The mechanical properties of light-activated composites using fillers treated with various γ-MPTS concentrations were investigated. The compressive strength became maximal at 11%, while the maximal diametral tensile strength was obtained at 8%. Then, the effects of concentrations of silane agent and heat treatment temperatures of fillers were studied. Although the effect of heat treatment was small at the lowest silane concentration, the strength of composites containing fillers heated higher than 110℃ decreased with the increased silane concentrations. Based on these results, hybrid fillers were treated by varying the next three factors, i.e. the shape of the macrofiller (irregular or spherical), the volume of microfiller and the sequence of mixing (fillers were mixed before/after silane treatment). Composites containing irregular macrofiller were stronger than those containing spherical macrofiller. Composites utilizing hybrid fillers treated after mixing the microfiller and macrofiller were stronger than those treated befor mixing. Maximal compressive strength was obtained at 30% microfiller. Both compressive strength and diametral tensile strength of composites containing more than 30% microfiller were decreased with increases in microfiller volume.

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Among spherically moulded specimens of Type III gold alloy, Ag-Au-Pd alloy and Ti were combined. One was fixed at the bottom of a glass vessel and the other was gyrated freely at 240 rpm for 5 days. After gyration, metal dissolution and cell viability in the extracts and filtrates were measured. There was a difference in the dissolution of constituent metallic elements between the extracts from a combination of two specimens, but no significant difference in cell viability.Although the Cu dissolution with the Type III gold alloy combination was the largest, the amount was only 0.83 ppm. Dissolution of other elements was less than 0.1 ppm.In the combination of the two specimens, gyrating the Type III alloy had the largest effect, while gyrating Ti had the smallest effect.

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Hydroxyapatite (HAp) microcrystals were synthesized by a neutralization reaction of Ca(OH)₂ suspension and H₃PO₄ solution using an ultrasonic homogenizer. The characterizations of HAp microcrystals were investigated by XRD, SEM and electroconductivity. HAp microcrystals consisted of a single phase of HAp, dispersed homogeneously and showed a remarkable increase in the initial solubility. Effect of the solubility of HAp microcrystals on the morphology of rat peritoneaafl macrophages was investigated by cell culture test. Ca, Mg and P concentrations in the media and the intracellular Ca contents were measured and morphological changes were observed by TEM and phase-contrast microscopy. Ca concentration in media cultured with HAp microcrystals decreased rapidly, but Mg and P concentrations did not change. Macrophages actively phagocytosed HAp microcrystals and formed ruffling membranes. HAp microcrystals were dissolved inside macrophages and the intracellular Ca content increased. The higher solubility of HAp microcrystals was related to morphological changes in the macrophages.

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Effects of testing conditions;length of supports, width and thickness of specimens, crosshead speeds and polishing methods were evaluated. As a result, it was demonstrated that each testing condition except width influenced the value of bending strength in three-point loading. Values for bending strength and S.D. increased when the span of specimens was less than seven times the thickness and/or width. Values for bending strengths increased when the thickness increased, cross head speeds increased and roughness of specimens decreased.

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Acrylic soft lining materials possess good handling properties during mixing and excellent viscoelastic properties after setting. These properties after setting, however, deteriorate rapidly in the mouth, compared with those of silicone of fluoro soft lining materials. Therefore, we tried to improve the durability of acrylic soft lining materials in distilled water or artificial saliva at 37℃. The variation in viscoelastic properties of acrlyic soft lining materials with storage was markedly reduced by adding ethylmethacrylate or butylmethacrylate monomer (10〜20% in weight of conventional liquid components), and by changing the materials being photocured. Durability was evaluated in the materials, which had been immersed for 6 months in distilled water or artificial saliva at 37℃, using viscoelastic measurements or surface roughness test. The experimental soft lining materials showed considerably improvement in durability by introducing a photocuring technique.

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It is known that immersing dental stone models in disinfectant solutions is a convenient method, but surface roughness is increased by this method. Accordingly, a disinfectant solution that dose not increase the surface roughness of dental stone models is needed. Therefore, we immersed dental stone models made of six commercially available dental stones in disinfectant solutions with glutaraldehyde and sodium hypochlorite containing potassium sulfate and evaluated the surface roughness of these models. Test results indicated that surface roughness of dental stone models immeresed in 2% glutaraldehyde and 0.1% sodium hypochlorite solutions were increased. However, models immered in disinfectant solutions containing 3% potassium sulfate showed a tendency toward decreased compared to that of those immersed in solotions without potassium sulfate.

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The effect of cooling shrinkage and reheating of rubber impressions on the reproducibility of stone models were evaluated. The models were prepared using an epoxy resin mold to simulate a full crown preparation with adjacent teeth. The models were measured using a three-dimensional measuring system. Impressions made at oral temperature during setting were reheated in water at oral temperature, and the effects of reheating on the reproducibility of models were investigated. 1. Models obtained from rubber impressions set at oral temperature showed dimensional change and deformation due to cooling shrinkage of the impression. 2. Reheating of the impression improved the reproducibility of models. 3. An immersion time of 5 to 30 minutes was acceptable for reheating the impression in water at oral temperature.

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Effect of the polishing period on the between Class V cavity and light-activated glass ionomer (Fuji II LC, GC), light-activated glass ionomer analog (Dyrect, DeTrey/Dentsply) and conventionally-cured glass ionomer restorations (Fuji II, GC) was determined. Restorations were polished either immediately after setting or after 1 day immersion in water. Determination of gaps was made on axially sectioned specimens. The number of gaps for Fuji II LC and Fuji II polished after 1 day immersion in water was significantly smaller than that of those polished immediately after setting (α=0.05). In the case of Dyract, no significant difference was observed between the number of gaps in specimens polished immediately after light-activation and that of those polished after 1 day immersion in water.

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Both photo-and redox-curabilities of dual-cured composite luting cements were investigated by infrared spectroscopy. The redox initators were effectively activated in unhardened matrices. However, it was observed that uneven cure resulting from uneven photoirradiation remained after 1 day storage at 37℃. Redox reaction was limited in gelled matrices even though their degree of conversion was low. Photo-irradiation increased the degree of conversion much more in gelled matrices than redox initiators did.It was concluded that, when uneven hardening of the luting composites by photo-irradiation is suspected, photoirradiation should be conducted after polymer matrices have gelled by redox polymerization to achieve a higher and more uniform degree of conversion.

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This study explored the feasibility of creating a dentin adhesive with long-term durability and anticariogenicity by combining fluoride with methyl methacrylate-tributylborane (MMA-TBB) resin. The effect of fluoride on tensile bond strength (TBS) to dentin pretreated with 10% phosphoric acid was examined after long-term water immersion with an aqueous 2-hydroxyethyl methacrylate (HEMA) primer containing sodium fluoride and MMA-TBB resin containing calcium fluoride or fluoride-containing glass powder. While TBS in the control groups without fluoride decreased with immersion time, those in all three groups using fluoride were retained up to 1year. These results were compared with those obtained with glass ionomer cement (GIC) containing fluoride. TBS of GIC, although low, did not change significantly up to 6 months in water. Thus, there seems to be some similarity between MMA-TBB resin bonding using fluoride and the bonding of GIC containing fluoride with regard to long-term stability at the dentin interface.

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As a part of a series of studies examining the role of polymerization initator systems in dentin bonding, the effects of various factors on bonding to dentin were studied in MMA resin initiated by a 1-cyclohexyl-5-ethyl barbituric acid (CEB)/cupric acetylacetonate (CAA)/vinylbenzyltetradecyldimethylammonium chloride (VB14) system. The use of 10% phosphoric acid conditioner containing 2〜3 wt% CuCl₂ and 35 wt% 2-hydroxyethyl methacrylate (HEMA) primer was significantly effective in improving the bond strength. The mean bond strength of 12.8〜14.4 MPa obtained under optimal conditions were comparable to those obtained with MMA-TBB resin.

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The application of electrolyzed acid water has been increasing because of its excellent bactericidal activity. Unlike sterilizing chemicals, the water has an additional merit that the used water can be drained without fear of drainage contamination. Therefore the present study examined effective methods of using the water to sterilize alginate impressions on which 4×10⁵ Staphylococcus aureus were attached while the impression was taken. Only several bacteria could survive after the impression was immersed for one-minute in the water, showing practically acceptable sterilization. A completely bacteria-free impression surface was obtained by immersion for more than ten-minute or one-minute of washing followed by one-minute immersion. Thus, the water is expected to become the preferred sterilizing solution for impressions.

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The upper and lower anterior teeth of 3 beagle dogs, were raised under strictly controlled conditions, were cut using air turbine handpiece or by Er:YAG laser irradiation. Changes in the pulp and dentin of these teeth were examined histopathologically under light microscope and scanning electron microscope (SEM). Influence of cutting with Er:YAG laser irradiation on pulp was little different from the cutting with the airturbine handpiece. Cutting with Er:YAG laser formed secondary dentin in approximately one week except one specimen showed edema. No dentin degeneration was showed on the surface irradiated with Er:YAG laser except in a few specimens. The tooth surfaces cut with Er:YAG laser displayed irregularities but did not have smear layers when observed by SEM, and showed intensely stained layers approximately 9 μm thick. On the tooth surfaces after cutting with the airturbine handpiece, smear layers and strae and collagen-like fibers as well as the images that might indicate denaturation of the dentin by heat were observed.

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The purpose of this research was to characterize the in vitro early cellular behavior of osteoblast-like cells, fibroblasts, and epithelial cells on both polished and wire-type electric discharge machined titanium surfaces prepared by glow discharge treatment. XPS analyses indicated glow discharge treatment produced relatively contaminant-free surfaces and improved surface wettability dramatically. Higher levels of early cell attachment were observed on surfaces after glow discharge treatment than on those without such treatment. SEM observation of attached cells on surfaces after glow discharge treatment showed better compatibility with the surface. These results suggested glow dischage treatment was useful to obtain excellent cellular behavior on prepared titanium surfaces.

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