Detection of bacterial species using 16S rDNA existed in deep layers of carious lesions with pulp exposure embedded with plastic material and analysis of the pathogenesis of pulpitis

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Resin-embedded human carious dentin was used as template for polymerase chain reaction (PCR) detection of bacterial 16 rDNA existed in deep layers of carious lesions. A total of 34 bacterial spesies were detected from 39 human carious samples. 4.8 bacterial species per carious sample of coronal caries, 3.9 species of root caries were detected.Characteristics of Toll-like receptor (TLR)-expressing cells in human dental pulp were studied. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis comfirmed the expression of TLR-2 Mrna in all of the inflamed pulps. In situ hybridization analysis using digoxigenin-labeled single strand Crna probe showed that TLR-2, 4 and 9 Mrna-expressing cells could be found in the inflamed pulps. Immunohistological analysis at a light microscopic level showed that TCR-2 and 4 protein in the cell body. In antigen-presenting cell (APC), dendritic cells were expressed TLR-2 protein, and macrophage-like cells were expressed TLR-4 protein in the cell body. These results suggested that TLR might be involved in the pathogenesis of pulpitis.