Analysis of resistance to fatigue between straight solid and anatomic abutments of Morse taper system

Abstract Background The study of the phenomenon of fatigue is essential because implant failures usually are caused by this process. Purpose The objective of this study was to examine the fatigue resistance of straight and anatomical abutments joints that were submitted to cyclic loads. Material and method We used 37 Morse taper implants and 37 abutments, divided into two groups (n= 16: straight abutment, n= 21 anatomical abutment). The sets were submitted to cyclic loading (5 million) using servo-hydraulic equipment. Three sets from each group were subjected to bending tests to determine the maximum load resistance, which served as the parameter for comparison of the cyclic tests. We evaluated number of cycles, load and bending moment. Result Of the 31 abutments cyclically tested, 17 (54.8%) fractured in fewer than 5 million cycles; 8 (25.8%) of these were straight abutments, and 9 (29%) were anatomical. A total of 14 samples (45.2%) resisted the cyclic loading. According to Fisher's exact test, there was no difference between groups as the fracture. Conclusion Despite of the straight abutments have higher average load and bending moment on the anatomical, both types of abutments showed similar performance as the fracture strength in vitro.

# 摘要
## 背景
疲劳现象的研究至关重要，因为种植体失败通常由该过程引发。
## 目的
本研究旨在探讨承受循环载荷的直基台与解剖型基台连接结构的抗疲劳性能。
## 材料与方法
本研究使用37枚莫氏锥度（Morse taper）种植体及37枚基台，分为两组（n=16：直基台组；n=21：解剖型基台组）。采用伺服液压（servo-hydraulic）设备对各组试件开展500万次循环载荷测试。每组各取3个试件组合进行弯曲试验，以测定其最大载荷抗力，作为循环载荷测试的对照参数。本研究评估的指标包括循环次数、载荷值及弯矩。
## 结果
在接受循环载荷测试的31枚基台中，17枚（54.8%）在500万次循环前发生断裂；其中8枚（25.8%）为直基台，9枚（29.0%）为解剖型基台。总计14枚试件（45.2%）通过了循环载荷测试。经费希尔精确检验（Fisher's exact test），两组间的基台断裂发生率无显著差异。
## 结论
尽管直基台的平均载荷与弯矩均高于解剖型基台，但两类基台的体外断裂强度表现相近。