Abstract
Objective Earlier results based on dental casts and radiographs have shown that additional X and Y chromosomes influence permanent and deciduous tooth crown sizes, with 47,XYY males exhibiting greater crown heights than 46,XY males. We studied here the effect of both X and Y chromosomes on tooth crown heights. Material and methods The series consisted of 48 47,XXY males, 22 of their male relatives, and seven 47,XXX females with five female relatives. The population controls consisted of 27 males and 33 females. Measurements of all applicable teeth except for the third molars on both sides of the jaws were made on panoramic radiographs with a sliding digital calliper. Results Apart from a few teeth, the mean crown heights in the 47,XXY males were greater than those in the male population controls, the differences being statistically significant for one tooth in the maxilla and ten teeth in the mandible. With the exception of two teeth, the 47,XXX females had taller tooth crowns than the female population controls, the differences in the two teeth being statistically significant. The 47,XXY males had greater tooth crown heights than the 47,XXX females, except in one tooth, and the differences were significant in two teeth. The tooth crown heights of the male relatives of the 47,XXY males and the female relatives of the 47,XXX females were close to those in the general population. Conclusions The present results demonstrated the effect of additional X and Y chromosomes in increasing crown heights. The differences between the 47,XXY males and 47,XXX females indicated a stronger effect of a Y chromosome on tooth crown height than of an X chromosome.
Highlights
Klinefelter syndrome is the most common sex chromosome variant, occurring in one out of every 660 newborn males [1]
Apart from three teeth in the maxilla, the mean tooth crown heights were greater in the 47,XXY males than in the male population controls, the differences being statistically significant in one tooth in the maxilla and ten teeth in the mandible, being highly significant (p < 0.001) in five of the latter (Table 2)
Measurements of tooth crown sizes in mesiodistal and labiolingual directions performed on plaster casts have shown the presence of sexual dimorphism in the permanent and deciduous tooth crowns, such that 46,XY males have larger teeth than 46,XX females [45], and the present results regarding the relative differences (RD(%)s) in tooth crown heights between the population control males and females (5.5 in the maxilla and 3.9 in the mandible) were of the same magnitude as those reported for tooth root lengths (4% in all teeth) [22]
Summary
Klinefelter syndrome is the most common sex chromosome variant, occurring in one out of every 660 newborn males [1]. Klinefelter syndrome is the most common genetic reason for male infertility (4%) [2] and is characterised by varying degrees of cognitive, behavioural, and learning difficulties. The most common karyotype (80%) is 47,XXY (a male with one extra X chromosome) [3]. Height is normal during childhood until the age of approximately six years, at which point growth is significantly accelerated as compared with healthy boys, resulting in a final average height that is 1.2 cm greater than in 46,XY males [4], the difference has been reported to be as great as 5.6 cm [5]. The excess body height in 47,XXY males is mainly caused by increased leg length [5]. It is important to note that normal stature, or even parentally inherited short stature, does not exclude Klinefelter syndrome
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