Purpose: Hydrodynamic theory is influential as the pathogenic mechanism of dentin hypersensitivity. The healing ratio of conservation, one of the treatment methods for dentin hypersensitivity, was reported to be 60-70%. We considered that desensitizers, when used as a conservation material, did not show sufficient effectiveness on dentin due to certain influences. In this study, we investigated the influence of dentin on dentin desensitizers by observing the movement of liquid in dentinal tubules. In addition, we investigated the influence of liquid in dentinal tubules when drying stimulation was given on the dentin surface on which dentin desensitizers were applied.
 Methods: Four kinds of dentin desensitizer which are classified into the resin system and oxalic acid system were used. To investigate the influence of dentin on dentin desensitizers, the dentinal tubules with or without pulp pressure, as well as different liquids in dentinal tubules, were examined and the ratio of inhibition of liquid movement was calculated. Drying stimulation on the dentin surface was given and the ratio of inhibition of liquid movement was calculated.
 Results: The inhibition ratio decreased significantly when dentin desensitizers were applied with pulp pressure. With regard to the influence of drying stimulation, the inhibition ratio between the resin system and oxalic acid system showed a significant difference.
 Conclusion: Two types of dentin desensitizer, the resin system and the oxalic acid system, were influenced by pulp pressure, and the movement of liquid in dentinal tubules was influenced by drying stimulation on dentin desensitizers due to differences in sealing mechanisms.

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 Purpose: To reduce the amount of tooth cutting during dental caries treatment, the improvement of dental caries-detecting liquid and development of apparatuses to selectively remove dental caries have been performed. We experimentally produced a dental caries-detecting liquid containing a compound with a primary amino group (HLA) to improve the absorptivity of the Er: YAG laser, and evaluated the removal efficiency of dyed artificial carious dentin irradiated by the laser.
 Methods: We used colorless and green experimental solutions in this experiment (Nihon Shika Yakuhin Co., Shimonoseki, Japan). In this experiment, we used an Erwin AdvErl Er: YAG laser generator (J. Morita Mfg. Co., Kyoto, Japan). It was set at 35 mJ and 10 pps for the Er: YAG laser, using a C600F tip.
 Conclusion: As a result, because the dental caries-detecting liquid containing HLA increased the laser absorptivity, as well as the depth of cavity preparation and volume of dentin removed by laser irradiation, it may be possible to selectively remove dental caries using a laser with a caries-detecting liquid containing the high laser-absorptive compound.

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 Purpose: Much attention has been focused in recent years on a possible relationship between periodontitis and rheumatoid arthritis (RA). The aim of this study was to evaluate whether periodontitis coincidence affects the disease activity of RA and serum antibody response to Porphyromonas gingivalis peptidylarginine deiminase (PPAD) in patients with RA.
 Methods: This study was approved by the Institutional Review Board of the Niigata University Faculty of Dentistry and Niigata Rheumatic Center. The study participants were 44 patients with RA and periodontitis (test group) and 13 patients with RA and non-periodontitis (control group) who provided informed consent. Assessments of periodontal parameters including plaque control record, gingival index, bleeding on probing, probing depth, and clinical attachment level, as well as evaluations of rheumatologic conditions such as the disease activity score including 28 joints using C-reactive protein (DAS28-CRP) and RA medications were performed. Serum levels of rheumatoid factor, CRP, matrix metalloproteinase-3, interleukin-6, tumor necrosis factor-alpha, and immunoglobulin G (IgG) to cyclic citrullinated peptide (CCP) and PPAD were also determined with an enzyme-linked immunosorbent assay. Significance of differences in the parameter values between the groups was assessed by the Mann-Whitney U test.
 Results: The test group showed significantly higher levels of periodontal parameter values than the control group. However, similar levels were observed in age, gender, smoking status, number of teeth present, and all rheumatologic and serum biochemical measurements between the groups. A trend toward increase was shown in the serum levels of anti-CCP IgG in the test group.
 Conclusion: The results of this study suggest that periodontitis coincidence has no effect on the disease activity of RA in patients with RA, although an evaluation of a large cohort is required.

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 Purpose: Dentin discoloration that appears like a cervical shadow is one of the most serious problems when making aesthetic ceramic prostheses. There are case reports that in-office bleaching can be used for discolored cervical dentin of abutment teeth as a pre-treatment of the crown prosthesis. In this study, the influence of in-office bleaching agent on root dentin was examined.
 Methods: The specimens were divided into four groups: non treatment group (cont), and three bleaching treatment groups (tre-2, tre-4 and tre-6). In the bleaching groups, Shofu HiLite, an in-office bleaching agent containing 35% hydrogen peroxide, was applied to each specimen according to the manufacturer’s instructions. One session consisted of three applications of bleaching agent. This session was repeated 2 times, 4 times and 6 times. The mineral profiles and integrated mineral loss (IML: vol%×μm) of each specimen were obtained with a system that combined transverse microradiography (TMR) with image-analysis software. In addition, Vickers hardness tests were performed on the dentin surfaces of the same groups. Differences in IML and hardness were compared between the groups by one-way ANOVA followed by Tukey’s test. All statistical analyses were performed using SPSS (version 10.1) with p<0.05 defined as statistically significant. Numbers of each group were 6.
 Results: Representative TMR images showed no significant difference in radio-opacity in all groups. Average mineral profiles showed that the surface mineral density of the tre-6 group was slightly decreased compared with the other groups. The mean IML showed a significant difference between cont and tre-6. By the Vickers hardness test, a significant difference was observed between cont and the other groups. Vickers hardness decreased with the increase of treatment time.
 Conclusion: It was concluded that consecutive applications of HiLite as an in-office bleaching to discolored dentin will demineralize its surface.

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 Purpose: Surface reaction type pre-reacted glassionomer filler (S-PRG filler) is a bioactive material able to release multiple ions, and S-PRG filler-containing dental materials are known to show various actions such as dentinal tubule occlusion, increase of dentin acid resistance and antimicrobial activity. In this in vitro study, we investigated the effect of a prototype S-PRG filler-containing endodontic paste (S-PRG paste; intended for use as an intracanal dressing) on root canal dentin with regard to dentinal tubule occlusion and incorporation of elements.
 Methods: Roots of bovine incisors were used in this study. Following instrumentation and irrigation with 2.5% sodium hypochlorite and 3% EDTA, the root canals were filled with the S-PRG paste. The specimens were temporarily sealed and immersed in phosphate-buffered saline for 7, 14 and 21 days, replacing the paste every 7 days. Roots without S-PRG paste filling served as controls. After given periods, longitudinal and cross sections of the roots were prepared. The dentin surfaces were then examined by scanning electron microscopy, and the dentin tubule occlusion rate was calculated. Elemental analysis of the surface area of the root canal dentin was made by wavelength-dispersed electron probe microanalysis (EPMA), and the incorporation depth of F and Sr into root canal dentin was measured.
 Results: On the surface of the root canal dentin treated with S-PRG paste, deposits containing S-PRG paste-derived elements, such as Al, Sr, F and Si, were formed and dentinal tubule openings were partially or completely occluded. The amount of deposits tended to show an application period-dependent increase, and the tubule occlusion rate increased significantly up to 2 weeks. EPMA detected uptake of F and Sr into the root canal dentin, and the incorporation depth tended to increase with time.
 Conclusion: Bovine root canal dentin exhibited surface deposit formation, occlusion of dentinal tubule openings and incorporation of F and Sr when S-PRG paste was applied in the presence of PBS.

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 Objective: File flexibility of the nickel-titanium (Ni-Ti) rotary file system was improved by M-Wire, which has made it possible to increase breakage resistance and shape severely curved root canals easily. In the ProTaper Next system, which was used in the present study, files suitable for managing curved root canals were developed. The present study assessed the educational effectiveness of using ProTaper Next, which provides excellent Ni-Ti file flexibility, in hands-on training for learning canal shaping by introducing the system in dental students’ hands-on practical classes using dental models.
 Methods: Ninety-six third-year dental students at a school of dentistry performed canal shaping with ProTaper Next in J-shaped curved root canals simulated in transparent epoxy resin blocks. After instrumentation, root canal transportation was evaluated. The canal shaping was completed with two ProTaper Next files, i. e. X1 and X2. For analysis of root canal transportation, pre- and post-instrumentation digital images of simulated transparent block canals were superimposed using a stereo microscope (Olympus SZX16) with a digital camera (Olympus DP71). The image data obtained were saved on a PC and transportation measurements were obtained using an image analysis application. Measurement was performed at depths of 1 mm, 2 mm, 3 mm, and 5 mm from the apex and the amount removed was compared between instrumentation by students and instructors.
 Results: In 96 root canals instrumented by 96 dental students, accidental cases of ledge (12 canals, 12.5%) and file breakage (1 canal, 1.0%) were observed. Analysis of root canal transportation in 83 properly-instrumented canals (86.5%) showed that transportation towards the inner and the outer aspects of the curvature were 0.2 mm or less and 0.4 mm or less, respectively, at every depth of 1-5 mm from the apex. Additionally, a comparison of root canal transportation between instrumentation by students and instructors showed comparable canal transportation in both inner and outer aspects of the curve. A statistically significant difference between students and instructors was observed at the apical 1-mm and 5-mm depths along the outer aspect of the curvature.
 Conclusion: As a result of introducing ProTaper Next in hand-on training of root canal shaping for dental students, successful canal shaping while maintaining the original root canal configuration was attained, suggesting that ProTaper Next is highly effective for training.

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