Occlusal plane orientation in Klinefelter syndrome (47,XXY males)

Occlusal plane position was analysed cephalometrically in 35 Klinefelter adults (47,XXY) and compared with 60 eugnath control males (46,XY). The significantly smaller angles between the occlusal plane and the cranial base (NSL-OLs) and between the occlusal plane and the Frankfort horizontal plane (Fr-OLs) were obtained in 47,XXY males (P < 0.01), while the angles between the maxillary base and the occlusal plane (NL-OLs) and between the Camper's line and the occlusal plane (Camp.-OLs) were not significantly different (P > 0.05) from the control group. Significantly smaller angles between the occlusal plane and the cranial base (NSL-OLs) and between the occlusal plane and the Frankfort horizontal plane (Fr-OLs) in Klinefelter males are attributed to the hereditary influence of an extra X chromosome on the smaller growth of the cranial base and the greater growth of the lower border of the mandible. Although the maxilla was also shifted forward in XXY males in relation to the cranial base it was not enough to compensate for the hereditary influence, due to the greater growth of the lower border of the mandible and the smaller cranial base in 47, XXY males, on the inclination of the occlusal plane to the Frankfort horizontal plane and the cranial base. The forward shift of the maxilla was sufficient to compensate for the inclination of the occlusal plane in 47, XXY males to the maxillary base and the Camper's line (P > 0.05).