We investigated the tendency of form change inside the cast crown using two kinds of heat treatment. We used Three-Dimensional Digitalizing System, following the manufacturer's instructions, to measure three commercially available casting alloys, Type 4 gold alloy, (Casting gold Type IV) high functional gold ally(Degunorm) and 12% Au-20% Pd-Ag-Cu(Kinpara S 12) under three conditions : casting, heat treatment solution, and age-hardening heat treatment. The following results are the displacements norted on the inside surfaces around the radiuses of the occlusal plane, at 2.0, 4.0, 6.0, and 8,O mm, and the cervical plane, and the heights, 1. Casting Gold Type 4 and Kinpara S12 showed marked displacement around the inside surfaces in terms of the radiuses and the height : the former showed the most marked displacement in terms of height. 2. All the cast crowns showed more shrinkage in the age-hardening heat treatment than the heat treatment solution in the inside surfaces.

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In this study the physical properties of low temperature ceramic fiber liners coated with polyethylene film (B-PE group) and the cushioning effect on the setting expansion of investment material were evaluated. Four B-PE group liners were used. The thickness, bulk density and density of the liners were O.66〜0.79mm, 0.866〜1.142g/cm³ and 2.085〜2.190g/cm³, respectively, The apparent rate of vacant space in the liners was 46.7〜60.2%. Water sorption of the liners entirely immersed in water for 1 min(WS-A) was 14.4〜22.5%, and water sorption after partial immersion in water for 1min(WS-B)was 2.7〜3.9%. Rate of water sorption [(WS-B/WS-A)×100] was 16.8〜21.7%. The cushioning effect of the liners seated by meeting the film side with the investment increased with time, and it reached a peak at 25〜30min, then markedly decreased by 65 min, and slightly increased afterwards, The coating of polyethy lene film reduced the cushioning effect of the liner seated by dry-liner method

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This study was conducted to investigate the basic properties and the hydrolysis of organicinorganic hybrid type filler as a new type of filler for composite resin. Organic-inorganic hybrid polymer (PMS-PS) was synthesized from poly(γ-MPTS) and polysiloxane by graft polymerization reaction, Powdered PMS-PS was prepared for PMS-PS filler. The molecular weight, the amounts of organic component and there fractive index of PMS-PS filler were analyzed and the hydrolysis was compared with that of conventional γ-MPTS treatment silicafiller. The mean molecular weights of poly(γ-MPTS) and polysiloxane were 11000 and 3200, respectively. The organic component of PMS-PS filler was 25.4wt%, and its refractive index was 1.472. Hydrolysis in the PMS-PS filler by boiling water treatment and alkaline solution treatment was lower compared to conventional γ-MPTS treatment sillca filler

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We measured the transverse strength, clastic modulus, knoop hardness, water soption and solubility of four kinds of crown and bridge resins containing high concentrations of filler (high-filler resins for crown and bridge) : Estenia (EE,ED), Artglass (AE,AD), belle Glass HP (BE,BD) and Gradia (GE,GD). All specimens were prepared according to the manufacturer's instructions. The data were analyzed usingt-test (p<0.05). Transverse strength was 96.2〜210,6MPa, EE>BE>AE>GE for enamel and BD,ED>AD>GD for dentin. Elastic modulus was 6.8〜24.6GPa, EE>AE, BE>GE for enamel and BD>ED>AD>GD fordentin. Knoop hardness ranged from 42.7 to 163.8, EE>BE>AE, GE for enamel and BD>ED>AD, GD for dentin. Water sorption was 9.7 to28.1μg/mm3, GE>AE, BE>EE forenamel and GD>AD>BD>ED fordentin, Solubility was 0.2〜0.6μg/mm^3, and there was no significant difference between enamel and dentin resins, The above results indicated that high-filler resins for crown and bridge should be used in an appropriate case or region taking their properties into account.

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We evaluated the tensile strength of denture base resin reinforced by shape memory alloy fiber. Fiber surface treatment with primer decreased the fiber-pull-out in a shape-memory-fiber reinforced denture base resin matrix composite and increased the tensile strength. We speculated that the increase in tensile strength was caused by an increase in interfacial strength between the fiber and the matrix. Since heat treatment at above 60℃ increased the composite tensile strength, this composite worked as a smartcomposite. Although there was no effect of heat treatment temperature on tensile strength, flexion of composite was observed after heat treatment at a higher temperature, suggesting that the heat treatment temperature should be lower. We speculated that the slight increase in tensile strength after heat treatment was caused by the higher martensite transformation starting temperature of the fiber.

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The effects of sand blasting and primer containing silane coupling agent on the bond strength of a CAD/CAM composite resin block and the durabillty of its bond strength were investigated. Two resin cement systems, dual curing type (Clapearl) and chemical curing type (Super bond C &B) were employed. The bond strength was determined using the compressive shear bond test : the durability was estimated changes of the bond strength before and after the thermocycl test. The bond strength improved with sand blast and primer when the dualcuring cement was employed ; however, the bond strength improved with sandblast but not with primer when the chemical curing cement was employed. The bond strength after themocycle decreased mainly due to change in the mechanical properties of the resin block. Therefore, the durability of the bond strength after proper surface treatment was acceptable.

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Fracture repair of resin base denture by shape recovery of shape memory alloy (SMA) was studied. The effectiveness of repair was estimated by changes of tensile strength and specimen dimension of SMA fiber reinforced denture base resin matrix composite before and after repair. Repaired at low temperature, the tensile strength did not decrease, but at high temperature it decreased. This decrease was possibly caused by the decrease of bonding strength between the repair resin and denture base resin. After repair at high temperature, the specimen reinforced by parent (austenite) phase fiber showed nearly no change, but that reinforced by stress induced martensite phase fibers howed shrinkage. We speculated that the shrinkage was caused by the increase of denture base resin compressive stress with fiber shrinkage and by softening of the denture base resin. The optimization of fiberproperties and repair temperature suggested that repair without change of strength and dimension is possible.

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To formulate a new dental root canal filling material with a comparatively low softening temperature, suitable fluidity and sctting characteristics, the relationships between the properties and composition of the mixture constituted by the raw guttaperchalike materials(Jelutong), bee's wax, and Japan wax, were investigated using X-ray diffractometry, differential scanning calorimetry and viscosity measurement of the mixtures. The transition temperature of the wax components lowered about 10℃ by the addition of Jelutong. The viscosity of the mixtur evaried with the composition depending upon both the inherent viscosity of each component and the change in the transition temperature. Thus, it was clarified that the thermoplasticity of the mixture consisting of a waxy component was related to the transition temperature, Viscosity and mutual compatibility of the components.

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