应用断口表面形貌分析法分析临床失败In-Ceram全瓷冠1例

Fractographic analysis of failed fragment of In-Ceram alumina crown

目的定义导致失效的裂纹初始源和相关缺陷,为临床医生改进设计和材料学性能提供形态学依据。方法将2009年1月临床收集到的1例In-Ceram氧化铝全瓷冠断片清洁处理后断面喷金,采用扫描电子显微镜结合断口形貌分析理论对断面的表面特征性形貌进行分析。结果失效断片肩台处饰面瓷截获线(arrest lines)和梳线尾迹(wake hackle lines)提示裂纹由核瓷指向饰面瓷;咬合面窝沟处饰面瓷厚度比咬合面其他处明显薄,该处核瓷与饰面瓷之间存在分离现象,核瓷由内向外断裂的晶型发生改变,由晶界断裂向穿晶断裂转变,提示随着裂纹尖端由稳定向不稳定状态进展,裂纹初始源由核瓷内侧面指向外侧面。Panavia树脂黏结剂与未经任何表面处理的核瓷之间破坏类型表现为黏结界面破坏和黏结层的内聚破坏。结论多晶陶瓷失效断片结合断口表面形貌分析法能够发现破坏裂纹初始源;In-Ceram氧化铝核瓷内面是全瓷冠的薄弱点,核瓷和饰面瓷的厚度比影响裂纹破坏的初始;未经内表面处理的核瓷与Panavia树脂黏结剂之间的黏结效果不可靠。

Objective To investigate an in vivo failed fragment of In-Ceram alumina all-ceramic crown using fractographic theory,in order to determine the fracture origin or related defects for the improvement of clinical design and mechanical properties of materials.Methods The in vivo failed fragment of In-Ceram alumina all-ceramic crown wasg old-coated following cleaning.Scanning electron microscopy was examined to analyze the surface fractographic featuresb ased on the fractographic theory.Results The arrest lines and wake hackle in the chamfer region of the failed fragment indicated the crack initiation from the core to the porcelain veneer.The thickness of the porcelain veneer in the occlusal surface fissure was thinner than the other occlusal surface,where an interface was inspected between the veneera nd the core.There was an apparent shift from an'intergranular'to'transgranular'type of fracture as the crack frontm ade the transition from stable to unstable growth,indicating the crack initiation from the core to the veneer.Without thei nner surface treatment,the fracture types between the panavia resin cement and the core were interfacial fracture between the core and resin cement and the cohesive fracture in the resin cement.Conclusion Within the limits of thiss tudy,the fractographic theory with SEM is suitable for the crack initiation analysis of polycrystalline ceramics.The inner surface of the In-Ceram alumina ceramic is a weak site from the mechanical point.The core/veneer thickness oratioi nfluences the crack origin.The adhesive bonding between the untreated In-Ceram alumina core and panavia resin cement is not reliable.