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目的探讨2种不同形态的固位螺钉对修复体稳定性的影响。方法采用三维有限元分析法,对锥形螺钉与平头直角螺钉分别进行实验,计算在相同扭力(200Nmm)下所获得的预负荷值(即夹紧力)及其分布,以及拧紧力矩、防松力矩;在上述扭力下,分别给修复体施加150N和300N垂直向力,比较其预负荷值、拧紧力矩、防松力矩的分布与变化。结果在给予同样扭力(200Nmm)时平头直角螺钉能够获得更大的预负荷;拧紧力矩和防松力矩在螺纹处分布较多,而在螺钉头处分布较少;而锥形螺钉分布相反,力矩主要分布在螺钉头处。在受到150N垂直载荷时,预负荷均下降,其中平头直角螺钉保留的预负荷明显高于锥形螺钉。当受到300N的载荷时,2种螺钉损失的预负荷及力矩值都很大,平头直角螺钉剩余力矩仍然大于锥形螺钉。结论平头直角型面固位螺钉的稳定性优于锥形螺钉。较大载荷会降低修复体的稳定性。
Objective To investigate the effect of two kinds of fixation screws on the stability of prosthesis. Methods Three-dimensional finite element analysis was used to test the taper screws and flat-head right-angle screws respectively. The values of preload (ie clamping force) and their distribution obtained under the same torque (200 Nmm), as well as the tightening torque, Under the above torque, the vertical force of 150N and 300N were applied respectively to the restoration, and the distribution and variation of preload value, tightening torque and anti-loosing moment were compared. Results When the same torque (200Nmm) was given, the flat-head right-angle screw could obtain more pre-load. The tightening torque and anti-loosing torque were distributed more at the screw and less at the head of the screw. The distribution of the conical screw was opposite, Mainly located in the screw head office. When subjected to 150N vertical load, the preload decreased, of which the flat-head rectangular screw retained preload significantly higher than the tapered screw. When subjected to a load of 300 N, the preload and moment losses of the two kinds of screws are large, and the remaining torque of the flat-head right-angle screw is still larger than that of the tapered screw. Conclusion The stability of flat rectangular facet retaining screw is better than that of tapered screw. Larger loads will reduce the stability of the prosthesis.