FAILURE OF ALL-CERAMIC FIXED PARTIAL DENTURES IN-VITRO AND IN-VIVO - ANALYSIS AND MODELING
FAILURE OF ALL-CERAMIC FIXED PARTIAL DENTURES IN-VITRO AND IN-VIVO - ANALYSIS AND MODELING
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DOI：
10.1177/00220345950740060301
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发表时间：
1995-06-01
影响因子：
7.6
通讯作者：
SORENSEN, JA
中科院分区：
文献类型：
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作者：
KELLY, JR;TESK, JA;SORENSEN, JA
在体外测试的20个全瓷固定部分义齿（FPD）的加载部位可见的赫兹圆锥裂纹导致了以下假设：失效是由于局部接触损伤裂纹系统（赫兹应力状态）的传播，并且这种损伤是不太可能的临床失效模式。对20个实验室失效和9个临床失效的全陶瓷FPD进行断口分析，以明确测试这些假设，并比较体外和体内失效行为。在所有情况下，故障发生在FPD连接器中（无接触损坏），约70%至78%来自芯和饰面陶瓷之间的界面。失效源之间的重合提供了强有力的证据，证明体外试验模拟了具有临床重要性的结构行为方面。断口观察结果与体外失效载荷数据相结合，提供了用于约束FPD连接器失效数学模型的非常具体的边界条件。实验室FPD的有限元分析（FEA）发现，只有在以下情况下，最大主拉伸应力才会出现在与断口观察结果一致的位置：（1）陶瓷之间存在适当的弹性模量差异;（2）允许少量基台旋转。结合FEA应力分布的Weibull失效概率（P-f）计算仅在以下情况下非常接近地复制了实验室失效分布：（1）饰面陶瓷比芯陶瓷弱得多;以及（2）芯-饰面界面的Weibull模量远低于游离饰面表面的Weibull模量（即，界面在缺陷方面具有较低的质量）。FPD连接器的结合断口分析和数学分析表明，芯-单板界面是一个重要的故障源，单板陶瓷压倒性地控制承载能力。失败的临床诊断的观察结果为验证实验室测试和关注数学故障模型提供了重要指导。
Hertzian cone cracks visible at the loading site of 20 all-ceramic fixed partial dentures (FPDs), tested in vitro, led to the hypotheses that failure was due to the propagation of localized contact damage crack systems (Hertzian stress state) and that such damage was an unlikely clinical failure mode. Fractographic analysis of the 20 laboratory-failed and nine clinically-failed all-ceramic FPDs allowed for definitive testing of these hypotheses and a comparison between in vitro and in vivo failure behavior. In all cases, failure occurred in the FPD connectors (none from contact damage), with approximately 70 to 78% originating from the interface between the core and veneer ceramics. The coincidence between failure origins provides strong evidence that the in vitro test modeled aspects of structural behavior having clinical importance. The fractographic observations, coupled with the in vitro failure load data, furnished very specific boundary conditions which were applied to constrain mathematical models of FPD connector failure. Finite element analysis (FEA) of the laboratory FPDs found that maximum principal tensile stresses would occur at locations consistent with the fractographic observations only if: (1) there were appropriate elastic moduli differences between the ceramics; and (2) a small amount of abutment rotation was allowed. Weibull failure probability (P-f) calculations, incorporating FEA stress profiles, very closely replicated the laboratory failure distribution only when: (1) the veneer ceramic was much weaker than the core ceramic; and (2) the Weibull modulus of the core-veneer interface was much lower than that for the free veneer surface (i.e., the interface is of lower quality with regard to defects). This combined fractographic and mathematical analysis of FPD connectors suggests that the core-veneer interface is an important failure source and that the veneering ceramic overwhelmingly controls load-bearing capability. Observations from failed clinical restorations provided critical guidance in validating a laboratory test and focusing a mathematical failure model.