The Epidemiologic Study Of Permanent Tooth Morphology And Oral Disease Of People Excavated From Shaolingyuan 3,000 Years Ago In Xizhou Dynasty

In the long history of evolution, human's tooth morphology, tooth wear, dental caries, periodontal disease and the eruption of the third molars have been changing with the change of dietary structure and life style. On one hand, soft food took place of rough food, which led to the weaken of functional stimulus to masticating apparatus and the developmental potentiality of occlusion system. Therefore, the masticating apparatus tend to degenerate. Studies on fossils of ancient human teeth can help us to know the morphological evolution of human jaw bones and teeth. On the other hand, human's oral diseases are ancient diseases. They also have been changing with human evolution. Studies on human's oral diseases can help us to know their origin and development and so to control them.The Xizhou graveyard of Shaolingyuan is located in Dongyangwan village, about 5 kilometers in the southeast of Chang'an district in Xi'an, Shaanxi. Archaeological Institute unearth the graveyard from November 2004 to October 2005. It is assessed to be a family graveyard about 3,000 years ago in Xizhou dynasty. People excavated from this graveyard were assessed to be civilians. So they can represent the average teeth morphology and oral diseases in their age. Studies on these fossils can help us to know people's life style, dietary structure and oral health in Xizhou dynasty.This study used the cross-sectional descriptive method to measure and record the tooth morphology, tooth wear, dental caries, periapical disease, periodontal disease and eruption of third molars of 147 skull fossils excavated in Xizhou dynasty so as to analyze their dietary structure, life style and oral health. Meanwhile, this study also provided a data to the study of oral evolution of Chinese people. The main results are as follows.In the study of tooth morphology, 1749 permanent teeth were measured and recorded. 63.4% of all the morphological parameters showed statistical differences between males and females (P<0.05). The differences were mainly concentrated in the length of root, breadth of dental neck, thickness of dental crown and neck in maxilla and the breadth of dental neck and crown, thickness of dental crown and neck in mandible.In the study of tooth wear, 1758 permanent teeth were observed and recorded. The results showed that the average degree was 2.10°. The constituent ratio of different tooth wear descended following the sequence of 3°> 1°> 2°> 4°> 0°.The degree of tooth wear descended following the sequence of I1 > C > M1 > I2 > P1 > P2 > M2 > M3. Tooth wear aggravated with the age increasing. There were statistical differences among different age groups. Meanwhile, there were statistical differences in C, P1, P2 between males and females.In the study of dental caries, 1760 permanent teeth were observed and recorded. The results showed that, 51.70% of all the subjects and 12.50% of all the teeth were afflicted with dental caries and 1.76% of all the teeth were afflicted with periapical disease. Caries prevalence rate, caries incidence and incidence of periapical disease all increased with the age increasing. Proximal dental caries and enamel caries were the most popular. There were statistical differences in constituent ratio among different age groups. However, there were no statistical differences between males and females.In the study of periodontal disease, alveolar bone of 1496 permanent teeth were observed and recorded. The results showed that, 96.00% of all the subjects and 78.61% of all the teeth were afflicted with periodontal disease. The condition of periodontal disease alleviated following the sequence of M1 > M2 > M3 > P2 > P1 > I1 > C > I2. The incidence of periodontal disease increased with the age increasing. There were no statistical differences between males and females.In the study of the eruption of the third molars, 276 third molars were observed and recorded. The results showed that the incidence of normally eruption, congenital missing and impaction were 60.95%, 32.48%, 4.38% respectively. There were no statistical differences between males and females. The incidence of congenital missing and impaction in maxilla were lower than those in mandible. While, the incidence of normally eruption in maxilla was higher than that in mandible. There were no statistical differences between left and right.To be concluded, there were some differences in tooth morphology of residents in Xi'an 3,000 years ago between males and females. Tooth wear, dental caries, periodontal disease, congenital missing and impaction of the third molar were prevalent at that age. The type and predilection site were different with modern people. Tooth wear and periodontal disease were more severe than modern people. Heredity and environment are the main factors that influence the evolution of human teeth and oral diseases.