Inter-Arch Tooth Size Discrepancies: Validity of Bolton Analysis

Study background: Bolton Index is one of the most commonly used analysis in order to evaluate tooth-size discrepancy. Even if this measure could represent an important tool in clinical practice, many Authors questioned its widespread applicability. The aim of this study was to compare the anterior and total tooth width ratios of an orthodontic population with the Bolton standards and analyse differences in Bolton Index among genders and three malocclusion groups. Methods: A sample of 647 dental casts form the Department of Orthodontics, University of Catania (312 male and 335 female patients between 12 and 21 years old, mean age 16.9 ± 3.1 years) were considered in this study between January 2012 and June 2013. Mesiodistal tooth diameters were evaluated from its mesial contact point to its distal contact point at its greatest interproximal diameter by using a digital calibre and then Bolton indexes were obtained on each model. A one-way ANOVA test was conducted to compare tooth size discrepancies among different malocclusion groups and a Dunn’s Multiple Comparison post hoc test was performed to test which means were different. Results: Mean values and standard deviations for maxillary to mandibular anterior tooth-width ratios were 78.8% ± 3.75% and 91.8% ± 2.50%. The discrepancies outside the ± 1 SD and ± 2 SD ranges from the Bolton means were also calculated the results were 16.9% and 61.5% respectively for BA and 21.5% and 33.8%, respectively for BO. Conclusion: No statistically significant differences have been found concerning tooth-size disharmony among the three malocclusion groups. Furthermore our population showed clearly a higher incidence of tooth-size discrepancies.