Purpose: The capacity of low-frequency plasma jets to generate various active species without exerting a heat load has recently attracted interest as a potential means of medical sterilization. In a previous study, we demonstrated a marked sterilization effect in vitro with these plasma jets in an acidic environment (the reduced-pH method). In this study, we evaluated the ability of plasma to sterilize the caries-infected dentin model by the reduced-pH method.
 Methods: Using extracted human teeth, a 3-mm diameter cylindrical cavity with a depth of 3 mm was prepared in the center of the occlusal surface and was autoclaved. To achieve demineralization with lactic acid for two days, Streptococcus mutans (ATCC25175) suspension (10^6-7 CFU/30 ml, trypticase soy broth with dextrose, 5% carboxymethyl cellulose sodium salt) was inoculated in the cavity every day for seven days. Extreme dentin softness was confirmed by dense staining obtained with caries detector solution, occurring in the outer layer of carious dentin.
 Using a plot type of low-frequency plasma jet generation system, the duration of plasma irradiation was set at 30, 60, 120 and 180 s and evaluated at pH 3.5. As a control, irradiation was performed with He gas only in the cavity for 180 s. Pre- and post-irradiation samples were extracted using a round bur, recovered and placed in brain heart infusion broth, and cultured on agar plates to determine CFU. In this way, dentin was extracted from each tooth pre- and post-irradiation. The detection limit was 2 CFU/round bur in this study. Data were statistically analyzed by Wilcoxon's signed-rank test (α=0.01).
 Results: Pre-irradiation viable bacteria count was 2.7±1.9×10⁵ CFU/round bur. The detection limit was 2 CFU/round bur in this study. Pre-irradiation viable bacteria counts showed no significant pH-based differences. Under pH 3.5 conditions, bacteria count decreased from pre-irradiation baseline levels with increased duration of irradiation, becoming undetectable after 180 s of irradiation, thus indicating almost complete sterilization. In other words, a significantly strong sterilization effect was obtained dependent on irradiation duration. In contrast, no significant decrease at pH 6.5 was observed, demonstrating a lack of sterilization effect under near-neutral conditions.
 Conclusion: These findings demonstrate that plasma irradiation under low pH conditions (pH 3.5) was effective for the sterilization of infected dentin with irradiation in a time-dependent manner. After 180 s plasma irradiation bacteria counts were below the detection limit.

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 Objectives: In today's super-ageing society, there is an urgent need to prevent periodontal diseases and to promote health. Periodontal diseases are the main cause of loss of teeth, which are indispensable for mastication, speaking and esthetics, and are also closely associated with diabetes mellitus and other fatal complications such as cardiovascular, brain and respiratory diseases. The present study investigated the effects of an immunomodulating diet containing hydrolyzed whey peptides (WHP) on clinical periodontal parameters, biochemical parameters including inflammatory cytokine levels in saliva and gingival crevicular fluid (GCF) from patients with periodontitis.
 Material and methods: The study was approved by the Institutional Review Board of the Faculty of Dentistry, Niigata University and was conducted in the university hospital. Thirty-six generalized chronic periodontitis patients (24 males and 12 females, 66.8 y±11.7) with informed consent were recruited in this study. Subjects were grouped (examiner-blinded) into two groups: 18 WHP and 18 control-diet patients. Each patient's clinical periodontal status was recorded, including probing pocket depth (PPD), clinical attachment level (CAL), gingival index (GI), plaque control record (PCR) and bleeding on probing (BOP) before and after the four-week experimental period. At the same time, saliva was collected every five minutes for free-hemoglobin (f-Hb) examination. GCF was also collected and the TNF-α, IL-6, alanine aminotransferase (ALT) and asparagic amino transferase (AST) levels were measured. The Mann-Whitney test was used to compare the variables among the two groups, and the Wilcoxon signed-rank test was used to compare the variables within each group. Correlation between the two values was analyzed by Pearson's correlation-test. A significance level of 5% was set for all the analyses.
 Results: TNF-α and IL-6 levels of the WHP group were significantly decreased at four weeks after the experiments compared to the baseline (p<0.05). In the control group no significant changes were observed. The levels of ALT, AST in GCF and f-Hb in saliva did not differ before and after the experiment period or between the groups. As to clinical parameters, GI, BOP and PCR scores of both groups tended to be improved. GI and BOP were significantly decreased only in the control group. No significant changes were observed in PPD and CAL in both groups.
 Conclusion: The present study suggested that improved periodontal clinical conditions can be expected with both WHP and control diets in patients with periodontitis. Significant decreases in TNF-α and IL-6 in GCF were observed only in the WHP group, suggesting the beneficial effects of WHP on immunomodulation.

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 Purpose: The maxillary lateral incisor is considered as a type of tooth, but it is difficult to treat because the prognosis after root canal filling is poor. Effective treatment is also difficult because, even though it is a single-rooted canal anterior tooth, it is curved in the distal direction or in the lingual direction near the root apex. Recently, µ-CT has been introduced, which enables three-dimensional observation without destroying the specimen, and it is frequently used for the study of internal structure. In the present study, we performed a study on maxillary lateral incisors by using µ-CT.
 Materials and methods: Fifty human extracted maxillary lateral incisors with no dental caries were used. Based on images obtained by three-dimensional structuring, we observed the morphology of the apical foramen and apical constriction, and also the positional relation between the root apex and pulp chamber.
 Results: The distance from the root apex to the physiological apical foramen was 1.9mm at maximum and 0.2 mm at minimum, and 0.7 mm on average. The difference between the apical foramen and the center of the anatomical apical foramen was 0.55 mm when observed from the mesiodistal direction and 0.37 mm when observed from the labiolingual direction. Observation of the apical constriction showed apparent constriction on 22 teeth when seen from the mesiodistal direction and on 17 teeth when seen from the labiolingual direction. Also, extreme variation was found in the positional relation between the root apex and the upper end of the pulp chamber. Access lines to facilitate insertion of a file, crossing on the labial side, were found on 43 teeth, and a cutting margin was seen in 7 teeth.
 Conclusion: The results of the present experiments revealed that it is necessary to secure access lines to facilitate insertion of the file. Furthermore, it was clarified that the morphology of the root apex and file operation on the root apex side are complex. Because the root canal of maxillary lateral incisors is highly varied, sufficient anatomical knowledge and careful operation of instruments are required.

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 Purpose: Gutta-percha points for root canal filling do not adhere to the root canal wall, and so root canal filling cement (sealer) is used to thoroughly coat the walls. However, some sealers used in clinical settings have tissue-destructive effects. Once the sealer has leaked from the apical foramen, it not only causes apical periodontal diseases but also prevents healing after root canal filling. The present study focused on α-TCP/Te-CP cement, which causes no irritation and shows marked bioaffinity. This cement does not show up radiographically, as is required for a sealer. Therefore, bismuth oxide is added to α-TCP/Te-CP cement as a radiographic contrast medium. Mechanical and physical properties and curing behavior of the cement were investigated, and the dye permeability and tissue-destructive effect were investigated histopathologically to evaluate the effectiveness of the cement as a sealer.
 Materials and Methods: α-TCP/Te-CP cement was produced using calcium carbonate and dicalcium phosphate dehydrate as base materials. The cement with 30 wt% bismuth oxide allowed similar radiographic visualization to Canals. The particle diameter of bismuth oxide was adjusted to under 25 µm and then it was added to the cement. Sodium dihydrogen phosphate solution (P) and sodium chondroitin sulfate solution (C) were used as mixing solutions. The consistency, film thickness, and setting time of cement were measured as mechanical and physical properties, and the solid phase of curing was investigated based on the pH of mixed paste, X-ray diffraction analysis, and electron scanning microscopy. Apical sealing was confirmed by a dye penetration test using an extracted human tooth, and histopathological evaluation was performed by filling a rat skull with cement.
 Results: The consistency of the cement met the JIS standard. A portion of C met the JIS standard for the film thickness of cement. The setting time ranged from 55 to 423 minutes. The pH behavior depended on the pH of the mixing solution. Apatite migration was observed with curing in a part of P. The dye penetration test showed a similar sealing property to CaN in all cements. Histopathological evaluation showed no tissue damage in any subject compared with CaN.
 Conclusion: When α-TCP/Te-CP cement with bismuth oxide added as a contrast medium is mixed with sodium chondroitin sulfate solution, it does not show apatite formation with curing. However, it fulfills the required mechanical and physical properties, has an apical sealing property similar to CaN, and shows bone-like hard tissue formation 14 days after filling, suggesting that it can be used as a sealer.

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 Purpose: Dental adhesive materials are widely used for dentinal hypersensitivity treatment. However, there is a problem in the long-term durability of dentin bond strength. Incomplete resin impregnation into the collagen network leaves an exposed zone of demineralized dentin at the base of the hybrid layer. It has been speculated that the exposed collagen fibrils in this region are susceptible to hydrolytic degradation over time, leading to a reduction in bond strength.
 Materials and methods: In this study,“Hybrid coat (HC) ” was used to create an experimental sealing coat material resin composite containing 1.5% calcium salts of 4-methacryloxyethyl trimellitate (CMET). We examined in vitro the mineral induction ability of CMET, compared with that of a model decalcified dentin matrix. We also examined the adhesion ability of HC and CMET to a dentin specimen by means of a micro-tensile bond test.
 Results: In order to analyze the structure of CMET, as a result of performing neutralization titration analysis, CMET presumed that the case where calcium causes the ionic bond to 4-MET within the molecule, and the case where two or more 4-MET (s) cause intermolecular association by the ionic bond by calcium, were intermingled. In the micro-tensile bond test and the fracture modes after bond testing, the sealing coat material containing CMET showed a high adhesive ability when stored in water for 2 years. Moreover, complex viscosity increased with CMET content, and indicated thixotropy. Calcium ions were released from the CMET-HC specimens. More mineralization occurred in the CMET-HC group incubated for 24 hours.
 Discussion: The CMET concentration increased the complex viscosity. As the residual volume of the bonding material to the tooth surface was increased after air blowing, the dentin bond strength was increased. Furthermore, it was suggested by melting CMET in HC that polymerization and a network structure are formed. Moreover, the structure of the bonding layer itself improved. It was considered that short-term bonding strength improved as a result. Dentin mineralization was induced by using the eluate from the hardening object of CMET-HC, and a good result was obtained for the micro-tensile bonding strength two years later. The nanospace formed underneath the bottom hybrid layer by using CMET-HC was blocked by the remineralization substance, inducing long-term durability.
 Conclusion: The CMET combination coat material showed excellent durability of dentin bond strength, and is considered to be effective for dental treatment for dentinal hypersensitivity.

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 Purpose: Root canal filling is important for the prognosis of endodontic treatment. The part of gutta-percha point material overfilled from the apical foramen induces histological reactions, but such reactions in bone tissue at the cellular level are not well understood. The purpose of this study was to examine the histological reactions induced by overfilled gutta-percha materials in bone tissues.
 Materials and methods: Tibiae of SD rats were subjected to an operation with a dental bur to implant gutta-percha particles (diameter 1.0±0.1 mm) . Two kinds of implanted gutta-percha particle made of absorptive and non-absorptive materials were used in this study. The rats were sacrificed at 1, 2, and 4 weeks after the operation and tibiae were removed for histological examinations. After fixation with 10% formalin neutral buffer solution, decalcification was carried out with 0.5 mol/l EDTA for 3 weeks. Then, the tissues were embedded in paraffin for serial sectioning. These sections were subjected to hematoxylin-eosin (H-E) staining.
 Results: Absorptive gutta-percha particles implanted in rat bone tissues were surrounded with fibrous connective tissues containing cells at 1 week after the operation, and new bone formation could be observed around the particles at 2 weeks after the operation. The bone formation was increased and infiltrated into the absorptive particles at 4 weeks after the operation. In contrast, non-absorptive particle-implanted bone tissues induced fibrous connective tissues containing few cells at 1 week after the operation. At 2 and 4 weeks after the operation, bone formation could be seen around the particles as well; however, no histological evidence showing infiltration of bone tissues into the non-absorptive particles was found.
 Conclusion: These results demonstrate that absorptive gutta-percha materials can be replaced by newly formed bone tissues in rat tibia.

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 Purpose: To observe tooth-coating materials on dentin by experimental swept-source optical coherence tomography (SS-OCT).
 Methods: This study was approved by the Showa University Institutional Review Board (approval number 2011-016). Nine tooth-coating materials were used in this study: three non-resin-based coating materials (Nano Seal[NS], MS Coat One[MS], and Teethmate Desensitizer[TD]); and six resin-based coating materials (Shield Force Plus[SF], Barrier Coat[BA], G Coat[GC], Biscover LV[LV], Beauti Coat[BC], and White Coat[WC]). The proximal dentin surface of the cervical part of each extracted human molar was exposed using a plaster trimmer and finished by polishing flat using 600-grit wet silicon carbide paper (Struers, Denmark). E-Lize Conditioner (Pentron Japan) was applied for 60 s and the specimen was then immediately washed in water and dried. The coating material was applied according to the manufacturer's instructions. The coating surface of each specimen was immediately observed using SS-OCT once preparation was complete. Furthermore, we determined the difference in the absolute value of the reflected light intensity between before and after the application of each coating material. Statistical analysis was then performed to compare the differences using the Tukey-Kramer test, with the level of significance set at 5%.
 Results: For NS, MS, and TD (non-resin-based coating materials), no differences in reflected light intensity were observed at any position on the dentin surface between before and after the coating application. For all of the resin-based coating materials, a reduction in reflected light intensity was observed at the dentin surface layer after application of the coating. Significant differences were found between non-resin-based NS, MS, and TD and resin-based SF, GC, LV, BC, and WC (p<0.05).
 Conclusion: For resin-based coating materials, the reflected light intensity at the dentin surface layer was lower after application of the coating and the coating material was clearly observed.

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