The relation between monomers eluted from resin systems and cytotoxicities was investigated by cell culture tests.L-cells in 3ml of Eagle's MEM supplemented with 10% FCS were cultured to confluent sheaths in a tissue culture dish.Primers, bonding agents and composite resins filled in glass tubes were immersed in the center of the tissue culture medium.After 24 hours cultivation, cytotoxicities were evaluated, and the amounts of monomers eluted into the medium were measured by high-performance liquid chromatography.The following results were obtained.The primers, uncured bonding agents and composite resins showed intensive cytotoxicity.However, the cytotoxicities of bonding agents and composite resins were decreased as the light illumination time increased.Adequately cured bonding agents and composite resins showed less or no cytotoxicity.However, small amounts of monomers were detected.L-929 cells were stimulated by HEMA and TEGDMA released from resins.

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The amount of monomers leached in extract with acetone from visible light-activated Bis-GMA-based composite resins was determined by means of liquid chromatography analysis to investigate the volume of leachable unreacted components in cured resins at several depths.The specimens of composite resins were cured under conditions that simulated specific levels(depth of 0, 1, 2 and 3mm)under the surface of restoration.The amount of leached monomers significantly increased with depth.Prolonged exposure duration(80 seconds exposure)decreased the amount of leached monomers.Leaching of TEGDMA was significantyl greater than that of Bis-GMA at greater depths.The results of this study suggested that there is a relatively large amount of unreacted monomer in the cured composites, and the monomer would have the potential of leaching into the oral environment.

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The purpose of this study was to detect the effects of additives in gypsum products and hydrocolloid impression materials, which tend to retard the setting of gypsums, on the compatibility of gypsum with hydrocolloid impressions.A type IV gypsum powder was mixed with the solutions of 0.03% sodium citrate, 0.3% borax and 0.5% sodium phosphate, and poured into agar, agar/alginate combined and alginate impressions.Surface roughnesses(Ra)of the stone models were measured.The stone surfaces were also observed with a scanning electron microscope.Mixing with sodium citrate increased the Ra in large for the stone models obtained from the agar impression, though it only slightly affected stone models obtained from other impressions.Borax was the main cause of the incompatibility of gypsum with agar and agar/alginate combined impressions.Sodium phosphate increased the Ra of models obtained from the alginate impression.

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An experimental alloy was developed with an increased Cu content compared to that in commercial Ag-Pd-Cu-Au type alloy as well as a smaller amount of Zn for deoxidation.Another experimental alloy with a higher Cu content and without Zn was also made.Various heat treatments were carried out on these two experimental alloys.Tensile and static three-point bending fracture toughness tests were then carried out on these heat-treated alloys.The effects of Cu and Zn on static fracture characteristics were investigated based on these test results.The 0.2% proof stress decreased due to the volume fraction of the α_1 phase in the higher copper content alloy while the tensile strength increased due to the increase in work hardening.The alloy with Zn exhibited greater strength and smaller ductility compared to the alloy without Zn.Static fracture toughness values were increased in the alloy with higher Cu content when a higher solutionizing temperature was used.Static fracture toughness values of alloy without Zn were decreased compared to those of the alloy with Zn.The tensile strength and static fracture toughness values of these experimental alloys tended to increase with increase in the solutionizing and aging temperature except in some cases, while elongation tended to decrease.The mechanical properties of both experimental alloys are equivalent to or greater than those of the commercial alloy.The experimental alloy with higher Cu content and smaller Zn content exhibited the greatest values of tensile strength and static fracture toughness.The experimental alloy without Zn seemed to have superior workability because its ductility was relatively greater.

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Leaching of monomers from four different types of chemically-activated direct relining materials was determined by means of high-performance liquid chromatography.Disk-shaped specimens(10mm diameter and 1mm thickness)of the cured relining materials were immersed in distilled water at 37℃ for 1 day, 1 week, 2 weeks, 3 weeks, 1 month and 2 months.Leaching of monomers into the water proceeded rapidly for the first week, and then declined to lower rates.Lower amounts of monomer leaching were still observed after immersion in water for 2 months.The results of this study suggested that monomer composition of the relining materials affects the behavior of monomer leaching in an oral environment.

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To develop a casting alloy with magnetics, three kinds of binary alloy were prepared as high-carat precious alloy, 72wt% Au-Cu, 75wt% Au-Fe, 40wt% Pd-Co by weight percent.All of these alloys could be fused by gas/oxygen flame.The Pd-Co alloy has the most homogeneous structure in a solid solution and a 182.5gf attractive force.It also showed the highest corrosion resistance in NaCl sol.and 12.7μg of Co ion/cm^2 was dissolved into the NaCl sol.at 37℃ for 7 days.It seems that there are some advantages in using a casting alloy with magnetics, but there were no precious metals, Au or Pd, detected in NaCl sol.from any of these alloys.

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