RESUMO
To evaluate, the mesiodistal dimensions of permanent teeth, frequency of Bolton ratio and the presence of Bolton discrepancy outside 2 SD of the Bolton's mean in an orthodontic population, irrespective of the type of mal occlusion. The study was carried out at the department of orthodontics Fatima Jinnah Dental College and Hospital, Karachi. The sample comprised of 150 pairs of good quality pre- treatment study models with fully erupted and complete permanent dentition from first molar to first molar, which were selected from the orthodontic patient pool. Dental casts having grossly carious teeth, prosthesis or anomalies of teeth were not included. The mean, range and standard deviation were calculated for the mesiodistal dimensions of the teeth, anterior ratio and overall ratio.A2- sample t- test was used to test for the statistical difference between means. In general there was no difference between the mesiodistal dimensions of the males and females so the subgroups were combined for further calculations. Mean overall ratio was found to be 91.54%[SD2] and the value ranged from 86.42%to 96.70%.Mean anterior ratio was found to be 78.85%[SD 2.3] and the values ranged from 72.49%to 83.14%. This study found that 13 subjects [9.1%] had overall ratioand 22 subjects [14.7%] had anterior ratio outside 2 SD of Bolton's mean.: With such a high number of significant discrepancies, it is important to routinely perform Bolton tooth size analysis before starting orthodontic treatment as TSD is prevalent among orthodontic patients