Archs oral Bid. Vol. 30, No. 1, pp. 83-84, 1985 Printed in Great Britain. All rights reserved

0003-9969185 53.00 + 0.00 Copyright C’ 1985 Pergamon Press Ltd

SHORT COMMUNICATION

THE SIZE OF PERMANENT TEETH TN KLINEFELTER (47,XXY) SYNDROME IN MAN

G. C. TOWNSEND* and L. ALvEsALot

*Department of Dentistry, The University of Adelaide, Adelaide, South Australia 5000 and ?Institute of Dentistry, University of Turku, SF-20520, Turku, Finland

Summary-The permanent teeth tended to be larger than normal in a group of 77 males with the syndrome, indicating that the presence of an extra X-chromosome has a growth-promoting effect which operates from early in development.

Studies of individuals with sex chromosomal abnor- malities have indicated that the differences in tooth size normally observed between males and females may result, at least in part, from direct genetic effects of the sex chromosomes (e.g. Alvesalo and Varrela, 1980). This brief report provides further relevant data obtained from 77 males with the karyotype 47,XXY (Klinefelter syndrome). All were confirmed by cyto- genetic tests as having two X-chromosomes and one Y-chromosome. Measurements were recorded from dental casts obtained from collections at the Royal Dental College, Copenhagen and the University of Turku, Finland. Initial statistical testing showed no significant differences between the Danish and Finn- ish groups which were combined for subsequent analysis. The control group comprised 150 caucasoid males, with no history of serious medical problems and included 17 first-degree relatives of the 47,XXY males. Tooth size among these relatives was not significantly different from the rest of the controls.

of the canines. Coefficients of variation tended to be larger in the 47,XXY group (19 of 28 possible comparisons), but the pattern of variability from tooth to tooth was similar in both groups, values being lowest for first molars and highest for upper lateral incisors. Our results accord with those of an earlier investigation in a smaller sample of 47,XXY males (Alvesalo and Portin, 1980).

Mesiodistal and buccolingual tooth diameters were recorded by one investigator (G.T.) to an accuracy of 0.1 mm. Measurement criteria and accuracy have been discussed in detail elsewhere (Townsend, 1982). Measurements were obtained for teeth on both sides of the dental arch, but as there were no statistically significant differences between sides, the mean values from right and left measurements were used in the final analysis. If a tooth was missing, the mea- surement obtained from its antimere, if present, was accepted. Descriptive statistics including mean val- ues, standard deviations and coefficients of variation were derived for all variables. The significance of differences between mean values was tested by Stu- dent’s t-test.

Mean height of the 47,XXY males (180 cm) was above average and, as there is a low positive cor- relation between body size and tooth size (Garn, Lewis and Kerewsky, 1968), larger teeth might be expected in the 47,XXY sample. However, the crowns of all the permanent teeth, excluding third molars, have mineralized by about 7 to 8 years postnatally and they are therefore largely unaffected by the hormonal and nutritional factors which oper- ate during adolescence to influence stature. For ex- ample, the larger first molars observed in 47,XXY males must have been formed during the period between initial tooth development at about 2-3 months in utero and final crown completion at about 3 years postnatally.

It appears that the presence of an extra X- chromosome has a growth-promoting effect which operates from early in development. It is possible that altered hormonal concentrations in 47,XXY fetuses are important, although there does not seem to be any evidence to support this hypothesis. Alterna- tively, the larger tooth size in 47.XXY males may reflect a direct genetic effect of the X-chromosome. Certainly the results of other studies of individuals with various sex chromosome abnormalities are per- suasive in this regard (e.g. Alvesalo and Tammisalo. 1981).

Table 1 provides a comparison of mean diameters Studies of permanent and deciduous tooth size in of permanent teeth between the 47,XXY males and 47,XYY males indicate that the Y-chromosome also control subjects. Mean values were larger in the has a growth-promoting role (Alvesalo, Osborne and 47,XXY group for 23 of 28 possible comparisons, 9 Kari, 1975; Alvesalo and Kari, 1977). The size of the differences being statistically significant at p < 0.01. canines was least affected in both 47,XXY and However, tooth-size differences were not uniform 47,XYY males; these teeth generally show the great- throughout the dentition. Mesiodistal and bucco- est size difference between normal males and females. lingual dimensions of both upper and lower first Whether this reflects developmental and genetic inde- molars were significantly larger in 47,XXY males, pendence of canines compared with other teeth whereas there was no evidence for a difference in size (Alvesalo er al., 1975) is not known. As more exam-

83

84 G. C. TOWNSEND and L. ALVESALO

Table 1. Crown diameters of permanent teeth in 47,XXY males and male control subiects

Tooth n

Maxilla I’ 51 I? 44 C 48 PM’ 40 PM’ 31 M’ 27 M’ 29

Mandible ‘1 55 ;; I 64 60

PM, 56 PM, 33 M, 24 M2 23

Maxilla I’ 44 I’ 33 c 42 PM’ 48 PM’ 43 M’ 48 M? 40

Mandible 1, 41 I, 44 C 50 PM, 56 PM2 31 M, 41 Ml 30

47,XXY Controls

z SD CV n B SD CV

Mesiodistal

9.06* 0.58 6.4 104 8.76 0.53 6.0 6.82 0.56 8.2 95 6.85 0.55 8.1 7.99 0.44 5.5 82 8.04 0.43 5.4 7.39* 0.50 6.7 74 7.07 0.39 5.6 6.95 0.47 6.8 74 6.77 0.44 6.5

I I .04* 0.62 5.6 81 10.65 0.50 4.6 10.35 0.63 6.1 65 IO.31 0.57 5.5

5.56 0.33 6.0 100 6.12 0.38 6.1 102 7.01 0.37 5.2 87 7.27 0.41 5.7 76 7.57* 0.51 6.8 79

I I .84* 0.54 4.5 72 Il.25 0.74 6.6 54

Buccolingual

5.47 0.32 5.8 6.04 0.35 5.8 6.99 0.40 5.7 7.19 0.46 6.4 7.29 0.46 6.2

Il.42 0.59 5.2 10.94 0.65 5.9

7.43 0.48 6.4 81 7.34 0.52 7. I 6.66 0.55 8.2 71 6.51 0.57 8.7 8.46 0.62 7.3 81 8.62 0.55 6.3 9.60 0.60 6.3 76 9.47 0.56 5.9 9.52 0.64 6.7 83 9.50 0.60 6.3

l2.13* 0.55 4.5 98 II.76 0.55 4.6 12.01 0.68 5.7 69 II.81 0.72 6.1

6.35 0.49 7.7 78 6. I8 0.45 7.3 6.70* 0.43 6.4 78 6.44 0.42 6.5 7.92 0.62 7.8 73 7.92 0.53 6.6 8.11 0.54 6.7 74 8.13 0.54 6.6 8.11 0.72 8.2 78 8.64 0.53 6. I

I I .46’ 0.58 5.1 92 10.83 0.49 4.5 11.17* 0.63 5.6 67 10.72 0.60 5.6

*Mean value significantly larger at p < 0.01.

ples become available for study, we may gain a clearer insight into how the sex chromosomes affect the different tooth classes.

AcknowledgemenfspWe sincerely thank Dr C. lngerslev and the Orthodontic Department, Royal Dental College. Copenhagen for permission to study the dental casts of Danish subjects. The study was supported in part by the National Academy of Finland.

REFERENCES

Alvesalo L. and Kari M. (1977) Sizes of deciduous teeth in 47,XYY males. Am. J. hum. Gener. 29, 486489.

Alvesalo L. and Portin P. (1980) 47,XXY males: sex chro- mosomes and tooth size. Am. J. hum. Genet. 32,955-959.

Alvesalo L. and Varrela J. (1980) Permanent tooth sizes in 46,XY females. Am. J. hum. Genet. 32, 736-742.

Alvesalo L. and Tammisalo E. (I 98 I) Enamel thickness in 45.X females’ permanent teeth. Am. J. hum. Genet. 33, 464469.

Alvesalo L., Osborne R. H. and Kari M. (1975) The 47,XYY male, Y chromosome, and tooth size. Am. J. hum. Genet. 27, 53-61.

Garn S. M., Lewis A. B. and Kerewsky R. S. (1968) The magnitude and implications of the relationship between tooth size and body sizes. Archs oral Biol. 13, 1299131.

Townsend G. C. (1982) Tooth size in children and young adults with trisomy 21 (Down) syndrome. Archs oral Bio/. 28, 159-l 66.