Bone and soft tissue changes associated with a removable partial denture. A novel method with a fusion of CBCT and optical 3D images.

BACKGROUND: The purpose of this study was to propose a novel method for 3D evaluation of bone and mucosal changes in removable partial denture (RPD) foundation area using a fusion of cone beam computed tomography (CBCT) and optical 3D images. METHOD: Two CBCT scans and three impressions, taken at insertion and after ten months of wearing the RPD, were acquired from five patients. 3D models of bone and surface were created from CBCT images and gypsum casts, respectively, spatially aligned and saved in Standard Tessellation Language file format. Visual and numerical analysis of differences between the models allows evaluation of surface, mucosal and bone changes in regions of interest (ROI) defined as narrow ROI (nROI), denture foundation area ROI (dROI) and wide ROI (wROI). Site-specific analysis was performed in mesiodistal and buccolingual direction. RESULTS: Visual evaluation of 3D color-coded deviation maps showed irregular distribution of bone and surface changes. The differences between mandibles and also between left and right sides were found. Mean volume of bone change in dROI was -135.86 (range = -456.18 to 21.20) mm(3). The average bone change thickness in dROI was -0.26 (range = -0.96 to 0.07) mm. The mean volume changes in nROI were -38.31 (range = -118.26 to 45.87) mm(3), -51.96 (range = -182.54 to 5.6) mm(3) and 13.66 (range = -80.62 to 79.46) mm(3) for surface, bone and mucosa, respectively. CONCLUSIONS: The proposed method facilitates separate visual and numerical evaluation of surface, mucosa and bone changes. It opens possibilities for a better understanding of denture-supporting tissues remodeling, objective evaluation and comparison of different treatment options.