Introduction: This study was designed to compare the tooth size discrepancy as a factor of skeletal mal-occlusion in orthodontic patient population of Shiraz.
Materials and Methods: The study employed the pretreatment models of 200 patients, which were selected through a random available sampling method. The mesiodistal dimensions of teeth were measured by digital electron calipers (accurate to 0.01 mm) and the Bolton indices were determined. The study population was divided into four malocclusion groups according to Angle classification (Class I, Class II Div 1, Class II Div 2 and Class III). The data were analyzed using ANOVA and Duncan tests by SPSS software and the level of significance was p<0.05.
Results: The mean anterior ratio (79.01) of the total malocclusion group had a statistically significant difference with that of Bolton (77.2) but no significant difference was found for the overall ratio. The posterior and overall ratios of Class III malocclusion group were statistically greater than the other malocclusion groups. However, regarding the anterior ratio, the Class Ill group had a greater mean than Class II with no difference with Class I malocclusion group.
Conclusion: Comparing the two types of Class II malocclusion for ratios, no significant differences were observed.