Purpose: Odontoblasts, which are located in the outermost layer of dental pulp, first recognize caries-related pathogens, sense such external mechanical and chemical irritations, and play important roles in the innate immune system of dental pulp tissues. We recently reported that nucleotide-binding oligomerization domain (NOD) 1, one of the pattern recognition receptors in innate immunity, is expressed in rat odontoblastic cells (KN-3) and functions to up-regulate the chemokines expression, and suggested that NOD1 may play important roles in the initiation and progression of pulpitis. It has been reported that epigallocatechin gallate (EGCG), one of the major active components of green tea catechin, has anti-inflammatory effects. The aim of this study was to determine the anti-inflammatory effects of EGCG on odontoblasts stimulated with NOD1-specific ligand or pro-inflammatory cytokines.

 Methods: The cytotoxicity of EGCG to KN-3, rat odontoblastic cell line, was analyzed by lactate dehydrogenase (LDH) cytotoxicity assay. γ-D-diaminopimelic acid (iE-DAP), NOD1-specific ligand, tumor necrosis factor (TNF) -α- or interleukin (IL) -1β-stimulated KN-3 was treated with EGCG and then the expression and production of pro-inflammatory mediators, such as chemokines and inducible nitric oxide synthase (iNOS), were determined by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), respectively.

 Results: EGCG (up to 10μg/ml) had no cytotoxic effect on KN-3. EGCG significantly inhibited the production of chemokines, such as cytokine-induced neutrophil chemoattractant (CINC) -2 and C-C motif chemokine ligand (CCL) 20, in a dose-dependent manner. The expression of iNOS mRNA was also significantly reduced by treatment with EGCG at 10μg/ml.

 Conclusions: These findings demonstrated that EGCG treatment significantly reduced the expression and production of various pro-inflammatory mediators via NOD1-mediated innate immune response as well as inflammatory response elicited by TNF-α or IL-1β stimulation in rat odontoblastic cells (KN-3), suggesting that EGCG might be useful therapeutically as an anti-inflammatory modulator of dental pulpal inflammation.

 Purpose: To compare the pathological structure with the recognition accuracy of caries-infected dentin using blue light with a wavelength of approximately 405 nm and evaluate it in relation to the qualitative and quantitative localization of Streptococcus mutans.

 Methods: Five molars extracted from different people with dentin caries were thinly sliced to obtain sections containing the caries region, and the boundary between sound dentin and caries-infected dentin identified by red fluorescence induced by blue light was compared with the pathological structure identified by transmitted light under a stereoscopic microscope. Furthermore, by using immunostaining via anti-WapA immunoglobulin G, the boundaries between sound dentin and caries-infected dentin were observed.

 Results: The boundary between sound dentin and caries-infected dentin identified with blue light was confirmed in a mixed layer of the pioneer bacteria layer and the turbid layer. The boundary between these layers was distinctly identified by immunostaining and was roughly in agreement with the boundary indicated by blue light. A real-time polymerase chain reaction method revealed that the number of S. mutans in the pioneer bacteria layer was significantly higher (p<0.05) than that in the turbid layer. The red fluorescence induced by blue light with a wavelength of approximately 405 nm characterized a fluorescence spectrum with peaks at around 620 and 680 nm.

 Conclusion: This study demonstrated that blue light at a wavelength of approximately 405 nm could accurately detect S. mutans in caries-infected dentin.

 Purpose: Nickel-titanium (NiTi) files are becoming more popular for root canal treatments, since they have the clear advantage of maintaining the original shape of curved root canals because of their low elastic modulus and flexibility. The present study assessed the educational effectiveness of preparing curved root canals with FKG RaCe in dental students' hands-on practical classes.

 Methods: A total of 49 third-year students in the School of Dentistry, Osaka University performed root canal preparation of J-shaped canals in transparent epoxy resin blocks with FKG RaCe twice. After measuring the length of root canals with a #15 K file, cervical preflaring was performed with a preRaCe and glide path preparation was performed with a #15 K file. Working length was determined by subtracting 1 mm from the root canal length and root canal preparation was performed with RaCe (#30/6%, #30/4%, #25/4%, and #20/4%). For evaluating the quality of root canal preparation, digital images of the epoxy resin blocks before and after the instrumentation were captured by micro-computed tomography. Using image analysis software, the images of pre- and post-instrumentation were superimposed and the distances between pre- and post-instrumentation were measured on both the inner and outer sides. Measuring levels were set at 1, 2, 3, 5, 7 and 10 mm from the root apex and the distances were compared between the outcomes by the students and by specialists accredited by the Japanese Society of Conservative Dentistry.

 Results: In 49 root canals instrumented by the students for the first time, 28 apical perforations, one separated file, and one apical blockage were observed. In 49 root canals instrumented by the students for the second time, five apical perforations and one apical blockage were observed. The distances between pre- and post-instrumentation at the different levels and working time showed no significant differences among the first and second trials by the students and specialists.

 Conclusion: In hands-on training of root canal preparation for dental students, successful root canal preparation was achieved by instructing students to pay attention especially when preparing a root apex.