Purpose: It has been demonstrated that the diffusion chamber system (DC) can be used to analyze cell proliferation and differentiation. In particular, a combination of the DC and bone marrow cells has been widely used to investigate osteogenic differentiation. It was hypothesized that dentinogenesis could be investigated using the DC and cultured dental pulp cells. The purpose of this study was to confirm the usefulness of the DC for analyzing dentinogenesis.

 Method: Dental pulp cells isolated from rat incisor were put into DCs for in vivo and in vitro experiments, i.e. some DCs were transplanted into the peritoneal cavities of host rats (transplanted DC, T-DC), and the others were cultured in dishes with mineralization medium (cultured DC, C-DC). Five weeks later, histological and biochemical examinations were performed. The results obtained with the DC were compared with those obtained via the primary culturing of isolated dental pulp cells.

 Results: Mineralization was recognized in both the T-DC and C-DC. Immunohistochemical examinations demonstrated a mineralized matrix containing dentin matrix protein (DSP) and bone Gla protein (BGP). Various dentin-related matrix mRNA molecules (alkaline phosphatase, typeⅠ collagen, DSP, BGP, and dentin matrix acidic phosphoprotein 1) were detected in both the T-DC and C-DC. Ectodin and Wnt10a mRNA, which are closely related to the canonical Wnt signaling pathway, were also detected in both the T-DC and C-DC. Ectodin and Wnt10a induce odontoblast differentiation and dentin matrix formation via Wnt signaling. The mRNA expression levels of all of the examined genes were the same or higher in the DC than in the primary culture.

 Conclusion: These results indicate that dentin-like matrices formed in both the C-DC and T-DC. Furthermore, they suggest that the DC is a useful tool for analyzing dentinogenesis.

 Purpose: Many patients experience fear and anxiety towards dental treatment. To ensure the safety and efficacy of dental treatment, it is important to reduce this fear and anxiety. Aromatherapy is thought to be a convenient method for doing so, but its use in the dental field has yet to be thoroughly investigated. Therefore, this study aimed to evaluate the effect of aromatherapy during periodontal probing and scaling in healthy young adults by measuring variance in autonomic nervous activity (ANA) using a novel system we developed.

 Methods: The subjects were 15 healthy young volunteers (mean age 26.1±1.1 years). Each subject participated in the no-sedation, aromatherapy, music sedation, and combination phases of this study. The sequence of the phases was randomly allocated to the subjects using a central allocation method. First, each subject’s anxiety towards dental treatment was evaluated using Corah’s Dental Anxiety Scale. In the no-sedation phase, our monitoring system was used to assess blood pressure (BP), heart rate (HR), and ANA for 3 minutes prior to periodontal probing and scaling (pre-treatment) in both the sitting and supine position, and for 3 minutes during periodontal probing, 5 minutes during scaling, and 3 minutes after treatment (post-treatment) in the supine position. In the other phases, the same measurements were taken after the initiation of each sedation method. Furthermore, anxiety of the subject pre- and post-treatment was evaluated using a visual analog scale (VAS). ANA was evaluated by analyzing the low-frequency (LF) and high-frequency (HF) spectral components of ECG R-R intervals. The ratio of LF to HF (LF/HF) reflects sympathetic nervous activity (SNA). Statistical analyses were conducted using the Friedman test and the Wilcoxon signed-rank test with a significance level of 5%.

 Results: BP, HR, and VAS scores showed little variance throughout the study. The LF/HF ratio was significantly lower during pre-treatment compared to treatment in the no-sedation phase and was significantly lower during pre-treatment in the sitting position and supine positions in the three sedation phases compared to the no-sedation phase.

 Conclusion: In healthy young adults, aromatherapy significantly decreases SNA in the sitting and supine positions before periodontal probing and scaling compared to no-sedation.

 Purpose: The purpose of this study was to develop a root canal disinfectant that is safe, easy to use, and can be widely used by general dentists. Food additives that were easily licensed by the government as medicaments were used.

 Materials and Methods: Extracts of 13 food additives were used in this study: nine existing food additives containing three essential oils, three natural aromatic origin materials containing two essential oils, and one specified food additive. The bactericidal activity of each extract was tested against Escherichia coli, Lactobacillus casei, and Enterococcus faecalis. Bactericidal activity was measured by cup and broth dilution methods.

 Results: In the cup method, all food additives, except the original essential oils and grapefruit seed extract (GSE), did not have bactericidal activity. The bactericidal activity of oregano was the strongest, followed by thyme. In the broth dilution method, ascorbic acid containing ferrous ions and protamine exhibited high bactericidal activity against E. coli, as well as high and low activities against L. casei and E. faecalis, respectively. Both ascorbic acid alone and GSE showed high activity against L. casei and E. faecalis.

 Conclusion: Food additives containing ascorbic acid showed bactericidal activity against three facultative anaerobes, including E. coli. The results of this study suggest that food additives may be useful as a root canal disinfectant.

 Purpose: Although step-back preparation (SBP) has been widely used, its scientific basis has not been established. Recently, the outcomes of various root canal preparations have been evaluated by using micro CT, thus improving the scientific basis. The aims of this study were to build an experimental system to evaluate possible factors for optimally preparing root canals by using micro CT and to investigate the effect of rotation angle of stainless steel (SS) files in the SBP.

 Methods: Forty-nine transparent root canal models made with resin templated from a maxillary canine were used in this experiment. The samples were prepared with SBP with five different rotation angles (15°, 30°, 60°, 90° and 180°) by using SS files (n=7). Both the JH Endo system and Ni-Ti rotary system (Reciproc) were used as controls. The 3-D root canal morphology of the samples was photographed both before and after instrumentation with micro CT. Digital images of the root canals from the apical foramen to 4 mm coronal site were superimposed and then evaluated using computer software. The distance of transportation of the prepared root canal and the volume of prepared root canal inner walls were calculated from the data of pre- and post-instrumentation images.

 Results: The distance of transportation of prepared root canals from the apical foramen to 4 mm coronal site was significantly longer in the five SBP groups than the two control groups and tended to be positively correlated with the degree of rotation angle. The volume of prepared root canal inner walls was significantly higher in the five SBP groups than the two controls and tended to be positively correlated with the degree of rotation angle. From the horizontal images, the optimal rotation angles were both 30° and 60° to maintain the original shape of the canal. The preparation time was significantly longer in the five SBP groups than the two controls.

 Conclusions: This study shows the effectiveness of our experimental system to investigate root canal preparation scientifically and that the optimal rotation angle of SS files in SBP is around 30 to 60 degrees.