Genetic basis of the crown-size profile pattern.

Abstract

Although genetic control of crown diameters has been documented by a number of workers (R. H. OSBORNE ET AL, Amer J Hum Genet 10: 350-356, 1958; S. M. GARN ET AL, J Dent Res 44:228-242, 1965; D. W. LEWIS and R. M. GRAINGER, Arch Oral Biol 12:539-544, 1967; and D. H. GOOSE, J Dent Res 46:959-962, 1967), genetic involvement in crown-size patterning has not been ascertained for the whole dentition. To investigate the genetic and chromosomal basis of crown-size profile patterning, crownsize patterns of 960 pairs of subjects from southwestern Ohio were compared. After converting individual measurements into normalized T scores (W. A. MCCALL, Measurement, 1939, pp 505-508) by using a computer program (C. R. BLACK, Ann NY Acad Sci 134: 538-540, 1966), dentitions of each pair of subjects were compared by the product moment correlation, r. The resulting correlation coefficients (rT), involving T-scored values of corresponding teeth, provided a simple expression of the degree of patterned similarity between any two individuals. The use of normalized T scores automatically corrected for sex made possible cross-sexed as well as like-sexed comparisons. Sibling correlations for tooth-size similarity approximated 0.22 for 246 like-sexed and crosssexed brothers and sisters (Table). Parent-child similarities in crown-size profile pattern approximated 0.20 as shown by 90 parent-child pairings. Similarly investigated, 58 pairs of cousins yielded a mean similarity coefficient value of 0.15. Finally, randomly paired, unrelated subjects had a pattern profile similarity value of 0.01, close to the theoretical 0.00 value. With profile-pattern similarity values ranging from 0.90 for monozygotic female twins through 0.20 for parents versus their children, 0.15 for cousins, and 0.00 for unrelated pairs, it is clear that crown-size profile patterns have a genetic basis. The values in the table also show evidence for X-chromosomal involvement in the pattern of the total dentition. Sister-sister values of rT exceeded the remaining sibling correlations.