下颌两侧对称性牙槽嵴形态对全口义齿稳定性影响的初步研究

Influence of the Bilateral Symmetric Mandibular Residual Ridge Shape on Complete Denture Stability

目的:探讨下颌两侧对称性牙槽嵴局部形态因素对全口义齿稳定性的影响。方法:利用激光三维扫描仪取得下颌无牙颌标准模型牙槽嵴表面形态数据,通过计算机辅助工程(CAE)软件形成下颌全口义齿,及9种左右形态对称的牙槽嵴黏膜三维有限元模型:1)建立标准牙槽嵴(A),及牙槽嵴高度为A的1/2(B)和1/4(C)的黏膜模型;2)以A,B为基础,按牙槽骨不同部位左右对称吸收至C高度为条件,分别形成磨牙区吸收(AC1,BC1),后牙区吸收(AC2,BC2)和前牙区吸收(AC3,BC3)的黏膜模型。在模型咬合面的双尖牙区(Pt及其颊侧Pb1和Pb2)及磨牙区(Mt及其颊侧Mb1和Mb2)设定共6个加载部位,单侧垂直加载9.8N的力,利用三维有限元分析各条件下义齿的位移。结果:牙槽骨整体吸收情况下,义齿基托位移量依A,B,C顺序递增,C条件下义齿位移最大;前牙区牙槽骨高度吸收(AC3和BC3)的条件下,义齿位移量在同系列条件中最大;在磨牙区加载时,AC2和AC3,以及BC2和BC3左右位移较大且相近,都大于AC1和BC1。结论:在单侧加载条件下,下颌两侧对称性牙槽嵴前牙区和双尖牙区牙槽嵴高度影响全口义齿稳定性,评价不同部位牙槽嵴相对高度可初步判断义齿固位条件及稳定性。

Objective：To investigate the influence of the bilateral symmetric mandibular residual ridge shape on complete denture stability,and determine the local morphological factor of edentulous alveolar ridges according to its influence on the movement of complete dentures.Methods：In this study,the denture movement under unilateral loads was analyzed using three-dimensional finite element method.Nine types bilateral symmetric model of alveolar ridge were prepared using CAE software：1）Standard mandibular alveolar mucosa and complete denture model was set up as model A,then model B which alveolar ridge height reduced to 1/2of the height of model A and model C which alveolar ridge height reduced to 1/4of the height of model A were set up.2）Based on those models,different alveolar parts of bone resorption to point C were analyzed as AC1and BC1demonstrate molar alveolar ridge height reduction;AC2and BC2demonstrate posterior alveolar ridge height reduction;AC3and BC3demonstrate anterior alveolar ridge height reduction.Sliding and detachment at the interface between a denture and mucosa were allowed.A vertical loading of 9.8Nwas applied on six load places：the occlusal surface of premolar region（Pt,Pb1and Pb2）,and molar region（Mt,Mb1and Mb2）.Results：Under the situation of overall resorption of alveolar residual bone,the more resorption results in the more displacement of denture as in our experiment model C demonstrate more displacement denture then model B and Model B get more than model A.As with the different parts of alveolar residual bone resorption,the height of anterior region affected the movement of denture base movement significantly,and the height of premolar region affected denture movement in the lateral direction.Conclusion：Under a unilateral load,the height of anterior and premolar region affects denture stability.By evaluating the relative height of different parts of alveolar ridge,the retention and stability of complete denture may be preliminarily predicted.