Qualitative and quantitative evaluation of central incisor movement by integration of three-dimensional images of dental cast and cephalogramQualitative and quantitative evaluation of central incisor movement by integration of three-dimensional images of dental cast and cephalogram 三次元歯列模型画像とセファログラムの統合による前歯移動の定性的および定量的評価
Purpose: The present study aimed to establish a method for qualitatively and quantitatively determining tooth movement by integrating three-dimensional (3D) model analysis and cephalometric analysis. Materials and methods: Superimposition of 3D images of dental casts before and after orthodontic treatment was performed in two steps. First, initial and final 3D images of dental casts were superimposed at the central incisor and then the reference axis of the incisor was constructed. Second, another superimposition was carried out at the medial points of the third palatal rugae and the palatal vault. The changes in the inclination of the central incisor were measured using an established method of 3D model analysis and cephalometric analysis. The error of measurement in 3D model analysis was compared with that in cephalometric analysis. Results: There was no significant difference in the degree of incisor tipping between times (Time 1 and Time 2) for cephalometric analysis and 3D model analysis, and between the averaged (Time 1 and Time 2) measurements from cephalogram and the 3D model. The error of measurement for 3D model analysis was 0.58°, and the 95% confidence interval (CI) was [-0.62, 0.62]. Corresponding values for cephalometric analysis were 2.02° and [-1.49, 2.73], respectively. Conclusion: The 3D model superimposition method established in the present study was found to be reliable enough to determine the degree of tipping and the location of the center of rotation of the incisor before and after orthodontic treatment.