种植体颈部微螺纹结构对种植稳定性影响的三维有限元分析

Influence of micro-threaded neck designs on the stability of dental implants: a finite element analysis

目的:通过分析种植体颈部螺纹结构,以及Von-Mises应力和应变分布情况,为种植体结构设计提供生物力学实验数据和理论参考依据。方法:本文通过运用三维计算机辅助设计CAD软件,设计建立颈部有螺纹和无螺纹三维种植体模型,利用CT扫描数据重建下颌骨三维模型,牙齿咬合面与上颌骨长轴面形成的倾角为45°,沿此方向施加120N的力作用在牙冠顶部,以模拟实际咬合状态受力。利用有限元分析软件模拟即刻负荷(即骨-种植体之间摩擦系数0.3)和骨愈合后期(即骨—种植体之间为绑定接触)两种加载情况下种植体与周围骨组织之间Von-Mises应力和应变峰值大小及分布状况进行比较和分析。结果:在即刻负荷的条件下,Von-Mises应力、应变在颈部光滑的种植体与皮质骨之间分布均匀,峰值分别为28.654MPa、0.01334mm;而颈部有螺纹种植体与皮质骨之间的Von-Mises应力、应变峰值分别为52.630MPa、0.015864mm。在骨愈合后期,颈部光滑的种植体,在相同咬合力作用下,皮质骨Von-Mises应力、应变峰值分别为36.975MPa、0.010272mm;而具有颈部螺纹设计的种植体所引起的Von-Mises应力、应变峰值分别为35.857MPa、0.010234mm。在骨愈合后期,增加种植体颈部的螺纹设计使得皮质骨所受Von-Mises应力减小1.118MPa、应变峰值也有减小的趋势。结论:即刻负载种植时,增加种植体颈部螺纹结构,在种植体-骨愈合后期,颈部的微螺纹结构可使种植体-骨接触界面的Von-Mises应力和应变峰值有所减小,并且有效改善了接触界面的应力分布状况,有助于其长期稳定性及种植成功率的提高。

Objective： To evaluate the effects of the micro-thread designs on implant neck by analyzing the stress and strain distributions between the implant and bones. Method： The solid models of human mandible as well as two dental im- plants with or without micro-threaded neck designs were constructed from the CT databases with computer-aided design software. To mimic the occlusal force, a 45 oblique force of 120 N was applied on top of the crown. Two circumstances were evaluated in this study. For the simulations of immediate loading after implant placement, non-linear surface-to-sur- face contact （coefficient t~ was set at 0.3） were adopted in the implant-bone interfaces. To simulate loading of osseointegrat- ed implants, a bonded condition was set at the implant-bone interfaces. Stresses and strains around the cortical bone-implant interfaces were calculated by ANSYS software. Results： Under the immediate loading, the stress distribution pattern was more even around the implant with smooth neck than the threaded neck in cortical bone. The peak value （threaded neck） of the stress and the strain were 28.654 MPa and 0.01334 into, respectively. Whereas, the implant with threaded neck showed a Von-Mises stress with a peak value of 52.630 MPa and a strain with maximum value of 0.015864 ram. After osseointegra-tion, the Von Mises stress and strain between cortical bone and implant with smooth neck showed a peak value of 36.975 MPa and 0.010272 ram, respectively; whereas, the implant with threaded neck showed a Von-Mises stress with a peak value of 38.091MPa, which was 1.118 MPa smaller than that of smooth neck in cortical bone. A strain with maximum value of 0.010286 mm was observed around the threaded implant neck. Conclusion： In the early healing stage, the implant with mi- cro-threaded neck design appeared to exhibit a stress concentration round the crestal region under the immediate occlusal load, which might have a negative effect on the surrounding bone tissue. After ossteointegration of implant, the mi- cro-threaded characteristics in implant neck area could reduce the stress and strain concentration of the cortical bone-im- plant interfhces under occlusal load and improve the long-term stability of the osseointegrated implants