目的

探讨在不同骨质条件中、达到骨整合时（40%的骨结合率），不同直径的8 mm 种植体骨界面应力分布的变化规律，为短种植体的临床应用提供一定的参考和实验依据。

方法

采用三维有限元方法分析6 种不同直径的8 mm 种植体在Ⅰ～Ⅳ类骨质条件中，受垂直和侧向力时，种植体骨界面的应力值大小及分布规律。

结果

在Ⅰ～Ⅳ类骨质中，无论垂直或是斜向加载，应力值随着种植体直径增加，呈现减小的趋势。 种植体直径3.3 ～5 mm 时，最大应力值大小变化较为明显（曲率约为-1）；种植体直径5.5 ～7.1 mm 时，变化趋于平缓（曲率接近0）。 另一方面，随着骨质密度降低，种植体骨界面的最大应力逐渐增大：Ⅳ类＞Ⅲ类＞Ⅱ类＞Ⅰ类。 在Ⅰ、Ⅱ类骨质中最大应力分布接近，Ⅲ、Ⅳ类骨质最大应力分布相近。

结论

在临床应用短种植体时，可尽量选择较粗直径的种植体（直径3.3 ～5 mm），但当种植体直径足够大时（直径大于5.5 mm），再增加种植体直径对临床效果的改善不明显；实验结果显示，Ⅲ、Ⅳ类骨质时的应力值远大于Ⅰ、Ⅱ类骨质，提示在临床实践中，可以将Ⅲ、Ⅳ类的骨质通过骨挤压、骨移植等方式来提高骨密度，以保证远期成功率。

Objective

To analyze the stress distribution on implant-bone interface， with varying diameter of 8-mm implant in different bone density （40% osseointegration） for the clinical application of short dental implant.

Methods

Three-dimensional finite element was used to simulate the stress of 8-mm implants with six different diameters in Ⅰ-Ⅳbone density， and a vertical loading and a 45 degree slope loading was applied in this study.

Results

Regardless of vertical loading or 45 degree slope loading， maximum Von-Mises stress decreased as the increase of diameter of dental implants in all four type of bone density. The maximum stress varied significantly when the diameter was bounded in 3.3 mm to 5 mm （slope was around-1）， while when the diameter was within 5.5 mm to 7.1 mm， the variation was much more slight （slope was near 0）. The maximum stress on implant-bone interface increased as the decrease of bone density， in summary， Ⅳ＞Ⅲ＞Ⅱ＞Ⅰ. The maximum stress in Type Ⅰand Type Ⅱhad similar distribution and so as that of in Type Ⅲand Ⅳ.

Conclusions

The larger diameter implant （the diameter in 3.3 mm to 5 mm） would be recommended in order to get better clinical effects.However， when the diameter was above 5.5 mm， much better stress distribution would not be achieved by increasing implant diameter. The result also indicated that the stress was far greater in type Ⅲand type Ⅳbone quality than that of in type Ⅰand type Ⅱbone quality. To achieve better clinical outcome， bone condensing or bone transplantation before inserting the implant， by which bone density can be ascended， would be recommended.