**5. Conclusions**

In conclusion, this study investigated the composition of the oral microbiome of supragingival plaque in relation to BS formation. Although the number of subjects was relatively limited, our study is the first species-level analysis of the pyrosequencing data in BS formation. We highlighted that compositional changes in the oral microbiome are essential, and several species in the genus *Neisseria, Porphyromonas* and *Streptococcus* may be major contributors to BS formation. The proposed species information will provide a foundation for understanding the complex ecology of BS and for identifying the causal agent for BS formation.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2076-3417/10/22/8054/s1.

**Author Contributions:** Conceptualization, J.Y.H. and S.C.C.; methodology, H.-S.L.; software, J.C.; validation, J.C.; formal analysis, O.H.N.; investigation, S.C.C.; resources, M.S.K.; data duration, H.-S.L.; writing—original draft preparation, J.Y.H. and S.C.C.; writing—review and editing, H.-S.L. and S.C.C.; supervision, project administration, funding acquisition, S.C.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF), funded by the Ministry of Education, Science and Technology (NRF-2016R1C1B1015005).

**Acknowledgments:** We thank the children that participated in this study.

**Conflicts of Interest:** The authors declare no conflict of interest.
