Methacryloyloxy aliphatic carboxylic acid(MAC)with different methylene chain lengths were designed as primers.The effects of the methylene number in the MAC molecule on the strength of interaction between MAC and dentinal collagen, and on the bond strength of resin to acid-etched dentin were examined. The carboxylic acid and ester group in the MAC molecule interacted with dentinal collagen.The carboxylic acid group in the MAC molecule formed a stronger interraction with dentinal collagen than the ester group.The application of thermocycling decreased the strength of resin bond to etched dentin treated with MAC primer.However, the decrease in the bond strength to etched dentin primed with O-methacryloyl glycolic acid (MGA)was lower than that obtained with 3-methacryloyloxy propionic acid(MPA).This was due to the fact that MGA formed a stronger interaction with dentinal collagen than MPA.

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We examined the thermal properties of six kinds of denture lining resins composed of methylmethacrylate resin (PM lining resin)and two kinds of denture lining resins composed of sulfone resin (PS lining resin). GC Acron (GA, control)was cured by hearting, Polysulfone pink (PP, control) was made from hardened cylindrical rtesin, GC Rebaron LC was cured by visible light and others were self-cured by mixing the powder and liquid under manufacturers′instructions. The size of specimens was φ10×1mm. Thermal properties were measured by TC-2000L (Shinku-riko), and thermal conductivity was calculated. Tehrmal conductivity (W/mk)of GA was 0.151 and those of PM lining resins ranged from 0.134 to 0.149. PP showed 0.160 and PS lining resins showed 0.132 and 0.141. There were no significant differences between control and denture lining materials (except one of the PS lining resins) by t-test (p<0.05)

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The cushioning effects of wet casting ring liners on the setting expansion of investment materials were evaluated by the cushioning ability in 15 wet ceramic liners (A:rockwool type, B:ceramic fiber low temperature type, C:ceramic fiber standard type, D:ceramic fiber low temperature standard type, E:kaolin type)and 3 wet asbestos ribbons (AS).Wet liners were seated inside the sliding frame of an appratus for expansion measurement, and then the setting expansion was measured for 120min.Cushioning effects were calculated by the difference between the setting expansion without liner and the setting expansion with liner. The cushioning effects of wet liners were classified into three groups.(1) No cushioning effect of wet liners in group A and one product in group D, where the filling rate of water in the vacant space of the liner was high.(2)Good cushioning effect of wet liners in group E and AS, where the filling rate of water was high.(3)Good cushioning effect of wet liners in group B, C and D (except for one product), where the filling rate of water was low.

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If strong acidic electrolyzed (SAE)water is used to clean full denture, the denture base resin should not affect the properties of the SAE water.In this study, pH, oxidation-reduction potential(ORP)and residual chlorine concentration of SAE water were determined after dipping denture base resin into SAE water. Also, the pH, ORP and residual chlorine concentration of SAE water were measured by adding saliva protein into SAE water. The pH, ORP and residual chlorine concentration of SAE water were not changed by dipping of denture base resin into SAE water.However, pH of SAE water was significantly increased, while ORP and residual chlorine concentration of SAE water were significantly decreased by adding saliva protein into SAE water.These results suggested that denture plaque control by SAE water is possible if the saliva, food debris and such materials are removed from the denture surface before applying SAE water to the denture.

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Using electron spin resonance spectroscopy, we investigated whether the active oxygen that bears the sterilization action of strong acidic electrolyzed water receives the influence by resin or not. Also, we examined whether the active oxygen species receive the influence by the saliva protein.The active oxygen species were examined by spin trap method using 5.5-demethyl-1-pyrroline-N-oxide(DMPO)and ferrous sulfate. The characteristic spectrum pattern that is derived from DMPO-OH from strong acidic electrolyzed water was observed.DMPO-OH was not affected by dipping resin.DMPO-OH of the strong acidic electrolyzed water that contained the saliva protein showed a decrease in comparison with control and was in density reliance nature.These results suggest that the effect of strong acidic electrolyzed water decreases if plaque and saliva that are adhering to the denture base are not washed mechanically before strong acidic electrolyzed water is applied to for denture plaqaue control.

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This study investigated method of measuring the change in the degree of polymerization (DP) of resin-modified glass ionomer (RMGI) cements by Raman spectroscopic analysis.External and internal standard methods were attempted.DP was calculated from the intensity of C=C stretching vibration divided by those of several reference bands in the Raman spectra. A benzene ring breathing vibration in the external standard method and the C=O stretching vibration in the internal standard method were both unsuitable as the reference band.With an internal standard method using the CH₂ scissoring vibration, it was possible to correct the DP value with a correction DP formula.DP of VM showed 100% immediate after light exposure, while DP of LC attained to 100% in 4 weeks.Therefore, the method is demonstrated useful to measure DP of the resin component in RMGI cement liquid.

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Recently, titanium-tantalum alloys have been studied as implant materials for dental and orthopedic surgery. For alloys used in a living body, it is essential to have biological characteristic such as being nontoxic and compatible with living tissue and dynamic characteristics such as high durability. It is well known that titanium and tantalum are difficult to use in alloys made in the more common melting furnaces, which are arc melting and induction melting, because titanium and tantalum have great differences in melting points and density (Ti:1, 680℃/4.5g/cm³, Ta:2, 990℃/16.6g/cm³).In addition, titanium and tantalum are very reactive metals. To make a Ti 85wt%-Ta 15wt% binary alloy, the Cold Crucible Levitation Melting (CCLM) method which is one of the induction melting furnaces is good for making this type composition. The CCLM apparatus consists of a water-cooled crucible made from oxygen-free high purity copper segments and coil wrapped around the crucible and connected toa frequency inverter power supply. We have successfully made 1.0kg of uniform composite Ti 85wt%-Ta 15wt% binary alloy with the CCLM furnace. This result shows that the CCLM furnace is very useful for obtaining a Ti-Ta binary alloy despite the great difference in specific gravity.

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Two type of poly (lactic acid)(PLA)/copoly (ethylene sebacate/hexamethylenesebacate) block polymer and their composites blended with 10% and 30% calcium phosphate, and poly (latic acid) as a control were examined for their degradability in vitro.The film samples were immersed in a phosphate buffer solution (pH7.4) at 37℃ for up to one year and changes in water absorption, tensile strength, molecular weight, and thermal properties of the films were followed over time. The changes in these properties varied with type of the block polymers and calcium phosphate content in the composites. Degradation of the polymers tended to be accelerated with increases in the content of the copolysebacate and to be retarded with increases in the calcium phosphate content.DSC analysis of the films revealed that crystallization of the polymers was involved in degradation.The present study suggested that preparation of various materials having different degradability is feasible by varying the PLA and copolysebacate ratio in the block polymer and by blending calcium phosphate with the block polymer.

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Octacalcium phosphate (OCP) setting for dental applications was prepared by mixing monocalcium phosphate monohydrate and calcium carbonate with sodium hydrogen phosphate buffer (pH=7.4). The OCP setting was improved in its mechanical properties by the addition 0f α-tricalcium phosphate (α-TCP). The setting with 69.0nass% α-TCP had a maximal compressive strength of 12.0MPa which was about 7 times higher than that of the α-TCP free setting at 7 days after mixing. Based on the data shown by SEM, the significant improvement was attributed to both the decreasing porosity induced by the increase in direct connection between the grains and the uniformity in its microstructure. The OCP setting with 69.0 mass% α-TCP transformed into brushite (DCPD) 1 day after mixing in simulated body fluid, and changed into the OCP and HAp at 6 weeks after mixing. The OCP setting with 69.0 mass% α-TCP was suggestted to be applicable to endodontic treatment in dentistry.

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Properties of new gypsum-bonded investments for the quick heating method which could be heated at 20 minutes after the start of mixing were evaluated.The setting reaction of these investments was faster than that of gypsum-bonded investments used in the quick heating method heating at 30 minutes after mixing ; however, the setting expansion continuously increased for more than 20 minutes after tha start of mixing when the investment could be placed into a furnace for heating. Obvious casting defects were observed when the new investments were employed. Dimensional accuracies of castings obtained from these investments were stable with changes in the timing of mold heating up to 60 minutes after the start of mixing ; however, casting demensional accuracies were slightly greater than that obtained from a conventional gypsum-bonded investment. The surface roughness of castings obtained from the new investment was not significantly different from that obtained from the conventional gypsum-bonded investments.

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The purpose of this study was to improve surface wettability on titanium by glow discharge treatment. In our previous study, we observed early cell attachment treated by the experimental device of glow discharge treatment. However, we could not examine the treatment condition of this treatment. Therefore, in this study, we developed the new device of glow discharge treatment to decide the treatment condition of improving surface wettability. In addition, we investigated the protein attachment and sterilization of titanium surfaces prepared by glow discharge treatment. The improving wettability depended hearvily on an electric current of this treatment.Higher level of protein attachment was observed on the surfaces after treatment. Furthermore completely sterilization was observed on the titanium plates with glow discharge treatment. These results suggested glow discharge treatment was useful to obtain excellent biocompatibility for titanium.

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To modify the properties of PMMA/MMA-TBB resin cement, I investigated the influences of PMMA with different powder characteristics on the properties of the resin cement such as setting time, working time, and cement film thickness. The cement properties were influenced by molecular weight, molecular weight distribution, particle size and shape of the powders. Among these factors, molecular weight distribution was suggested to be especially important. Pulverizing the spherical PMMA powders provided some variations in the cement properties but these variations were limited. However, the pulverized powders blended with small PMMA beads were effective in increasing working time and minimizing film thickness over prolonged period.Thus, this type of the PMMA blend was suggested to make a useful MMA-TBB resin cement with good adhesiveness to dentin, improved working property, reduced upheaving, and easy removability of excess.

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This study investigated the effect of coating on the mechanical properties of glass ionomer materials. Two brands of each conventional glass ionomer cement (Fuji IONOMER TYPE II, GLASIONOMER-F), light-cured glass ionomer cement (Fuji IONOMER TYPE II LC, Vitremer), or glass ionomer-modified composite (compomer)(Xeno, Dyract) were tested. A commercial light-cured coating agent (BELLFEEL BRIGHTENER II)was used to coat the cement specimens. Brinell hardness number and the 3-point flexural strengths of specimens with or without coating were determined at 24 hours and 1 week after specimen preparation. When applied to the conventional glass ionomer cements. coating significantly(p<0.05) increased the hardness values. For all the materials tested, except for Dyract, the flexural strengths of the specimens with coating were significantly greater than without coating. Coating appeared to effectively improve the mechanical properties of the conventional glass ionomer cements.

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This study evaluated the pressure behavior of both the casting chamber and the cavity in the mold using an enclosed one-chamber casting unit. An experimental device with a pressure sensor modeled on the casting system was attached to the casting unit. The chamber pressure rose rapidly and reached half of the preset casting pressure within 0.2s after introducing argon gas into the chamber. Both the preset casting pressure and the gas permeability in the mold strongly influenced the differential pressure between the chamber and the cavity. When a mold with a high level of rising pressure in the cavity, i.e.a mold with higher gas permeability, was used, a large quantity of argon gas penetrated the cavity through the mold wall before the cavity was filled by the molten metal. For this reason, it was thought that some casting defects, such as incomplete casting or gas inclusion, often occur. This study showed that it is desirable to use a mold with lower gas permeability in an enclosed one-chamber casting unit.

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In order to reduce the dental casting procedure time, application of a high frequency induction heating method using a coil-shaped soft iron wire was investigated for reduction of mold heating time. The temperature of the center of a mold made from a gypsum-bonded investment for the quick heating method reached 700℃ after 8 minutes at 1.1kW output and 9 minutes at 1.8kW output of the high frequency induction heating. There was no casting fin on the casting obtained from the mold heated after 8 minutes at 1.1kW output and 8 minutes at 1.8kW output ; however, contamination of the investment was observed on the casting surface. This contamination was improved when the mold was heated for 8 minutes at 1.1kW output and 6 minutes at 1.8kW output. The size of casting obtained from the mold by the high frequency induction heating was larger in the long axis direction of the casting ring and smaller in the ring diameter direction compared to that of the wax pattern. This phenomenon was suposed to be resposible for the existence of the coil wire inside the mold. The accuracy of casting must be improved ; however, dental casting could be obtained within 14 minutes after the start of investment mixing using this high frequency induction heating method.

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