Purpose: We examined the effects on composite resin filling repair of differences in pretreatment conditions (e. g., primer treatment) and the surface roughness of the adhesive surface.
 Methods: Two types of resin, namely, Clearfil AP-X (AP) and Beautifil Flow F02 (BE), which differed in composition and fluidity, were compared under various pretreatment conditions (no treatment, bonding treatment (Clearfil Photo Bond), silane coupling treatment (Clearfil Photo Bond and Clearfil Porcelain Bond mixture)) for different adhesive surfaces (pressure-contact surface or diamond-point ground surface). Filling was performed with the same resin material as the adhesive surface, and the shear bond strength was compared after the resins were stored for 1 week in water.
 Results: When comparing between the adhesive surface types, a significant difference in shear bond strength was observed for only BE with bonding treatment, and no significant differences were observed for the other BE cases or any of the AP cases. When comparing between the adhesion treatments, the bonding treatment group and the silane coupling group for AP with the pressure-contact surface exhibited a significant difference in shear bond strength compared with the no-treatment group. In the case of BE, significant differences were observed in the case of the diamond-point ground surface and silane coupling processing. On the pressure-contact surface, a significant difference was observed only between no treatment and silane coupling treatment.
 Conclusion: The effective method for treating the adhesive surface differs depending on the composite resin, and it is necessary to perform the surface treatment that is optimal for the composite resin to be applied. Good fluidity of the component resin is effective for ensuring good adhesive properties.

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 Purpose: Mouth rinse with chlorhexidine gluconate (CHG) has been reported to be effective as a chemical plaque control. However, undesirable side effects such as allergy are known problems. Therefore, we developed a new mouth rinse formulated with both chlorhexidine hydrochloride (CHH) and cetylpyridinium chloride (CPC) as anti-microbial constituents and tested its effects on oral bacteria in patients with chronic periodontitis.
 Methods: This was a short-term, randomized, controlled clinical trial. Systemically healthy 30 patients with ≥20 teeth were enrolled if they had 1 to 7 sites of residual pockets ≥5 mm after initial periodontal therapy with scaling and root planing. Patients were assigned to three groups and used placebo (control group), or rinse with 0.05% CHG (CHG group), or rinse with 0.05% CHH and 0.05% CPC (CHH+CPC group), for 4 weeks. In each patient, saliva, tongue coating and supragingival plaque were collected and microbiological parameters were measured with real-time PCR. Terminal restriction fragment length polymorphism (T-RFLP) analyses were also performed.
 Results: No adverse event was observed. At the baseline, no difference was found in age, sex, number of teeth, or clinical periodontal parameters between the groups. Comparing the data at baseline and after 4 weeks, total bacterial counts and S. mutans in saliva, total bacterial counts in tongue coating and total streptococci in supragingival plaque were significantly decreased in the CHH+CPC group. In the CHG group, total bacterial counts in supragingival plaque were significantly decreased. Significant decreases of total bacterial counts and streptococci in tongue coating were detected in the control group. As the results from T-RFLP analyses, saliva from the CHH+CPC group showed significant reductions of presumed numbers of Streptococcus group in the digested fragments by Msp I, and Streptococcus, Eubacterium group, Parvimonas group and Porphyromonas, Prevotella group in the digested fragments by Hha I. Additionally, in supragingival plaque obtained from the CHG group after 4 weeks, presumed Streptococcus, Veillonella group from Hha I digests were significantly reduced. No change was observed between baseline and after 4 weeks in the other bacterial data.
 Conclusion: The new mouth rinse formulated with CHH and CPC might be used safely and have equal to greater effects reducing oral bacteria than existing mouth rinse formulated with CHG alone.

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 Purpose: Restorations with gold-silver-palladium alloy discolor in the oral cavity of patients and produce a large amount of volatile sulfur compounds (VSCs). Zeolite A and Hydrotalcite have been developed as new materials to adsorb VSCs (VSC adsorbents). In the present study, the effects of VSC-producing bacteria on gold-silver-palladium alloy and the inhibitory effects of VSC adsorbents on the discoloration were investigated.
 Methods: Gold-silver-palladium alloy was added to BHI media (supplemented with L-cysteine) containing three periodontal pathogenic bacterial species (Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum) and one cariogenic bacterial species (Streptococcus mutans), followed by anaerobic culture at 37℃ for four weeks. This culture was conducted with or without a VSC adsorbent. After the culture, the glossiness and color of the gold-silver-palladium alloy were examined.
 Results: After the culture, the glossiness of the gold-silver-palladium alloy was reduced in the presence of all four bacterial species. The addition of a VSC adsorbent significantly suppressed the reduction. Discoloration was also observed. The VSC adsorbent tended to reduce color difference values. Of note, the color difference values were significantly reduced by adding Zeolite A after culture with Porphyromonas gingivalis.
 Conclusion: The tested bacteria reduced the glossiness and caused the discoloration of the gold-silver-palladium alloy. The tested VSC adsorbents adsorbed the VSCs of oral bacteria, suppressing the discoloration of gold-silver-palladium alloy.

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 Purpose: This study aimed to evaluate the current status of endodontic treatment performed in the Department of Endodontics at Showa University Dental Hospital.
 Methods: Data were collected on endodontic treatments (total number, number of root canal-filled teeth, prevalence of pulpitis, and prevalence of apical periodontitis) performed on outpatients between April 2012 and March 2013 for comparison with similar data from a previous study conducted between April 2009 and March 2010.
 Results: The following results were obtained:
 1. In total, 863 outpatients received endodontic treatment.
 2. Of the 953 total root canal-filled teeth, 372 had pulpitis and 581 had apical periodontitis. Among the root canal-filled teeth with pulpitis, there were 69 lower molars, 83 maxillary molars, 46 lower premolars, 53 maxillary premolars, 66 lower anteriors, and 55 maxillary anteriors. Of the root canal-filled teeth with apical periodontitis, there were 154 lower molars, 112 maxillary molars, 68 lower premolars, 89 maxillary premolars, 49 lower anteriors, and 109 maxillary anteriors.
 3. The mean number of treatments was 2.8 for root canal-filled teeth with pulpitis and 3.5 for those with apical periodontitis.
 4. A comparison of the data from the previous study with the present data revealed that the total number of outpatients (419 to 863) and the total number of root canal-filled teeth (348 to 953) had increased between the two time periods. In contrast, the mean number of treatments decreased for both teeth with pulpitis (3.9 to 2.8) and teeth with apical periodontitis (5.7 to 3.5).
 Conclusion: The total number of outpatients and root canal-filled teeth had increased and the mean number of treatments had decreased when compared to the previous survey. The reduction in the average number of treatments could be attributed to the introduction of cone beam computed tomography and microscope-enabled detection of perforation, apical foramen destruction, and root fracture at an early stage. As a result, surgical procedures can be performed more precisely. In addition, work efficiency when using a nickel-titanium rotary file was improved. In order to promote medical cooperation in the future, we plan to evaluate the status of endodontic treatment in our department and report statistical observations on a regular basis.

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 Purpose: Nickel-titanium (NiTi) rotary files have been shown to be effective for root canal preparation due to their superelastic mechanical properties. However, they can sometimes fracture in the root canal, and yet few studies have examined the removal of file fragments, and a method for removing files that have fractured in the root canal has yet to be firmly established. To establish a simple method for removing NiTi file fragments by corrosion with a chemical solution, basic studies on the corrosion effects of several kinds of chemical solution have been carried out. This study analyzed the mechanisms of corrosion of NiTi file fragments by two chemical solutions and examined the effects of different solution temperatures, immersion methods, and interactions between the two types of solution on dissolution, with the aim of reducing dissolution time.
 Methods: The NiTi rotary files used were #25 F2 ProTaper (Dentsply, Maillefer, Switzerland). The two chemical solutions were APF, composed of 2% (w/v) sodium fluoride in phosphoric acid (pH of 4.5), and NCN, composed of 10% (w/v) sodium hypochlorite+19% (w/v) sodium chloride. Deionized water was used as a control solution. Corrosion mechanisms were analyzed both by SEI observation and elemental mapping with an X-ray micro analyzer and by quantitative and qualitative analysis with an electron probe micro analyzer. To examine the effects of corrosion on dissolution, we investigated the effects of the following: (1) solution temperature; (2) method of immersion in the solution; and (3) interactions between the two types of solution. The progress of dissolution was calculated by measuring the differences in weight from before immersion to three hours after immersion. Morphological changes were also observed.
 Results: Elemental analysis revealed that Ti dissolution was greater in APF and that Ni dissolution was greater in NCN, thereby suggesting different corrosion mechanisms in the two solutions. In addition, corrosion progressed faster with higher solution temperature and intermittent immersion rather than continuous immersion in the solution. Regarding solution interaction, dissolution was fastest when the fragment was immersed in NCN after APF.
 Conclusion: These results demonstrated that the corrosion mechanism differed for APF and NCN. Dissolution of NiTi file fragments by corrosion can be accelerated by elevating the solution temperature, immersing the fragments in the solution intermittently, and utilizing the interaction between the two kinds of solution.

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 Purpose: The aim of this study was to assess the effectiveness of Er:YAG laser in pulpectomy.
 Methods: Human single-rooted mandibular premolars with straight single canals and mature apices were used. Sample teeth were decoronated and working lengths (WLs) were determined by inserting a size 15 K-file passively into the canal until it was visible at the apex and then retracting by 2 mm. A cone-shaped quartz-fiber tip for Er:YAG laser devices was inserted up to the WL. First, stationary irradiation was performed for 10 s at 30 mJ and 20 pps with air and water cooling (step 1). Then, the laser was irradiated four times with backward movement (step 2). Finally, laser-activated irrigation using NaOCl solution was conducted four times with backward movement (step 3). The ultrastructures of the root canal surface after each irradiation step were examined under scanning electron microscopy. In addition, during laser irradiation, temperature changes were analyzed by using an infrared thermal camera in order to examine root surface temperatures.
 Results: SEM analysis showed that step 1 produced enlarged canals showing an apical stop-like structure; step 2 samples revealed either ablated or non-ablated areas, while the step 3 group showed a calcospherite appearance with open dentinal tubules on the entire root canal surface. The thermal analysis demonstrated that the stationary irradiation for 10 s induced an average temperature increase of approximately 2.5℃, possibly without causing structural damage or anatomical alteration on periodontal tissues.
 Conclusions: These results suggest that the use of an Er:YAG laser device with a thin cone-shaped tip might be feasible in pulp extirpation procedures.

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 Purpose: To maintain healthy oral function, continued maintenance is very important after active therapy. However, in Japan, the maintenance consultation rate is remarkably low compared with those in other developed countries. This study analyzed the relationship between the long-term maintenance and the patient background factors in an effort to identify ways to increase the maintenance consultation rate in Japan.
 Methods: Thirty long-term maintenance patients were interviewed, and the interviews were recorded on video. The conversation between the patient and interviewer was converted to text from the video, and the data were analyzed qualitatively with the Steps for Coding and Theorization (SCAT) method.
 Results: The mean age of the patients was 60.7 years old, and the average maintenance duration was 10.4 years. The majority (93.1%) of patients cared about their dietary habits, and 79.3% of the patients understood the importance of physical activity. All the patients wished to continue the maintenance, and 75.9% of them had good feelings about the dental clinic staff. However, recognition of the description of primary prevention was low, with only 24.1% of the patients responding.
 Conclusion: The long-term maintenance patients had a high level of awareness of their health and good feelings about the dental clinic staff. To increase the maintenance consultation rate, it is suggested that oral hygienists who are the main staff for maintenance are important.

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 Purpose: The effects of the storage conditions of resin pastes on their mechanical properties were investigated by measuring flexural strength, Knoop hardness and width of contraction gap.
 Methods: Estelite Σ Quick, BeautifilⅡ, Filtek Supreme Ultra, Solare and an injectable resin composite MI Fill were used. The storage conditions employed were 5℃ (cold condition), 23℃ (room condition), or 45℃ by using a composite softener (heat condition). Flexural strength, elastic modulus, and Knoop hardness were measured. Contraction gap widths of the restorations filled into the cavities in the bovine teeth were measured.
 Results: Flexural strength and elastic modulus were higher for the specimens stored at the room and heat conditions. Knoop hardness was higher for the specimens stored at the room and heat conditions, but different between resin pastes used. Contraction gap formations were observed for the cold condition, and the gap width decreased with higher temperature.
 Conclusion: Mechanical properties and contraction gap formation were affected by the storage temperature of resin pastes.

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