It was intended to develop the composite resin with desirable characters.Compostite resins containing colloidal silica were prepared for this purpose and their properties were examind.The experimental composite resins were prepared from the comonomers of Bis-GMA and TEDMA and the following fillers:1)MF, surface-treated 0.05μ AEROSIL, 2)CF, crushed resin composite containing 50% of MF, and 3)the mixture of MF and CF.It was found that although the smaller filler, the greater the compressive strength, there was little influence of the filler size on other physical properties of the cured resin containing 50% of CF.The experimental resins improved the physical properties in proportion to the silica contents.The rise rate of physical properties divided by the silica contents were defined as the composite effects.The composite effect of the compressive strength was 3.7, that of the elastic modulus was 2.3, and those of the Rockwell hardness, the coefficient of thermal expansion and the diametral tensile strength were 1.The viscosity of the experimental resin containing MF measured by a cone-plate viscometer was decreased inversely to the shear rate, showing thixotropy.There was little influence of the shear rate on the viscosity of the resin containing CF and there was an intermediate tendency to the composite resin containing MF+CF.

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The bending characteristics and corrosion resistance were investigated using TiN ion-plated specimens of Al-Cu, Al-Mg system wrought alloys and Al-Si system casting alloy.Results:1.Bending characteristics 1)The proof stress values of these specimens ranged from 91.1 to 231.1MPa.Those of ion-plated materials to wrought used alloy, however, reduced to half of those of the original materials.It was suggested that this was due to the thermal effects of ion-plating procedures.2)The elastic coefficients of these specimens ranged from 7.1 to 8.1×10⁴MPa.3)It was estimated that the practical thickness of aluminum system alloys ion-plated for use as a denture base was from 0.8 to 1.3mm.2.Corrosion resistance 1)Pitting corrosion was only observed on ion-plated specimens of Al-Cu system alloy by means of immersion in an artificial saliva.2)From the results of an electrochemical test, it was suggested that the material had a tendency to give rise to pitting corrosion when the breakdown potential was closed to the corrosion potential.3)The current density of ion-plated specimens of Al-Mg and Al-Si system alloy decreased to 1/50 or 1/170 in comparison with that of original specimens at zero voltage on an anodic polarization technique in an artificial saliva.

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In order to study the compatibility of dental stones with agar impression materials, the surface roughnesses of five commercial stones that were set against eight agar impression materials were measured.X-ray diffraction analysis and X-ray microprobe analysis were performed for each surface of the set stones to examine the surface products such as calcium sulfate dihydrate, calcium sulfate hemihydrate and syngenite, as well as the distribution of potassium.The correlation between the surface roughness and the diffraction X-ray intensities(cps)of the surface products as well as the distribution of potassium on the set surfaces were statistically analyzed.The results are summerized as follows:1)A significant positive correlation was found between the diffraction X-ray intensity(cps)of calcium sulfate hemihydrate and the surface roughness.2)A significant negative correlation was found between the logarithm of the diffraction X-ray intensity of calcium sulfate dihydrate and the surface roughness.That is, the surface of the set stones was drastically roughened when the intensity of calcium sulfate dihydrate was very low.3)Syngenite was not detected on the surface of the tested stones at 1 minute but after 24 hours following the removal from the impression.No significant correlation was found between the diffraction X-ray intensity of syngenite and the surface roughness.4)No significant correlation was found between the potassium distribution and the surface roughness.

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The correlation between standard-specification tests(JIS, ADAS and ISO)of dental zinc phosphate cements by mechanical mixing mentioned in our previous papers was studied.A student's t-test was used for statistical analysis.GC Crown Bridge & Inlay Cement(BB)and GC Elite Cement 100(E)were used, and the ratio of powder to liquid 3.0g/1.0ml, and 2.8g/1.0ml, respectively.1.Consistency measured by ISO Showed standard consistency.However, date measured by JIS and ADAS showed 8% higher hardness.The value of BB was significant at 5% level and that of E was significant at 1% level compared with data measured by ISO.2.Setting time in each test was longer.Data by ISO was significant at 1% level compared with data by JIS as well as ADAS(no significance).3.Compressive strength satisfied every restriction.Only data concerning E measured by JIS compared with data by ADAS was significant at 5% level.4.Film thickness satisfied every restriction.Only data concerning BB measured by JIS compared with data by ADAS and ISO was significant at 5% level.5.Disintegration satisfied every restriction.Data concerning E as well as BB measured by JIS compared with data by ADAS was significant at 5% level.

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Dimensional changes of 23 brands of conventional and dustless alginate impression materials in various environments were directly measured by restraining the deformation induced by measuring load on materials soon after the initial setting.A wide range of contraction due to syneresis of the material itself was observed in 100% relative humidity.The expansion due to imbibition in water was greatly influenced by syneresis.An additive for dustlessness seemed to be less of an influence on the dimensional stability of the alginate, but an alternation of filler contributed to reduce the contraction in 100% relative humidity and in air.

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It has previously been reported that higher-order structure of dentin collagen is significant for adhesion between dentin and 4-META/MMA-TBB resin.The effect of FeCl₃ on the adhesion to dentin by a new method was investigated in this study.It was found that dentin collagen denatured by phosphoric acid and citric acid.But the denaturation was not observed in collagen treated with an aqueous solution of 3% ferric chloride in 10% citric acid(10-3).Dentin collagen heated at 60℃ in a buffer solution for 8hr was completely denatured.The bond strength of 4-META/MMA-TBB resin to 10-3 etched dentin, which had been heated to 60℃ for 15 min in water, decreased to 7MPa.On the other hand, the strength was 18MPa on the dentin heated in FeCl₃ water solution.These results indicate that ferric ion in 10-3 is effective to stabilize dentin collagen.

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With a view to investigating the effect of various functional monomers on the adhesion of dental alloys, adhesive tests of dental alloys were carried out using MMA-TBB type resins with acid anhydride or carboxylic monomers.Indeed, addition of a functional monomer was effective in cases using a monomer with an acid anhydride or a carboxylic group as well as using a small amount of crosslinking agent, but durability made the difference between structure of monomers.Sandblasting of the alloy surface was broadly effective to suppress decreasing adhesive strength, but even in this case the effects of various monomers were clearly observed.Judging from the fact that acid anhydride groups of monomers were hydrolyzed during long term storage, it is believed that carboxylic groups of monomers played an important role in adhesion of dental alloys in underwater conditions.

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Cylindrical enamel and dentin specimens, 0.8-1.0mm in diameter and 0.8-2.2mm in length, were prepared from freshly extracted third molars from teen-age females.Improved methods of preparing specimens of hard tooth tissues using a hollow drill made of pure copper with aluminium oxide paste as the abrasions at a rotation speed of 2, 000rpm and a load of IN(100gf)have been developed for the determination of proportional limit, yield strength, crushing strength, modulus of elasticity, and contraction.Specimens were prepared from different regions in the same teeth and different orientations of the structure, and were compressed at a rate of 0.1mm per minute.The following results were obtained.1.The compressive properties of enamel were affected significantly by the orientation of the specimens, but those of dentin were not affected.2.When the load parallel to the long axis of the enamel rod was applied, the values of compressive properties were at the minimum.When the load was applied through the head and the tail of the key-holl unit of the rod, the values of compressive properties were intermediate, and when the load was perpendicular to the axis through the head and the tail, the maximum values were obtained.3.Compressive yield strength of enamel could not be measured, but crushing strength was 270-440MPa.4.Compressive yield strength of dentin was 210-220MPa.

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Tensile strength at room temperature and 950℃, flexure at 1, 000℃ and hardness of Vickers between room temperature and 900℃ along with sag resistance were evaluated on six commercial and a home-made Au-Pt-Pd alloys for porcelain-fused-to-metal restorations.The results showed that tensile strength and flexure were correlated to each other and also that hardness and flexure were correlated.All of the properties examined for the home-made alloy were found to be inferior to those of the commercial alloys.The present results suggest that the tensile strength and hardness could be used in estimating the sag resistance of all types of alloys employed.Further, the finite element stress analysis for self-weight sagging of a two-point supported beam substantiated the present experimental results in that flexure(sag)is dependent on the resistance to tensile force.

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In the course of studies to prepare new functional monomers which improve adhesive properties of MMA-PMMA/TBBO resin to teeth or metals, the N-(4-mercaptophenyl)methacrylamide(MPMA)monomer was found.The monomer enhances adhesive strength to teeth, gold, palladium, copper, iron and dental alloys.MMA-PMMA/TBBO resin exhibited excellent adhesion when MPMA monomer was applied as a liner to human enamel or dentin treated with 10% citric acid aqueous solution containing 3% of either ferric chloride or cupric chloride.The monomer provides firm adhesion to gold, palladium, copper, and iron as well as teeth.Especially, the adhesion to palladium and gold-silver-palladium alloys was found to be stable and durable.On the other hand, N-(4-mercaptophenyl)isobutylamide(MPIA)which does not possess double bonds for polymerization but has a mercapto group did not show sufficient adhesion to palladium surfaces coated with the liner.This clearly demonstrates that compounds used as liners in MMA-PMMA/TBBO resin system must possess a double bond for copolymerization in order to improve adhesive properties.In the case of the N-phenylmethacrylamide monomer which has a similar structure to MPMA, but without a mercapto group, durable and stable adhesion was not obtained by coating the monomer as a liner.It is especially worth noting that the chemical bond between MPMA and palladium was confirmed by ESCA analysis, after the surface of palladium was washed by acetone followitng the coating treatment.On the basis of the results, it was proved that MPMA exhibits durable and strong adhesion to dental gold-silver-palladium alloys due to the copolymerization with MMA-PMMA/TBBO resin.

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Molecular composities are prepared by dispersion of rigid molecules into a matrix resin for reinforcing resins.In this study, polyfunctional siloxane oligomers with ladder-like structures were used as rigid molecules which were obtained by cohydrolysis of variety ratio of γ-methacryloxypropyl trimethoxysilane and phenyl triethoxysilane.Physical properties of PMMA composites which contained 10 and 20wt% of the siloxane oligomer were measured and compared with the composites containing the same amount of polyfunctional methacrylates, such as 3G, Bis-GMA and TMPT-MMA copolymers.Compressive strength of the composites containing 20wt% of the oligomers was higher than that of the Bis-GMA-MMA copolymer, and increased with the content of double bonds in the siloxane oligomer.Hardness of the composites was higher than that of the 3G-MMA copolymer, and was almost same as that of the Bis-GMA and TMPT-MMA copolymers.Water sorption was lower than that of the other PMMA copolymers.Based on the results obtained, it is expected that molecular composites of the siloxane oligomer-PMMA will be used as materials for crown and brige, other PMMA copolymers.

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In order to improve the mechanical properties of dental composite resins, organic fillers were prepared.We polymerizied composite resins containing these fillers with BPO-Amine and examined the effect of organic filler on the mechanical properties of composite resin.TMPT filler was proved to have better mechanical properties than UDMA filler as organic filler because of the reactivity of residual double bonds in TMPT filler.Furthermore, we examined the monomer which was compatible with TMPT filler, and found that EDMA or TEGDMA was adaptable monomer of the TMPT composite resin matrix, but at the same time the disadvantage in these compositions was the amount of water sorption.Then we used RDMA monomer as the component of resin matrix to reduce the amount of water sorption and measured the mechanical properties.Composite resin which was the mixture of TMPT filler and EDMA/RDMA or TEGDMA/RDMA had good mechanical properties such as Brinell hardness, compressive strength, water sorption and coefficjent of thermal expansion, compared with other organic filler composite resins.

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The biocompatibility of pure nickel and Ni-Ta binary alloy were histopathologically and chemically evaluated in rat subcutaneous tissue.The tissue around the pure nickel showed necrotic-like or eosinophilic amorphous masses with severe inflammatory changes.A large amount of Ni²⁺ was detected in the subcutaneous tissue around the nickel metal in all of the experimental animals.The tissue around Ni-10wt% Ta, Ni-20wt% Ta and Ni-30wt% Ta was formed by fine fibrous tissue layers without inflammatory cells infiltration, and granular foci showing good biocompatibility.However, a small amount of Ni²⁺ was detected in the tissue around these alloys.These findings indicate that Ni-Ta alloys corrode and that nickel is released as Ni²⁺ or nickel compounds and remains in the tissue without destroying the tissue.The experiments show that nickel, which causes serious inflammation in the tissue, is released from Ni-Ta alloys and remains in the surrounding tissue.Even when there is no evidence of any cellular changes in the surrounding tissue, small amounts of Ni²⁺ can be detected.

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It is difficult to cast pure titanium by usual dental casting methods, because titianium has a high melting temperture and much chemical reactivity with mold materials and air at high temperatures.These problems may be solved by developing new titanium alloys which have lower melting points and less reactivity.it was found in our last report that some binary systems of titanium alloys have potential for dental casting alloys.The purpose of this study is to investigate the effects of Pd or Cr in Titanium on mechanical properties, microstructure, surface of castings and castability.Ti-Pd, Ti-Cr alloys were cast into Phosphate bonded investments and magnecia investments by using an argon arc melt/argon pressure casting machine.The following results were obtained:Ti-20〜25wt% Pd and Ti-15〜20wt% Cr have high tenisle strength, good ductility, adequate hardness, good castability, and good fitness for dental casting alloys, but the surface roughness of these titanium alloy castings using phosphate bonded investments is less good than those of Ni-Cr alloys and Co-Cr alloys.Mechanical properties of these titanium alloy castings using magnecia investments were almost the same as those of the castings using phosphate bonded investments but surface roughness of castings was much improved by using magnecia investments.

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In a previous paper, it was found that Ti-15〜20wt% Cr and Ti-20〜25wt% Pd have high tensile strength, good ductility, adequate hardness, good castability and good fitness as dental casting alloys.The purpose of this study is to investigate the effects of third elements in Ti-20wt% Cr and Ti-25wt% Pd on mechanical properties and microstructure, surface of casting and castability.(Ti-20Cr)-Al, (Ti-20Cr)-B, (Ti-20Cr)-Si and(Ti-25Pd)-Cr were cast into phosphate bonded investments by using an argon arc melt/argon pressure casting machine.The following results were obtained:(Ti-20Cr)-0.1, 0.2Si, (Ti-25Pd)-1, 2, 5Cr have better mechanical properties, castability, and fitness than Ti-20Cr or Ti-25Pd.Especially, surface roughness of these castings are smoother than those of Ti-20Cr or Ti-25Pd.(Ti-20Cr)-1, 2Al have a few problems in the fluidity of the melts, but besides that possess exceptional characteristics as dental casting alloys.

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A study about functional monomers containing phosphoric acid and an initiator which is capable of self-curing was carried out in order to make an adhesive resin which shows excellent adhesion to teeth.It was found that an improved adhesion might be developed by use of methacrylate monomer containing mono basic phosphate and a ternary initiation system composed of salt of sulfinic acid-peroxide-amine.The methacrylic phosphate monomers substituted by aromatic groups showed improved adhesion among phosphate monomers and 2-methacryloyloxyethyl phenyl phosphate(Phenyl P)gave the highest bond strength to teeth.The adhesive strength was improved by increasing the concentration of salt of sulfinic acid;thus, the ternary initiation system was found to be suitable for application as a bonding agent.

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Improvement in shape recovery ratio in Ti-V-Fe-Al alloy at the temperature between 40℃ and 80℃ was attempted, and its application as a dental implant was discussed.In Ti-11.5V-1.7Fe-3.3Al alloy melted by an argon arc melting furnace with a low vacuum system, the shape recovery ratio at 80℃ was significantly improved from 44% to 85% by aging for only 3 seconds at 400℃ and succesive low temperature bending at -20℃.Furthermore, in the same alloy melted by an argon arc melting furnace with a high vacuum system, even better results with a higher recovery ratio and a low scatter value were obtained;that is, 98.5±0.8% at 80℃ and 89.9% even at 60℃ by the same treatment mentioned above.According to the oxygen analysis, approximate correlation between shape recovery ratio and oxygen concentration was observed, and reduction in oxygen concentration seems to be effective.The best condition to obtain the highest recovery at present is as follows:solution treat Ti-11.5V-1.7Fe-3.3Al with low oxygen concentration at 800℃ and age for 3 seconds at 400℃, then bend plastically at -20℃.According to the condition mentioned above, a model implant with 0.6mm thickness was prepared, and an opening angle with 50° in its edge part was memorized.After spape recovery treatment at 80℃, an opening angle with 40° was recovered.Based on these results, this alloy might have further room for improvement, but seems to be possible to use in dental implants.

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In the first paper, I discovered and reported that SUPERBOND C&B, PANAVIA-EX, and experimental resins which I made adheres to VMK68 porcelain(:products of Vita corp.).I also examined a surface treatment method using silane coupling agent to obtain more tight adhesion.These adhesive methods enabled realization of about 200kgf/cm² of adhesive strength between Vita procelain and adhesives within as short a period as 1 week.But, in a long term, the adhesive strength gradually decreases after 1 month and the adhesive strength become less than 50kgf/cm².In this experiment, in order to investigate the method by which to realize more durable and firm adhesion, adhesion to each element of porcelain was examined.And a surface treatment where silane coupling agent was applied and adherend was heated is tested.Etching surface of porcelain was also examined.Dental Porcelain contains mainly SiO₂(silica), Al₂O₃(alumina), and some kind of modifing oxidized metals which control fusion point, color, and other characteristics.So the adhesive strength to pure silica and pure alumina as well as dental porcelain are examined.Alumina, silica, and dental porcelain show higher adhesive strength in this order.Concerning long term durability of adhesive strength, PANAVIA-EX is superior to the MMA+PMMA+TBB-O system.A surface treatment where a solution of silane coupling agent is applied to the surface and then the test specimen is kept at 110℃ is found to be effective.The most firm example keeps more than 219kgf/cm² of adhesive strength to dental porcelains even after 6 month's water immersion.It is considered enough for clinical application.Although only one kind of adhesive was examined and observation with SEM are carried out here, an etching method is supposed to be helpful in obtainning durable adhesion.

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