Khanaphot Jiwanarom. The Association between oral microbiome and disease severity in oral potentially malignant disorders. Master's Degree(Dentistry). Chiang Mai University. Library. : Chiang Mai University, 2026.
The Association between oral microbiome and disease severity in oral potentially malignant disorders
Abstract:
Background: Oral cancer, predominantly oral squamous cell carcinoma, remains a significant public health burden in Thailand. Oral potentially malignant disorders (OPMDs) frequently precede malignant transformation, and growing evidence suggests that oral microbiome dysbiosis may contribute to disease progression through immune modulation and microbial metabolitemediated effects on inflammation, cell proliferation, and genomic stability. Objective: To investigate the association between oral microbiome and disease severity in OPMDs patients. Materials and methods: This cross-sectional study was conducted at the Chiang Mai University Faculty of Dentistry and included OPMDs patients and surgical controls. Clinical information, dental plaque, and mucosal biopsy samples were collected. Microbial communities were characterized using 16S rRNA gene sequencing. Alpha and beta diversity analyses and differential abundance analyses were performed to evaluate associations with disease status and severity. Results: Sequencing was successful in 98% of plaque samples and 57% of tissue samples. OPMDs tissue exhibited significantly reduced microbial evenness (Pielous index p = 1.5 × 10⁻⁹) without loss of richness, indicating compositional imbalance. Beta diversity analysis demonstrated significant separation between tissue and plaque microbiomes (Bray-Curtis dissimilarity, p = 0.017). Gemella, Leptotrichia, Streptococcus, and Corynebacterium were significantly enriched in OPMDs tissue. Leptotrichia showed preliminary enrichment specifically in mild dysplasia tissue, though this finding requires validation due to small sample size. Among these, Gemellawas consistently detected in both tissue and plaque and showed progressive associations with clinical severity. Additional analyses suggested that host demographic characteristics, comorbidities, and lifestyle factors may be associated with variations in microbial composition. Conclusion: OPMDs are associated with site-specific oral microbiome dysbiosis characterized by reduced evenness and enrichment of selected bacterial genera. Tissue sampling provides detailed lesion-specific information, whereas plaque sampling offers practical, non-invasive screening potential. These findings support the relevance of oral microbiome profiling for risk stratification and early detection of OPMDs.