Comparative analysis of deep dentinal caries microbiota in teeth with normal pulp, reversible pulpitis, symptomatic and asymptomatic irreversible pulpitis.

Aim: To characterize the deep dentinal caries microbiota in teeth diagnosed with normal pulp with deep caries (NP), reversible pulpitis (RP), symptomatic irreversible pulpitis (SIP), and asymptomatic irreversible pulpitis (AIP), and to identify potential key pathogens associated with pulpitis progression, exploring their roles in disease advancement.

Methodology: In this cross-sectional study, we collected 108 dentinal caries samples, categorized into NP (n = 27), RP (n = 27), SIP (n = 27), and AIP (n = 27), according to the American Association of Endodontists' diagnostic criteria. 2 NP samples and 2 RP samples were excluded due to contamination. Samples were processed using Illumina MiSeq high-throughput sequencing. Alpha and beta diversity, taxa abundance differences, co-occurrence network analysis, and functional prediction were evaluated. Correlation analysis between the abundance of bacteria associated with clinical diagnosis, clinical signs, and pulp exposure status was performed with Spearman analysis and the Mantel test.

Results: The bacteriome of deep dentinal caries exhibited statistically significant differences among NP, RP, SIP, and AIP groups. NP and RP showed similar microbial community structures, with comparable alpha diversity, beta diversity, bacterial phenotypes, functions, and network structures. In contrast, AIP and SIP displayed distinct microbial community profiles. AIP was characterized by higher alpha diversity and a greater abundance of gram-negative bacteria, with Propionibacterium and Prevotella_7 identified as bacteria associated with AIP pathogenesis. On the other hand, SIP showed lower alpha diversity and a higher abundance of facultative anaerobes, with Lactobacillus and Limosilactobacillus identified as bacteria associated with SIP pathogenesis. Fusobacterium, Prevotella, Treponema, and Selenomonas were identified as bacteria associated with both AIP and SIP. Compared to NP and RP, the microbial networks in AIP and SIP are more complex and contain more gram-negative endodontic pathogens. These pathogens form complex positive correlations with each other and numerous negative correlations with lactic acid bacteria.

Conclusions: The bacteriome of deep dentinal caries differs significantly across teeth diagnosed with NP, RP, AIP, and SIP. NP and RP exhibit similar microbial communities, whereas SIP and AIP display distinct microbial profiles.