基牙不同倾斜角度对固定义齿牙周应力分布的影响

Effect of different tilting angels of molar as a fixed bridge abutment on the periodontal stress distribution

目的:用三维有限元方法对近中倾斜不同角度的下颌第2磨牙作为固定桥基牙后受力时牙周支持组织中的应力分布进行比较和分析。方法:实验于2004-05/12在第四军医大学口腔修复学实验室完成。选择牙列完整,咬合关系正常,无明显牙周疾患及牙体缺损或明显磨耗的身体健康的成年男性志愿者1例。采用薄层CT扫描技术和Ansys有限元软件建立下颌第1磨牙缺失、第2磨牙分别近中倾斜10°,20°,30°,40°,50°的三维有限元固定桥修复模型,施加载荷计算并分析牙周应力分布状况。结果:①牙模型应力云图观测结果:在50°的模型之中,牙根整个近中侧从近中嵴顶到根尖处均有较明显、连续性的应力集中现象。②牙周组织应力值:当近中倾斜达到40°,50°时,修复后的模型中应力极值和近中嵴顶应力值都急剧增大,明显高于倾斜10°,20°,30°时牙周应力值。结论:从生物力学角度来说,在40°的倾斜角度内,固定修复有利于倾斜基牙的牙周健康。

AIM： To evaluate the influence of different tilting angles of the mandibular second molar on the stress distribution in the periodontal tissues as bridge abutments with three-dimensional finite element analysis. METHODS： The experiment was conducted in the laboratory of Department of Prosthodontics, College of Stomatology, Fourth Military Medical University of Chinese PLA from May to December 2004. One male volunteer with complete dentition, normal occlusion and healthy periodontal conditions was selected. Five three-dimensional finite element models of 3-unit fixed partial dentures in which the first molar was lost, and the second molars were tilted 10°, 20°, 30°, 40° and 50° toward the second premolar were constructed by the combination of the computed tomographic （CT） scanning technology and Ansys software. A vertical load was applied to the second molar on the central fossae in each case. Stress distribution in the periodontal tissue was calculated and analyzed after loading. RESULTS：①Contour results： There was obvious and continuous stress concentration in the whole mesial part of the periodontal tissues in the model of 50°.②Stress results： The magnitude of stress distribution around the roots of the abutments was increased with the increase of tilting angle. And the stress increased significantly with the angle of 400 and 50°, which was significantly higher than that at the angle of 10° ,20° ,30°. CONCLUSION： If the tilting angle is within 400, the fixed bridge is helpful for the periodontal health of tilting molar from the aspect of biomechanics