Objective  To investigate the relationship between oral microbiota disorders and salivary immune biomarkers in infants and young children with early childhood caries(ECC).

  Methods  A total of 600 children with ECC were selected as study subjects, and were divided into low-caries group (n=267) and high-caries group (n=333), and 100 healthy infants and young children examined in our hospital during the same period were selected as control group. The number of colonies of Streptococcus, Lactobacillus, Actinobacillus and Bifidobacterium in each group was recorded. The levels of matrix metalloproteinases (MMP)MMP-2, MMP-3 and MMP-9, inflammatory factorsinterleukin (IL)-6, IL-8, tumor necrosis factor-α(TNF-α)and immunoglobulinA(IgA), immunoglobulin G(IgG), complement C3 and complement C4 in saliva of each group were detected.

  Results  The number of bacterial colonies of Streptococcus, Lactobacillus and Actinobacillus in the high caries group was significantly more than that in the low caries group and control group, and the number of bacterial colonies of Bifidobacterium was significantly less than that in the low caries group and control group (P < 0.05). The number of colonies of Streptococcus, Lactobacillus and Actinobacillus in the low caries group was significantly more than that in the control group, and the number of colonies of Bifidobacterium was significantly less than that in the control group (P < 0.05). The levels of MMP-2, MMP-3, MMP-9, IL-8, IL-6 and TNF-α in the high caries group were significantly higher than those in the low caries group and the control group (P < 0.05), and above indexes of the low caries group were significantly higher than those in the control group(P < 0.05). The IgA, IgG, C3 and C4 levels of the high caries group were significantly lower than those of the low caries group and the control group (P < 0.05), and were significantly lower in the low caries group than those of the control group (P < 0.05). Pearson correlation analysis showed that Streptococcus, Lactobacillus and Actinobacillus were positively correlated with the levels of MMP-2, MMP-3, MMP-9, IL-8, IL-6 and TNF-α, and were negatively correlated with the levels of IgA, IgG, complement C3 and complement C4 (P < 0.05). Bifidobacteria was negatively correlated with levels of MMP-2, MMP-3, MMP-9, IL-8, IL-6 and TNF-α, while was positively correlated with levels of IgA, IgG, complement C3 and complement C4 (P < 0.05).

  Conclusion  Oral microorganism disorder is easily occur in children with caries, and the status of immune protection mechanism changes with the progression of the disease, so improvement of the immune function may have a positive effect in prevention and treatment of caries in children.