The purpose of this study was to determine the effect of contaminated air of a three-way syringe on the bond strength of single-step self-etch adhesives. Three single-step self-etch adhesive systems, Bond Force (Tokuyama Dental), G-Bond (GC), and Clearfil tri-S Bond (Kuraray Medical), were used. Bovine mandibular incisors were mounted in self-curing resin and enamel or dentin surfaces were ground wet on 600-grit SiC paper. Adhesives were applied according to the instructions of each manufacturer, followed by air blowing with a three-way syringe or CO₂ spray. After air blowing, the resin composite Clearfil AP-X (Kuraray Medical) was inserted into the mold on the enamel or dentin surface and light-irradiated. These specimens were stored in 37℃ distilled water for 24 hours, then shear bond strengths were measured and fracture modes after testing were observed with a scanning electron microscope (SEM). The results were as follows: 1. The enamel bond strength of G-Bond with CO₂ spray air was higher than that with three-way syringe air blowing. No significant difference was found with Bond Force and Clearfil tri-S Bond. 2. The dentin bond strengths of Bond Force and G-Bond with CO₂ spray were higher than with three-way syringe air blowing. No significant difference was found with Clearfil tri-S Bond. 3. From the SEM observations of fractured resin surfaces, mixed failures were more frequently observed with CO₂ spray than with three-way syringe air blowing.

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Objective; This study examined the physical properties, anti-plaque effects and biocompatibility of tooth coating materials containing surface reaction type pre-reacted glass-ionomer (S-PRG) filler. Materials and Methods; Tooth coating material containing S-PRG filler as the experimental group (BW) and commercially available WhiteCoat (WC) as the reference group were tested. Physical properties were determined by analyzing the following: flexural strength, flexural modulus, Knoop hardness, radiopacity, toothbrush abrasion and surface roughness. Materials were observed by scanning electron microscopy and transmission electron microscopy. Each sample was applied to the buccal surface of a first molar, and then observed. After application of each material they were either polished (BW-GP group) or light-cured (BW-GE group). Streptococcus oralis was used in the bacterial adhesion test for evaluation of anti-bacterial effects. The samples were immersed in sterile distilled water and cell culture medium, and elution elements were quantified. The cytotoxic test was performed using HeLa cells. Results; BW exhibited a greater flexural strength and flexural modulus than WC. Regarding the Knoop hardness, BW had approximately 3 times greater strength than WC. WC was not radiopaque. The surface roughness test showed no significant differences between each material. The toothbrush abrasion in BW was higher than that in WC. SEM analysis revealed a filler of about 1-15μm in BW. As a result of the TEM observation, nano filler was confirmed at filler and matrix division of about 1μm in BW, and nano filler of about 100nm was observed in WC. Several bacteria were observed on the surface of BW-GE and WC applied to the buccal side of the first molar. On the other hand, no bacterial adhesion was observed and the surface structure layer was visible for BW-GP. Bacterial adhesion to BW-GE and BW-GP was less than that to WC. In the antibacterial test, no significant difference was observed between the materials. The elution elements B and Sr were detected from BW immersed in sterile distilled water, and Na and F were detected in WC. In the cytotoxic test, there was a significant difference between the materials. The degree of cell proliferation in BW was 98.4%, and that in WC was 61.8%. Conclusions; BW containing S-PRG filler exhibited good anti-plaque effects, physical properties and biocompatibility. Therefore, clinical application of BW is suggested.

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The necessity of resin partitions for treatment of infected root canals (n=56) was investigated at the Department of General Dentistry and Clinical Education, Tsurumi University School of Dental Medicine. Twenty-one cases (37.5%) needed partitions for root canal treatment. The classification of resin partitions by location was as follows: subgingival, 23.8% (n=5); supraginvival, 61.9% (n=13) and between subgingival and supraginvival, 14.3% (n=3). The classification of resin partitions by number of walls required was as follows: 1 partition wall, 33.3% (n=7); 2 partition walls, 23.8% (n=5); 3 partition walls, 4.7% (n=1); 4 partition walls, 23.8% (n=5) and others, 14.3% (n=3). Working time required to build up the partitions was 17.8±8mins. Finally, the classification according to the type of tooth was as follows: maxillary anteriors, 14.3% (n=3); maxillary premolars, 14.3% (n=3); maxillary molars, 9.5% (n=2); mandibular premolars, 9.5% (n=2) and mandibular molars, 52.4% (n=11). In conclusion, this study proved that construction of resin partitions was required in 37.5% of cases of infected root canals. Furthermore, flowable resin was found to be a suitable material during the build-up procedure. As for the partition procedure using flowable resin composite, its clinical application is possible.

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In this in vitro and clinical study, cocoa powder, which is used as a drink and a food ingredient, was tested to evaluate its usefulness as a dentifrice. In the in vitro study, cocoa solution (0.2g/ml) was prepared by mixing pure cocoa powder and distilled water. The control group consisted of CaHPO₄ solution (0.2g/ml) and distilled water. The surface of extracted bovine teeth was stained after immersing in a tea solution. These stained teeth were divided into three equal groups and polishing was carried out for each group using cocoa solution, CaHPO₄ solution and distilled water. Polishing was per-formed on the labial surface of the teeth using a polishing brush while conforming to the same experimental conditions for all three groups. The color of the labial surface of each group was measured with a spectrocolorimeter using the CIEL*a*b*, before being subjected to staining, after staining, 3min after polishing and 6min after polishing. The color difference (ΔE*ab) between after staining and 3min after polishing, and between after staining and 6min after polishing were measured, and the significance of difference for each polishing agent was calculated using Tukey's multiple comparison (α=0.05). To investigate whether cocoa solution itself causes staining, bovine teeth were immersed in a separately prepared cocoa solution (4g/100ml). The color change after this procedure was compared with that caused by immersing the teeth in a tea solution. In the clinical investigation, anterior teeth were divided into two groups and polished with either of two solutions: polishing solution containing cocoa or a placebo solution which did not include cocoa. The patients were instructed to brush their anterior teeth using one of these two solutions for 1 month, after which the color difference was measured. The results were analyzed with the Mann-Whitney U test (α=0.05). In the case of the in vitro experiment, there was a statistically significant difference between the color difference after polishing with cocoa solution and that of the distilled water. Moreover, as for the color difference, there was no significant difference between cocoa solution and CaHPO₄ solution. There was no difference between 3 and 6min after application for each polishing agent. Unlike tea solution, no color change was observed when the teeth were immersed and kept in cocoa solution. As for the clinical test, there was no significant difference between cocoa solution and placebo solution. From the above results, the solution containing cocoa was shown to remove stains from the surface of teeth in vitro, however, such capability was not confirmed under the limited conditions employed in the clinical investigation.

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Amalgam restorations have been used in posterior occlusal cavities since the 19th century, and are considered to be relatively reliable and long lasting. However, the use of amalgam has decreased over the years due to the effects of mercury on the environment and the human body, and composite resins for posterior teeth were developed as an amalgam substitute. Clinically, composite resin restorations are now more frequently used because they do not have the disadvantages associated with amalgam restorations such as poor esthetics and lack of adhesion to enamel or dentin. In order to examine the shift from amalgam restorations to composite resin restorations in posterior cavities and determine the current trend, the chronological changes in the percentages of composite resin and amalgam restorations placed in occlusal cavities of premolars and molars, excluding wisdom teeth, were determined by reviewing the dental examination records of 1,159 students entering the Department of Dental Hygiene, K Women's College, from 1997 to 2006. From 1997 to 1999, the percentage of composite resin restorations and amalgam restorations were both approximately 30%; however, from 2002 to 2006, the proportion of composite resin restorations in posterior occlusal cavities increased yearly, reaching 55.0%, while the percentage of amalgam restorations progressively decreased to 4.0%. The chronological changes in the percentages of amalgam and composite resin restorations in molar, maxillary posterior, mandibular posterior, and posterior cavities from 1997 to 2006 were comparable. However, for premolars, the percentage of composite resin restorations did not fluctuate over this 10-year period. The above results clarified that since 1990, composite resins have been used more often than amalgam to restore posterior occlusal cavities. Furthermore, the percentage of composite resin restorations increased each year while that of amalgam restorations decreased. In 2006, the percentage of composite resin restorations in occlusal cavities was about 14 times that of amalgam restorations. Also, the percentage of composite resin restorations in premolar cavities did not change markedly over a 10-year period, suggesting that the increase in the percentage of composite resin restorations in posterior occlusal cavities reflected the increase in use of composite resin restorations in molar cavities.

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The present study aimed to obtain information on the formaldehyde vapor concentration of the surrounding air of a dental clinic during root canal dressing using Formalin Guaiacol (FG). The measurements were made at Tohoku University Hospital Dental Center, Clinical Division of Endodontics, for five days in the summer and winter of 2008. A human extracted lower first molar tooth was prepared for root canal dressing using a cotton point soaked in FG. The tooth was fixed to the headrest of a dental chair, and a total of 2 liters of surrounding air was collected in 10 minutes using an automatic gas sampling device. The collection was carried out under four treatment conditions as follows: 1) root canal dressing using FG without any suction of surrounding air (treatment 1), 2) root canal dressing with suction of surrounding air using a suction installed to the dental chair (treatment 2), 3) root canal dressing with suction of surrounding air using an extra-oral suction (Denpax®NDP-510, Denpax) (treatment 3), and 4) leaving the cotton point soaked with FG on the headrest of the dental chair (treatment 4). Preceding the treatment, surrounding air was collected as background data. The concentration of formaldehyde vapor in the collected air was later estimated by high-performance liquid chromatography. The concentration of formaldehyde vapor in the collected air was lower than the legally designated limit in Japan. There was no significant difference between background concentrations under the different treatments. However, background concentrations in the summer were significantly higher than those in winter (repeated measurement ANOVA, p<0.01). The concentrations under the four treatments were significantly different both in summer and in winter (repeated measurement ANOVA, p<0.01), and treatment 4 led to a concentration significantly higher than that under the other three treatments (Scheffe's test, p<0.01). Our results indicated that root canal dressing using FG produces formaldehyde vapor at an acceptable concentration designated by law and the use of a dental vacuum effectively reduced the formaldehyde concentrations of surrounding air in the clinic.

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This study aimed to evaluate a newly-developed HEMA-free one-step adhesive system, G-bond Plus® (GC, GBP), regarding the ultrastructural features of tooth-adhesive interfaces and marginal leakage. G-Bond® (GC, GB), Bond Force® (Tokuyama Dental, BF) and Clearfil tri-S Bond® (Kuraray Medical, TS) were used as reference materials. Enamel and dentin surfaces of extracted human molars were treated with one of the four adhesive systems and then observed by either scanning electron microscopy (SEM) or confocal laser scanning microscopy (LSCM). For the assessment of marginal leakage, class V cavities prepared in extracted human premolars were treated with one of the four adhesive systems and filled with flowable resin composites (n=5). After 7 days of storage in water at 37℃, specimens were subjected to mechanical load cycling, immersed in a 50% silver nitrate solution for 24h, and then sectioned bucco-lingually. The degree of silver penetration along enamel- and dentin-adhesive interfaces was scored under a stereomicroscope and then the interfaces were observed with SEM. Enamel prism ends and dentinal tubule openings were more evident in GBP- and TS-treated specimens compared with those treated with GB and BF; LSCM also demonstrated that GBP and TS caused deeper step formation along the boundary between treated and untreated regions. The degree of silver penetration along enamel- and dentin-adhesive interfaces was larger in GBP and TS than in GB and BF, although no statistically significant difference was found (p>0.05, Kruskal-Wallis test). SEM also demonstrated that gap formation along the enamel-adhesive interface was more frequent in GB than in GBP, TS and BF, and that gap formation and silver penetration along the dentin-resin interface were more often seen in GB and BF than in GBP and TS. These findings suggest that the self-etching potential and sealing ability of GBP are comparable to or better than those of GB, BF and TS.

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Since normal cells in a primary cell culture possess a Hyflick limit, which is the number of times cells divide before they stop due to the telomere reaching a critical length, it is difficult to analyze odontoblasts in vitro sufficiently. As a result, little is known about the mechanism of odontoblasts differentiation; extending the life time of odontoblasts may enable a detailed analysis of them in vitro. The purposes of this study were to establish an immortal dog dental pulp cell line by the gene transfection of human telomere reverse transcriptase (hTERT), human papilloma virus (HPV) E6 and E7 into dog dental pulp cells (DDP) in vitro and to analyze its characteristics. First, we obtained an immortal dog dental pulp cell line, DDP (E6E7/TERT) by infection of retrovirus recombined with hTERT, HPV E6 and E7 to DDP derived from dog anterior teeth. Next, ALPase staining and Alizarin Red staining were carried out to monitor differentiation and mineralization in DDP (E6E7/TERT) in vitro. In both stainings, positive staining was defined in DDP (E6E7/TERT) on day 6. Moreover, the expressions of hard tissue related genes (osteopontin, type I collagen, Runx2) were observed by the RT-PCR method. These results indicated that DDP (E6E7/TERT) was immortalized while maintaining the same characteristics as normal cells, suggesting the immortalization system used in this study is effective for the immortalization of dog dental pulp cells. Also, it was suggested that DDP (E6E7/TERT) might be a useful tool for clarifying the mechanism of odontoblasts differentiation and developing a novel pulp capping agent.

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This study examined the change in color of reinforced glass ionomers for restorative filling. Disc specimens (10mm dia., 1mm thick) were fabricated from a hand-mixed-type reinforced glass ionomer for restorative filling (Fuji IX GP, GC: A) and two mechanical-mixed-type reinforced glass ionomers for restorative filling (Fuji IX GP Fast Capsule, GC: B; Fuji IX GP Extra, GC: C). The specimens were immersed in deionized water (37±1℃) one hour after the start of mixing (baseline) up to 336 hours. The color differences (ΔE*ab, n=6) between the baseline and 24, 168 or 336 hours after the start of immersion and the Translucency Parameter values (TP value) were determined using a spectrocolorimeter. The specimens were also weighed after water immersion. The results were statistically compared using ANOVA/Scheffe's test. The TP values of the cements at 24, 168 and 336 hours of immersion were significantly higher than the baseline values (p<0.05). There were no significant differences in the TP values of cements B and C after 24 hours (p>0.05). The ΔE*ab values and the weights of the cement A and B specimens after 168 and 336 hours were significantly greater than for the specimens immersed for 24 hours (p<0.05). An increase in the TP values of the cement specimens could be attributed to the progress of the setting reaction during the first 24 hours after the start of mixing. The mechanical-mixed-type cement C exhibited superior color stability compared to the other cements tested. This finding may be due to the fact that cement C has improved chemical composition and powder particles, and reaches stable water sorption soon after mixing.

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