种植体直径和长度在Ⅳ类骨质中的优化选择

Bivariate evaluation of the cylinder implant diameter and length in type Ⅳ jaw bone

目的:应用Ansys DesignXplorer模块,进行圆柱形种植体直径和长度同时连续变化时对Ⅳ类骨质的颌骨应力影响的分析。方法:建立了包含圆柱状种植体的下颌骨Ⅳ类骨质的骨块三维有限元模型,设定种植体直径(D)变化范围为3.0～5.0mm,种植体长度(L)变化范围为6.0～16.0mm,观察D和L变化对颌骨Von Mises应力峰值的影响。同时进行颌骨Von Mises应力峰值对变量的敏感度分析。结果:随着D和L的增加,垂直向加载时,皮质骨、松质骨的EQV应力峰值分别降低了63.9%和87.9%,颊舌向加载时,皮质骨、松质骨的EQV应力峰值分别降低了76.2%和92.7%;当D>4.0mmL>11.0mm时,应力峰值的响应曲线的切斜率位于-1～0之间;在垂直向加载和颊舌向加载时,变量L和D分别对皮质骨的EQV应力峰值的影响更明显。结论:颊舌向力的力学分布更易受种植体参数影响;松质骨的应力更易受种植体参数影响;种植体直径增加更有利于改善颌骨颊舌向加载下的应力分布,种植体长度的增加更有利于改善皮质骨垂直加载下的应力分布。从生物力学角度而言,对于Ⅳ类骨质在临床上选择种植体时,种植体的直径应≥4.0mm,种植体的长度应≥11.0mm。

Objective： To evaluate continuous and simultaneous variations of screwed implant diameter and length in the region of type IV bone. Method： Created the mandible segment finite element model of type IV bone with screwed im- plant. The range of implant diameter （D） was set from 3.0 mm to 5.0 mm, and that of implant length （L） from 6.0 mm to 16.0 mm. And forces of 200 N and 100 N were applied along axis of implant （AX） and buccolingual direction （BL） respec- tively. The maximum equivalent stresses in jaw bone were evaluated, and the sensitivities of stresses to the variables were also evaluated. Result： Under axial load, the maximum Von Mises stresses in cortical and cancellous bones decreased by 63.9% and 87.9% respectively with D and L increasing. And under buccolingual load, those decreased 76.2% and 92.7% respectively. When D exceeded 4.0 mm and L exceeded 11.0 mm, the tangent slope rate of the maximum Van Mises stress response curves ranged from -1 to 0. The variation of the maximum Von Mises stresses in cortical bone was more sensitive to L and to D under axial and buccolingual load respectively. Conclusion： Buccolingual force is apt to be influenced by the two implant parameters. Stress in cancellous bone is apt to be influenced by the two implant parameters and implant diameter favors cancellous bone stress distribution more than length does. Implant diameter affects the stress of jaw bone more than length does under buccolingual force and implant length favors stress distribution in cortical bone under axial load than implant diameter does. Implant diameter exceeds 4.0 mm and implant length exceeds 11.0 mm are optimal selection for a screwed implant in the type IV bone by biomechanical consideration.