Aim: Malocclusion may be caused by tooth size discrepancy and it is impossible to achieve perfect treatment results without regarding this etiologic factor. The aim of present study was to determining and comparing the mesiodistal width of permanent teeth in normal occlusion group and patients with class 1 crowding malocclusion in Hamedan.
Material and Method: Based on Andrews normal occlusion criteria among 3335 students of Hamedan pre-university schools 32 persons were selected as normal group. In matched sex and range of age , 32 patients with class 1 crowding malocclusion were selected from a private office . Orthodontic dental casts of all samples were prepared. Mesiodistal width of all teeth (except 2nd molars), overbite, over-jet and Bolton indices were measured 3 times. Student t test and Mann whiteny u test were used for analysis.
Results: In crowding group the mesiodistal width of all teeth except for the first molars, were significantly greater than normal group specially in upper lateral incisors and lower premolars. Maxillary tooth material was 5.3 millimeter (p=0.0005) and mandibular tooth material was 5.4 millimeter (p=0.0036) greater in crowding patients. In crowding patients, overjet was significantly less and overbite was significantly more than normal group (p=0.0001) There was not significant difference in Bolton index between 2 groups.
Conclusion: It seems there is more crowding tendency in cases with large teeth. According to results. Bolton discrepancy (tooth size discrepancy) cannot be considered as a frequent factor in developing class 1 crowding. 2006; 1: 66 - 69)