We have analysed the chemical components of sixteen commercial soldering fluxes using atomic absorption spectroscopy, spectrophotometry and X-ray diffractometry.We have examined the weight change in the fluxes with a thermobalance apparatus.The major elements were K, B, F in all fluxes and Na was a minor element.Small amounts of Al, Si, Cl were detected in three fluxes.Decrease in weight with the heating of the flux was probably a result of dehydration and evolution of CO₂.We have identified some of the chemical compounds such as KBF₄, KF, KCl, K₂CO₃, KHCO₃, K₂B₄O₇・4H₂O, KB₅O₈・4H₂O, K₂[B₃O₃(OH)F₄], K₂SiF₆, Na₂B₄O₇・5H₂O, H₃BO₃ in fluxes.One of the fluxes was amorphous.In conclusion, we found that commercial soldering fluxes consist of same limited number of elements and contain some materials well-known as chemical components of fluxes.

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The precision of entire surface of stone casts was evaluated in terms of surface undulation(waviness).Two hydrocolloid impression materials, three rubber impression materials and two stones were used.Impressions of an acrylic plate were taken with perforated ring trays, and hardened at 23 and 32℃.The surface undulation of casts obtained from each impression was measured by a surface texture and profile measuring instrument.The deformation of the cast surface was classified according to the shape of the obtained effective profile.The surface undulation in casts from rubber impressions was less than that in casts from hydrocolloid impressions when the impressions were hardened at 23℃.The effect of temperature at impression hardening was significant in all impression materials.Hardening of the impressions at 32℃ decreased the surface undulation in the casts from hydrocolloid impressins while it increased that in the casts from rubber impressions.

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The effect of absorbed water on the tensile properties of composite resins was examined.Four different light cured composite resins(OC, PH, FU, SI)were selected and specimens for tensile test were stored in both air and deionized water at 37℃ for 24 hours, 1 week and 1 month.Tensile strength of wet specimens was lower than that of dry specimens and the difference increased as the storing time increased.OC and PH were considered to have suffered mainly physical deterioration by the water sorption because the tensile strength of these materials was recovered very well after they were dried.On the other hand FU and SI were considered to have suffered from both physical and chemical deterioration because the tensile strength of these materials did not recover well after they were dried.Absorbed water tended to make the composite resin more brittle in the tensile test.

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The reproducibility of sylindrical stone casts obtained from two types of alginate impression materials was evaluated according to the temperature during setting(23℃ and 32℃), storage environment(in air of 50% and 100% relative humidity and in water)and storage time(0, 15 and 60 minutes)of impressions using a three-dimensional measuring system.The three-dimensional accuracy of the cast was affected by the type of impression material.The diameter of the cast became smaller as the degree of hygroscopic expansion of impression was larger when the stone was poured without storage.Thermal shrinkage had no effect on the dimensional change of the cast.The effects of the duration and environment of impression storage appeared as coresponding changes in directions opposite to the dimensional change of the impression materials.

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Dental bonding agents with phosphate monomers recently were applied in dentistry and produced the desired clinical effect due to the increase in adhesion between resin system and teeth or metal.The phosphate monomers from three commercial bonding agents were separated by a reversed-phase HPLC using a linear gradient elution method with 0.1% trifluoroacetic acid/CH_3CN(100:0⇒0:100).Monomers(MDP)were identified by NMR spectroscopy.

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Several light-cured polymers with excellent physical properties were prepared using five reducing agents and two photo-sensitizers.The five reducing agents were 2-dimethylaminoethyl methacrylate(DMAEMA), N, N-dimethyl-p-toluidine(DMPT), p-dimethylamino benzaldehyde(DMABA1), dimethylamino benzoic acid(DMABA)and N-phenyl glycine(NPG).The two photo-sensitizers were camphorquinone(CQ)and benzoine methyl ether(BME).The monomer mixture consisted of 50weight% triethyleneglycol dimethacrylate(TEGDMA)and 50weight% di(methacryloxyethyl)trimethylhexamethylene diurethane(UDMA).The optimal photo-initiator system for TEGDMA-UDMA-based light-cured opaque resin was determined.The type of amine reducing agent affected the physical properties of light-cured polymers, such as Knoop hardness number, transverse strength, transverse elastic modulus and amount of residual monomer eluted from polymers.The compressive strength, however, was not affected.The polymers with DMAEMA and DMABA had physical properties inferior to those with the other three amines.The Knoop hardness number and amount of residual monomer were affected when DMPT and NPG were used as reducing agents compared with DMABA1.The physical properties of polymers with two CQ-BME photo-sensitizers were superior to those of polymers with a single CQ sensitizer in all conditions.These results suggest that the physical properties of light-cured polymers depend upon the type of photo-initiator system.Light-cured polymers with CQ-BME as a photo-sensitizer and DMABA1 as a reducing agent showed excellent physical properties and this CQ-BME-DMABA1 photo-initiator system was optimal for the TEGDMA-UDMA-based light-cured resin.

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A 4-META/MMA resin initiated with oxidized tributylborane(TBBO), which is known commercially as Super-Bond, shows excellent adhesion to dentin only when the dentin is pretreated with a citric acid(CA)solution containing ferric chloride(FC).However, no detailed study has been made on the mechanism of this strong adhesion, role of FC and 4-META, or long-term stability of the adhesion.From my experiments on polymerization of(4-META/)MMA with TBBO in the presence of a dentin slice and the effect of FC posttreatment on the adhesion between the resin and acid-etched dentin, I have drawn the following conclusions:(1)FC adsorbed onto dentin collagen is involved in the promotion of polymerization of MMA, (2)4-META increases the molecular weight of the polymer formed, and(3)thus the combined effect of(1)and(2)enhances the bond strength of the resin to dentin.The resin containing 4-META seems to be more susceptible to immersing environment than that without 4-META.

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The physical and chemical properties, toxicity, fitness to the model and relining procedure of light curing type new soft denture lining materials(NewS and NewH), consisting of vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene copolymer(2-4-6FL)and 2, 2, 3, 3, tetrafluoropropyl α-fluoroacrylate(4FFA)were compared with those of commercial soft denture lining materials.The mixture of 2-4-6FL and 4FFA was kept in a dough state until irradiation.The new lining materials after curing showed the following properties:The amount of residual monomer was less than 0.01wt%.Water sorption after immersion for 8 weeks was 0.60mg/cm²(NewH)and 1.08mg/cm²(NewS), and less than that obtained in the commercial soft denture liners of a monomer/polyer curing type.Solubility in water after 8 weeks was very low(0.10mg/cm²).At a water contact angle of 92 degrees, the material had a water-repellent nature.Oil sorption after 3 weeks was the lowest;0.03mg/cm²(NewH)and 0.09mg/cm²(NewS).Hardness(JIS A)of 30(NewS)and 44(NewH)revealed them to be soft enough and they had a viscoelastic property.They had good adhesiveness to usual acrylic denture base material.Fitness of the materials cured by inttermittent irradiation was better than that obtained in the conventional heat-curing acrylic resin.This suggested that they would be applicable not only for indirect relining but also for direct relining.Cytotoxicity was the lowest among the materials tested.The new materials had many properties suitable as a soft denture lining material, and should be worth applying to practical use.

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To develop a new visible-light initiator system for adhesion of resin to dentin, we examined the curing time of MMA/PMMA resin and adhesive strength between the resin and dentin using the following new initiator systems:tertiary-butylperoxymaleic acid(MA), which contains the carboxylic acid group having an affinity with dentin, was combined with camphorquinone(CQ)or 7, 7-dimethyl-2, 3-dioxobicyclo[2.2.1]heptane-1-carboxylic acid(DDHCA)as a photosensitizer and dimethylaminoethyl methacrylate(DMAEMA), 1, 3, 5-trimethyl-2-thiobarbituric acid(TMTB)or N-phenylglycine(NPG)as a reducing agent.Addition of MA to the photoinitiator systems usually shortened the curing time and improved the adhesive strength significantly.The adhesive strength of 10MPa was obtained without adhesion promoting monomers and the adhesive resin layer fractured cohesively.

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The relationship between the titanium flow in plate molds visualized by the tracer element molten method and the casting defects has been investigated.In the case of Cyclarc, laminar flow, which tends to cause the large internal defect at the cener of the vortex, was observed.The solidification shell of the pattern was usually made at an early stage.In the case of Titaniumer, a turbulent flow was observed, and the intense centrifugal force affected the filling process in the mold and the distribution of small porosities.In the thinner molds, the obstruction of subsequent flows by the initial soldification layers provides a new type of filing for the mold.

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A cytotoxic estimation method was developed for denture adhesives based on their elution properties.Their defined amounts were dialyzed(cut-off MW:12000 to 14000)against the culture media for 1 and 5 days.The dialysates containig eluates from the adhesives were subjected to a cell culture test using HeLa cells and their toxicities were estimated by the relative number of living cells to the control.When applied to different types of commercially available denture adhesives, all products except one brand showed significant cytotoxicities with the tendency to increase in an elution time-dependent manner and gum-type products appeared to be the most toxic.Several products acidified or alkalized the dialysates, while such pH changes scarcely influenced the cell growth.The present method proved to have high versatility for various denture adhesives that enables estimation of their cytotoxicities in identical conditions regardless of diversity in their types(powder, cream or gum).

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The surface characterization and adherence of bacterial cells to their polishing surface of a calcium phosphate crystalline ceramics, a 12% Au-Ag-Pd alloy and a photopolymerization resin, were examined.The roughness of the surface was measured by a 2 and 3 dimensional profilometer and then the initial adherence of Streptococcus mutans OMZ 175 to various restorative materials was observed by scanning electron microscopy(SEM).The adherent area of S.mutans cells was calculated by image analysis technology.Plaque-retaining capacity in vitro was investigated by the anthron method.The surface roughness value of calcium phosphate crystalline ceramics was larger than that of the 12% Au-Ag-Pd alloy, and smaller than that of the photopolymerization resin.Radioisotopic studies and SEM observation revealed that fewer cells of S.mutans were attatched to the calcium phosphate crystalline ceramics with or without saliva treatment compared with other materials.There was no relation between surface roughness of various restorative materials and the number of S.mutans cells.Low plaque-retaining capacity in calcium phosphate crystalline ceramics was recognized compared with other materials.

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The static bending test of crown and bridge resin facing metal frame was carried out under a scanning electron microscope, and the relationship between the bending properties and a combination of surface treatments of metal and adhsive or bonding system was studied.The resin facing metal frames constructed by a combination of Sn galvanizing-Panavia and that of oxidation-Bondingliner had a static breaking stress of about 65kgf/mm².All of these specimens were destroyed between the metal frame and the resin.The specimen, when constructed by the Sebond system, had a stress of about 80kgf/mm² and were destroyed by cracking the resin.Then the resin facing metal frames treated with 250μm Al₂O₃ sand, when constructed with Silicoater MD, had a stress of about 80kgf/mm², and were also destroyed by cracking the resin.

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We have tried to develop shape memory alloys which show martensitic transformation at a lower temperature and have better mechanical properties for use as biomaterials.The influence of alloy composition and heat treatment upon the phase transformation of TiPd and TiPd-Co alloys has been examined in this study.The phase transformed temperature of the TiPd-Co alloys which had a part of Pd contained in the Ti-42.5mol% Pd alloy exchanged for Co was lowered increasing Co concentration.The phase transformed temperature of the TiPd-Co alloys was lower than that of the Ti-42.5mol% Pd alloy.The hardness number of the Ti-37.5mol% Pd-5mol% Co alloy(VHN 260)was smallest in the TiPd and TiPd-Co alloys(0mol%<Co<15mol%)with heat treatment at 900℃ and showed a shape memory effect at a lower temperature(100℃〜200℃)than the TiPd alloys.These results indicate that TiPd-Co alloys will be useful biomaterials for shape memory alloys, such as orthodontic wire, clasp and implant denture.

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CP titanium specimens treated by alumina sandblasting, HF/HNO₃ chemical polishing, and electric discharge machining in kerosine oil were prepared and the adhesion to two composite resins for veneering which had different adhesing systems was evaluated by the compressive shear test.Adhesion of titanium treated by sandblasting to composite resins was equivalent to that of Co-Cr alloys and the clinical application of titanium to composite resin veneered crownbridges was thought to be promising.Surface treatment of titanium was found to affect the adhesion of titanium to composite resins and titanium treated by chemical polishing and electric discharge machining showed lower adhesion.

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Specimens with heat treatment and without heat treatment of four commercially available composite resin inlay products and two composite resins for posterior use were prepared and fracture toughness test, tensile test and compressive test were performed.Fracture toughness test was performed using the single edge notched three-point bending specimen with three different shapes of notches.As the angle of the notch became smaller, fracture toughness became smaller.The tests were not affected by the method of the preparation of fatigue crack.Tensile strength and compressive strenth of composite resin inlay products were similar or better than those of composite resins for posterior use, but fracture toughness of some composite resin inlay products was inferior to those of composite resins for posterior use.Fracture toughness of composite resins increased after heat treatment when they showed some permanent deformation before fracture without heat treatment, but not much after heat treatment when they became brittle before fracture.

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In this study, the electroforming method was evaluated to fabricate the electrode for the ram type electric discharge machining.A small electroforming device was experimentally developed and copper electrode was fabricated using the copper sulfate bath, and the electrodeposition process, surface texture, reproducibility, deformation, efficiency and the mechanical properties were evaluated.Suitable electroformed products with good surface texture, good reproducibility, and less deformation were fabricated under the condition of the initial current density 1A/dm², the final current density 10A/dm² and the distance of electrodes 200mm in this device.Electroformed products which were deposited on the impressions of the crown and bridge metal dies were found to have high accuracy for use as an electrode.On the other hand it was found difficult to fabricate uniform electroformed products for the die shape when using the normal direct current.Uniformity was improved by the supplemental platinum electrode but this method was difficult for manipulation and was not practical.Use of the pulse current as a final deposition improved the uniformity and blending of a brightening agent in the bath also caused uniformity and improvement of the mechanical property of the electroformed products.Titanium was machined by the ram type electric discharge machining using the electrodes fabricated by the electroforming, and improved electrode produced equivalent or superior machining properties to the commercial electrolytic copper electrode.

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Infrared spectra of light-cured composite materials were obtained from microareas(100μm×100μm each)of the thin composite film by a Fourier transform infrared spectrometer equipped with a microscopic unit.To allow transmission IR measurement, the thin composite films were prepared by cutting out a cured composite mass perpendicular to the photoirradiated surface.The variation of degree of conversion(DC)determined spectroscopically was examined along the distance from an irradiated surface, and then compared with that of Knoop hardness.The results are as follows:1)Individual maximum in DC of the materials Palfique Light and Silux appeared at ca .1.0mm deep from the photo-irradiated surface.2)The material P-30 kept nearly constant its DC at ca.70% in the 0.4-3.0mm depth range.The DC rapidly decreased with the increase in the depth.3)The maximum in DC of Palfique Light and Silux increased by prolonging photoirradiating time up to 60s.On the other hand, the maximum in DC of P-30 was constant at ca.70% DC after the 10-60s irradiation.4)The inhibition of polymerization by oxgen extended to 1.0mm deep from the irradiated surface of each material.5)Knoop hardness was proportional to DC for each material.The slope of the regression line was considerably influenced by inorganic filler content.The slopes for the materials P-30, Palfique Light and Silux decreased in that order.The results indicate that, especially for highly filler-loading composites, the hardness may be considerably varied by a slight change of the DC.

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