Digitally comparing traditional two point measurements with curvilinear measurements in relation to the Bolton analysis

OBJECTIVE: To investigate the application and feasibility of a newly introduced method of Bolton tooth size ratio measurements as compared to the conventional ratios. MATERIALS AND METHODS: Ninety-five post-treatment three-dimensional (3-D) models were used for the study. All models included in the study had Angle Class I molar and canine relationship with proper incisor overjet and overbite. Curvilinear measurements were made in the anterior segment on the lingual of the upper and facial of the lower arches with linear measurements used in the posterior segments of both upper and lower arches. A new ratio was calculated with the mandibular values divided by the maxillary values. The new curvilinear means and standard deviations were compared to the traditional Bolton analysis ratios from the samples collected for both the anterior and overall measurements. The Shapiro-Wilk test was conducted to determine the normality of the distribution of the data. Intraclass correlation coefficients were computed to evaluate the correlation of the curvilinear data to the traditional Bolton measurements. Level of significance was set at p<0.05. RESULTS: Mean and standard deviations for the newly proposed anterior and overall Bolton ratios were 86.60% +/- 3.78% and 95.10% +/- 2.12%, respectively. The Shapiro-Wilk test revealed that the new ratios were not distributed normally (p<0.05) for either anterior or overall ratios. Therefore, data was transformed using the square root approach. Intraclass correlation coefficients revealed that there was only moderate correlation between the curvilinear data and the conventional Bolton ratios. CONCLUSIONS: Conventional Bolton ratios obtained from the SureSmile cases confirmed the standards established in the original Bolton analysis. However, newly established Bolton ratios did not demonstrate a strong correlation with the original method.