942 © 1997 Blackwell Science Ltd Journal of Oral Rehabilitation 1997 24; 942–946 Occlusal plane orientation in Klinefelter syndrome (47,XXY males) A. C ˇ ELEBIC ´ , H. BRKIC ´ , Z. KAIC ´ , D. VOJVODIC ´ , Z. POJE & Z. SINGER* School of Dentistry, University of Zagreb and *University Hospital ‘Merkur’, Zagreb, Croatia SUMMARY 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) w e re 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) Introduction A chromosomal aneuploidy known as Klinefelter syndrome, characterized by an extra Xchromosome in human cells, is manifested in numerous phenotypic differencesfrom normalmales, includingthe differences in craniofacial complex and tooth morphology (Gorlin, Redman & Shapiro, 1965; Darbyshire, Witkop & Cervenka, 1989; Brkic ´ et al., 1992; Brkic ´ et al., 1994a,b). In 1942, Klinefelter et al. first published an article on a syndrome ‘characterized by gynaecomastia, aspermatogenesis without a-Leydigism, and an increased excretion of the follicle-stimulating hormone’ (Klinefelter, Reifenstein & Albright, 1942). Today, the term Klinefelter’s syndrome is used to designate the 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). characteristics associated with the male 47,XXY chromosomal constitutions. Diagnosis of Klinefelter syndrome is rare in infancy and multiple minor anomalies are usually overlooked until puberty (Bandman & Breit, 1984). When the diagnosis has been established, usually after puberty, multiple minor anomalies in the head and face region can also be noticed, which had been neglected previously (Bandman &Breit, 1984; Varrela &Alvesalo, 1988; Brkic ´ et al., 1994b). In addition, the effects of an extra Xchromosome on the teeth shape and morphology have been reported in these patients (Gorlin et al., 1965; Gardner & Girgis, 1978; Poonawalla et al., 1980; Varela & Alvesalo, 1988; Witkop et al., 1988; Alvesalo, Tammisalo & Townsend, 1991; Brkic ´ et al., 1992; Brkic ´ et al., 1994b).