Analysis of interjaw ratios in relation to permanent tooth size in subjects with class I malocclusion

Abstract

A certain ratio of maxillary to mandibular tooth size is very important for the proper occlusion formation. In regular occlusion, the teeth must be proportional to size. A discrepancy in tooth size between the mandibular and maxillary arch is usually the cause of disharmonious occlusion ratios. One of the most widespread methods in determining of discrepancy in tooth size between the upper and lower jaw is the Bolton analysis of mesiodistal width of permanent teeth. The subjects of both sexes with the permanent dentition and occlusive ratio of Angle Class I classification had had the precise impressions taken on the basis of which the study models were obtained. 60 patients were selected for this investigation (30 males and 30 females) according to the following criteria: the presence of completely erupted teeth of permanent dentition from the first molar on one side to the first molar on the other side of the dental string; good quality of the study models; the absence of mesiodistal and occlusive abrasion, caries lesions, Class II fillings; the absence of prosthetic or composite restoration;the absence of anomalies in regard to shapes, structures and tooth development. We measured the mesiodistal width of each tooth from the first molar on one side to the first molar on the other side, from the mesial contact point to the distal contact point with the greatest interproximal distance. The obtained results for mesiodistal tooth width of the right and left side do not show statistically significant differences. The mean values of the Bolton anterior ratio showed neither the sexual dimorphism nor did the mean values of the Bolton total ratio show any differences in sexes. The mean values of the Bolton anterior ratio in our examinees of both sexes are significantly higher compared to the values of Bolton norms. The mean values of the Bolton total ratios in our examinees of both sexes were not statistically different compared to the values of Bolton norms. Determining of intermaxillary ratios is an important diagnostic and prognostic value in orthodontics since it offers a possibility to predict the outcome of orthodontic therapy applied on persons with tooth size discrepancy related to the upper and lower jaw.