Purpose: We have previously reported the influence of blood contamination on adhesion of 4-META/MMA-TBB resin to dentin. Our results showed that blood contamination after surface treatment with an aqueous solution of 10% citric acid and 3% ferric chloride (10-3 solution) significantly decreased the adhesion, even if the blood was washed away. If contaminated, it was recommended that the surface be retreated with 10-3 solution and rinsed with water. Therefore, we concluded that blood coagulation inhibits adhesion. In the present study, we evaluated the influence of duration of blood contamination after surface treatment on the leakage and bond strength of 4-META/MMA-TBB resin to dentin. Methods: Bovine root dentin surfaces were contaminated with blood for 2, 5 and 15 seconds after dentin surface treatment with 10-3 solution. The contaminated surface was then rinsed with water (15 seconds), air-dried, or retreated with 10-3 solution (5 seconds). The dye leakage test, microtensile bond strength (MTBS) test, and SEM observation were employed to evaluate the leakage and bond strength of 4-META/MMA-TBB resin to dentin. Results: Results showed that leakage increased and MTBS decreased with an increase in the duration of blood contamination after surface treatment. This is due to the difficulty of removing blood contaminants by simple rinsing as coagulation progresses. However, the leakage value and MTBS were similar to those of the uncontaminated group on re-treatment with 10-3 solution. This may be due to the decalcifying ability and anticoagulant action of citric acid in 10-3 solution, which might effectively remove the blood components. Conclusion: It is recommended that the contaminated surface be thoroughly rinsed with water and re-treated with 10-3 solution, regardless of the duration of blood contamination in the process of adhesion of 4-META/MMA-TBB resin to dentin.

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Purpose: Self-adhesive resin cements (SARCs), in which polymerization can be initiated by both chemical and light activation, are used in some clinical applications. SARCs have been marketed to simplify clinical procedures and overcome the technique sensitivity of multiple-step systems. However, their setting behavior in different conditions is not known in terms of light irradiation and temperature of the cement. The purpose of this study was to monitor the influence of light irradiation and temperature on polymerization behavior of SARCs by use of ultrasound measurement. Methods: Three SARCs, Clearfil SA Cement Automix (Kuraray Noritake Dental), RelyX Unicem 2 Automix (3M ESPE) and BeautiCem SA (Shofu) were used. Ultrasound measurements were carried out using a pulser-receiver, transducers and an oscilloscope. The SARCs were mixed, inserted into a transparent mold, and then placed onto a sample stage. Power densities of 0 (no light irradiation), and 600mW/cm² were used for light irradiation, and temperatures were set at 23℃ and 37℃. The transit time through the SARCs was divided by the specimen thickness to obtain the longitudinal ultrasound velocity (V). The mean and standard deviation for the SARCs were subjected to a one-way analysis of variance (ANOVA) and Tukey's Honestly Significant Difference (HSD) test at a significance level of 0.05. Results: The increase rate of V was slower when the SARCs were not light-irradiated, and became faster when irradiated. The increase rate of V had a tendency to retard when the SARCs were stored at lower temperature. Conclusions: From the results of this study, it was indicated that the polymerization behaviour of the SARCs was affected by the light irradiation and temperature of the specimen. Light irradiation with a sufficient power density is necessary to achieve optimal setting reaction, even in materials with a dual-cured setting reaction.

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Purpose: Dental erosion is defined as the pathologic, chronic, localized loss of hard tooth tissue that is chemically etched away from the tooth surface by acid and/or chelation without bacterial involvement. Although numerous chemical factors have been identified to influence the erosive potential of acids, limited information exists about the effects of the physical or physico-chemical aspects of the acid on dental erosion. The purpose of this study was to investigate the influence of phosphoric acid solutions on impact sliding wear characteristics of bovine enamel. Methods: Bovine enamel samples were embedded in acrylic resin, and specimens were successively wet ground on #400〜#2,000-grid SiC paper. Phosphoric acid (PA) solutions at pH levels of 3, 5, and 7 were obtained with the mixture of phosphoric acid and disodium hydrogen-phosphate into deionized water. Specimens were immersed into PA solutions and then subjected to an impacting-sliding wear test at an impact load of 25 N in a wear simulator for up to 5,000 cycles. The volume loss and line profile of the wear facets were obtained for each specimen using laser scanning microscopy (LSM). Knoop hardness measurements and scanning electron microscopy observations were also conducted. Two-way ANOVA followed by Tukey's HSD test were performed (α=0.05). Results: The wear loss and surface roughness of enamel after the impacting-sliding wear test differed, depending on their pH values. The volumetric loss ranged from 18.1 to 207.6×10^-4mm³ for pH 3 group, from 12.1 to 78.6×10^-4mm³ for pH 5 group, and from 7.8 to 37.0×10^-4mm³ for pH 7 group. Lower Knoop hardness was detected for the specimens immersed in pH 3 solution than the other solutions. From the LSM observations, different worn surfaces were observed due to the impact and environmental pH. Conclusion: From the results of this study, it is indicated that the wear pattern of the enamel might be affected by the different pH conditions.

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Purpose: To provide safe periodontal therapy, it is important to understand the systemic influence of such therapy. Therefore, we developed a novel system for evaluating autonomic nervous activity during dental treatment. This study examined the effectiveness of the system for monitoring vital signs, and in so doing, for assessing autonomic nervous activity and evaluating the characteristics of variability in autonomic nervous activity during initial periodontal therapy among healthy volunteers in their twenties. Methods: Blood pressure, heart rate, arterial oxygen saturation and autonomic nervous activity were measured in 10 patients during oral examination, periodontal pocket examination, ultrasonic scaling and impression-taking using the novel system. Autonomic nervous activity was evaluated as follows :R-R intervals of heart rate were divided into high-frequency (HF) and low-frequency (LF) components by power spectrum analysis. HF reflects parasympathetic nervous activity and LF/HF reflects sympathetic nervous activity. Questionnaires concerning the system were completed after treatment. Results: Compared with the resting state, blood pressure, heart rate and arterial oxygen saturation values did not differ significantly among treatments. Conversely, sympathetic nervous activity values tended to increase when sitting, immediately before dental treatment and in the first half of dental treatment. This result suggests that the emotional stress may have a larger influence on autonomic nervous activity than the noxious stimulus during initial periodontal therapy in healthy young adults. Conclusion: This novel system can be used to easily and non-invasively evaluate changes in autonomic nervous activity without stress during initial periodontal therapy. Sympathetic nervous activity values tended to increase when sitting just before treatment and in the first half of the initial periodontal therapy in healthy volunteers in their twenties.

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Purpose: This study evaluated the objectivity of caries removal in clinical situations numerically by an objective color method, a laser fluorescence device (DIAGNOdent, KaVo) and Knoop hardness evaluation (Cariotester, Sanei ME). Methods: This experiment examined 22 permanent teeth with dentinal carious lesions (13 acute lesions and 9 chronic lesions) from patients in Osaka University Dental Hospital. The clinical pulpal conditions of these teeth were clinical normal pulp or pulp hyperemia and the teeth did not have pulp exposure. The carious lesions of the teeth were removed clinically with a caries detector dye (Caries Detector, Kuraray Noritake Dental) and the cavities were restored with a resin composite. After removal of carious dentin, images of the residual dentinal surfaces stained with the caries detector dye, together with color-matching stickers, were taken with a CCD camera. In addition, the dentinal surfaces were evaluated by the DIAGNOdent and their Knoop hardness numbers were measured by the Cariotester. Next, corrected L*, a* and b* values of the surfaces (CIE 1976 L*a*b* color system) were calculated from the color changes of the stickers in the images. Results: In both acute and chronic lesions, the range of the coefficient of variation of the L*, a* and b* values, DIAGNOdent values and Knoop hardness numbers of the surfaces were 14.7-95.0. Therefore, these diagnostic parameters of the surfaces vary widely. In addition, the range of the intraclass correlation coefficients of the L*, a* and b* values in both acute and chronic lesions and those of the DIAGNOdent values in acute lesions were 0.87-0.98 The range of the DIAGNOdent values in chronic lesions and those of the Knoop hardness numbers in both acute and chronic lesions were 0.42-0.65. Conclusions: The objectivity of the clinical diagnosis of carious dentin in both acute and chronic lesions was insufficient. In addition, the reproducibility of laser evaluation in acute lesions and color evaluation were very high. However, those of laser evaluation in chronic lesions and hardness evaluation were moderate.

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Purpose: Although high success rates of direct pulp capping using resin bonding systems have been reported, damage to subjacent pulp lymphocytes has never been discussed. The purpose of this study was to evaluate the effects of bonding systems on mouse spleen lymphocytes (MSL). Methods: The bonding systems used included a self-etching primer and a bonding monomer (Clearfil SE Bond, Kuraray Medical). MSL were adjusted to a 5×10⁶ (cells/ml) concentration and placed into a modified micro-centrifuge tube. Simulated pulp exposure was created on the tube lid with a 16 G needle. A drop of primer and adhesive was poured into the exposure and light-cured. A drop of saline was used as a control specimen. Reacted MSL were collected from the top, middle, and bottom (corresponding to the root apex) of each tube. The survival rates of MSL were determined by a hemacytometer. Results: The results indicated that the cell survival rate of the primer plus bonding specimen was significantly lower than that of other specimens at both the top and bottom areas (n=5, p<0.01, ANOVA). Conclusion: It is suggested that the primer used in this study may have adverse effects on lymphocytes.

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Objective: In our rapidly aging society, the prevention and treatment of oral mucosal disease is increasingly important. Diseases such as mycotic stomatitis, a mucosal disease with an increased incidence in the elderly, are of particular significance to dentistry because of the risk of fatal aspiration pneumonia in immunocompromised patients or patients with underlying disease. We have synthesized a silane coupling agent having a quaternary ammonium salt group (N-allyl-N-decyl-N-methyl-N-trimethoxysilylpropylammonium iodide or 10-I) with the aim of conferring antimicrobial properties to the surface of dental materials. The aim of this study was to investigate the antibacterial activity and minimum inhibitory concentration of this compound against oral microorganisms. Materials and methods: 10-I was added to brain heart infusion agar and blood agar at concentrations of 100, 200, 400, 600 and 800 ppm. Each plate was inoculated with a 10μl suspension of microorganisms. The lowest concentration of 10-I to inhibit growth of the microorganisms was recorded as the minimum inhibitory concentration. To test the antibacterial activity of the 10-I treated surface against Candida albicans, solutions were prepared containing 6.2×10⁷, 1.1×10⁵, or 1.1×10⁴ CFU/ml of C. albicans. Four ml of each bacterial solution was added to glass plates treated with 400 ppm of 10-I, and then cultured aerobically for 24 hours at 37℃ under shaking conditions. After incubation, the antibacterial activity was measured by counting bacteria on each plate and comparing the decrease in bacterial count between the control plates and experimental plates. Results: The minimum inhibitory concentration of Actinomyces viscosus, Fusobacterium nucleatum, Lactobacillus casei, Porphyromonas gingivalis, and Prevotella intermedia was 200 ppm, and for C. albicans, Staphylococcus aureus, and Streptococcus mutans, the minimum inhibitory concentration was 400 ppm. The antimicrobial activity of the 10-I modified surface against C. albicans decreased by 92.5% at 1.1×10⁴ CFU/ml. Conclusions: The compound 10-I exhibited antimicrobial activity against C. albicans and all oral bacteria tested. This suggests that surface treatment with 10-I could be an effective means of decreasing the incidence in elderly and immunocompromised patients of systemic diseases such as aspiration pneumonia as well as dental diseases caused by specific bacteria found in the oral cavity.

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Purpose: We previously reported the effectiveness of carbon dioxide laser for promoting bone formation. In an aging society, carbon dioxide laser therapy, which is one method of inducing new bone formation, is expected to enhance bone formation in restorative, implant, and orthodontic treatments. However, there are many unclear points regarding the use of carbon dioxide laser for the treatment of osteoporosis. This study examined the biological effects of carbon dioxide laser on bone formation based on morphological and immunohistochemical analyses in ovariectomized (OVX) and sham (Sham) rats. Methods: Twenty-week-old female Jcl/SD rats underwent bilateral ovariectomy or a sham operation under nembutal anesthesia. At 4 weeks postoperatively, rat tibias were irradiated with a carbon dioxide laser. Irradiation was performed once at 28.3 J/cm², using the right proximal tibiae as the focus point. At 1 week post-irradiation, tibiae and femurs were used for the following analyses: dual-energy X-ray absorptiometry (DEXA), soft X-ray, bone morphometry, histochemistry, and immunohistochemistry. Results: Soft X-ray images demonstrated new bone formation in the irradiated regions of OVX and Sham rats, but no clear differences were detected, whereas hematoxylin and eosin stained sections in the Sham rats showed accelerated new bone formation. In immunohistochemistry-stained sections, SOST/sclerostin protein levels showed differences in osteocytes in laser-irradiated and newly-formed bone tissues between the OVX and Sham groups. OVX rats showed an increased positive sclerostin protein level. Conclusion: These findings indicate that carbon dioxide laser irradiation was less effective for new bone formation in OVX rats than in the Sham group.

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