Microbial alteration after intensive fluoride varnish treatment in children with early childhood caries: An...

In this study, we aimed to evaluate the effect of an intensive fluoride varnish (FV) regimen on oral microbial communities in children with early childhood caries (ECC).

Twenty-six children, aged 2 to 5 years, diagnosed with early-stage ECC, were included. They were treated with 5% NaF varnish three times over 2 weeks. Pooled supragingival plaque samples (n = 70) were collected and used for extracting total bacterial DNA. The microbial composition was analyzed using the Human Oral Microbe Identification Next-Generation Sequencing (HOMINGS) method.

Analysis of 6172,618 high-quality 16S rRNA amplicons revealed significant changes in the relative abundance of oral microbiome taxa at the phylum level immediately after FV treatment (p = 0.021). Although the relative abundance of several known cariogenic species decreased, none of the shifts were statistically significant at the 1-week visit or persisted at the 2-week visit. At the genus level, children with higher mutans streptococci levels showed higher relative abundance of Bacteroidetes, Firmicutes, and Spirochaetes (p = 0.001, p = 0.023, and p = 0.001), respectively. At the species level, FV treatment significantly increased the relative abundance of Corynebacterium durum (p = 0.009) and Neisseria sicca (p = 0.031) but did not significantly disrupt commensals within the microbial community.

Intensive FV application alone does not significantly alter the core oral microbiome of children with untreated ECC. The treatment may temporarily reduce the cariogenic microbial burden immediately after treatment. However, the long-term effects of FV on the oral microbiome still remain uncertain.