Purpose: We measured the Knoop hardness of demineralized dentin over time using Cariotester to determine the effectiveness of several types of pulp-capping agent for atraumatic indirect pulp capping (AIPC).

 Methods: Extracted human molars were used to prepare dentin samples with a diameter of 10 mm and thickness of 2 mm. Sound dentin samples were immersed in lactic acid solution and were regarded as demineralized when the value obtained using Cariotester was approximately 20 KNH. A new bioactive glass-compounded pulp-capping agent (Shofu), Bio MTA cement (J. Morita), and NEX MTA cement (GC) were used as the pulp-capping agents in the present study. Each pulp-capping agent was applied to the surface of demineralized dentin and covered with Base cement. After the Base cement solidified, pulp-capped dentin samples and controls were divided into two groups: those placed in a container with 100% humidity and those immersed in remineralization solution, and stored at 37℃ in a thermostatic chamber for l month and 3 months. The hardness of the capping agent-applied region was then measured. Data were analyzed using a one-way analysis of variance and Tukey's test (α=0.001). Pulp-capping agent-applied surfaces were also observed under SEM.

 Results: The hardness of demineralized dentin increased with the application of a new bioactive glass-compounded pulp-capping agent, Bio MTA cement, and NEX MTA cement, and mineralized substance-like aggregates were deposited on the surface of and between collagen fibers. It is assumed that the demineralized dentin had remineralized as the bioactive glass-compounded pulp-capping agent was pasted.

 Conclusion: These results indicate the effectiveness of the new bioactive glass-compounded pulp-capping agent in the remineralization of demineralized dentin.

 Purpose: A bulk-fill resin composite was developed to reduce the chair time for direct composite restoration. However, there was concern that a large polymerization shrinkage stress was generated when filling a deep cavity with a bulk-fill resin composite. This study investigated the polymerization shrinkage stress during hardening and the mechanical properties of commercial bulk-fill resin composites.

 Methods: Three bulk-fill resins, SDR (SDR), Bulk Base Hard (BBH), and Beautifil Bulk Flow (BBF), were used as experimental specimens. For these specimens, the behavior of shrinkage stress, bending strength, elastic modulus, polymerization shrinkage and polymerization rate were measured. In addition, in order to confirm the influence of shrinkage stress on the cavity and bulk-fill resin, metal cavities and bovine cavities were filled with bulk-fill resin and the longitudinal section of the cavities was observed with a microscope.

 Results: The shrinkage stress of SDR and BBH showed a gradual rise, but BBF showed a sharp rise. The bending strength was small in the order of BBH, SDR and BBF, and a significant difference was observed in each specimen. The elastic modulus of SDR was significantly smaller than that of BBH and BBF. The polymerization shrinkage of BBH was significantly smaller than that of SDR and BBF. The polymerization rate was higher in the order of SDR, BBF, and BBH. In the observation of the longitudinal section of the metal cavities, SDR and BBH showed no contraction gap or cracks in the resin. BBF had no contraction gap, but cracks were observed in the resin. In the observation of the longitudinal section of the bovine tooth cavities, no contraction gap or cracks in the resin were observed in SDR, BBH and BBF.

 Conclusion: The shrinkage stress generation behavior and mechanical properties of bulk-fill resins varied among the specimens. Cross-sectional observation of the metal cavities showed that only BBF had cracks in the resin due to the higher elastic modulus and polymerization shrinkage and lower bending strength than the other two specimens. However, no gaps or cracks were observed in the longitudinal section of the bovine cavities, suggesting that the effect of shrinkage stress on the cavities was low in the clinical use of bulk-fill composites.

 Purpose: In the undergraduate educational curriculum of dentistry, there are two main teaching/learning methods for dental students before clinical training: traditional lectures and phantom training. The purpose of this study was to explore effective educational systems for periodontology by examining the test results of both lectures and phantom training.

 Methods: Both a written test and a practical test of periodontology were administered to students of dentistry. A total of 43 dental students of Tokushima University Dental School were recruited. Written tests were performed before and after the lectures on periodontology. A practical test of scaling and root planing was performed after phantom training. Associations between the results of the written test and practical test were analyzed statistically. P values of less than 0.05 were considered statistically significant.

 Results: The results of the written tests after lectures were higher than those before lectures. A significant positive correlation was found between the results of the written test and practical test.

 Conclusion: In the students' education on periodontology, the results of the practical test were correlated statistically to the results of the written test. These findings may contribute to establishing effective educational systems for periodontology in dentistry.

 Purpose: Recently, the application of composite resin restorations has expanded. Although chromatic studies of composite resins have progressed, color differences measured by colorimeters and visual color evaluation do not always match. The aim of this study was to establish a method of evaluating the visual color of composite resins by using the visual analog scale (VAS), which evaluates subjective data as a continuous variable, and to examine its validity.

 Method: One structural color composite resin (experimental resin : ECM-001) and three commercial composite resins of shade A3 were used in this study. Class Ⅴ and class Ⅲ cavities were prepared in artificial maxillary central incisors of four shades (A1, A2, A3, and A3.5) and each composite resin was filled and its color matching was evaluated on a black-and-white background using VAS. The correlation between VAS value and visual evaluation was analyzed. The color matching of teeth and composite resin were statistically analyzed using one-way analysis of variance and Tukey's HSD test (p<0.05). Background differences in the same sample were analyzed by the t-test (p<0.05).

 Results: In the Class Ⅴ restoration, ECM-001 showed better color matching than other composite resins. In the Class Ⅲ restoration, ECM-001 showed excellent color matching with a wide range of teeth shades on the white background. The VAS values of the other composite resins were higher on the black background than on the white background. However, the VAS value of ECM-001 on the black background tended to decrease. Because the evaluation of VAS color matching by evaluators showed the same tendency, the VAS value reflects information that can be recognized by visual observation. It is suggested that the evaluation of VAS value correlates with visual evaluation.

 Conclusion: It is suggested that the evaluation of color matching of composite resin restorations using VAS is useful for structural color composite resins, providing a new method of visually evaluating composite resin restorations.

 Purpose: Dental treatment requires long-term precision dentistry under an enlarged field of view using a dental operative microscope or magnifying scope, providing accurate medical support for dentists and dental hygienists, and assisting dental treatment by reducing the physical burden. The development of a dental treatment assistance suit is required. The purpose of this study was to improve the clinical accuracy and success rate, while reducing fatigue on dentists and dental hygienists by developing an assistance suit.

 Methods: This study investigated the effects of the dental clinical assistance suit on reducing upper arm fatigue, which was evaluated by analyzing surface electromyograms and cavity preparation using a skill evaluation system.

 Results: In both cases, the average amplitude of the biceps and triceps was significantly decreased, and the fatigue on the upper arm was reduced. The overall evaluation of the posterior cavity formation showed higher scores after the operation than before the operation using the assistance suit.

 Conclusion: It has been shown that the dental clinical assistance suit can improve the accuracy of treatment and reduce the fatigue on the operator by reducing the tension of the biceps and triceps.

 Purpose: One of the key factors of root fracture, which has increased as a cause of tooth extraction, has been found to depend on the difference in elastic modulus between post metals and root dentin. To address this issue, attempts have been made to approximate the elastic modulus of the abutment construction to that of dentin by using a fiber post with composite resin. Recently, with the aim of increasing the bond strength between root dentin and resin abutment construction, the method of using resin cement for the post part with flowable resin for the core part has been used. However, there have been no reports on the assessment of bond strength between resin cement and flowable resin. In this study, we used two types of resin cement, methyl methacrylate (MMA) resin and composite resin, and 1) analyzed the difference in bond strength between each resin cement and composite resin, and 2) assessed the bond strength by observing the morphology of the fractured surface of the samples.

 Methods: Two resin cements, MMA resin (Super-Bond; SB) and composite resin (ChemiaceⅡ; CAⅡ), and a flowable resin, Bulk Base Hard (BBH), were used. Each resin cement was attached to BBH at 10, 60 or 600 s after filling into the mold, and was stored for 15min at 37℃ after hardening BBH by light irradiation. Furthermore, shear strength was analyzed after warm bathing for 24 h at 37℃ and the morphology of the fractured surface was observed by optical microscope.

 Results: In SB, the group of 10 s after beginning of polymerization exhibited significantly higher shear strength than the group of 600 s. However, CAⅡ showed no significant difference between any groups. Furthermore, the SB group of 10 s showed higher shear strength than the 10 s group of CAⅡ whereas there was no significant difference between the SB and CAⅡ groups of 60 and 600 s. Regarding the morphology of the fractured surface, SB indicated 90% mixed destruction of SB and BBH at 600 s whereas 90% BBH destruction was observed in the other conditions. CAⅡ showed BBH destruction of 100%, 90% or 70% at 10, 60 or 600 s, respectively. There was no destruction in SB and CAⅡ.

 Conclusion: Unpolymerized SB demonstrated the highest bond strength by attaching to BBH in 10 s after filling into the mold. Furthermore, the bond strength of SB was almost equivalent to that of composite resin when BBH was attached to SB in 60 s. The bond strengths of SB and CAⅡ were stable because there was no destruction in both cements.

 Purpose: We have developed a resin-modified-type mineral trioxide aggregate (MTA) material to improve operability and sealing property. The purpose of this study was to evaluate a novel resin-modified MTA material in terms of its sealing property to dentin, and its adhesive property to the resin-based restorative material.

 Methods: A novel resin-modified MTA material (PCX-TBB) consisting of white Portland cement, zirconia, hydroxypropyl methacrylate, and partially oxidized tri-n-butylborane (TBBO) as a polymerization initiator, and powder-liquid mix type MTA material (Exp-MTA) were used. The bovine root canal was filled with PCX-TBB or Exp-MTA and stored in simulated body fluid for 10 days. Then the sealing properties of both materials to dentin were evaluated by dye penetration into the interface of dentin and material. In addition, the sealing state of the interface was observed by SEM. Second, PCX-TBB and Exp-MTA were bonded with Super-bond (SB), which is an adhesive resin cement, and the tensile bond strength after storing at 37℃ for 24 hours was evaluated.

 Result: In the dye penetration test using bovine root canals, PCX-TBB showed no penetration of dye in all specimens. In seven-tenths of the Exp-MTA specimens, Exp-MTA peeled from the root canal during specimen preparation, and dye penetration occurred in all specimens. SEM observation showed that PCX-TBB and dentin were intimately joined and a large number of tag-like structures had formed in dentinal tubules. The bond strength between PCX-TBB and SB (4.6±2.13 MPa) was significantly higher than that of Exp-MTA and SB (0.9±0.37 MPa). In the comparison of fracture modes, all of the PCX-TBB specimens were fractured inside PCX-TBB, and all of the Exp-MTA specimens were fractured at the interface between Exp-MTA and SB.

 Conclusion: PCX-TBB showed a stable sealing property to dentin and had adhesive property to resin-based restorative materials. The present results suggested that PCX-TBB has excellent marginal sealing properties.

 Purpose: Sulfated vizantin (Viz-S) possesses anti-biofilm activity against Streptococcus mutans as well as immune-stimulating properties. However, the mechanism associated with this activity and cellular toxicity remained unclear. The purpose of this study was to answer these questions utilizing an in vitro biofilm model. In addition, we also analyzed whether a high concentration of sucrose in the growth media would degrade anti-biofilm activity.

 Methods: Human gingival epithelial cells were incubated in the presence of Viz-S at the concentrations of 0, 5, 10, 50, 75, 100 and 500 μmol/l for 3 h at 37℃. The cellular viability was assessed using an MTT assay. S. mutans biofilm was developed in a brain-heart infusion broth (BHI) supplemented with 0.2, 0.4, 0.8 and 1.6% sucrose using a chambered coverglass containing Viz-S at the concentrations of 0, 10 and 50 μmol/l for 24 h at 37℃ under anaerobic conditions. The wells were washed two times with phosphate-buffered saline and the amount of residual biofilms was measured by the method of crystal violet staining. The expression of genes related to biofilm formation in the biofilm cells in the absence and presence of 50 μmol/l Viz-S was investigated using a real-time polymerase chain reaction. The expression of proteins of cell-associated glucosyltransferase (CA-GTF) and cell-free glucosyltransferase (CF-GTF) was investigated by western blot analysis.

 Results: Supplementation with Viz-S at a concentration of less than 75 μmol/l did not affect the gingival cells. Viz-S at the concentration of 50 μmol/l significantly upregulated the expression of gtfB and gtfC in the biofilm cells developed in the BHI supplemented with more than 0.4% sucrose, whereas the expression of gtfD was significantly downregulated by 0.44- to 0.66-fold in all culture conditions. CA-GTF, corresponding to GTFB and GTFC, showed reduced expression in the presence of a low concentration of sucrose, however, expression in the presence of 1.6% sucrose was elevated. Surprisingly, CF-GTF, corresponding to GTFD, mostly was not detected.

 Conclusion: Viz-S disrupted the localization balance between CA-GTF and CF-GTF, resulting in detachment of S. mutans biofilm.

 Purpose: Complete disinfection of infected root canals is a critical challenge to prevent potential tooth fracture and extraction and contribute to good health and longevity in a super-aging society. In teeth refractory to root canal treatment, facultative anaerobic gram-positive bacteria, typically Enterococcus faecalis resistant to various medications, including calcium hydroxide, may be prominent, deeply infiltrate dentinal tubules and form biofilm on the apical root surface. Nanobubbles (Nac Corp.) contain pressurized air, have negatively charged surfaces and are approximately 100-200 nm in diameter. We previously demonstrated in an experimental in vitro porcine root canal model that nanobubbles promote enhanced delivery of medication into dentinal tubules and complex root canals, as well as removal of the smear layer. Therefore, the aim of this investigation was to examine the effects of nanobubbles on some medications in a canine model of intractable periapical disease.

 Methods: The root canal was kept open for 1 month in 2-year-old dogs, and then access was closed without any medication for more than 2 months to construct an intractable periapical disease model. Nanobubbles were used in combination with doxycycline hydrochloride hydrate or antibacterial cyanoacrylate nanopolymers (Nano CAME Co., Ltd.) for irrigation and administration of intracanal medication. The efficacy of disinfection was demonstrated by the number of bacterial colonies in the bacterial anaerobic culture. The root canal treatment process was repeated 4 times every 1 to 2 weeks. Autologous transplantation of dental pulp stem cells was performed at 2 months after the root canal treatment with antibacterial nanopolymers. Cone beam computed tomography (CBCT) was performed before and at 2 months after the root canal treatment, and at 2 months after cell transplantation. The teeth were extracted at 2 months, and then paraffin-embedded sections were subjected to Gram staining for biofilm detection.

 Results: The root canal could not be completely disinfected by doxycycline hydrochloride hydrate with nanobubbles, which was repeated four times. However, further irrigation and administration of intracanal medication with nanobubbles together with antibacterial nanopolymers significantly reduced the number of bacterial colonies under the limit of detection at the third application, and demonstrated little biofilm on the outer surface of the root and lacunae in the cementum and periapical tissue. CBCT analysis indicated that the periapical lesion was reduced in volume; however, treatment with antibacterial nanopolymers alone resulted in little change. The periapical tissue and dental pulp were regenerated by cell transplantation in the root canal disinfected with nanobubbles together with antibacterial nanopolymers.

 Conclusions: These results demonstrated that nanobubbles together with antibacterial nanopolymers have potential application in the complete disinfection of teeth with intractable periapical disease, leading to pulp regeneration by cell therapy.

 Purpose: To prevent caries and periodontal diseases, daily plaque control is important, and so toothbrushes are used for removing plaque and oral irrigators for removing oral debris with water flow. To improve the performance of the oral irrigator for debris removal, we performed an in vitro study using artificial plaque on the debris-removal effects of water flow discharged from a nozzle that generates cavitation air bubbles. In addition, for clinical application, the safety of the oral irrigator, which discharges water flow containing cavitation air bubbles, and its usefulness and safety for improving the health of periodontal tissue were evaluated.

 Results: Compared with water flow not containing cavitation bubbles discharged from the conventional nozzle, that containing cavitation bubbles discharged from a cavitation nozzle significantly removed artificial plaque. In addition, for clinical application, the oral irrigator had no adverse effects on the oral cavity, and may be useful for improving the periodontal tissue in gingival sulci and periodontal pockets with water flow containing cavitation air bubbles.

 Conclusion: Oral cleansing with water flow containing cavitation air bubbles is useful for daily oral plaque control.

 Purpose: We report a case of non-surgical root canal treatment of chronic apical abscesses (chronic apical periodontitis with a sinus tract) in the maxillary right first and second molars, and the one-year follow-up of this case after filling the root canals with bioactive glass (BG) -based root canal sealer using the single-cone obturation technique.

 Case: A 42-year-old male with a persistent sinus tract in the gingiva of the maxillary right molar region was referred to us from a dental clinic. By a clinical intraoral inspection, intraoral radiography, and dental cone beam computed tomography (CBCT), the maxillary first and second molars were diagnosed with chronic apical abscesses. Periapical lesions of both molars were fused, and buccal root apices of both molars were included in the fused lesion. After non-surgical retreatment, the root canals of both molars were filled with a BG-based root canal sealer using the single-cone obturation technique. Adequate root canal filling was confirmed by intraoral radiography. A comparison of CBCT images at pretreatment and one year after treatment showed that the fused periapical lesion of both molars had almost disappeared. Furthermore, a thickening of the maxillary sinus mucosa close to both maxillary molars had significantly improved and the area appeared normal.

 Conclusion: The successful non-surgical root canal retreatment in the present case suggests that obturation with BG-based root canal sealer using the single-cone technique is a viable option.

 Purpose: Several clinical reports have demonstrated benefits of minimally invasive surgical approaches for periodontal regenerative therapy. A novel modality using an erbium: YAG (Er: YAG) laser for blood coagulation during non-surgical and surgical periodontal procedures could expand the application of lasers in periodontal therapy. We report a case of using an Er: YAG laser in a modified minimally invasive surgical technique (M-MIST) for an intrabony defect.

 Methods: A 57-year-old woman presented with an intrabony defect of 7-mm periodontal pocket depth (PPD) in the mesiopalatal region of the maxillary right first premolar. After the initial periodontal therapy, the PPD was 5-6 mm with bleeding on probing (BOP). To minimize surgical intervention, the buccal gingiva was raised without elevation of the interproximal papilla. Incision and debridement of the root surface and bony defect were performed using an Er: YAG laser, with a water coolant. Furthermore, hemostasis was effectively enhanced by coagulating the surface of blood within the defect using defocus laser irradiation without water spray. The flap was repositioned and sutured.

 Results: No adverse events were observed, and the patient did not complain of pain in the healing period, except for the immediate postoperative pain, for which she received a single administration of an analgesic. After 11 postoperative months, PPD had reduced to 2 mm, with BOP (−) and a clinical attachment gain of 3-4 mm. Radiographically, the newly formed bone was observed in the intrabony defect as well. With supportive periodontal therapies performed every 3 months, the periodontal tissue was maintained for 7 years.

 Conclusion: Er: YAG laser application in a surgical periodontal procedure with M-MIST was successfully used to treat an intrabony defect with filled bone and the periodontal tissue was maintained for 7 years. This case suggested that the combined use of minimally invasive surgery with Er: YAG laser may have potential for periodontal regeneration.