The third national epidemiological investigation on oral diseases conducted in 2005 revealed that, gingival bleeding and calculus occur in over a half of 12-year-olds (57.7% and 59.1% respectively), most middle-aged people (77.3%, 97.3%) and many elderly people (68.0%, 88.7%) ( Table 7) . Periodontal conditions of all age groups were found to be better in cities, females and eastern areas than in rural areas, males, middle and western areas. The findings of this investigation did not differ much from the previous one [8] [9] . In all factors contributing to periodontal diseases, smoking and diabetes should not be ignored. Tobacco consumption related to oral disorders is one of the major sources of the global oral disease load. Over a half of adult periodontitis cases are triggered by it. China has become the biggest tobacco consuming country in the world. Its tobacco consumption increases at an annual rate of 5.3%. China's tobacco yield is equal to the sum production of the other 7 biggest tobacco producing countries. About 160 thousand billion cigarettes are sold in China each year, accounting for over 30% of the world total tobacco consumption [12] [13] . On the other hand, in recent years, the incidence rate of diabetes has been growing in China. According to a survey of the Chinese Academy of Endocrinology, the prevalence of diabetes is reaching 11% in urban and suburban areas. The sufferers of diabetes in China are ranked second in the world. According to the WHO assessment, there will be about 50 million diabetes patients in China by the year of 2025.