Purpose: Several desensitizers that are routinely used in clinical situations for dentin hypersensitivity are also expected to have a demineralization inhibition effect. Because of the increasing incidence of root caries in an aging society, it is crucial to establish preventative and restorative procedures. The purpose of this study was to evaluate the effectiveness of sealing materials for demineralization inhibition and increasing fluorine uptake by the acid-treated root surface of the human tooth, through the use of automatic pH cycling.

 Methods: Seven extracted human molars were used in the study. One of the teeth was divided into four specimens and demineralized in a buffer solution (0.2 mol/l lactic acid, 3.0 mmol/l CaCl₂, 1.8 mmol/l KH₂PO₄, 2% carboxymethyl cellulose, pH 4.5) at 37°C for 72 hours. Three different fluoride-containing materials, namely “MS Coats F” (MS), “MS coat HyS Block gel” (HS), and CTX2 Varnish (FV), were used in this study. Each material was applied to the original root surface, which was then stored in a phosphate-buffered saline (PBS) solution (pH 7.5) at 37°C for 24 hours. Single sections, 300 μm thick, were obtained from each specimen. Untreated specimens were used as controls. The fluorine and calcium distributions in the carious lesion in each specimen were evaluated using the proton-induced gamma emission (PIGE) and proton-induced X-ray (PIXE) techniques, respectively. All surfaces of the specimen, except the outer surface, were covered with wax, and the automatic pH-cycling system simulated daily acid changes (pH 7.0-4.5) occurring in the oral cavity for 2 weeks. Caries progression was analyzed using transverse microradiography (TMR), taken before and after the pH cycling. The increment of integrated mineral loss (ΔIML) after the pH cycling was calculated from the TMR images and analyzed using the Games-Hawel test (p<0.05).

 Results: In-air μPIXE/PIGE analysis demonstrated that all sample groups showed increased uptake of fluorine in the root surface compared with the controls. However, only the HS group showed significantly higher fluoride uptake. TMR analysis found that both HS and FV showed significantly lower values of ΔIML than the control group. There were no significant differences between the control and MS groups.

 Conclusion: All three samples demonstrated a tendency towards increased uptake of fluoride from fluoride-containing hypersensitivity desensitizers and a demineralization inhibition effect on root dentin. These results suggest that fluoride-containing hypersensitivity desensitizers can be used for the prevention of root caries.

 Purpose: Interdental cleaning is an important aspect of oral self-care. Using the results from our previous survey on erosive tooth wear, the aim of this study was to evaluate the frequency of use of dental floss and interdental brushes among Japanese adults of varying ages.

 Methods: The study sample comprised 969 subjects aged 15 to 89 years residing in Tokyo, Japan. To evaluate the prevalence of erosive tooth wear, all subjects were asked to complete a self-administered questionnaire that asked about daily dietary intake, general health and oral hygiene, including the frequency of dental flossing and interdental brush usage. The factors that encouraged subjects to commence interdental self-care were also asked. The results were analyzed using the Pearson chi-square test with Bonferroni correction to determine the differences in the frequency (almost daily, sometimes, none) of use of dental floss and interdental brushes among different age groups.

 Results: For all age groups, the frequency of use of dental floss (almost daily) was 30%, while that of interdental brushes was 28%. The frequency of use of dental floss (almost daily) of the 60-69 age group was significant higher than that of the young age group (15-39 years) (p<0.05). The frequency of use of interdental brushes (almost daily) of the 50-89 age group was significantly higher than that of the 15-49 age group (p<0.05). Except for the 30-39 age group, the main factor that encouraged subjects to commence interdental care was clinical recommendation received from dentists and dental hygienists.

 Conclusion: The frequency of use of dental floss and interdental brushes depended on the respondent’s age. The main factor that encouraged respondents to commence interdental self-care was clinical recommendation received from dentists and dental hygienists.

 Purpose: The influence of different etching modes (phosphoric acid [PA] or self-etch [SE] adhesive) on the adaptation of resin-based pit and fissure sealant to the enamel and dentin was examined by optical coherence tomography (OCT).

 Methods: Bovine teeth were used as substitutes for human teeth, and standardized preparations were made. Six specimens were used for each test group to evaluate the adaptation of the material. One etching-mode group of the specimens was treated with 35% phosphoric acid (PA) for 15 s and then rinsed with a water spray for 10 s. The specimens in the second etching-mode group were treated with self-etch (SE) adhesive according to the manufacturer’s instructions. Subsequently, the sealant was inserted into the cavity and light-irradiated for 20 s. Specimens were stored in distilled water at 37°C for 24 h and then subjected to 50,000 thermocycles (TCs) between 5°C and 60°C, with a dwell time of 30 s. With the use of OCT, the peak intensity (dB) at selected locations on the sealant surfaces was measured in A-scan mode, and the B-scan images were observed. Data were subjected to two-way repeated-measures analysis of variance and the Tukey-Kramer test (α=0.05).

 Results: Representative B-scan images of the PA-treated enamel specimens showed a weak and narrow signal from the sealant-enamel interface, with no backscattered intensity before the TCs, and with slight changes to the OCT images after 50,000 TCs. For the SE group of enamel specimens, visible signals from the sealant surface were observed, with backscattered light considerably greater than the noise level. There were significant differences in the peak signal intensity at the sealant-tooth interface before and after the TCs for the PA-treated enamel and dentin specimens. Conversely, there were no significant differences for both substrates of the SE test groups.

 Conclusion: A comparison of PA etching and SE adhesive for use with pit and fissure sealants revealed that employing a universal SE adhesive might promote effective adaptation of the material to both the enamel and the dentin.

 Purpose: The aim of this study was to investigate the separation incidence and reasons for discarding nickel-titanium (NiTi) rotary instruments in clinical use.

 Methods: All discarded NiTi rotary instruments were collected from the Endodontic Clinic of Showa University Dental Hospital over 3 years. During this period, we used EndoWave (J. Morita) with size 35, 0.06 taper; size 35, 0.04 taper; size 30, 0.06 taper; size 30, 0.04 taper; size 25, 0.06 taper; size 25, 0.04 taper and size 20, 0.06 taper. After inspection under stereomicroscopy, the discarded instruments were classified into three categories: (ⅰ) no deformation after eight uses; (ⅱ) plastic deformation; and (ⅲ) file separation. The number of clinical uses at the time of file separation or plastic deformation was also recorded. The incidences of total file separation, as well as the size of individual file showing separation, were calculated. The difference in the reason for discarding the instruments of different sizes was statistically analyzed using the χ² test. Also, the difference in the number of uses before discarding the instrument with plastic deformation and file separation was statistically analyzed using Kaplan-Meier survival analysis and log rank test. A significant difference was set at α=0.05.

 Results: A total of 647 NiTi rotary instruments were discarded with a significant difference among the instrument sizes (χ²=166.3, p<0.05). The overall incidence of separation in this study was 4.0%. The size 35, 0.06 taper demonstrated the most frequent separations in 17 out of 26 NiTi rotary instruments. Separations were recorded even during the first clinical use, whereas above five uses accounted for over half of the incidence of instrument separation. The mean clinical uses (number of uses±standard deviation) at the time of discarding the instruments in the file separation and plastic deformation categories were 4.3±2.2 and 3.8±12.4 respectively, with no significant difference (p>0.05).

 Conclusion: The study results indicate that relatively large instruments are highly vulnerable to file separation. While using the NiTi rotary instruments in clinical situations, the clinicians should be aware of the size and the duration of usage that render the instrument susceptible to separation and plastic deformation.

 Purpose: In Tsurumi University Dental Hospital, chemical cleaning (shock treatment) of dental unit waterlines (DUWL) has been carried out to maintain cleanliness. In this research, we reviewed the short-time treatment effect of low corrosion-inducing cleaning against heterotrophic bacterial contamination in DUWL, as well as the importance of daily flushing of DUWL.

 Methods: As the cleaning solution, NaClO (500, 10,000 ppm) and slightly acidic water (SAW) were used. After shock treatment, water was collected from the dental unit before and after flushing on the day after the day of closure, and the free chlorine concentration and heterotrophic bacterial number were determined. Measurement was continued until 10 weeks.

 Results: The free chlorine concentration of the stationary water before shock treatment was lower than the limit of tap water standard (0.1 ppm) in all DUWLs, and recovered by flushing. However, in some cases, additional flushing was needed to reach the required level of chlorine. The logarithm value of heterotrophic bacterial count in the stationary water showed a significant correlation with the free chlorine concentration. The collected water after flushing showed a significant decrease in the logarithm value of the bacterial count and a significant increase in the free chlorine concentration as compared with the stationary water. After shock treatment with NaClO at 500 ppm and 10,000 ppm, heterotrophic bacteria were not detected in the collected water. After 2 weeks of shock treatment, the number of heterotrophic bacteria in stationary water in all units exceeded 2,000 CFU/ml, which is the upper limit for water quality management in Japan. The bacterial number in flushing water samples from SAW-treated, 500 ppm NaClO-treated and 10,000 ppm NaClO-treated units exceeded the level of 2,000 CFU/ml at 3, 7 and 10 weeks after cleaning, respectively. Although cleaning using 10,000 ppm NaClO was most effective, the liquid was suspected to have a corrosive action on brass.

 Conclusion: For DUWL maintenance, shock treatment with 500 ppm NaClO and reliable flushing seemed to be the most suitable method to avoid corrosive effects on the parts of the DUWL. In dental clinics where shock treatment is difficult to perform, it is important to thoroughly perform daily flushing as DUWL management.

 Purpose: Caries-related immune response is first recognized by dental pulp fibroblast cells and is tightly regulated to avert pulpitis. Nucleotide-binding oligomerization domain protein (NOD) 1 signaling, which is essential for initiating the innate immune response to bacterial infection, is subject to many regulatory mechanisms. However, little is known about post transcriptional regulation of NOD1 dependent responses in dental pulp fibroblast cells. NOD1 recognizes D-glutamyl-meso-diaminopimelic acid (iE-DAP). RIP2 is associated with NOD1 and play critical roles in the immune system. Matrix metalloproteinases (MMPs) such as MMP-1, 2, 3, and 14 were also shown to be expressed in inflamed dental pulp tissue. MMP-3 can degrade the extracellular matrix (ECM) and activate other MMPs. MMP-3 is considered to be involved in wound healing, inflammation, and tumor initiation. Dental pulp destruction may be regulated, in part, by matrix metalloproteinase-3 (MMP-3), and other MMPs activated by MMP-3 have been shown to regulate the degradation and regeneration of dental pulp tissue. In the present study, we investigated that MMP-3 production in response to iE-DAP and its cell signaling in human pulp fibroblasts (HPFs).

 Methods: HPFs were incubated in serum-free α-MEM containing iE-DAP at the concentration of 0, 5, 10, 20, 50 μg/ml for 24 h,, and the MMP-3 production was analyzed by Western blot analysis. Next, HPFs stimulated by iE-DAP (10 μg/ml) for 24 h were further incubated with or without the RIP inhibitor, 0.5, 1, 5, 10, 15, 20 μmol/l Gefitinib to evaluate the expression of MMP-3 and RIP2 by Western blot analysis. HPFs were incubated in serum-free α-MEM containing iE-DAP (10 μg/ml) for 24 h with or without the JNK inhibitor, AS601245 or SP600125. The production of MMP-3 and activation of JNK by iE-DAP were evaluated by Western blot analysis of JNK phosphorylation and MMP-3.

 Results: iE-DAP enhanced the production of MMP-3 in a dose dependent manner in HPFs. RIP2 inhibitor suppressed the production of MMP-3 on iE-DAP stimulated HPFs. We demonstrated that MMP-3 was produced from HPFs in response to iE-DAP in a JNK-dependent manner.

 Conclusion: These results suggest that iE-DAP/NOD1 induced the production of MMP-3 in HPFs through a signaling cascade involving RIP2-mediated phosphorylation of JNK.

 Purpose: Both periodontal disease and malocclusion are related to the deterioration of pathological conditions. Therefore, it is considered necessary not only to control inflammation but also to control occlusal power, such as stabilizing occlusion and dispersing occlusion force.

 Case: A 47-year-old man initially visited the Department of Periodontology, Matsumoto Dental University Hospital with the chief complaint of gingival swelling. Under a diagnosis of broad-type moderate chronic periodontitis with skeletal mandibular prognathism caused by overgrowth of mandibular bone, surgical orthodontic treatment was performed after the initial periodontal therapy, and the opposite occlusion was improved. Subsequently, the patient got good results by improving the environment of periodontal tissue and the continuity of dentition by implant and prosthetic treatment.

 Conclusion: We report a case of comprehensive treatment of a patient with broad-type moderate chronic periodontitis with skeletal mandibular prognathism.