Among many factors affecting dental caries, bacteria are its initiating factor. From the perspective of ecological plaque hypothesis, the application of modern molecular biology methods enable scholars to deeply explore the relationship between the microbial population distribution, biodiversity, microbial community changes of dental plaque biofilm and the occurrence of dental caries in children. The decrease in microflora diversity is closely related to the occurrence of dental caries, which can be detected as early as 6 months before the occurrence of dental caries, providing an important basis for caries monitoring and caries risk assessment. Differential bacteria such as Lactobacillus and Veillonella may be used as biomarkers of caries in children to judge the risk of caries in children. However, current studies have shown that the dominant bacteria in the microbial community structure vary in different processes of caries occurrence and development, that the interaction between different flora is still not clear, and that the specific cariogenic mechanism of the oral plaque microbial community in the process of caries occurrence and development has not been clarified. Further research is still needed to explore the changes in plaque microbial diversity and composition during the development of dental caries and to screen specific dental caries biomarkers. This paper also summarizes the related research findings.

Objective : To explore from the perspective of microorganisms the changes in plaque microbial community of children with severe early childhood caries (S-ECC) before and 3 months after dental treatment. Meanwhile to show the effect of treatment on the maintenance of long- term caries-free state. Methods: S-ECC children completed dental treatment under general anesthesia. We collected plaque from caries-free dental surfaces before treatment (caries, C) and at the postoperative follow-up review time points of 7 days (C-7D), 1 month (C-1 M), and 3 months (C-3 M). We included caries-free children (caries free, CF) as the control group to analyze the dynamic modification process of the plaque microbial community in the short-term pre- and postdental treatment. Results: Species clustering analysis showed that the compositions of the microbial communities of the S-ECC and CF groups were highly similar. The α diversity index was not statistically significant (P>0.05). From the analysis of the relative abundance, Leptotrichia spp. and Aggregatibacter spp. decreased after treatment compared with before treatment (P<0.05). Streptococcus sanguinis in the C-7D group increased compared with that in the C group and gradually decreased within 3 months. Veillonella spp., Actinomyces spp., Allprevotella spp., Capnocytophaga spp., and Streptococcus mutans differed between the C and CF groups (P<0.05), Streptococcus mutans did not differ significantly between the C-7D and C-1 M groups and the CF group after treatment, while C-3 M showed an increase compared with the CF group (P<0.01). Conclusion The rapid change in the structure of the flora of children with S-ECC after treatment. The plaque microbial community structure in a caries-free state gradually starts to be established 1-3 months after treatment. There is a "core microbiota" in the oral plaque community that jointly maintains microecological stability. Veillonella spp., Allprevotella spp. and Streptococcus mutans have potential as possible microbial markers.