Salivary microbiota composition and caries status in children with hearing impairment: a cross-sectional comparative study.

OBJECTIVES: To characterize the salivary microbiota structure in children with hearing impairment using 16 S rRNA gene sequencing and explore its potential association with caries burden. METHODS: A total of 114 hearing-impaired children aged 6–16 years underwent oral clinical examination and completed a questionnaire. From this cohort, 20 children (HI group) and 20 age- and sex-matched healthy children (HS group) were randomly selected for salivary microbiome sequencing. Analyses included alpha and beta diversity, LEfSe, and caries-stratified subgroup comparisons. RESULTS: Hearing-impaired children carried a heavy caries burden (overall prevalence: 93.9%; mean DMFT/dmft: 6.4 ± 3.9). Oral hygiene practices were generally suboptimal, with only 54.5% brushing twice daily and 41.6% using fluoride toothpaste. Beta diversity analysis significantly differed between groups (ANOSIM, R² = 0.057, P < 0.05). The HI group exhibited trends of increased Proteobacteria, Neisseria, and Gemella and decreased Veillonella and Capnocytophaga (all P > 0.05). LEFSe analysis revealed richer signature taxa in controls (e.g., Selenomonas, Tannerella), whereas hearing-impaired children showed limited enriched taxa, especially in the low-caries subgroup, indicating microbiota simplification. CONCLUSIONS: The oral microbiome of hearing-impaired children displays alterations in overall community structure, characterized by reduced diversity of signature microbial taxa and a trend toward ecological simplification. CLINICAL RELEVANCE: These findings identify oral microbial trends associated with hearing impairment, providing potential insights for early caries risk assessment and tailored preventive interventions in this vulnerable population.