Purpose: Root canal filling sealer requires good operability, root canal sealing ability, and high biocompatibility with periapical tissue. However, at present, there are no sealers that satisfy these requirements. A sealer showing ideal physico-chemical characteristics and biocompatibility as a biological material, to induce proper wound healing of the periapical tissue after root canal treatment, needs to be developed. In this study, we examined the sealing abilities of a newly developed bioactive glass-based sealer (BG-based sealer) and existing sealers, and their effects on root canal dentin.

 Methods: After filling human extracted teeth by each sealer (eugenol-based, non-eugenol-based, bioceramic-based, and BG-based sealer), the sealing ability of each sealer was examined by the dye leakage test, and the sealer/dentin interface was analyzed by FE-SEM and EDX.

 Results: The amount of dye leakage of BG-based sealer was significantly less than those of the other sealers. FE-SEM analysis of the BG-based sealer and bioceramic-based sealer showed the formation of hydroxyapatite-like crystals in the dentinal tubules.

 Conclusion: The root canal sealing ability of BG-based sealer may result from the formation of hydroxyapatite-like crystals in the dentinal tubules, suggesting that BG-based sealer may be useful as a root canal filling sealer.

 Purpose: Calcium phosphate cement (CPC) is converted to hydroxyapatite (HA) as a major product and also has high biocompatibility and osteoconductivity. Thus, CPC has received considerable interest in dental and medical applications as a bone graft material. Recent studies have shown that the inclusion of fluoride (F) in hydroxyapatite enhances bone formation and causes it to be considerably less soluble than HA under an acidic physiological-like environment. Therefore, fluorapatite (FA)-forming CPC may be suitable for not only bone graft materials but also for endodontic applications such as root-end filling, perforation repair, and direct pulp capping. The purpose of this study was to investigate the in vitro properties of FA-forming CPC.

 Methods: A conventional CPC powder consisting of equimolar amounts of tetracalcium phosphate (TTCP; median particle size=4.0 μm) and dicalcium phosphate anhydrous (DCPA; median particle size=1.0 μm) was used in this study. Various amounts of sodium fluoride (NaF) powder were added to the CPC powder to obtain F/Ca molar ratios for the FA-forming CPC ranging from 0-0.4. A 0.5 mol/l phosphate (pH 5.6, P/L=2.5) solution was used as the cement liquid. The FA-forming CPC was subjected to measuring setting time (ST), diametral tensile strength (DTS), and porosity. Additionally, two types of F present in the set specimens were determined by sequential extraction: CaF₂ (1 mol/l KOH solution) and apatitic F remaining in the specimen (0.5 mol/l HClO₄). The reaction products of the samples were identified by powder X-ray diffraction. A one-way analysis of variance (ANOVA), following Tukey’s test, was performed on the ST, DTS, porosity, and F content of the hardened cement (p<0.05).

 Results: The addition of F to the cements decreased ST (14.3-16.8 min) and DTS (1.0-3.4 MPa), but increased porosity (40.7-49.0 vol%). Additionally, the amounts of F incorporated into the cement product increased with the F/Ca ratio. The ANOVA of the results revealed significant differences among the groups. A higher F/Ca ratio increased the crystallinity of the apatitic products formed.

 Conclusion: Higher crystallinities of the apatitic products formed at higher F/Ca molar ratios. Most of the FA-forming CPC used in this study exhibited valuable in vitro properties for not only bone graft materials but also for endodontic materials that require biocompatibility and osteoconductivity and also non-bioresorbability.

 Purpose: The purpose of this study was to investigate in detail the morphological changes of enamel irradiated with CO₂ laser with different wavelengths (λ: 10.6 and 9.3 μm).

 Materials and Methods: One of the specimens prepared from freshly extracted bovine teeth was irradiated by CO₂ laser with 9.3 μm wavelength (9.3-laser, experimental apparatus by Takara Belmont Corp., Japan) using three energy densities (119.0 J/cm², 158.7 J/cm², 238.1 J/cm²) for 0.1 sec. The other specimen was irradiated by CO₂ laser with 10.6 μm wavelength (10.6-laser, Bel-Laser, Takara Belmont Corp., Japan) in the same way. The morphological changes of the 9.3- and 10.6-lased enamels were examined using a scanning electron microscope (SEM). Then, the three-dimensional shapes of the 9.3- and 10.6-lased enamels were observed and analyzed using a laser scanning microscope.

 Results: Under the SEM observation, the morphological changes produced in the 9.3-lased enamel consisted of stratified morphologies like fish scales, hyaline morphologies, craters and cracks. The morphological changes were the same as those in the 10.6-lased enamel. However, the degree of morphological changes was different between the 9.3 μm-lased and 10.6 μm-lased enamels: the 9.3-lased enamel showed greater changes compared to the 10.6-lased enamel. Furthermore, cracks appeared within the irradiated area of the 9.3-lased enamel, but outside of the irradiated area of the 10.6-lased enamel.

 Conclusion: Under these experiment conditions, it was suggested that the 9.3 μm-laser irradiation demonstrated the same characteristic changes as those of 10.6-laser irradiation at the same energy density. However, the degree of morphological changes was more remarkable with the 9.3 μm-laser irradiation.

 Purpose: Er: YAG laser is often used for dental treatment as it has been shown to be excellent for preparing the hard tissues of teeth. However, it has been reported that the bond strength of composite restorations is adversely affected in dentin irradiated by Er: YAG laser compared with non-irradiated dentin. The denatured layer formed on the laser irradiated dentin surface is considered to be the cause. In this study, we examined the effect of pre-conditioning methods with clinical instruments for removing the denatured layer formed on the irradiated dentin surface, on the bond strength of composite resin for laser irradiated dentin.

 Methods: A dentin flat surface was formed on the labial side of extracted bovine lower incisors. The specimens were divided into seven groups according to the type of surface treatment given 1) non-irradiation (Control), 2) laser irradiation of 100 mJ, 10 pps (LI), 3) laser irradiation and etching with phosphoric acid (PA), 4) laser irradiation and cutting with a steel burr (RB), 5) laser irradiation and cutting with a spoon excavator (SE), 6) laser irradiation and air abrasion (AA), and 7) laser irradiation and cutting with a smart burr (SB) (n=5). An adhesive system (Clearfil Mega Bond) was applied after each pre-conditioning method following the manufacturer’s instructions. The tensile bond strengths (TBSs) were measured and data were evaluated for statistical analysis by the one-way layout ANOVA and Scheffé’s test (p<0.05).

 Results: The TBSs of the RB and AA groups were lower than those of the Control group, but no significant difference was found. The TBSs of the LI, PA, SE and SB groups were significantly lower than those of the LI group. The TBSs of the RB group were significantly higher than those of the LI, SE and SB groups.

 Conclusion: We found that the bond strength of composite resin restorations for Er: YAG laser irradiated dentin was improved by removing the denatured dentin layer with a steel burr or air abrasion.

 Objective: To develop an easily applicable oral health education program comprising saliva testing and a questionnaire survey, we investigated the usefulness of the program.

 Methods: Of the 110 guardians of children who participated in the dental health services for mother and child organized by Yokkaichi Dental Association, the subjects consisted of 75 guardians (one man and 74 women; mean age: 36.5 years) who responded to the questionnaire two months after completing the oral health education program, and 61 guardians (one man and 60 women; mean age: 37.3 years) who responded to the questionnaire and participated in saliva testing 8 months after completing the program. Saliva testing measured turbidity and hemoglobin concentration in a mouth rinse solution, and the questionnaire assessed 11 items pertaining to periodontal disease, such as subjective symptoms and oral hygiene habits. These results were plotted on a radar chart, and subjects received individual health guidance from dental hygienists.

 Results: 1. Of the subjects who had not visited a dental clinic in the past year, 11.8% and 16.7% visited a dental clinic by two and eight months, respectively, after completing the program. 2. The frequency of dental flossing increased significantly two months after completing the program (p<0.05) when compared to the frequency observed in the initial assessment; however, no difference was observed at eight months after completing the program. At two and eight months after completing the program, 50.7% and 32.8% of the subjects, respectively, showed new self-care behaviors for maintaining tooth and gingival health. 3. Turbidity and hemoglobin levels in the mouth rinse solution had decreased significantly at eight months as compared to those observed in the initial assessment (p<0.05 and p<0.01, respectively). 4. Turbidity levels in the saliva test were significantly correlated with visiting a dental clinic in subjects who had not visited a dental clinic in the past year (p<0.05), and there were many dental clinic visits in the group which showed high turbidity. Moreover, hemoglobin levels were significantly correlated with new self-care behaviors for maintaining tooth and gingival health (p<0.01), and there were many new self-care behaviors in the group which had high hemoglobin levels.

 Conclusion: These results suggest that the oral health education program combining saliva testing and a questionnaire survey may lead to increased frequency of patient visits to dental clinics and a change in self-care behavior for maintenance of tooth and gingival health.

 Purpose: Our previous studies have shown the potential effect of He-Ne laser irradiation on the proliferation activity of cancers. This study investigated the effects of He-Ne Laser irradiation with various irradiation conditions on proliferation in cultured human gingival fibroblasts and cultured human oral squamous cell carcinomas.

 Materials and Methods: The HGF-1 cell, which is a fibroblast cell line, and the H157 cell and H314 cell, which are oral squamous cell carcinomas, were used as cultured cells. The cells were irradiated with low-energy He-Ne laser with the following three different power and duration combinations: L1: 1.38 J/cm², 10 min, L2: 5.75 J/cm², 42 min, and L3: 5.75 J/cm², 10 min. L1 and L2 were irradiated at a distance of 20.2 mm; L3 was irradiated with the tip contacting at the bottom. Various cells were incubated in 24-multiwell plastic culture dishes with Dulbecco’s modified Eagle medium (D-MEM) containing 10% fetal bovine serum. After the laser irradiation, cell numbers were determined at 0, 3, 6, 12, 24, 36, 48, 72 and 120 hours, and the proliferation was examined using WST-8.

 Results: In the case of L1, regarding initial growth compared with that in the non-irradiated control, HGF-1 and H314 showed enhanced proliferation by the He-Ne laser irradiation. In the case of L2, we demonstrated that the He-Ne laser used in the present study has a potential suppressive effect on HGF-1, H157 and H314. In the case of L3, cell proliferation was significantly higher in HGF-1 and H157 on initial growth and on H314 on late growth.

 Conclusion: The present study showed that irradiation conditions are most important for the LLLT effects of He-Ne laser, and that He-Ne laser irradiation may contribute to the proliferation of various cultured cells. However, the degree of proliferation differs depending on the optimal condition of the cell.