusional surfaces. A static preload weere applied and then increased at a rate of 10mm/min until fracture were occurred. The fracture loads were recorded and the data were analysed using Kraskal-Wallis test. Results: The fracrure strength of the centre porcelain on the occlusional surfaces of metal-ceramic crowns is much more higher than that of the margin porcelain (about 2.286 to 1, p<0.01). Conclusion: Metal-ceramic junction (margin porcelain) is the weak link of the metal-ceramic crowns and must be taken more precautions against.