Maxillary arch size and shape in American blacks and whites.

American blacks have larger teeth than whites, but they less frequently exhibit crowding--apparently because of larger arch dimensions. This study quantified differences in arch size and shape in these 2 constituents of the US population. Eighteen dental and bony landmarks were digitized from the maxilla of each of 332 subjects with permanent, intact dentitions, proportionately divided between blacks and whites, men and women. Linear, angular, and area measurements were computer-generated. Arch widths averaged 10% greater in blacks than whites, and mesiodistal arch depths had a greater difference, at 12%. Blacks, with a more square palate and significantly larger palatal index, were distinguished from whites primarily by greater intercanine and interpremolar widths. Arch perimeter was greater in blacks by 8%, and cross-sectional area of the arch was 19% greater in blacks than whites, so blacks and whites differ substantially for these parameters not only in size, but in shape as well. These differences are relevant in prosthodontics and orthodontics since individualization of treatment leads to more effective treatment by working within the patient's natural arch form instead of making patients fit a single standard.