Purpose: In line with the increasing number of remaining teeth per person, the incidence of noncariogenic hard tissue diseases other than dental caries and periodontal disease has been increasing. Among noncariogenic diseases, micro cracks of enamel (enamel cracks) may be a cause of hypersensitivity with no substance defect. Furthermore, exposed dentin is a cause of dentin hypersensitivity to transient cold water and abrasion pain. A new high-penetration resin material for tooth substrates having high flowability, hydrophilicity and wettability also has high penetrability for enamel cracks and dentinal tubules. Considering the sealing of enamel cracks and dentinal tubules with resin-based dentin desensitizers, we measured the permeability inhibition rate using a tooth model of hypersensitivity.

 Methods: Enamel crack specimens and dentin disc specimens were prepared using healthy human teeth with no dental caries. Using a device prepared following the method reported by Pashley et al., the specimen was connected to the device and the inner pressure was set at 25 mmHg. The materials used in the experiment were the new high-penetration resin material for tooth substrates (KE, Kuraray Noritake Dental) and resin-based desensitizers G-Premio BOND (GP; GC) and Scotchbond Universal Adhesive (SU; 3M ESPE). After application of each desensitizer, the enamel crack and dentinal tubule permeability inhibition rate was measured. The surface and longitudinal cross-sectional surface in the enamel crack specimens and dentin disc specimens were observed under SEM, and the penetration depth of resin in enamel cracks was measured.

 Results: The permeability inhibition rate of the enamel cracks in the KE, GP and SU groups was 96.0, 96.3 and 94.0%, respectively. The permeability inhibition rate of the dentinal tubules in the KE, GP and SU groups was 90.0, 94.2 and 93.7%, respectively. There was no significant difference in the permeability inhibition rate of the enamel cracks and dentinal tubules between the KE, GP and SU groups, and the permeability inhibition rates of all groups were high. SEM images showed that the superficial layer of the enamel cracks and dentin was covered with a resin coating in all the groups, and that the longitudinal cross-sectional surface of the enamel cracks was sealed with resin in all the groups. The penetration depth of resin in the enamel cracks was significantly higher in the KE group than in the GP and SU groups. On the longitudinal cross-sectional surface of the KE group, we observed long resin tags which penetrated into the dentinal tubules. However, we did not observe any resin tags penetrating the dentinal tubules in the GP group, and observed resin tags that penetrated slightly into the dentinal tubules in the SU group.

 Conclusion: It is considered that the new high-penetration resin material for tooth substrates delivered a better sealing ability than conventional resin-based desensitizers for enamel cracks and dentinal tubules.

 Purpose: The purpose of this study was to investigate the influence of active application and etching mode on the enamel bond performance of a universal adhesive based on shear bond strength (SBS) tests and surface free-energy (SFE) measurements.

 Materials and Methods: A universal adhesive, Clearfil Universal Bond Quick (CU, Kuraray Noritake Dental), was used. Bovine enamel surfaces were ground with silicon carbide papers, ending at #400-grit. The prepared enamel specimens were divided into four groups following surface treatment: (1) etch-&-rinse mode with active application; (2) etch-&-rinse mode with inactive application; (3) self-etch mode with active application; (4) self-etch mode with inactive application. Ten bonded specimens per group were stored in 37°C water for 24 h, and then SBS tests were performed. The SEF of the enamel surfaces with different application modes was measured after rinsing with acetone and water. Representative treated enamel surfaces were observed with a scanning electron microscope (SEM). One-way ANOVA followed by Tukey’s honestly significant difference test (α=0.05) was performed for analysis of the SBS and SFE data.

 Results: The SBS values in etch-&-rinse mode were significantly higher than those in self-etch mode regardless of with or without active application. On the other hand, there were no significant differences in SBS between the active and inactive application groups. For baseline, the enamel surface after phosphoric acid etching showed a significantly higher total SFE value than the initial (just ground) enamel surface. A reduction in total SFE was observed for the active application groups compared with the inactive application groups. From the SEM observations, although typical etching patterns were observed in etch-&-rinse mode, the spicular etching pattern appeared to be collapsed in active application.

 Conclusion: The results of this study indicated that the SBS values of the universal adhesive tested were significantly higher in etch-&-rinse mode than in self-etch mode, regardless of the adhesive application mode. Regarding the SFE, the universal adhesive showed higher polar force in etch-&-rinse mode than in self-etch mode.

 Purpose: Diabetic patients are susceptible to severe periodontitis. Sudachitin, which is a polymethoxyflavone derived from the peel of Citrus sudachi, possesses antioxidant properties. The purpose of this study was to explore the biological activities of Sudachitin on severe periodontitis in diabetic patients by targeting human gingival fibroblasts (HGFs) cultured under high glucose (HG) conditions.

 Methods: HGF cell line CRL-2014 (ATCC) was maintained in DMEM containing 5.5 mmol/l glucose (normal glucose condition, NG) or 25 mmol/l glucose (HG), and cells were stimulated with calprotectin. To investigate the productivity of MCP-1, IL-6, MMP-1 and TIMP-1 after calprotectin stimulation, cell supernatants were collected for enzyme-linked immunosorbent assay. Next, total cell lysates were collected for western-blotting in order to investigate the NF-κB signaling after calprotectin stimulation. To examine the effects of Sudachitin on the production of inflammation-related molecules or NF-κB signaling, Sudachitin was added 60 min prior to the calprotectin stimulation.

 Results: Calprotectin increased MCP-1, IL-6 and MMP-1 production significantly in HGFs. HG enhanced significantly calprotectin-induced production of MCP-1 and MMP-1, but not IL-6. Sudachitin suppressed calprotectin-induced MCP-1 and MMP-1 production in HGFs cultured with both NG and HG significantly. Sudachitin also inhibited dramatically the calprotectin-induced IκBα and p65 phosphorylation.

 Conclusion: HG enhances calprotectin-induced production of MCP-1 and MMP-1 in HGFs. Sudachitin suppresses MCP-1 and MMP-1 production in HGFs via the NF-κB pathway. Sudachitin might be a useful polyphenol for severe periodontitis in diabetic patients.

 Purpose: This study examined the effect of taper on the dynamic cyclic fatigue resistance of nickel-titanium (NiTi) rotary instruments.

 Methods: This study examined three NiTi instruments with a tip size of 0.25 mm and 25 mm in length; i. e., Vortex Blue (Dentsply Sirona; size #25/0.04 taper and #25/0.06 taper; Group VB 0.04 and Group VB 0.06, respectively), and ProTaper Gold F2 (Dentsply Sirona; size #25/0.08 taper; Group PTG 0.08) (n=10 in each group). An artificial stainless steel canal with a 60° angle and 3 mm radius of curvature was used. The instruments were rotated in the artificial canal using a custom-made dynamic cyclic fatigue test device operated at an up-and-down speed of 50 mm/min and an axial amplitude of 1 mm. Rotational speeds were set according to the manufacturer’s recommendation. The canal was filled with a silicone oil to reduce the generation of frictional heat during the rotation of instruments. The time to fracture was measured using a digital stopwatch, and the number of cycles to fracture (NCF) was determined by multiplying the time by the number of rotations per minute. The length of the fractured tip was measured with an electronic digital caliper. NCF and the length of the fractured fragment in the three groups were statistically analyzed using the Kruskal-Wallis test followed by multiple comparisons with the Steel-Dwass test, with 5% set as the level of significance.

 Results: NCF of Group VB 0.04 showed significantly higher values compared with that of Groups VB 0.06 and PTG 0.08 (p<0.05). There was no statistically significant difference between NCF of Groups VB 0.06 and PTG 0.08 (p>0.05). The length of the fractured fragment of Group VB 0.04 was significantly shorter compared with that of Group VB 0.06 (p<0.05). None of the other intergroup comparisons were statistically significant (p>0.05).

 Conclusion: Under the present experimental conditions, the 0.04 taper Vortex Blue instrument showed a significantly higher dynamic cyclic fatigue resistance compared with the 0.06 taper Vortex Blue instrument. The dynamic cyclic fatigue resistance of the ProTaper Gold F2 instrument was similar to that of the 0.06 taper Vortex Blue instrument.

 Objectives: The clinical failure of hybrid resin crowns fabricated using computer-aided design and computer-aided manufacturing (CAD/CAM) involves various factors. The aim of this study was to evaluate the effect of decontamination agents for saliva contamination on the bonding of CAD/CAM crowns.

 Methods: CAD/CAM resin blocks (KATANA AVENCIA Block Universal, Kuraray Noritake Dental) were bonded to the dentin surface with and without artificial saliva contamination. A newly developed decontamination agent containing MDP (DC-200C, Kuraray Noritake Dental) and two commercially available decontamination agents (Ivoclean, Ivoclar Vivadent; Multi Etchant, YAMAKIN) were used in this study. Flat dentin surfaces were prepared and divided into eight groups. CAD/CAM resin blocks were bonded to the dentin surface using PANAVIA V5 (Kuraray Noritake Dental) as follows: 1) control group without saliva contamination on either resin block or dentin, 2) resin block with saliva contamination, 3) resin block with saliva contamination and Ivoclean decontamination, 4) resin block with saliva contamination and Multi Etchant decontamination, 5) resin block with saliva contamination and DC-200C decontamination, 6) dentin with saliva contamination, 7) dentin with saliva contamination and Multi Etchant decontamination, and 8) dentin with saliva contamination and DC-200C decontamination. After 24 hours, the samples were subjected to microtensile bond strength testing at the crosshead speed of 1.0 mm/min. A saliva protein staining test was performed by the pigment binding method to investigate the effect of removing saliva protein. The results were statistically analyzed at the significance level of p=0.05.

 Results: The obtained bond strength values in MPa were as follows: 1) 35.74±4.81, 2) 16.75±4.79, 3) 26.49±4.21, 4) 23.94±2.64, 5) 33.50±6.38, 6) 21.58±5.73, 7) 30.65±2.92, and 8) 34.43±5.33. The saliva contamination on both the CAD/CAM resin block and dentin surface showed significantly lower values than the control group (p<0.05). All the decontamination agents could significantly restore the bond strength from the saliva contamination (p<0.05), and DC-200C showed no significant difference from the control (p>0.05). From the results of the saliva protein staining test, DC-200C showed higher removal effect of saliva protein for the CAD/CAM resin surface than the other materials due to the surface active effect of MDP salt.

 Conclusion: The bond strength of the saliva-contaminated CAD/CAM hybrid resin block was restored to the same level as before the contamination by using a new decontamination material (DC-200C). It is suggested that DC-200C has a higher salivary protein removal effect than the other decontamination materials.

 Purpose: Calcium hydroxide and mineral trioxide aggregate (MTA) are the most widely used for direct pulp capping. However, these agents induce the large pulp necrosis beneath the materials. Therefore, there is a need to develop non-toxic agents for pulp capping. RVX-208, a bioactive compound, plays important roles in inflammation and bone metabolism by epigenetic regulation of the expression of various genes. However, the functions of RVX-208 in dental pulp cells are still unknown. Thus, in this study, we investigated the toxicity and functions of RVX-208 on dental pulp cells to evaluate whether it offers the necessary features as a good next generation candidate for direct pulp capping materials.

 Methods: The first premolars were extracted from patients undergoing orthodontic treatment at the Osaka University Dental Hospital. Then, dental pulp was extracted from the premolars and human dental pulp cells (hDPC) were isolated by primary outgrowth cultures. The cytotoxicity of RVX-208 on hDPC was examined by probidium iodide (PI) staining. The effect of RVX-208 on proliferation of hDPC was analyzed using Bromodeoxyuridine (BrdU) assay. In addition, the effect of RVX-208 on calcification nodules produced by cytodifferentiation of hDPC was evaluated by alizarin staining. Furthermore, the effect of RVX-208 on mRNA expression of odontoblast-related genes during cytodifferentiation of hDPC was examined by real-time PCR.

 Results: The frequency of occurrence of PI⁺ cells was not significantly different between hDPC in the presence of 1, 10, 100 and 0 nmol/l of RVX-208. BrdU assay revealed that RVX-208 (0-100 nmol/l) did not affect the proliferation of hDPC. In contrast, on day 18 of cytodifferentiation of hDPC, alizarin staining showed that RVX-208 increased the calcification nodules of hDPC in a concentration-dependent manner. In addition, real-time PCR analysis revealed that DSPP and DMP1 mRNA expression was up-regulated in hDPC treated with RVX-208 during cytodifferentiation, whereas ALPL and COL1A1 mRNA expression was down-regulated in these cells. On day 6 of cytodifferentiation of hDPC, there was no significant difference in RUNX2 mRNA expression between hDPC treated with or without RVX-208. In contrast, on day 18, RUNX2 mRNA expression was significantly down-regulated in hDPC treated with 100 nmol/l of RVX-208, compared to that treated without RVX-208.

 Conclusion: A bioactive compound, RVX-208, enhanced cytodifferentiation and calcification of dental pulp cells. RVX-208 might be a good candidate for a safe and effective biological direct pulp capping agent.

 Purpose: The purpose of this study was to investigate the influence of light irradiation of universal adhesives on the bonding performance of self-adhesive resin cements based on shear bond strength (SBS) tests and SEM observations of resin/dentin interfaces.

 Materials and Methods: Three combinations of universal adhesive and self-adhesive resin cement were used: OptiBond Universal/Maxcem Elite Chroma, G-Premio Bond/G-CEM LinkAce, and Scotchbond Universal/RelyX Unicem 2 Automix. Bovine enamel and dentin surfaces were ground with SiC papers, ending at #320 grit. Each universal adhesive was applied to the ground surface in self-etch mode according to the manufacturers’ indications. The treated specimens were divided into two groups, with or without light irradiation of the adhesive applied surface. A stainless-steel metal ring was placed over the bonding area, and the self-adhesive cement was condensed into the ring and light irradiated. Ten specimens per each group were stored in 37°C water for 24 h, and then SBS tests were conducted. Two-way ANOVA followed by Tukey’s honestly significant difference test (α=0.05) was used for analysis of the SBS data.

 Results: Although SBS value was material dependent for both enamel and dentin, the light irradiation groups tended to show higher SBS values than the non-irradiated groups. In the SEM observations, the adhesive layers with light irradiation were thicker than those without.

 Conclusion: The results of this study indicated that appropriate light irradiation of universal adhesives may increase the bond performance of self-adhesive resin cements.

 Objective: Plaque control by daily brushing is important to prevent oral diseases. The usefulness of electric toothbrushes for effective plaque control has been demonstrated. In this study, the usefulness of a new electric toothbrush for removing plaque was evaluated from multiple aspects.

 Subjects and Method: The subjects were males and females, regardless of age, who had knowledge of and were able to perform the oral cleaning method, and met the study conditions. For the test teeth, 6 Ramfjord teeth (16, 21, 24, 36, 41, and 44 or alternative teeth) without restoration with marked plaque accumulation were used. For the tool, two types of sonic toothbrush, the new Doltz and the conventional Doltz (Panasonic), were used. First, to evaluate oral plaque removal, plaque was scored using the Rustogi Modification Navy Plaque Index before and after use of the sonic toothbrush. For statistical analysis, the Wilcoxon test was used. Then, to evaluate oral cleaning, the following evaluation items were measured before and after use of the toothbrush: probing depth (PD), bleeding on probing (BOP), and gingival index (GI). For statistical analysis, the Wilcoxon test was used.

 Results and Discussion: The plaque removal rate was higher in the conventional Doltz group than in the new Doltz group in all regions, but the differences between the two groups were not significant. On evaluation of periodontal pocket cleaning, the improvement rates of all parameters (PD, BOP, and GI) were higher in the new Doltz group than in the conventional Doltz group. In addition, significant differences were noted after use in all parameters on intra-group comparison (p<0.05).

 This study clarified that the new Doltz has greater improvement effects on periodontal tissue than the conventional Doltz; this may be due to the tapping amplitude newly added to the main unit of the new Doltz, which appropriately stimulates the gingiva, as well as the dense extra-fine toothbrush, which is optimal for periodontal pocket cleaning, exhibiting synergistic effects to improve the gingiva. Sonic toothbrushes are expected to be effective for plaque control to prevent caries and periodontal disease.

 Purpose: The influence of irradiation conditions on tensile bond strength (TBS) was evaluated using Clearfil Mega Bond (MB, Kuraray Noritake Dental) and Clearfil Mega Bond 2 (MB2, Kuraray Noritake Dental) which contain a highly active photopolymerization catalyst.

 Methods: The surface of human teeth was ground with wet SiC paper up to 600 grit to prepare the dentin surface. The prepared surface was then conditioned by applying primer of MB, followed by bonding agent of MB. The applied bonding agent was light-irradiated from approximately 2.0 mm, 7.0 mm and 12.0 mm above the adherend surface under the following conditions: 1. Using a halogen irradiation device (XL3000, 3M ESPE, USA) for 10 seconds, 2. Using a conventional LED light irradiation device (PenCure, Morita) for 10 seconds, and 3. Using a high-output LED light irradiation device (PenCure 2000, Morita) in high-power mode for 3 seconds. The resin composite was filled and cured by the XL3000. TBS was determined after 24-hour storage in water at 37°C (n=5).

 Results: In the case of the irradiation distance of 2.0 mm, MB2 attained enough TBS under the conditions of high-output LED light irradiation by the PenCure 2000 in high-power mode for 3 seconds. However, when the irradiation distance was long, MB2 could not attain enough TBS with 3 seconds of irradiation and enough TBS was attained only when irradiating with the PenCure for 10 seconds.

 Conclusion: Even if the irradiation distance of PenCure was long, MB2 attained enough TBS. In addition, it was possible to obtain sufficient TBS by conducting light irradiation for 10 seconds, even when the irradiation distance was longer.

 Purpose: The erbium: YAG (Er: YAG) laser is used for decontaminating implant surfaces in the treatment of peri-implantitis. In this study, we quantified lipopolysaccharides (LPS) before and after decontaminating the contaminated layer on the implant surface, using an Er: YAG laser. In addition, we report that the peri-implantitis of the patient improved, based on the results of clinical evaluation, bacteriological examination, and cone-beam computed tomography (CBCT).

 Patient: A 68-year-old woman visited our hospital with the chief complaint of drainage from an implant. Her implant superstructures had been installed eight years ago, and she had no systemic disease except periodontal disease. X-ray examination revealed high resorption of the alveolar bone around the implant, and CBCT images revealed bone resorption; the resorbed bones were half the length of the implant. In addition, bacterial examination of the peri-implant pocket revealed Tannerella forsythensis, Treponema denticola, and Fusobacterium nucleatum. Although the implant showed no mobility, the probing periodontal pocket depth (PPD) of the labial center was 14 mm, and the distopalatal PPD was 10 mm. After the initial periodontal therapy, the PPD was 10-13 mm, and it bled on probing. Therefore, a surgical procedure was performed to treat the peri-implantitis. After administration of anesthesia, a full-thickness flap was raised, and a vertical bone defect with three walls on the apical side and one wall on the crown side was observed. The inflammatory tissue around the bone defect and the implant surface were decontaminated using an Er: YAG laser with water spray. LPS on the implant surface were sampled twice before and after decontamination and quantified using the Limulus amebocyte lysate method. The average of all the values was used as the LPS value, which decreased from 10.3755 to 0.0015 EU/ml. Bio-Gide was applied after insertion of Bio-Oss, and the flap was repositioned and sutured.

 Results: The PPD of the implant site stabilized at 2-3 mm 10 months after the procedure. A comparison of periodontal disease-related bacterial tests before and 12 months after surgery revealed that the numbers of T. forsythensis, T. denticola, and F. nucleatum decreased after surgery. Newly formed bone was observed in the intrabony defect from the CBCT images.

 Conclusion: In this case, the contaminated layer on the implant surface was decontaminated by an Er: YAG laser used for the treatment of peri-implantitis, along with reduction of LPS on the implant surface, facilitating long-term bone regeneration.