Development of an objective and practical method to evaluate the morphology of edentulous alveolar ridges based on the analysis of the movement of complete dentures

本研究的目的是建立一种基于全口义齿运动的有限元分析方法来评估无牙牙槽嵴。采用无牙铸造和上蜡全口义齿（78个下颌骨，38个上颌，29个两者）。我们制作了定制的有限元模型，每个模型由粘膜和义齿组成，这些数据来自使用非接触式三维数字化仪获得的表面数据。所有病例均在双侧人工磨牙负荷和下颌单侧人工磨牙负荷下进行有限元分析。我们对义齿三个节点的位移进行主成分分析（PCA）。另一种PCA是通过对牙槽嵴表面进行规则划分来确定网格上点的坐标。原主成分分析表明，全口义齿的位移可以用几个主成分来表示。后一种PCA表明，每条脊的形态也可以用6个或7个PCA表达。虽然这些形态学pc与先前建议的方案一致，但其他的被认为不太注意，并且有潜在的必要性来评估无牙槽嵴的形态学因素。接下来，我们以每个“位移”PC为因变量，“形态”PC为自变量，采用多元回归分析研究了义齿脊形态对义齿位移的影响。然而，由于决定系数太低，本研究中提取的“形态学”pc被认为不足以表达或估计义齿的位移。为了进一步研究，建议对部分形态学进行PCA，增加样本量，关注“异常”病例，以及/或研究“形态学”pc对功能和预后的影响。

The purpose of this study was to develop a method to evaluate edentulous alveolar ridges based on the movement of the complete dentures calculated with finite element (FE) analysis. Edentulous cast and waxed complete dentures (78 mandibular, 38 maxillary, and 29 both) that passed trials were used. We made customized FE models, each consisting of mucosa and a denture from the surface data obtained using a non-contact 3-D digitizer. The FE analysis was performed under bilateral loads on artificial molars on each side on every case and unilateral loads on mandibular cases. We performed principal component analysis (PCA) of the displacement at three nodes on the dentures. Another PCA was performed with coordinates of the points on the grid defined by regularly dividing of the surface of alveolar ridges.The former PCA showed that the displacement of complete dentures could be expressed with a few principal components (PCs). The latter PCA showed that the morphology of each ridges could also be expressed with six or seven PCs. Although most of these morphological PCs were coincided with protocols previously suggested, others were considered to have been less attentive and to have a potential necessity for protocols to evaluate morphological factors of edentulous alveolar ridges.Next, we investigated the effect of morphology of the ridges on the displacement of dentures using multiple regression analysis with each "displacement" PC as dependent variables and "morphology" PCs as independent variables. However, the coefficients of determination were so low that the "morphology" PCs extracted in this study were considered to be insufficient to express or estimate the displacement of dentures. To progress this study, PCA for partial morphology, more sample size, focusing on "outlier" cases, and/or investigation of the effect of "morphological" PCs on function and prognosis were suggested.