Three-dimensional analysis of occlusal curvature in Korean

Objectives: There have been several studies regarding occlusal curvature. Most focused on the curve of Spee, moreover conventional methods have a limitation for measuring occlusal curvature because of its 3-dimensional structure. Therefore, this study aimed to develop measurement parameters and analyze the curve of Wilson and the sphere of Monson in Koreans using virtual 3D dental models and specialized software. Methods: Mandibular dental casts from 79 young adults were scanned and rendered as virtual models with 3D scanner. 26 landmarks were digitized on the virtual models by specialized software program. The Monson's sphere was estimated by fitting a sphere to the cusp tip points from first premolars to second molars based on least-squares method. Two curve of Wilson were generated by finding the intersection circle between the Monson's sphere and two virtual vertical planes generated in the canines and the fist molars, respectively. A sample independent t-test for gender difference and one-way ANOVA for morphological variation effect were performed for statistical analysis. Results: The mean radius of Monson's sphere was 4.37±1.01 inch in Koreans and very similar to that of curve of Wilson. There was statistical difference between males and females in all measurements (p<0.01), within 0.66~0.68 inch range. The morphological variations of the second premolar and molar have no influence and no interaction on occlusal curvatures (p>0.05). Conclusion: It was concluded that radius of 3D occlusal curvature in Korean was larger than the classical 4-inch value advocated by Monson, recommending ethnic difference in sphere radius, and the tendency was particularly noticeable in males (p<0.05).