Abstract: PURPOSE: To identify the microbial characteristics and diversity in supragingival plaque and caries tissue of patients with different dental caries phenotypes. METHODS: From January 2019 to December 2019, randomized double-blind method was used to select 10 healthy people without caries and 33 patients with caries of mild, moderate and severe degrees in dental clinic of our hospital. Supragingival plaque and caries tissues were collected, and detected by pyrosequencing through amplification of the 16S rRNA-cDNA hypervariable regions. Then the microbial species and relative abundance were compared among patients with different severity degrees. SPSS 23.0 software package was used to analyze the data. RESULTS: Compared with non-caries group, the content and abundance of microorganisms in supragingival plaque and carious tissue of caries group were significantly decreased (P<0.05). The main caries tissue of three severity degree groups were dominated by Bacteroidetes, Spirochaetes, Proteobacteria, Fusobacteria, Firmicutes and Actinobacteria, and the proportion of the predominant bacteria had significant difference among three groups(P<0.05). There were 21 species of supragingival bacteria in three groups, among which Fusobacteriales, Coriobacteriales, Neisseriales, Actinomycetales and Lactobacillales accounted for a high proportion, and the remainings were all below 1%, while the proportion of five main bacteria showed no significant difference among three groups (P>0.05). CONCLUSIONS: Caries is caused by a variety of bacteria, and is the result of microbial communities rather than a single pathogen; Moreover, the microbial abundance of plaque and caries tissue vary among patients with different dental caries phenotypes, and the microbial diversity has a decreasing trend in the progress of dental caries.

Key words: Dental caries, Supragingival plaque, Caries tissue, Microbe