Variability of Exostoses on Human Jaws During the Past Six Millennia in Northern China/Variabilidad de las Exostosis en las Mandibulas Humanas Durante los Ultimos Seis Milenios en el Norte de China

The aim of this study was to survey oral exostoses in human populations that belonged to the same region encompassing five periods over 6000 years, to determine the prevalence and its changing trend over time. A total of 306 human jaws belonging to the modern Xi'an region and four archeological sites, Banpo (6700-5600 years BP), Shaolingyuan (3000 years BP), Shanren (2200 years BP) and Chang'an (1000-1300 years BP), were investigated. The degree of buccal exostosis (BE), torus mandibularis (TM) and torus palatinus (TP) and the TP shape were recorded. The prevalence of BE, TM, and TP in the five groups was 20.8 %-62.5 %, 17.5 %-71.5 %, and 31.7 %-74.2 %, respectively. The differences in the three types of exostoses among the five groups were all statistically significant, but only TM and TP showed a decreasing trend over time. A high and quite diverse prevalence of oral exostoses was found in the five groups of samples. Decreasing trends in relation to time for TM and TP were detected. KEY WORDS: Buccal exostosis; Torus mandibularis; Torus palatinus; Ancient populations; China.