铸造支架式可摘局部义齿折断分析

Fracture analyses of casting framework removable partial dentures

目的:对比纯钛与钴铬合金支架式可摘局部义齿(removable partial denture,RPD)的临床折断失败率,分析两种金属支架的断裂方式和原因,以及缺陷的产生在断裂过程中的作用。方法:通过大样本回顾性研究的方法追踪纯钛和钴铬合金支架式RPD共30 618件,分别统计18个月的临床折断失败率。收集断裂的金属支架,分析断裂原因,扫描电子显微镜(scanning electron microscope,SEM)观察其断裂面微观形貌,分析断裂方式和损伤特征。X线衍射能谱分析(energy-dispersive X-ray spectroscopy,EDS)化学成分变化。结果:纯钛支架的折断失败率为1.75%,钴铬合金为0.57%。分析可能的折断原因涉及到临床牙体预备、支架设计和支架制作缺陷。纯钛和钴铬合金支架的断裂方式均呈现韧性断裂特征,裂隙缺陷存在于断裂后的纯钛和钴铬合金支架内部,气孔发现于纯钛支架的断裂面。结论:纯钛支架的临床折断失败率高于钴铬合金支架,原因与铸造过程产生的缺陷相关。

Objective： To compare the clinical fracture rates of removable partial denture（RPD） made of titanium with that of Co-Cr alloy,to analyze the fracture modes and reasons of two kinds of metal frameworks,and to explore the effect of defects on the fracture process.Methods： Following totally 30 618 RPDs made by titanium and by Co-Cr alloy,the fracture rates in 18-month were calculated individually.The fractured surfaces of failed RPDs were examined by fractography investigations using a field emission scanning electron microscope to disclose the fracture mode and damage character.The energy-dispersive X-ray spectroscopy analysis was performed to examine the chemical compositions.Results： The fracture rate of titanium framework was 1.75%,comparing with 0.57% of Co-Cr alloy framework.The reasons included teeth preparing,framework design,and defects during casting.The fracture modes of titanium and Co-Cr alloy framework performed toughness fracture character.The fissures were found in both titanium and Co-Cr alloy frameworks,and pores were detected in titanium frameworks.Conclusion： The higher fracture rate of titanium framework is related to the defects during casting.