骨吸收对平台转换种植体周围骨组织内部应力的影响

目的:观察骨吸收对平台转换设计种植体周围骨组织内部应力的影响。方法:利用COSMOS 2.85软件包建立不同程度骨吸收的种植体支持下颌第一磨牙金属冠三维有限元模型共10个。种植体-基台的连接形式分别采用平齐对接(模型A)和平台转换(模型B)设计,模型又分为无骨吸收(A0,B0)和骨吸收的深度分别为0.5mm(A1,B1)、1.0mm(A2,B2)、1.5mm(A3,B3)和2.0mm(A4,B4)5种。采用垂直和斜向两种形式加载,载荷均为200N。观察骨吸收程度对种植体周围骨组织内部应力的影响,并比较不同程度骨吸收时两种设计种植体周围骨组织内部应力的不同。结果:平台转换种植体和平齐对接种植体周围骨组织内部的应力分布相似,应力主要集中在种植体颈部。随着骨吸收程度的增加,应力集中的范围增大;当皮质骨完全吸收后,种植体根部也出现应力集中的趋势。种植体周围骨组织内部的最大等效应力随着骨吸收程度的增加而减小,当皮质骨完全吸收后改变最明显。同等程度骨吸收时,平台转换设计种植体周围骨组织内部的最大等效应力小于平齐对接设计;随着骨吸收程度的增加,两者的差距逐渐减小。结论:骨吸收会导致种植体周围骨组织内部应力集中的范围加大而最大等效应力减小;骨吸收后平台转换设计改善种植体周围骨组织应力分布的作用变得不明显。

Influence of Marginal Bone Resorption on Stress around Implant with Platform Switching Design

Objective: To investigate the influence of marginal bone resorption on the stress around implant with platform switching design.Methods: Three-dimensional finite element models of implant supported metal crown for the mandibular first molar were computed by COSMOS 2.85.Traditional butt joint connection was used in model A and platform switching design in model B.The depth of bone resorption around implant was designed as 0.5mm,1.0mm,1.5mm,and 2.0mm respectively.Loading conditions were a vertical load of 200 N and inclined load of the same magnitude at 45 degrees to the vertical axis of the implant.The stress distribution and maximum von Mises stress around implant with different depths of bone resorption were analyzed.The stress around implant with platform switching design was compared with that of with butt joint design.Results: Stresses in the peri-implant bone were observed circumferentially around the implant neck and the stress intensity and distribution increased with the increase of bone resorption.When the cortical bone was lost,the higher stress began to concentrate around the implant apex.The maximum von Mises stress decreased with the increase of bone resorption,especially when the cortical bone was lost.With the same amount of bone resorption,the maximum von Mises stress around implant with platform switching design was lower than that with butt joint design.However,with the increase of bone resorption,the difference decreased.Conclusion: With the increase of bone resorption,the stress concentration area around implant increases and the maximum von Mises stress decreases.The advantage of platform switching design to improve stress distribution is compromised with the increase of bone resorption.