To explore the structure of oral microflora in children aged 3 to 5 years old in Mianyang area, and to analyze its effect on dental caries.

An oral epidemiological survey was conducted on 136 children aged 3 to 5 years old in 10 kindergartens in Mianyang from March to June 2023. Total of 68 children with caries and 68 children with oral health were selected as observation group and control group, respectively. Saliva samples of both groups were collected, and the whole genomic DNA was extracted and sequenced with 16s ribosomal DNA (16S rDNA). Independent sample t-test, permutational multivariate analysis of variance (PERMANOVA), analysis of similarity (ANOSIM) and Wilcoxon rank sum test were used to compare the diversity of microflora, species composition, dominant flora and functional differences between the two groups.

The results of α diversity analysis showed that the Shannon index (3.02 ± 0.70) and Simpson index (0.86 ± 0.35) of the observation group were significantly higher than those of the control group (2.70 ± 0.46; 0.67 ± 0.15), with significant differences (t = 3.150, P = 0.002; t = 4.115, P < 0.001). Principal coordinate analysis (PCoA) showed that the oral flora of both groups were significantly separated (F = 3.428, P < 0.001), and the Bray-Curtis distance between the control group and the observation group (0.58 ± 0.22) was significantly higher than that of the group (R = 0.659, P = 0.003). At the level of genera, the abundance of Streptococcus, Leptotrichia, Megasphaera and Prevotella in saliva samples of the observation group were significantly higher than those of the control group, while the abundance of Haemophilus, Fusobacterium and Escherichia-Shigella of the observation group were significantly lower than those of the control group, with significant differences (all P < 0.05). At the species level, the abundance of Haemophilus parainfluenzae of the observation group was significantly lower than that of the control group, while the abundance of Leptotrichia_IK040, Prevotella melaninogenica and Prevotella loescheii of the observation group were significantly higher than those of the control group, with significant differences (all P < 0.05). The abundance of pentose phosphate pathway, pyruvate metabolism and propanoate metabolism of the observation group were significantly lower than those of the control group (all P < 0.05).

Compared with healthy children, children with caries have increased oral microbial flora diversity and structural disturbances.