Purpose: Calcium-binding proteins termed S100 proteins are involved in the pathogenesis of various inflammatory diseases. Among the S100 proteins, S100A8 and S100A9 expression is associated with the pathology of chronic inflammatory diseases. In this study, the expression of two S100 proteins (S100A8 and S100A9) in human periapical granulomas was investigated.

 Methods: Periapical lesions were excised from 44 patients during endodontic surgery or tooth extraction. The samples were divided in half immediately after the periapical lesions were excised. One half of the divided tissues was fixed with 10% neutral-buffered formalin and paraffin sections were prepared. The other half of the tissue samples was fixed with 4% paraformaldehyde prepared in phosphate-buffered saline, embedded in OCT compound, and frozen in dry-ice acetone. These samples were then used for RNA preparation. Five healthy gingival tissue samples were also prepared as described above. After 32 samples were diagnosed as periapical granulomas based on histological evaluation, paraffin sections were examined using two-color immunofluorescent staining with anti-human S100A8 and anti-human S100A9 antibodies to search for the expression of S100A8 and S100A9 in human periapical granulomas. In addition, a quantitative analysis of S100A8 and S100A9 mRNA expression was performed using real-time PCR, using total RNA extracted from frozen samples of periapical granulomas and gingival tissues. The assays were performed using Smart Cycler, and gene expression levels were normalized by dividing the calculated values for the mRNA samples by those of GAPDH mRNA. Healthy gingival tissues were used as a negative control. Real-time PCR data were statistically analyzed using the Mann-Whitney U test. Significance was considered at p<0.05.

 Results: S100A8 positive inflammatory cells in periapical granulomas were stained with S100A9 Abs. S100A8 and S100A9 mRNA were expressed in human periapical granulomas, and their expression levels in periapical granulomas were significantly higher than in the negative control.

 Conclusion: The results indicate the possibility that S100A8 and S100A9 expression could be associated with pathogenesis and growth of human periapical granulomas.

 Purpose: The kallikrein-kinin cascade is involved in vascular permeability and pain during inflammation. Kallikrein-related peptidase (KLK), called tissue kallikrein, not only plays a role in the cascade, but also performs various functions within the tissue. Additionally, lipopolysaccharide (LPS), an adventitial component of gram-negative bacteria, is one of the pro-inflammatory substances, and it affects the induction and progression of inflammation in the dental pulp. This study was conducted using cultured human pulp cells, assuming that LPS enhances the expression of KLK8 and promotes pulpitis.

 Methods: Human dental pulp cells were cultured in 10% fetal calf serum (FCS)-supplemented alpha-minimal essential medium (α-MEM). When the cells were confluent, they were incubated in α-MEM containing 1% FCS for 24 h, and then stimulated with LPS or KLK8. The expression of KLK8 mRNA was determined by reverse transcription-polymerase chain reaction. KLK8 or cyclooxygenase (COX)-2 protein expression was detected by Western blotting, and the prostaglandin (PG) E₂ concentration in the culture medium was measured using an enzyme immunoassay kit. The intracellular Ca²⁺ concentration was determined by fluorescence measurement using the fluorescent calcium probe Fura-2.

 Results: In the human dental pulp cells, LPS promoted KLK8 mRNA expression and protein expression in a time- and concentration-dependent manner. KLK8 protein expression by LPS was suppressed by extracellular signal-regulated kinase 1/2 and P38 mitogen-activated protein kinase inhibitors. Furthermore, KLK8 promoted COX-2 protein expression and PGE₂ secretion in a protease-activated receptor (PAR)-1-independent manner, but its effect was suppressed by a tyrosine kinase inhibitor.

 Conclusion: This study suggests that LPS is involved in the production of KLK8 and in the kallikrein-kinin cascade, thereby affecting the progression of pulpitis. Furthermore, KLK8 may promote the production of COX-2 and the secretion of PGE₂ in the dental pulp in a PAR-1-independent and tyrosine kinase-dependent manner.

 Purpose: This study used transverse microradiography (TMR) to investigate changes in active root caries-like lesions following the application of a gel-type desensitizer containing copolymer and sodium fluoride with different application times.

 Materials and Methods: Acid-resistant varnish was applied to the surface of 48 bovine root dentin samples, except over 2×3 mm test areas. These samples were immersed in demineralization solution (1.5 mM CaCl₂, 0.9 mM KH₂PO₄, 50 mM acetic acid, 0.2 ppmF, pH 5.0) at 37°C for 24 h to make baseline lesions. The samples in the Control group were immersed in deionized water for 30 s, and those in the 30 s-Tr and 5 min-Tr groups were treated with a MS Coat Hys Block Gel containing fluoride for 30 s and 5 min, respectively. Then, the samples of these three groups were further immersed in the demineralization solution for 96 h at 37°C. Thin sections from samples in all groups were analyzed by TMR for demineralization depth and mineral loss. Statistical analysis was performed using the Kruskal-Wallis test and the Steel-Dwass multiple comparison test at a significance level of 5%.

 Results: The mineral profile of the 5 min-Tr group showed a remarkably higher mineral density compared to the Control and 30 s-Tr groups, and particularly the surface layer vol% of the 5 min-Tr group was about 45%. The lesion depth (μm) of each group was 71.5 in the Baseline lesion group, 165.8 in the Control group, 155.7 in the 30 s-Tr group, and 100.1 in the 5 min-Tr group, and the depth of the 5 min-Tr group was significantly shallower than that of the Control and 30 s-Tr groups. Mineral loss (vol%×μm) was 2,020.0 in the Baseline lesion group, 4,727.5 in the Control group, 3,592.5 in the 30 s-Tr group, and 2,102.5 in the 5 min-Tr group, and mineral loss of the 5 min-Tr group was significantly smaller than that of the Control and 30 s-Tr groups.

 Conclusion: Five-minute treatment, which is longer than the manufacturer’s recommendation of 30 s, by MS Coat Hys Block Gel effectively stopped the progression of active root caries-like lesions.