ABSTRACT
A proper relationship of the total mesiodistal width of the maxillary dentition to that of the mandibular dentition will favor an optimal post treatment occlusion, the purpose of this study is to compare the mesiodistal crown dimension and tooth size discrepancy in subject with class II div.1 malocclusion with spacing or crowding in the upper and lower arches. Sixty pairs of dental casts were obtained [30 crowding, 30 spacing] were measured and analyzed, the results indicates males generally have greater mesiodistal crown dimension than females in both crowding and spacing groups, and there was a significant difference between both groups with greater mesiodistal width for the crowding group, and non significance difference regarding tooth size analysis [Bolton ratio]