Complete Digital Workflow for Evaluation of the Three-Dimensional Monson's Sphere Using Digital Scanning.

Background: As a combination of curve of Spee and curve of Wilson, the Monson sphere reflects the arrangement of teeth in three-dimensional (3D) space. For occlusal analysis, the Monson sphere can provide an important reference for prosthetic reconstructions or orthodontic treatments.

Objectives: The purpose of this study was to generate and investigate the 3-D Monson sphere through a complete digital workflow with intraoral scanning models and custom software.

Material And Methods: Sixty-four Chinese adults (32 males and 32 females) with individual normal occlusion were recruited, and their intraoral scanning models were obtained using a digital intraoral scanner. Twenty-six landmarks on the scanning models were digitized using a reverse engineering software. Monson's sphere was generated and evaluated by fitting a sphere to the cusp tips using a least-squares method by means of custom software program. Mann-Whitney's U test was performed to test the radius difference of Monson's sphere between males and females. One-sample t-test was used to test the statistical significance (α = 0.05).

Results: Monson's sphere could be generated by means of digital scanning combined with customed software. The mean radius of Monson's sphere was 77.35 ± 13.38 mm, which was lower than the theoretical value proposed by Monson. Furthermore, there were significant differences between males and females in Monson's sphere radius (p < 0.001).

Conclusions: This study explores a new best-fit algorithm for generating 3-D Monson's sphere by complete digital workflow. The radius of Monson's sphere in Chinese adults was lower than the classical value of four-inch proposed by Monson. There was a significant difference between males and females. Monson's sphere value found in this study could be used as a reference for prosthetic reconstruction and orthodontic treatment and be applied to improve dental treatment results.