Revisiting Bolton Analysis Using American Board of Orthodontics Cast Models

Hypothesis: Tooth size ratios for an ideal occlusion proposed by Bolton 1958 are significantly different than the ratios obtained from American Board of Orthodontics (ABO) certified orthodontically treated cases. Objectives: To compare tooth size ratios from cases that passed ABO exam, with Bolton’s tooth size ratios. To determine the correlation between tooth size ratios and over jet, overbite, anterior tooth inclination, and thickness. Methods: 94 stone models and cephalometric radiographs of finished cases that passed ABO examination were used to measure the anterior and the overall ratios and 52 cases were used for the overall ratio. The Mesiodistal width of each tooth, overjet, overbite, and teeth proclination was measured. Results: T-test shows both overall and anterior ratios have no significant difference from Bolton ratios. The test of correlation showed that both overall and anterior ratios had a significant correlation with overjet, overbite, and upper incisors thickness. Tooth angulation shows no significant correlation with tooth size ratios. Conclusions: Bolton's tooth size ratios are identical to those obtained by ABO certified cases. There is a relatively low inverse correlation between tooth size ratios and overjet, overbite, and upper incisors tooth thickness. Funding: Thanks to Orthopli Corp. for donating the digital gauge caliber. IRB protocol: 20120640-69258-1