Tooth Size Discrepancies and Dental Asymmetry in Different Malocclusions

PMalocclusion results from a combination of dental and skeletal disharmonies. Tooth size discrepancy (TSD) and dental asymmetry may play a significant role in the etiology of malocclusion. The aim of this study was to compare the degree of dental asymmetry among patients with Class I, II, and III malocclusions and to correlate measures of asymmetries to the anterior and overall Bolton’s discrepancies. The samples comprised 131 patients aged 13 – 20 years (62 males and 69 females) with different types of malocclusions (39 Class I, 57 Class II, and 35 Class III). All measurements were performed on 3D virtual models using ATOS viewer version 6.A.2 software (GoM mbH, Braunschweig, Germany). Crown length and width of 14 teeth in each dental arch were taken. The Bolton’s ratios and total weighted asymmetry (TWA) were calculated. The analysis of variance was used to compare differences between groups. Pearson's correlations were used to assess associations between the measures of TWA and the Bolton's ratios. The means for the Bolton’s ratios between different types of malocclusion showed no significant differences. The TWA values were low but they differed significantly between the groups of malocclusion. Composite TWA measures of fluctuating asymmetry for dental variables were the highest in Class III, and lowest in Class I malocclusion. Males displayed a higher degree of asymmetry than females. The mean values of the Bolton’s total ratio showed the strongest correlation with TWA of MD tooth size in maxilla (P < 0.01). TWA affects the Bolton’s ratio and may be associated with the etiology of malocclusions. The highest FA in Class III indicates that patients with this class of malocclusion may experience higher levels of genetic and environmental stress in the course of early craniofacial development.