Polyfunctional silanes were synthesized and their effects on surface treatment were investigated to develop silane coupling agents that have more durability. The contact angle of water and the tensile strength of poly(Bis-GMA)against the silica plate surface treated with several kinds of polyfunctional silanes increased with the number of silicone functional groups in the silane and also with the concentration of the silane. The adsorption behavior was investigated in the silica surface treated with polyfunctional silanes and washed with methyl ethyl ketone. A decrease in the contact angle of water was observed with washing as a result of the desorption of the silane, and this decrease was inversly related to number of silicone functional groups. It is concluded that polyfunctional silanes were highly effective for silica surface treatment.

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The dimensional changes of three types of alginate impression materials in various concentrated solutions of the viral disinfectants (sodium hypochlorite, glutaraldehyde, irgasan DP300 wash liquid, irgasan DP 300 soapy water and ethanol) were examined by a non-pressure method using an electronic micrometer, and the optimal immersion time in effective concentrations was determined with respect to the dimensional stability of alginate impression materials. The expansion of alginate impression materials decreased with the increase in the disinfectant concentration of the solution. The relation between the concentration of disinfectant and dimensional changes of alginate impression materials was liner in the solutions except with sodium hypochlorite at concentrations over 1%. The results suggested that the optimal immersion time for alginate impression materials within a clinically acceptable range of dimensional (0±0.2%) was about 5 minutes in 0.5〜2% sodium hypochlorite solution, about 60 minutes in glutaraldehyde solution at 5% for a high-expanded material in water and at 2% for a low-expanded material in water, about 15 minutes in irgasan DP 300 wash liquid at 5% for the high-expanded material, about 15〜60 minutes in other materials, and about 15 minutes in irgasan DP 300 soapy water of undiluted solution.

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Fourteen commercial dental precious metal casting alloys were immersed in three kinds of solution;Ringers, 1% lactic acid, and 0.05% hydrochloric acid, for 7 days at 37℃.Quantitative analysis of released metal elements was performed by inductively coupled plasma emission spectrometry.The results indicated that high gold content alloys also released copper elements.Corrosion resistance of alloys containing an excess of 24% palladium was comparable to that of gold alloys.Total released metal elements for indium-silver alloy were less than those for coppersilver alloy and tin-silver alloy.Precious metal system alloys were found to be superior to chromium-nickel system alloys in corrosion resistance.

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Nine kinds of Ag-Pd-Cu ternary alloys having compositions of 20, 25 and 30wt% Pd, 10, 15 and 20wt% Cu and Ag were melted and casted.After softening and hardening heat treatments of the alloys, their mechanical properties and tarnishing resistance were investigated.After softening heat treatment of the experimental alloys, the tensile strengths ranged from 39〜48kgf/mm², while after hardening heat treatment, they ranged from 69〜91 kgf/mm², being proportional to the Pd content increase, and the composition showing the maximum tensile strength was about 52〜54wt% Ag, 30wt% Pd and 16〜18wt% Cu with both softening and hardening heat treatments.The specimens immersed in 0.1% sodium sulfide solution at 37℃ for 3 days showed brightness(L^*)distributed in the range of 63〜67 and their tarnishing resistance was hardly improved with the increase in the Pd content.Segregation in the castings was less than that with the Ag-Pd-Cu alloy containing Zn, but local segregation of the Ag-Cu(-Pd)phase was observed depending on the alloy.

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Abrasion resistance of nine kinds of hard resins for crown and bridge works was compared to understand their characteristics.Their surface hardness, abrasion resistance and roughness of abrasioned surface were affected by the quality and the quantity of the fillers.The surface hardness increased with the amount of the inorganic fillers.The abrasion resistance was improved remarkably by adding fillers, but the degree of improvement did not necessarily depend upon the amount of fillers.The roughness of abrasioned surfaces was least when the difference of the wear resistance between filler and matrix was minimum.The abrasion resistance of the unfilled resins that were coated with smoothing and hardening agents was equivalent to that of filled resin.

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To clarify the mechanism of hemolytic activity of Bis-GMA, we studied the interaction of Bis-GMA analogs with liposomes by differential scanning calorimetry(DSC).Monomers partitioning into liposomes changes the phase transition temperature(T), the enthalpy(ΔH), the entropy(ΔS)and the temperature width at half-height(ΔT_½)in a DSC peak.Therefore, DSC data provide much information about the interaction of monomers with biological membranes at the molecular level.We prepared dipalmitoyl phosphatidylcholine-cholesterol(DPPC-CS)liposomes as a membrane model.To clarify the hemolytic mechanism, we also examined the changes in the T, ΔH, ΔS, and ΔT_½ of DPPC-CS liposomes induced by Bis-GMA analogs by DSC.DSC changes caused by Bis-GMA and ISO-Bis-GMA were larger than those of Bis-MEPP and Bis-MPP.There appeared to be a relationship between the hemolysis and DSC changes.It was concluded that Bis-GMA and its isomer can penetrate cholesterol and disturb the membrane structure.

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The influence of eccentricity of air turbine rotary instruments on the drilling operation was investigated.Three different air turbine handpieces with eccentric test burs were tested.The run-out of the test burs was measured with a microscope.The run-out of air turbine rotary instrument was influenced not only by the degree of its eccentricity on the rotary instrument itself, but also by the construction of air turbine bearings.Rotary instruments having large eccentricity had the run-out with a node under specific conditions between the rotation speed and load.The usage of the eccentric rotary instruments may caused metal fatigue of such rotary instruments.The drilling surface became rough when it was drilled with an eccentric diamond bur.

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The purpose of this study was to investigate the influence of additive metal elements in Au-Pd-Ag alloys on the bonding to porcelain.Three Au-Pd-Ag alloys for porcelain(alloy H, C and P)were used.The high-temperature oxidation behavior of additive metal elements in alloys, structure of oxidation zones on the alloys and the appearance of bonding between alloy and fused porcelain at the interface were studied by SEM, ESCA and EPMA.By SEM observation of the alloy surface, a granular texture was observed after degassing.From the observation of the interface between alloy and fused porcelain, a number of air bubbles were observed when the alloys were not degassed.From ESCA analysis, metal oxides such as SnO₂ and In₂O₃ were formed on the surface of the alloy after degassing.In the case of alloys H and C, the concentration of SnO₂ increased with oxidation after degassing, but the concentration of In₂O₃ decreased.On the other hand, for alloy P, the concentration of SnO₂ decreased with oxidation after degassing, and the concentration of In₂O₃ increased.The amount of Sn and In concentrated on the alloy surface was measured by their characseristic X-ray using area analysis of EPMA.The following technical conditions for analysis were employed;A)Acc.voltage 10kV, Abs.current 40nA, B)Acc.voltage 20kV, Abs.current 10nA.Consequently, the amount of Sn and In concentrated on the alloy surface which was detected in condition A)was larger than those in condition B).These analysis were also performed on specimens prepared by different technical processes.The following technical processes were employed;1)as cast-oxidation, and 2)as cast-degassing-oxidation.Consequently, the amounts of Sn and In detected from the specimen prepared process 1) was larger than those from process 2).From the EPMA observation of the interface between alloy and fused porcelain, cross-sections of alloys showed that the additive metal elements were oxidized in the alloy matrix, forming an internal oxide layer or particles.The structure of oxidation zones showed a significant difference between degassed and non-degassed alloys.

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The effects of the additive ratio of Rh and Ir on Ag-Pd-Cu ternary alloys were investigated.Addition of Rh and Ir to Ag-20wt% Pd-7wt% Cu alloy produced a grain refinement effect, and somewhat improved the mechanical properties.Grain refinement effects of Rh and Ir added to Ag-Pd-Cu alloys were affected by these contents.The optimum Rh/Pd ratio was about 1/100 and the Ir/Pd ratio was about 1/50.Addition of elements that have distribution coefficients much large than 1 produced a grain refinement effect and reduced the segregation of Cu.The distribution coefficients of Rh and Ir in these alloys were calculated to be 3×10² and above 6×10², respectively.Addition of Rh and Ir to Ag-Pd-Cu ternary alloys accelerated the refinement and homogenization of equiaxial crystal grains during the solution heat treatment of alloys.

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The dimensional changes of 50 commercially available agar impression materials were measured by a non-pressure method.Effects of temperature during impression taking in the mouth and impression thickness of a product were also examined.The tendency of the dimensional changes of agar impression materials in air, in 100% relative humidity and in water was similar to that of alginate impression materials.The rate of dimensional changes varied with the products.The dimensional changes in 100% relative humidity and in water were significantly affected by type and color.The expansion in water of a cartrige-type for repack decreased with an increase of water content during boiling or storage.The thermal shrinkage of a product was slightly larger than that of alginate impression materials.No proportional relation was noted between impression thickness and dimensional changes of a product.

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It was investigated with the properties of commercial root canal sealing materials according to the ISO specifications decided in 1986.Experiments were performed on the following 12 items.;flow, working time, setting time, film thickness, radio-opacity, solubility and disintegration in the specification, and water absorption, compressive strength, setting shrinkage, bond strength to dentin, filling ability and antibacterial action.Great differences in all the properties of the products were observed due to the presence of small elements.Therefore, many products did not satisfy the ISO specifications.However, they could not be regarded as inadequate sealing materials, because all were made before the establishment the ISO specifications.As the filling ability affects the sealing of the root canal, a new standard should be hased on general conditions such as viscosity, flow, working time etc in relation to filling ability.The measurement method of working time recommended in the ISO is not adequate.It should be the time until constant flow values obtained for all sealing materials, because the flow values varied greatly among the materials.

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We have developed a new polyurethane impression material.This material is hydrophilic, therefore it is more suitable for obtaining accurate impressions of wettable mucous membranes and teeth than hydrophobic rubber impression materials.It has excellent elasticity and dimensional accuracy as rubber, but it is easier to handle and less expensive than rubber.This material shrinks slightly with time.Avoid this problem, it is necessary to pour a gypsum slurry immediately after an impression is processed.

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The relationship between immersion period and tensile bond strength to bovine dentin with 4-META/MMA-TBB resin was investigated.Tensile bond strength rapidly decreased from 18MPa to 8MPa in the first few months, then slowly decreased to 4MPa after two years.When the pulp cavities of test specimens were sealed with resin to minimize the influence of water, the decrease of bond strength caused by water immersion became slower.These test specimens were examined by thermal cycling tests.Large differences were observed between decrease of bond strength due to water immersion for long periods and those due to thermal cycling test.Embedding the test specimen in epoxy resin prevented water flow from pulp cavity to the adhesive interface.The process of embedding has an adverse effect on the tensile bond strength to dentin.

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To develop a new adhesive liner without monomer permeation into tooth substrate, we synthesized methyl methacrylate(MMA)-p-styrene sulfonic acid(SSA)copolymer, and investigated its effects on the adhesion between tooth and adhesives.A 10% solution of the polymer was used to pretreat bovine tooth, then bovine tooth and PMMA rod were adhered with dental adhesive(4-META/MMA-TBB resin).We found that this polymer solution demineralized the tooth strongly and bond strength between bovine enamel pretreated with this polymer solution and 4-META/MMA-TBB resin is as high as that between phosphoric acid etched bovine enamel and 4-META/MMA-TBB resin.We also found that 4-META/MMA-TBB resin adhered to bovine dentin pretreated with this polymer[MMA/SSA=2/1(mole ratio)].

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Methyl methacrylate/poly(methyl methacrylate)(MMA/PMMA)resin containing a camphorquinone-amine photoinitiator and pigments was studied as a denture base material, and depth of cure, fitness, physical properties and bonding to metals were evaluated.Complete dentures with various colors ranging from clear pink to dark pink were prepared by mixing appropriate amounts of white, red, brown or violet pigments, and the depth of cure exceeded 10mm.The fitness of the experimental MMA/PMMA resin was comparable to that of heat-curing acrylic resin, and its phyaical properties were comparable to the cold-curing resin.Thus, clinical application of this light-curing MMA/PMMA resin seema feasible.

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Heat-curing resin base dentures made by various packing methods and under various polymerization conditions were investigated with respect to movement of artificial teeth and adaptability.The adaptability, that is, the space between the stone cast and the base resin, and threedimensional movement of artificial teeth were measured by using Fit-Checker and multiple projector, respectively.The measurments of the adaptability and the movement of the artificial teeth were carried out after one hour, one week, one month and two months.The method of injection of doughlike resin into the denture mold was superior to the conventional packing method, that is the trial-packing procedure.Compared with the dentures polymerzed in water bath or in a hot press(dry heat), the dentures polymerized by microwave heating had several advantages in terms of adaptability and movement of the artificial teeth.

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When dough-type fluoropolymer soft liner"Kurepeet dough"is applied to some brands of denture base resins, the surface of this liner becomes rough and porous after processing, and in some cases contamination occurs during use.To solve these problems, compatibility between denture base resins and this soft liner, and the coating effect of a coating material were examined.The roughness and porosity of the surface were the result of the difference of peak period of polymerization between denture base resins and this material.In other words, this material is not suitable for denture base resins having early peak period of polymerization and produces roughness and voids on the surface.As for coating effect, by painting the coating material for tissue conditioner onto the surface, it became smooth, and water resistance and abrasion resistance improved.This suggests that the anti-contamination of Kurepeet dough improves with the coating material.

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To develop a new bonding agent to dentin methyl methacrylate(MMA)-p-styrene sulfonic acid copolymers(MS copolymer), which are considered to react with calcium in the dentin, were synthesized and their bonding ability was investigated.When a poly(MMA)rod was adhered by the 4-META/MMA-TBB resin to the ground dentin coated with 3% MS copolymer aqueous solution or the dentin etched with 0.3M EDTA and then coated with 0.3% MS copolymer aqueous solution containing 0.02% ferric chloride, the bond strength was 8MPa.This adhesion mechanism was different from that based on the diffusion of monomer into the dentin.Thus, it is possible to obtain products made by the reaction between MS copolymer and calcium in the smear layer and/or dentin combine resin and the dentin.

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The structure of polymer powder and the dynamic viscoelastic properties of four proprietary tissue conditioners were investigated.The infrared spectra of films of polymer were obtained in the region of 400 to 4, 000cm^-1.The storage modulus G′ and dynamic viscosity η′ were determined over the frequency range of 0.05 to 70Hz at different temperatures.The polymer powders used in three proprietary materials were poly(ethyl methacrylate)and vinyl chloride-vinyl acetate copolymer.The storage modulus G′ and dynamic viscosity η′ of a mixuture of powder and liquid increased with time, because of progress of dough-forming and evaporation of the alcohol.By the application of the time-temperature superposition principle for each material, the curves of G′ and η′ versus frequencies at different temperatures were supperimposed to a single master curve.The structure of polymer powder had clearly influenced the viscoelastic properties of the materials.The elastic moduli of polymethacrylate materials at low frequencies were one order of magnitude lower than those of tissue in several references.

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The effect of a experimental composite resin system composed of 4-META containing bonding agent and UDMA based composite resins on the adhesion to dentin was investigated by measuring the wall-to-wall contraction gap in cylindrical dentin cavities.The optimum filler content was for obtaining the flow during polymerization 66% in the UDMA resin.The adhesion of the experimental bonding agent was improved by adding 35% HEMA by volume although the pretreatment by 35% aqueous solution of HEMA exhibited remarkable cavity adaptation.

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Mechanical polishing characteristics of titanium were examined by using conventional dental laboratory wheels.Polishing of titanium showed greater wear of wheels and a smaller grinding ratio than polishing of Co-Cr alloy.The amount of grinding of titanium increased as the rotational speed and the grinding load increased, but the wear of wheels also increased and the grinding ratio did not improved.Final finishing was performed by buffing with diamond paste and a glossy surface was easily obtained.

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Titanium was polished by an ultrasonic polisher at a frequency of 28.5kHz and the polishing efficiency and surface texture were examined.The amount of grinding by the sintered diamond grinding wheel increased as the grinding load increased.The diamond wheel with mesh 1000 was found to be efficient to obtain a better finish.Final finishing was performed by ultrasonic lapping using diamond paste and a mirror-like surface was obtained with 0.5μm paste.

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