This study applied hydrodynamic voltammetry used a rotating ring-disk electrode to examine corrosion behavior of binary silver alloys.Rotating ring-disk electrode experiments can demonstrate on ring electrode that any soluble products that can be detected during oxidation or reduction of the disk electrode.Initially, the experimental conditions for hydrodynamic voltammetry were determined and the calibration of the experimental system was performed for the hydrodynamic voltammetry by primary study using the rotating gold ring-gold disk electrode.And then the cyclic voltammograms of gold ring-binary silver alloy disk electrodes were measured in two kinds of electrolytes;1% lactic acid and 1% sodium chloride.The results provided detailed information on the behavior of elements released from binary silver alloys.Hydrodynamic voltammetry used a rotating ring-disk electrode is useful to investigate corrosion behavior of dental alloys.

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This study was designed to further clarify the mechanisms of wet dentin bonding.MMA-TBB or 4-META/MMA-TBB resin was bonded to wet dentin demineralized by 10% citric acid(10-0)or 10% citric acid and 3% ferric chloride(10-3)for 10s and then primed with 5% 4-META in acetone for 60s.Their tensile bond strengths were measured on mini-dumbbell bonded specimens developed to examine the existence of remaining demineralized dentin which shows a defect in the bonded samples.The bond strength of MMA-TBB resin to wet 10-0etched dentin was only 5.7MPa but that of 4-META/MMA-TBB resin increased significantly to 11.9MPa.Those of MMA-TBB and 4-META/MMA-TBB resins to wet 10-3 etched dentin were 14.2 and 18.9MPa, respectively.It was concluded by tensile test and SEM examinations that the hybridized dentin prepared with 4-META/MMA-TBB resin to wet 10-3 treated dentin was excellent and provided good durability.

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Dentin bonding was studied using MMA/PMMA resin initiated by 2-methyl-1, 3-cyclohexanedione(MCHD)/cupric acetylacetonate(CAA)/vinylbenzyltetradecyldimethylammoniumchloride(VB14)system.Use of a 10% phosphoric acid conditioner containing 2〜9% FeCl_3 and 2-hydroxyethyl methacrylate(HEMA)primer was significantly effective:Mean bond strengths of 12.7〜17.6MPa were obtained under optimal conditions, which were not less than the value obtained with 4-META-MMA/TBB resin.The addition of initiator component, 1, 6-hexanediol demethacrylate, or glutaraldehyde to the HEME primer was advantageous in stabilizing bond strength.Cohesive failure occurred just above the dentin surface in tensile bond strength testing.FT-Raman spectroscopic study suggested that it was due to the increased residual monomer there, which in turn was correlated with the phenomenon that polymerization and curing of the MCHD resin was extremely delayed when a thin layer was applied.

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To investigate color differences on resin composites in an oral environment, composites were immersed in several food-simulating solutions for up to 1, 000 days and color differences were compared to the initial condition.After the immersion in solutions the specimens were dried, and their color differences were also measured.The results indicated that the reflectance of a resin matrix changed by the absorption of solutions, and caused them to change their color.By prolonged immersion in solutions the interface between filler and matrix is weakened specimens, these numerous flaws occur in the interface.In dried specimens flaws became small voids.So color differences in dried should be greater than those in wet specimens.When filler components of composites were dissolved by acidic solution, large color differences were observed.The test for transmittance of light on composites was also conducted in wet and dried specimens.These results also supported the explanations presented above.

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The author devised new bone defect fillers(BDFs).Briefly, mixtures of α-tricalcium phosphate(α-TCP)-chitosan or α-TCP-alginate with accelerator were kneaded.These materials would be an excellent filling for bone defects, because of their plastic, insoluble and easily absorbable properties.With an increased amount of α-TCP or an accelerator, both chitosan-BDF and alginate-BDF showed greater compressive stregth and the time required to solidify was shortened.The BDFs were insoluble in a saline solution and their resistance to compression gradually weakened over time in solution.The BDFs were implanted in femurs.The tissues around chitosan-BDF became moderately inflamed and the material was well absorbed and ossified including the BDF itself.Alginate-BDF also induced a slight inflammation and bone formation.However.encapsulation was seen.These two BDFs would be easily available and showed good mechanical properties.Especially, chitosan-BDF may be more promising because of its rapid ossification.

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