As one of the most common chronic diseases of the oral cavity, caries gradually accumulate over the lifetime and affect approximately 80% of the world population. The epidemiological characteristics of the disease are specific in terms of regional distribution, temporal distribution and population distribution. Caries prevalence and mean decayed, missing and filled permanent teeth (mean DMFT) scores are the most commonly used indexes in oral epidemiology. Caries prevalence is used to describe the frequency of caries over a certain period of time. In addition, DMFT scores reflect the severity of caries in the population. The caries prevalence and the severity of caries are assessed as part of a dynamic process. In developing countries, caries prevalence is higher among urban populations than among rural populations. Currently, the epidemic characteristics of caries in urban and rural areas are changing, and the caries prevalence of urban residents is lower than that of rural residents. This article is a chronological review of the Oral Health Epidemiological Surveys of China from 1983 to 2015, the Preventive Dentistry study and other related studies. It is concluded that the epidemic characteristics of caries in urban and rural areas in China have changed from a higher caries prevalence in urban areas compared to that in rural areas to a lower caries prevalence in urban areas compared to that in rural areas. Several factors, such as the dynamic development of differences in dietary habits, economic levels and access to oral medical resources of urban and rural residents might have led to changes in caries prevalence in urban and rural areas. The caries prevalence of rural residents has increased greatly, which indicates that the caries prevention efforts of the relevant departments should be focused more on rural areas in the future.

As a professional method to prevent decayed teeth and an oral public health project, pit and fissure sealant is widely used domestically. How to evaluate the effect and benefit of the community pit and fissure closure project, especially the community full coverage pit and fissure closure project, requires investigation. The Guangzhou Children′s Pit and Fissure Sealing Project was carried out in an orderly manner and was administered normatively. A retrospective cohort study with use of a sample survey was used in this program. According to cavity occurrence and reservations of sealant in the first permanent molar, the samples were divided into the following two groups: the sealing group with indication and the sealing group without indication. Reservations of sealant, cavity incidence, reduced incidence, net profit, cost-effectiveness and cost-benefits of the program were evaluated. Some promotable experiences were summarized during this project. Various relevant theories and reports of the pit and fissure sealant project evaluation were reviewed and previous studies were discussed in this article. By analyzing the methods and results of the pit and fissure sealant project in Guangzhou, suggestions are made for project evaluation, especially sample grouping and evaluation indicators, which was refer to a further study for the pit and fissure sealing project.