Abstract
The purpose of this tooth-size study was to compare the crown index—the ratio of buccolingal to mesiodistal crown size—in the primary teeth of contemporary American blacks and whites. Maximum MD and BL drown dimensions were obtained with sliding calipers from dental casts of children attending the graduate pedodontic and orthodontic clinics at the University of Tennessee, Memphis (n = 226). The crown index (BL/MD times 100) was calculated for all 10 tooth types (left and right sides were averaged prior to calculation). Only the maxillary first molar exhibited a significant sex difference (girls have a higher crown index). In contrast, 9 of the 10 tooth types have signficantly higher crown indices in blacks than whites. Analysis of the MD and BL crown diameters reveals that the race differencs are due exclusively to differences in mesiodistal crown lengths; the buccolingual crown breadths do not differ between these two races. Consequently, the crown indices are higher in blacks because of their larger MD dimensions. Differences in the indices conform to prior findings that American blacks have larger tooth crowns than whites in both the primary and permanent dentitions, and this study shows that the differences are due to the MD not the BL crown axis. Study of the crown components will shed light on how the crown shapes differ between these two races.
Highlights
The purpose of this tooth-size study was to compare the crown index—the ratio of buccolingal to mesiodistal crown size—in the primary teeth of contemporary American blacks and whites
It is commonly appreciated that teeth differ among human groups both as regards shape as well as size. Part of this is due to differences in the prevalence and degree of crown traits, such as incisor shoveling (Hrdlička, 1920) and molar cusp number (Harris and Bailit, 1980), but other differences involve the proportionality of crown components such as relative cusp sizes (Turner et al, 1991; Townsend et al, 2003; Harris and Dinh, 2006)
We are aware of two studies of the primary dentition; both show a precedence of American blacks compared to American whites (Ferguson et al, 1957; Infante, 1974)
Summary
The purpose of this tooth-size study was to compare the crown index—the ratio of buccolingal to mesiodistal crown size—in the primary teeth of contemporary American blacks and whites. Differences in the indices conform to prior findings that American blacks have larger tooth crowns than whites in both the primary and permanent dentitions, and this study shows that the differences are due to the MD not the BL crown axis. Anderson (2005, 2006, 2007) described tooth crown sizes of a large sample (n ≈ 1,124) of American blacks from Howard University (Washington, D.C.). The purpose of the present study is to compare tooth crown shapes—ratios of BL width to MD depth—in the primary teeth from samples of American blacks and whites from the U.S Mid-South. This report was stimulated by exploratory findings that suggested that blacks have significantly different crown indices than whites, and the present study explores that finding in more detail
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