Objectives: To compare the mesiodistal diameters (M-D) of permanent teeth of four ethnic groups to determine tooth size patterns and relate this to the control of dental development.
Methods: M-D diameters were obtained by standardised manual measurements on the dental study models of teenagers and young adults from four ethnic groups: Southern Chinese (50 male and 50 female); North Americans of European ancestry (91 male and 93 female); Modern Britons of European ancestry (30 male and 30 female) and Romano-Britons from approximately 200-400 A.D. (30 male and 30 female). Reliability testing showed the measurements in all samples were accurate to 0.1mm.
Results: Overall the Southern Chinese had the largest total M-D diameters from the central incisor to 1st molar and the Romano-Britons the smallest (Table 1).
Table 1: Total mean M-D size (mm)
ORIGIN | Males | Females | Overall Total | ||
Maxillary | Mandibular | Maxillary | Mandibular | ||
S. Chin | 49.3 | 45.2 | 48.0 | 44.0 | 186.5 |
Mod.Brit | 47.3 | 44.0 | 47.3 | 43.4 | 182.0 |
N.Amer | 48.1 | 44.4 | 46.4 | 42.1 | 181.0 |
Rom.Brit | 45.4 | 42.5 | 43.7 | 40.1 | 171.7 |
The differences, Southern Chinese>Modern, European ancestry>Romano-Britons were highly significant (p<0.001). However, the Southern Chinese did not have the largest teeth for all tooth types, with the populations of modern European ancestry having the largest central incisors and maxillary molars. Comparisons of coefficients of variation between the first and second teeth of each tooth type, e.g. upper central incisor vs upper lateral incisor, showed that the later forming teeth had greater variation in M-D size (Table 2).
Table 2: Coefficients of variation
ORIGIN | TOOTH TYPE | |||||
| UI1 v UI2 | UPM1 v UPM2 | UM1 v UM2 | LI1 v LI2 | LPM1 v LPM2 | LM1 v LM2 |
S. Chinese | ||||||
Male | 6.0 v 7.4 | 5.3 v 6.6 | 5.0 v 6.0 | 5.3 v 6.1 | 5.7 v 5.9 | 4.1 v 5.5 |
Female | 5.4 v 9.2 | 4.9 v 5.3 | 3.3 v 5.3 | 6.2 v 6.2 | 5.6 v 6.2 | 5.2 v 6.8 |
Discussion: The pattern and size differences in M-D dimensions between the groups reflect genetic and environmental differences. For example, major environmental insults during early life in the Romano-Britons included recurrent illnesses, poor nutrition and excessive lead ingestion and may have acted with genetic differences in that group.
Conclusions: Using a standardised methodology, significant differences in M-D crown dimensions have been demonstrated between ethnic groups. There were different patterns of tooth size between groups and the later-forming teeth in each tooth type showed greater size variation.