Preliminary study on the quantitative analysis of tooth preparation for crown based on digital model

This study explored a method for quantitative evaluation of tooth preparation for crown based on the three-dimensional (3D) scanning and reverse engineering (RE) technique. The maxillary left first molar in the standard gypsum model was prepared for all-ceramic crown. The three-dimensional data of relative objects were acquired by D700 Scanner, which contained prepared tooth, neighbor teeth, antagonist and the intact tooth. Then the 3D data were imported into the RE software. The undercut-detecting surface was constructed based on the interactively-extracted feature margin lines; the quantitative distribution of tooth reduction amount was analyzed by the 3D comparison between the prepared and intact tooth, while the quantitative values of taper and shoulder width were explored in a two-dimensional plane using cloud segmentation and extraction. In this study, the quantitative parameters of tooth preparation (undercut, tooth reduction amount, taper and shoulder width) were obtained by point clouds analysis in the RE software.