*Article* **Core Microbiota Promotes the Development of Dental Caries**

**Jing Chen †, Lixin Kong †, Xian Peng †, Yanyan Chen, Biao Ren, Mingyun Li, Jiyao Li, Xuedong Zhou \* and Lei Cheng \***

> State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Department of Cariology and Endodontics West China School of Stomatology, Sichuan University, Chengdu 610041, China; chenj@stu.scu.edu.cn (J.C.); 2017224035094@stu.scu.edu.cn (L.K.); pengx@scu.edu.cn (X.P.); 2017224035129@stu.scu.edu.cn (Y.C.); renbiao@scu.edu.cn (B.R.); limingyun@scu.edu.cn (M.L.); jiyaoliscu@163.com (J.L.)

**\*** Correspondence: zhouxd@scu.edu.cn (X.Z.); chenglei@scu.edu.cn (L.C.)

† These authors contributed equally to this work.

**Abstract:** A previous longitudinal study about using microbiome as a caries indicator has successfully predicted early childhood caries (ECC) in healthy individuals, but there is no evidence to verify the composition of core microbiota and its pathogenicity in vitro and in vivo. Biofilm acidogenicity, *S. mutans* count, and biofilm composition were estimated by pH evaluation, colony-forming unit, and quantitative PCR, respectively. Extracellular polysaccharide production and enamel demineralization were observed by confocal laser scanning microscopy (CLSM) and transverse microradiography (TMR), respectively. A rat caries model was established for dental caries formation in vivo, and caries lesions were quantified by Keyes Scoring. We put forward that microbiota including *Veillonella parvula*, *Fusobacterium nucleatum*, *Prevotella denticola*, and *Leptotrichia wadei* served as the predictors for ECC may be the core microbiota in ECC. This study found that the core microbiota of ECC produced limited acid, but promoted growth and acidogenic ability of *S. mutans*. Besides, core microbiota could help to promote the development of biofilms. Moreover, the core microbiota enhanced the enamel demineralization in vitro and increased cariogenic potential in vivo. These results proved that core microbiota could promote the development of dental caries and plays an important role in the development of ECC.

**Keywords:** early childhood caries; core microbiota; *Streptococcus mutans*; biofilms; demineralization
