Abstract: This paper described the incidences of the caries and periodontitis in a sample including 283 individuals of the Three-Yan Cultures from Lamadong cemetery in Beipiao, Liaoning and discussed the relationship between the frequency of dental disease, on the one hand and sex and age on the other. The result is as follows: (1)the frequency of the caries had no marked sexual difference, and the frequency of the periodontitis had sexual difference. (2)the frequency of the caries had certain association with age, but periodontitisis considered to be strongly associated with age. (3)in addition to the association with the host susceptibility and the activeness of the bacteria the formation of a human bental disease had certain association with the roughness of food. To a great extent, the detritions of the teeth in Lamadong cemetery were serious. The degree of attrition of the teeth is usually corresponding to that occurred in modera human individual 5 —10 years older. The heavy worn of the teeth made the residual food and bacteria easies to be inlaid in the space between neighboring teeth. So that the dentition became more difficult to be self-cleaned. As a result, the periodontitis and the caries occurred. In addition, the inlet of food between teeth would necessarily cause the mesiodistal interproximal caries. Hence, to a large extent, the frequently ocurring spot of the caries of this population was interproximal, whereas that of modern peoplewas occlusal surface. (4)the oral hygiene conditions were closely related to the formation of dental disease. During the process of the investigation, no example of cervical wedgeshaped defect was found. Hence,we inferred that the residents buried in this cernetery were not conscious enough of the oral health, and meanwhile they did not care their oral hygiene. This is one of the most important factors that led to the high frequency of the dental disease in Lamadong cemetery. In addition, the supernumerary tooth, the congenital anodontia, the fused teeth, the maloccluded tooth and the impacted tooth were also recorded and analyzed.

Key words: Dental caries; Periodontitis; Lamadong cemetery; The Three-Yan Cultures