The human oral cavity contains a plethora of habitats and tissue environments, such as teeth, tongue, and gingiva, which are home to a rich microbial flora including bacteria, fungi, and viruses. Given the exposed nature of the mouth, oral tissues constantly encounter infectious agents, forming a complex ecological community. In the past, the discussion of microbiological aspects of oral disease has traditionally focused on bacteria and fungi, but viruses are attracting increasing attention as pathogens in oral inflammatory diseases. Therefore, understanding viral prevalence, pathogenicity, and preference regarding oral tissues is critical to understanding the holistic effects of viruses on oral infections. Recent investigations have demonstrated the abundance of certain viruses in oral inflammatory diseases, suggesting an association between viruses and disease. Human herpesviruses are the most extensively studied viruses in different oral inflammatory diseases. However, challenges in viral detection and the lack of reproducible in vitro and in vivo infection models have limited our progress in understanding viruses and their contribution to oral diseases. This review presents a summary of major mammalian viruses and associated diseases in the human oral cavity. The emergence of a recent pathogen SARS-CoV-2 and its tropism for salivary and periodontal tissues further

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Objective: Assess microRNA (miRNA) expression in healthy and diseased gingival tissue of human subjects and identify potential miRNA-target gene interactions and biological pathways relevant to periodontal pathogenesis. Methods: Gingival biopsies were obtained from subjects meeting the criteria for “healthy” or “diseased” according to the current AAP guidelines. Total RNA (including miRNA) was isolated using miRNeasy kit (Qiagen). Global human miRNA expression was quantified using microRNA microarray (LC Sciences μParaflo® technology platform). Potential gene targets and biological pathways of differentially expressed miRNAs were predicted using bioinformatics analysis. Results: Our results show significantly different expression levels of miRNAs when comparing inflamed and healthy gingival biopsies. Among differentially expressed miRNAs, 35 were upregulated and 29 were downregulated in diseased tissue. Using pathway analysis, these miRNAs were predicted to influence the following pathways: ECM-receptor interaction, cell adhesion molecules (CAMs), MAPK signaling pathway, and cAMP signaling pathway. Genes associated with these pathways were scanned for potential miRNA binding sites. We identified IKBKB as a target gene, an endogenous inhibitor of NF-kappa-B and MAPK signaling, which possesses multiple binding sites for candidate miRNAs including hsa-miR-195-5p. Conclusion: Our findings reveal human miRNA expression profiles are significantly different in healthy and diseased gingival tissues. Post-transcriptional regulation of gene expression by miRNAs can modulate inflammatory biological pathways, suggesting their integral role in periodontal pathogenesis.