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

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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.