Assessment of oral microbiome diversity in adolescents with varying caries risk

Abstract

Background: Dental caries remains a globally prevalent chronic oral disease among adolescents. Contemporary understanding recognizes caries as a microbiome-driven dysbiotic process rather than a mono- infection. However, detailed characterizations of oral microbiome diversity patterns across stratified caries risk levels in adolescent populations remain insufficiently explored using modern high-throughput sequencing technologies. Objective: This study aimed to evaluate oral microbiome diversity, compo- sition, and structural differences among adolescents stratified into low, moderate, and high caries risk groups, and to identify microbial biomarkers distinguishing these risk categories. Methods: A cross- sectional study was conducted on 210 adolescents aged 12–18 years, stratified into three equal groups (n = 70 each) based on CAMBRA (Caries Management by Risk Assessment) protocols. Unstimulated saliva and supragingival plaque samples were collected and subjected to 16S rRNA gene sequencing tar- geting V3–V4 hypervariable regions on the Illumina MiSeq platform. Alpha diversity (Shannon, Simpson, Chao1), beta diversity (weighted UniFrac, Bray-Curtis), and differential abundance analyses were per- formed. Results: Shannon diversity index decreased significantly from the low-risk group (4.32 0.42) through moderate-risk (3.61  0.39) to high-risk (2.76  0.51) groups (p < 0.001). Beta diversity anal- yses demonstrated distinct microbial clustering among risk categories (PERMANOVA R = 0.213, p = 0.001). Streptococcus mutans relative abundance was significantly elevated in high-risk adolescents (21.34 6.12%) compared with low-risk (3.87 1.96%) (p < 0.001). Conversely, health-associated genera in- cluding Neisseria, Rothia, and Corynebacterium showed significant depletion in high-risk participants. Logistic regression identified S. mutans abundance (OR = 3.82, 95% CI: 2.14–6.81) and Shannon in- dex (OR = 0.38, 95% CI: 0.21–0.67) as independent predictors of high caries risk. Conclusion: Oral microbiome diversity demonstrates progressive decline with increasing caries risk among adolescents, accompanied by characteristic compositional shifts from commensal-dominated to pathobiont-enriched communities. These microbial signatures hold potential as adjunctive biomarkers for enhanced caries risk prediction.