It has been reported that tea leaves have anticariogenic properties that can be attributed to the inherent catechin and predominant fluoride present within tea leaves. Our earlier research demonstrated that enamel and dentin lesions treated with PF-4 (partially refined green tea extract; fluoride concentration 3,900μg/g) containing an acidic buffer exhibited significantly low mineral loss. The aim of this study was to evaluate the remineralization enhancement potential of PF-4 on incipient dentin lesions in vitro. Samples were cut from bovine root dentin and a 1×3mm flat experimental window was made on each sample. The baseline subsurface lesion was made by immersing samples in a methylcellulose gel and acetic acid buffer demineralization system (1.5mmol/l CaCl₂, 0.9mmol/l KH₂PO₄, 25mmol/l acetic acid, 0.4ppm F, pH5.0). Remineralization buffers (1.5mmol/l CaCl₂, 0.9mmol/l KH₂PO₄, 130mmol/l KCl, 20mmol/l Hepes, pH7.0) containing 0, 0.025, 0.05 and 0.1 weight percent of PF-4, and 1.0ppm F as NaF were prepared. Samples were immersed in one of these remineralization buffers for 14 days at 37℃. The mineral profile, integrated mineral loss (IML) and lesion depth (LD) were analyzed by transversal microradiography. Remineralization was observed in all groups, and "hyper-remineralization" was detected in the PF-4 containing groups. The IML of the PF-4 containing groups was significantly lower than the baseline, 0%, and NaF groups. Furthermore, the IML of the PF-4 groups decreased with PF-4 concentration in a dose dependent relationship. The IML and LD of the 0.025% group were significantly lower than the NaF group, which contained the same amount of fluoride. This difference can be accounted for by the organic substrates present in PF-4. Our results suggest that PF-4 has superior remineralization potential caused by the contained fluoride and macromolecules together with calcium and phosphate in saliva.

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We have considered that decreasing the surface free energy of the tooth surface may contribute to the prevention of caries and periodontal disease. We have successfully synthesized 1H, 1H, 2H, 2H-henicosafluorododecyltriisocyanatosilane (10F2S-3I) of the silane coupling agent having a fluorocarbon chain and two novel phosphate-type hybrid surfactants sodium 1-(4-heptadeca-fluorooctylphenyl) hexylphenylphosphate (FH5) and 1-[4-(perfluorooctyl)phenyl] hexylphosphate (F8H5P). Each modifier was effective in decreasing the surface free energy of the enamel surface. In this study, we investigated the cytotoxicities of these modifying agents. The cytotoxicities of various modified agents were evaluated according to 50% inhibitory concentration (IC₅₀). The IC₅₀ value of FH5 was 75%. The IC₅₀ values of F8H5P and 10F2S-3I showed more than 100% respectively. It suggested that FH5 has slight cytotoxicitiy, and F8H5P and 10F2S-3I have no cytotoxicities.

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The aim of this study was to evaluate short-term fluoride uptake of the tooth structure using a fluoride-containing material and the effect of thermocycling on dye penetration. The materials tested included two giomers, Beautifil® and Imperva Fluoro Bond® (Shofu, BF), Reactmer® and Reactmer Bond® (Shofu, RR), a resin composite, Clearfil® ST and Clearfil® Mega Bond® (Kuraray, CM), a resinmodified glass ionomer cement, Fuji II LC Capsule® and cavity conditioner (GC, F II), and a conventional glass ionomer cement, HY-Bond Glasionomer-F® (Shofu, HY). Identical cervical cavities (5mm wide×3mm long×3mm deep) were prepared on extracted bovine teeth. Each material was used according to the manufacturer's instructions to restore five cavities for each group. The surfaces of the specimens were coated with nail varnish except for the cavity margins. Group C (control) was stored in distilled water at 37℃ for 2 weeks. Group F was immersed in 1,000ppm NaF solution for 5 minutes everyday, and thermocycled for 2,500 cycles with a 30 dwell time each in a 4℃ and 60℃ water bath. Then, all specimens were immersed in 0.2% basic fuchsin dye for 3 days and sectioned longitudinally through the center of the restoration. The sections were examined for microleakage and the superficial enamel and dentin cavity walls were analyzed for fluoride uptake using an EPMA device. The microleakage scores were determined using the dye penetration distance ratio against the total distance of the cavity. The data was statistically analyzed by the Kruskal-Wallis test and Mann-Whitney U-test (p<0.05). With the exception of HY, there was no significant difference in the dye penetration distance ratio between group C and group F. The width of the fluoride zone in HY and F II was about 200μm and RR and BF was about 90μm and 40μm, respectively. There was no significant difference in the width of fluoride uptake between group C and group F. One condition of this study, immersion in NaF solution, did not influence the width of the fluoride uptake. There was no significant difference of the fluoride uptake distance at any of the point of the cavities between group C and group F; therefore, it was recognized that the fluoride uptake to the cavity wall was not affected by the ability of restorative fluoride recharge.

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It is well known that ambient light such as room light or dental unit light hastens the polymerization of resin composite. When a cavity is complicated or large, the polymerization rate during the operating time is of particular concern. This phenomenon occurs because these light sources include the wavelengths that cure photo-polymerized resin composite. Of these two ambient light sources, dental unit light seems to have a larger influence because of its strong intensity. This study examined the influence of dental unit light on the polymerization rate of light-cured composites. The optical characteristics of dental light used in our department were measured, and the operating time for three kinds of resin composite was measured under the light of a typical unit used in our dental office. The results were as follows: 1. The illumination of dental light was 2 to 3 times the ISO standard. 2. Dental light included the wavelength band related to resin polymerization. 3. The operating time of rein composites used was remarkably shortened under dental light.

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This study examined how polishing after office-whitening influences the surface properties of enamel. On the labial surface of bovine enamel, flat surfaces were prepared by successive use of SiC papers, then one half of the surface was treated by a 35% hydrogen-based office-whitening agents without polishing (control group), and the other half was treated with the same whitening agents followed by surface polishing (polished group). Three different polishing pastes composed of three different sizes of abrasive were used for the polishing. Polishing was done immediately after whitening once a week up to 4 weeks. Before and after whitening with and without polishing, surface roughness (Ra) was determined (n=5) and morphological change was observed by a scanning electron microscopy (SEM). The results were as follows: 1. Without polishing no change was found in the surface roughness of enamel after whitening at every measuring period. With polishing, however, the surface roughness of enamel changed depending on the type of paste and the methods of using pastes. 2. SEM images demonstrated that the smear layer on the enamel had been removed after whitening and the morphology varied depending on the type of paste and the methods of using pastes.

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In recent years, dental pulp stem cells, which can differentiate into odontoblast-like cells secreting a reparative dentin matrix, have received much attention. If an extracted tooth is preserved, the pulp cells can be used in the future. This study investigated how cryopreservation affects the characteristics of pulp cells using a Cell Alive System (CAS)-programmed freezer® in comparison with -80℃ cryopreservation. The mandibles of two 5-week-old male rats and those of six rats were soaked in α-MEM medium and cellbanker-1® respectively, preserved by CAS-programmed freezer® for one month, and then thawed in a water bath at 37℃. The pulp tissues were removed from the extracted incisors and digested at 37℃ in a sterile enzyme solution containing collagenase, trypsin and EDTA to obtain a single-cell suspension, and incubated in α-MEM medium supplemented with 10% fetal bovine serum at 37℃ in a humidified atmosphere supplemented with 5% CO₂. Cell viability was measured by trypan blue staining. After 1 week, the cells were seeded into 12-well plates (4×10⁴/well) in the medium with 300μg/ml β-glycerophosphate and 50μg/ml ascorbic acid. After 7 and 14 days, total RNA was extracted from the pulp cells and converted to cDNA for RT-PCR, and the expressions of Dspp, osteocalcin and TGF-β1 gene were detected. The structures of the cells were observed immunologically under a confocal laser scanning microscope using goat polyclonal antibody against a peptide of actin of human origin. Control mandibles were subjected to -80℃ cryopreservation. The viability rates of pulp cells in α-MEM medium and cellbanker-1® by CAS-programmed freezer® were 3% and 22%, and that in cellbanker-1® by -80℃ cryopreservation was 7%. The expressions of Dspp, osteocalcin and TGF-β1 gene were detected in the pulp cells in the medium with β-glycerophosphate and ascorbic acid after freezing in cellbanker-1® by CAS-programmed freezer®. Confocal laser scanning microscope observation of immunolocalization of actin showed that the cell membrane was preserved after freezing in cellbanker-1® by CAS-programmed freezer® These results suggest that cryopreservation of pulp cells by CAS-programmed freezer® shows higher cell viability and advantages for future application compared with -80℃ cryopreservation. The preservation liquid used for freezing plays an important role and affects the condition of cells.

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MMA-based resin cements, composite resin cements and self-adhesive resin cements are widely used in clinical dentistry. This study evaluated the bonding properties of resin cements by measuring the tensile bond strength (TBS) to various adherends, such as enamel, dentin, Au-Ag-Pd alloy and ceramic. Super Bond C & B® (SB, Sun Medical) and Multi bond II (MB, Tokuyama Dental) were used as MMA-based resin cements. ResiCem (RC, Shofu) and Panavia® F2.0 (PF, Kuraray Medical) were employed as composite resin cements. RelyX™ Unicem Cliker™ (UC, 3M ESPE), Clearfil® SA luting (SL, Kuraray Medical) and Maxcem (MC, Kerr) were used as self-adhesive resin cements. The facial surface of bovine incisors was ground with wet SiC paper up to 600 grit to prepare the enamel and dentin surfaces. Au-Ag-Pd alloy and a ceramic block were sand-blasted by Al_2O_3 particles. A composite resin block was fabricated by Clearfil® CR Inlay (Kuraray Medical) and adhered with the cements to various adherends according to the manufacturer's instructions. TBS was determined after storage for 24 hours in water at 37℃ (n=8). The data was analyzed by one-way ANOVA and Tukey's test (α=5%). TBS with the self-adhesive resin cements tended to be significantly lower than those with the cements based on composite resin and MMA. Although the self-adhesive resin cements were easy to handle because no pre-treatment was necessary, the lower TBS values may endanger their clinical performance.

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Dental caries are manifestations of a disease caused by acid-producing bacteria in the oral cavity. They have also been elucidated as an endogenous disease caused by cariogenic bacteria, typified by Streptococcus mutans. Caries prevention is currently done by applying fluoride, which is intended to enhance the tooth structure of hosts as a preventive measure. Aside from this countermeasure, however, no effective caries prevention measure is widely used. Recently, various studies have been conducted on ways of reducing the morbidity rates of dental caries, and to prevent them. Various agents for oral use, as well as foods and beverages which have caries-prevention effects, have been created. Anthocyanin, a kind of flavonoid, is a pigment used as a food additive. It is of vegetable origin and is reported to have antioxidant effects, anti-hepatotoxic effects, and curative properties for optic nerve dysfunction and arterial sclerosis. In this study, we examined nasunin, a polyphenol included in the skin of eggplant and which is included among pigments of the anthocyanin family. This study investigated, using in vitro experiments, whether nasunin, belonging to delphinine-type anthocyanins, can prevent caries through its antibacterial effect. The following conclusions were obtained. 1. The minimum inhibitory concentration against S. mutans was revealed to be 500μg/ml. 2. The minimum inhibitory concentration against Streptococcus sobrinus was revealed to be 250μg/ml. 3. The minimum inhibitory concentration against Actinomyces viscosus was revealed to be 500μg/ml. 4. The antibacterial activities were found to be a bactericidal effect against resting cells of S. mutans, S. sobrinus and A. viscosus. 5. Nasunin considerably inhibited sucrose-dependent water insoluble glucan synthesis activity of crude glucosyltransferase produced by S. mutans PS-14 and S. sobrinus 6715. From the above, nasunin was found to have a prominent bactericidal effect against cariogenic bacteria, suggesting that it has anticariogenic effects.

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A cotton pellet soaked with a disinfectant solution under hydraulic sealing cement is expected to maintain aseptic conditions in the pulp chamber during root canal treatment. However, a disinfectant solution might hinder the setting of the hydraulic sealing cement. A soft cement is likely to be worn and consequently collapse, and leakage will cause contamination of the pulp chamber. The aim of this study was to examine the effect of disinfectant solutions on the setting of hydraulic sealing cement. One hundred pulp chamber models were made with polyethylene terephthalate tubing. Fifty of them were filled with hydraulic sealing cement (Caviton®, GC). The remainder were divided into five groups and each model was filled with a cotton pellet soaked with one of the following; Group A: 6% sodium hypochlorite (Jiaen 6% "Yoshida", Yoshida Pharmaceutical), Group B: 83% ethanol and 3.7% isopropanol (Medialcotto ME-S, Hakujuji), Group C: Calcium hydroxide (Calcipex® II, Nippon Shika Yakuhin Kogyo), Group D: Distilled water, and Group E: no solution as the control. For Group C, calcium hydroxide was sealed without a cotton pellet. Each was joined to a tube filled with Caviton® and covered with utility wax except for the surface of Caviton®. They were kept in 37℃ water for 3 days. The surfaces of Caviton® were polished with water-resident paper #2,000. The penetration depth of the measurement needle from the surface to the test material was measured by a texture analyzer (EZ-TEST, Shimadzu). Statistical analysis was performed using a one-way ANOVA and Tukey-Kramer test with 0.05 confidence. The penetration depth of Groups C and E were significantly longer than Group D. There were no statistically significant differences among A, B and D. The results suggested that a cotton pellet soaked with 6% sodium hypochlorite, 83% ethanol or distilled water in the pulp chamber may increase the setting of Caviton® in the deep layer compared with a dry one.

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It is well known that mechanical forces have beneficial effects on bone regeneration after implant and periodontal treatment. Recently, LIPUS (Low-intensity Pulsed Ultrasound) treatment, which is one method of inducing mechanical force, has been shown to facilitate repair of bone defects, because ultrasound can not only provide good stimulus for bone formation, but also induce the differentiation of osteoblasts. However, cellular events induced in bone cells by LIPUS have not yet been clarified. This study examined the biological effects of LIPUS on bone remodeling in bone defects using morphological and immunohistochemical analyses. Female SD rats were used in the experiment. Bone defects were created in the tibiae by mechanical drilling using dental burs. Then LIPUS irradiation was repeatedly applied 24hrs post-operatively. The left tibiae (LIPUS groups) were treated daily with 15min of LIPUS (1.0MHz, 0.24W) for 1, 2, 3, and 4 weeks, and the right tibiae (control group) were treated without LIPUS. The tibiae were used for the following analyses; three-point bending test, dual energy X-ray absorptiometry (DEXA), soft X-ray, bone morphometry, and histochemistry. Soft X-ray pictures demonstrated a greater amount of new bone formation in the bone defect regions in the LIPUS groups than in the control groups 2 and 3 weeks post-operatively. The tibiae in the LIPUS group were stiffer than those in the control group on the three-point bending test 2 weeks post-operatively, but there were no significant differences BMD between the control and LIPUS groups in DEXA analysis during all experimental periods. On H-E stained sections, the thickness of the cortical bone in the defect region of the LIPUS groups was greater than that in the control groups 2, 3 and 4 weeks post-operatively. Bone morphometric analysis using calcein labeling in the bone defect regions demonstrated that the mineral apposition rate in the LIPUS group was twice that in the control group. The anti-osteopontin antibody was localized in osteoblasts and osteocytes in the newly formed bone tissues in the bone defect regions, and there were no differences in the distribution of bone tissues in the defect regions between the LIPUS and control groups. These findings indicate that LIPUS stimulates osteoblast in periosteum to form bone matrix, and suggests that the repair process in bone defects was accelerated by LIPUS as a result of stimulating bone formation in the cortical bone.

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The aim of this study was to evaluate the coupling effect of silanes by adding an acid catalyst and prolonging the elapsed silanization reaction period (5min-14 days). The coupling agents used were 3-methacryloyloxy-propyltrimethoxysilane (3-MPS), nonafluorohexyltrimethoxysilane (4F), 3-{[(1'-perfluoro-3-methylbucyl)methyl-2'-(methacryloyloxy)]-ethoxy} propyltrimethoxysilane (MA5bF), and 3-{[(1'-perfluoro-9-methyldecyl)methyl-2'-(methacryloyloxy)]-ethoxy} propyltrimethoxysilane (MA11bF). MA5bF and MA11bF contain a hydrophobic fluoroalkyl and a methacryloyl group in each molecule. The concentration of each silane solution was adjusted with ethanol to 2 mass%. In addition, 10vol% acetic acid was added to each silane as a catalyst, i.e. 3-MPS-Acid, a mixture of 3-MPS and 4F (4F/3-MPS)-Acid, MA5bF-Acid and MA11bF-Acid. The eight silane solutions were applied to glass plates and were stored for 5 minutes, 60 minutes, and 1, 2, 7, and 14 days in a constant temperature and humidity chamber. After the storage periods, the contact angle of the resin monomer mixture to the glass plates modified with each silane solution was measured. Using the same storage periods, a chemically cured resin composite was bonded to the silanized glass plates. Bonded specimens were divided into two groups; one group was stored in distilled water for 7 days at 37℃, and the other group was thermally stressed for 10,000 cycles. The specimens were then subjected to the tensile bond strength test. The 3-MPS group had a lower contact angle after 2 days, and a higher tensile bond strength after 5 minutes, while the 3-MPS-Acid group had a higher contact angle and a lower tensile bond strength at the same points in time. The 4F/3-MPS group had a lower contact angle after 2 days and a significantly higher tensile bond strength after water storage or thermal stress compared with the 5-minute bonded group, regardless of whether the acid catalyst was present. MA5bF and MA11bF had contact angles that decreased as the elapsed period increased, and the MA5bF-Acid and MA11bF-Acid groups both had higher bond strengths after 1 day and 2 days storage than 5 minutes of storage. In particular, the bond strength of the MA5bF group after 7 days was significantly higher than that of the 3-MPS group after storage in water or following thermal stress, and cohesive failure was observed on the resin composite or glass surface. In case of modification with higher formula weight silane coupling agents, it has been shown that prolonging the elapsed time produces better wettability and higher tensile bond strength rather than adding an acid catalyst.

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The purpose of this study was to evaluate the clinical healing effects of the calcium hydroxide preparation "Calvital®" on refractory apical periodontitis. Refractory apical periodontitis cases can be divided into apical periodontitis associated with procedural accidents and true apical periodontitis caused by a bacterial biofilm. In this study, we describe interesting results obtained when using the calcium hydroxide preparation "Calvital®" for root canal treatment in patients diagnosed with refractory apical periodontitis. A total of 100 patients diagnosed with refractory apical periodontitis by local dentists were referred to the General Dentistry Department of Tokyo Dental College, Suidobashi Hospital. In these patients, Calvital® was applied for root canal treatment at 1-month intervals starting at week 2 and the course was observed. Symptoms disappeared in 91 of the 100 subjects, while the symptoms were alleviated but did not disappear in 9 patients. Of these, 3 patients underwent surgical treatment, and 6 patients were diagnosed with neurogenic pain. The symptoms disappeared or were alleviated in 91% of patients. The action of calcium hydroxide seemed to be effective for healing the wound and bacterial biofilm on the outside of the root apex. A change in the root canal environment by long-term application of a potent alkaline agent in patients with true refractory disease could be responsible for the observed pharmacological effects. From these findings, it is suggested that the application of Calvital® in patients with refractory apical periodontitis is useful in refractory root canal treatment.

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