The mechanism of the hydrolytic deterioration of the silane coupling agent layer on silica filler of composite resin was examined. As a result of the desorption of the absorbed silane molecules, the contact angle between water drop and the silica plate treated with the silane coupling agent decreased when the plate was soaked in hot water and the rate of the decrease in the contact angle leveled off with an increase in the concentration of the silane coupling agent solution. With an increase in the soaking time in hot water, the strength of adhesion of poly (BIS-GMA) to the silica treated with the silane coupling agent decreased and the position of the fracture shifted from the matrix resin (adherend failure) to the silane coupling layer (adhesion failure). The time when the adhesion failure took place depened on the concentration of the silane coupling agent solution and there was the optimum concentration for waterresistant adhesion.

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In this study the efficacy of the primer on adhesion of MMA(TBB-O) resin to dentin was investigated. The primer consists of two parts. One is 6% MTYA and 70% HEMA aqueous solution, and the other is 2% glutaraldehyde aqueous solution. As an etching agents, 10% citric acid-3% FeCl₃(10-3), 40% phosphoric acid, 10% citric acid, and 0.5M EDTA were used. After etching, the two parts of the primer were mixed well and applied on the etched surface. Then MMA(TBB-O) resin or p-MBA/MMA(TBB-O) resin was applied on the treated surface. The tensile bond strengths after storage in 37℃ water were measured. It revealed that the primer treatment increased the bond strength despite the kind of etching agents. Though the thickness of the resin reinforced dentin was the same as that of demineralized dentin, it was not propotional to the bond strength. Then the durabilty of the adhesion to dentin treated with primer was examined by the thermal cycling tests. After 2000 thermocycles between 5℃ and 55℃, the decrease in the bond strength was very small.

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A newly developed light-cured anterior restorative composite resin "Graft LC" by GC Co.is characterized by having Vita VMK 68 shades and containing glass filler particles treated with graft binders. Several properties of the resin were examined by using the SEM, surface recorder, and color analyzer. The Graft LC resin was classified as semihybrid resin. The filler particles of Graft LC resin comprised two kinds of glass filler in which Si, Ba and Al, and Si were detected. Graft LC resin showed a relatively small surface roughness after polishing in spite of the semihybrid resin. According to the degradation test in the alkaline solution, the polished surfaces of Graft LC resin became rough and the depth of subsurface damage layer increased with time. However, the filler particles were retained in the subsurface damage layers. An Ar ion etching employed for SEM preparation is useful to observe the subsurface damage layer distinctly under the SEM. No color change was found even after long-term immersion in a distilled water, though the color of Graft LC resin changed greatly due to irradiation.

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Titanium dioxide-polymethacrylate composites were prepared with triethyleneglycol dimethacrylate (TEGDMA), 1, 6-bis(methacryloxy-2-ethoxycarbonylamino)-2, 4, 4-trimethylhexane (UDMA) and rutile structure titanium dioxide. The coupling agents used were isopropyldimethacrylisostearoyl titanate (KR7), isopropyltri(dioctylphosphate)titanate (KR12) and 4-methacryloxyethyl trimellitate anhydride (4-META). Compressive and transverse strengths of composites were determined under various experimental conditions. Compressive strength of composite with KR7-treated titanium dioxide was higher than that with untreated titanium dioxide. Transverse strength of the composite with 4-META-treated titanium dioxide was higher than that with untreated titanium dioxide. Both compressive and transverse strengths increased when the titanium dioxide was treated with the mixture of KR7 and 4-META. Scanning electron microscopic observations of fractured composite surfaces showed titanium dioxide polymer interface failure with untreated specimens and polymer cohesive fracture with KR7+4-META-treated specimens. The results suggest that titanium dioxide treated with both KR7 and 4-META is useful as a pigment of the opaque material of fixed prosthodontic composite.

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The anterior palatal area may be related with the flexural rigidity and bending strength of the upper complete dentures. Therefore, the deformation of this area should be measured widely and continuously when new materials were applied to the dentures. The influence of the photoelastic coating on the mechanical properties of the upper complete dentures was investigated, prior to the measurement of surface strains on the denture bases by the photoelastic coatings. In this experiment, the uniform-moment bending method was employed simulating the occlusal situation. The flexural rigidity of the denture bases depended on the palatal materials in spite of the presence of the coating. The strains concentrated on the anterior palatal area were slightly decreased when the coating was bonded to the polished surface of the palate. The reinforcing effect was significant when the resin dentures of low elastic modulus were coated. The photoelastic-coating method was suitable for the qualitative analysis of the strain distribution of the denture base and selecting the test points to make strain measurement accurate.

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The biological effects of adhesive resins were studied by an organ culture method using chick embryo femurs, of which usefulness was investigated to evaluate the biocompatibility of biomaterials. Superbond C & B and Panavia EX were processed to form test pieces of 0.35mm in diameter and 2mm in length. The test piece was inserted into the distal epiphysis of the femur, which was cultured at 37℃ for 7 days. The biomaterials were evaluated by relative growth rate, relative wet/dry weight ratio (W/D) and histological examination. The femurs with insertion of Superbond C & B or Panavia EX did not show growth inhibition, but W/D of Panavia EX was significantly higher than that of control. Histologically, undifferentiated cartilage cells and immature cartilage matrix were observed in the tissue adjacent to Panavia EX. These results suggested that Panavia EX had a slightly toxic effect on the chick embryo femur.

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The cytotoxic effects of pure metals on L-929 mouse fibroblasts were examined using extracts obtained by dynamic extraction of Cu, Al, Ti, V, Cr, Mo, Mn, Fe, Co and Ni. The order of cytotoxicity expressed in ppm was Cr>V>Co>Fe>Mn>Cu>Ni>>Mo. On the other hand, the order in mM was Cr>Co>V>Fe>Mn>Cu>Ni>>Mo. Al and Ti showed no cytotoxicity. Thus, the cytotoxicity of pure metals was dependent on their concentration and the chemical state in the extracts.

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The grinding techniques and the constituent element of vitrified wheels suitable for a 13% Cr-Ni dental casting alloy were determined. The lever-type grinding test machine used in the previous study was modified so that a work might be ground under a constant pressure as it moved reciprocally within a short stroke along the tangential direction of a rotating wheel. The grinding performance of two marketed wheels and eleven experimental wheels with different constituent elements was tested. Abrasive grains on the working surface of alumina wheel wore extremely due to abrasive attrition. Carborundum wheels proved to be more suitable for grinding of the comparatively soft Ni-Cr alloy. Not only depressing a wheel against a work but also moving the wheel over it with heavier pressure should be desired for the maximal grinding efficiency. The experimental carborundum wheels exhibited much the same performance as the marketed carborundum wheel under a less grinding pressure than 100gf. Only the wheel of grain size #150 bonded with 19% binder wore obviously under the pressure of 150 or 200gf and provided about two times the performance of the marketed wheel.

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The grinding techniques and electro-deposited wheels suitable for a 13% Cr-Ni dental casting alloy were determined. The lever-type grinding test machine modified in the previous study was used to investigate the grinding performance of experimental wheels of CBN- and diamond-particles. Depression of the diamond wheel against the work yielded unfavorable grinding results. Not only depression of the wheel against it but also moving the wheel over it with a heavier pressure is desired for higher grinding efficiency and its durability. Probably, the undurability of this wheel is associated with abrasive attrition due to oxidation or some chemical reaction with the work. The CBN wheel had not been suitable for the Co-Cr alloy tested in the third paper, but it exhibited very excellent performance for grinding of the Ni-Cr alloy, even without being moved over the work. Although being high in cost, the CBN wheel may pay for the very high performance and its durability.

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To clarify the interface reaction between porcelain and a commercial Ni-Cr dental alloy (containing higher Cr and Si) during porcelain firing, electron probe microanalyzer (EPMA), X-ray diffraction and X-ray fluorescence analysis have been used to characterize the interface which has emerged by means of selective dissolution of the alloy caused by a bromine-methanol solution. At the early stage of firing, tin oxides (SnO₂), contained in the porcelain powder, were reduced to Sn metal and the resultant reduction layer was about 10μm in thickness from the interface. Although in the beginning of firing some Cr oxides were formed at the interface, with increasing retention time (within a few minutes) at 960℃, extremely low oxygen partial pressure caused reduction of even such products.

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A heating method using micro-waves was utilized to obtain strong thermosetting resin for crown and bridge. The physical and mechanical properties of the thermosetting resin were examined. The resin was cured in a shorter time by the micro-waves heating method than by the conventional heat curing method and the working time was reduced markedly. The base resins of the thermosetting resin for crown and bridge for the micro-waves heating method were 2PA and diluent 3G. A compounding volume of 30wt% for diluent 3G was considered good the results of compressive strength, bending strength and diametral tensile strength. Grams of 200-230 of the filler compounded to the base resins of 2PA-3G system provided optimal compressive strength, bending strength and diametral tensile strength. A filler gram of 230 provided optimal hardness and curing shrinkage rate, the coefficient of thermal expansion became smaller with the increase of the compounding volume of the filler. The trial thermosetting resin for crown and bridge formed by the micro-waves heating method was not inferior to the conventional resin by the heat curing method or the light curing method.

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Nine experimental Au-Ag-Cu alloys with different surface finishes were measured for various kinds of glossiness using a digital variable gloss meter. Eight different methods of measurement for glossiness were chosen from the ones described in Japanese Industrial Standard Z 8741-1962. In addition to glossiness, color coordinates in the CIELAB color scale and surface roughness were measured. The compositions of the alloys were 40, 50, or 60 at% gold, 0, 20, or 40 at% copper, and 0-60 at% silver (balance). This study was initiated to collect fundamental data necessary to determine the most appropriate characteristic which could express the degree of tarnishing of various dental alloys independently of their own colors and compositions. Only one type of contrast glossiness based on two different receptor apertures with an incident angle of 60° could demonstrate statistically significant differences between all the combinations of the different surface conditions analyzed. Effects of compositions on the values of various kinds of glossiness and color coordinates of the alloys with highly polished surfaces were statistically significant except contrast glossiness of different receptor apertures. Specular gloss and contrast gloss were considered to be as inappropriate as color of total reflected light in measuring the degree of tarnishing of dental alloys.

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The dimensional changes of four alginate impression materials and the surface roughness of stone casts following the treatment with 0.07% Povidone-Iodine solution were evaluated. The impressions were treated by either immersing or spraying. The dimensional change was measured by an electronic micrometer with a non-pressure direct method for 60 minutes. The surface roughness of stone casts obtained from the impressions following optimal treatment was also measured. Two products were dimensionally stable for 60 minutes after spraying with the solution, while the other two were stable for 30 minutes in the solution. No effect of the treatment was observed on the surface roughness of stone casts.

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The properties of dental cyanoacrylate cement "FH", which has protective and bacteriostatic effect on dental pulp, were compared with that of glass-ionomer cement. The operational properties such as setting time and consistency were good, but the mechanical properties as dental cement were a little inferior. These properties were affected definitely by temperature and humidity than the glass-ionomer cement, especially the influence of humidity was very high. However, the influence on bond strength was almost nothing, especially in the early period of setting. The factors affecting it could be very low disintegration. The bond strength for dentin after 24 hours the start of mixing of FH cement was much higher than that for enamel, but the strength rapidly decreased by thermal cycling between 4℃ and 50℃ in water.

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The effects of metal ions and mechanical stress on cells were examined in vitro, to shed light on tissue response to metal prosthesis. Seven commercial base alloy plates, four Co-Cr alloys, one pure Ti, one Ni-Cu-Ga alloy and one Ni-Cr alloy for solder were used. Two kinds of static load, 5gf/cm² and 10gf/cm², were applied to three kinds of tissue culture cells, L-929, HEp-2 and Gin-1 cells, for 24 hours, and then the cells were incubated for 7 days under normal culture conditions. Cell recovery was evaluated by cell number and protein content. The amount of dissolved metal ions was measured by atomic absorption spectroscopy (Experiment 1). A concomitant study of cell culture with known amounts of Co, Cr, Ni was carried out, and cell recovery was examined (Experiment 2). Atomic absorption spectroscopy showed that dissolution of either Co or Cr from the alloys tested was extremely small. However, the maximum amount of Ni and Cu dissolved from Ni-Cu-Ga alloy and Ni-Cr alloy for solder was over 10ppm. Ti was not dissolved from pure Ti. Four Co-Cr alloys and pure Ti did not inhibit cell recovery or protein content with loading. However, Ni-Cu-Ga alloy and Ni-Cr alloy significantly inhibited cell recovery and protein content, and the effects were etnhanced by loading. The cytotoxicity of Co, Cr or Ni ion at a static load of 10gf/cm² was higher than that at 5gf/cm². These results suggest that mechanical stress increases the cytotoxicity of dissolved metal ions.

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The setting expansion of a dental stone poured in addition silicone impression materials was evaluated. Impressions were made of two different addition silicones (hydrophilic and hydrophobic) that had three different consistencies (injection, regular and putty). A dental stone which did not contain any additives was poured in the impressions and the setting expansion of the stone was automatically measured using an electric micrometer and a computer. The setting expansion of the stone that was poured in the impression did not significantly vary with the consistency of the silicones. On the other hand, the setting expansion of the stone in the hydrophilic silicone was significantly larger than that in hydrophobic silicone.

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EDTA metal ammonium salt solution containing Fe³⁺, Co³⁺ or Cu²⁺ was studied to determine the pretreatment reagent that causes no denaturation of dentin collagen and promotes good adhesion to dentin. After application of EDTA 3-2(Fe・NH₄), EDTA 3-2(Co・NH₄) or EDTA 3-2(Cu・NH₄) at pH7.4 on the dentin surface, the amount of Ca²⁺ demineralized and the tensile bond strength were measured. The pretreated dentin surfaces were also observed with SEM. No correlation was obtained between the amount of Ca²⁺ demineralized and the tensile bond strength. On the EDTA 3-2(Fe・NH₄) treated dentin a small amount of smear remained partially, but the tensile bond strength of 4-META/MMA-TBB resin to the dentin was higher than 13MPa. This indicates that complete removal of the smear on dentin is not always necessary for better bonding.

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To develop the visible light-cured FRP denture base, we investigated the physical properties and the warp of FRP plate by using various combinations of matrix resin and reinforcement. From the results of the bending test, hardness test and manipulation processing, the matrix resin of Bis-GMA/UDMA/3G at 48/48/4wt% was determined. The sateen weave's glasscloth as the reinforcement of the prepreg was used. The maximum plies included FRP of 0.5mm, 0.8mm and 1.0mm thickness have the same maximum bending strengths of 45kgf/mm², which is about 5 times larger than that of conventional acrylic resin. The warp of these FRP plates were not found.

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The purpose of this study was to examine the influences of thermal cycling on the adhesive strength of the adhesive resin cements. Four kinds of adhesive resin cements, which belonged to the commercial composite resin inlay products, were used for the study. They were CR Inlay Cement, Duo Cement, Dual Cement and P-30 diluted with Enamel Bond. The shear adhesive strengths to tooth substance and composite resin inlay were measured. Adhesive strength to etched enamel : CR Inlay Cement showed the highest values of 274kg/cm² after immersion in water at 37℃ for 24 hours and 230kg/cm² after 300 thermal cycles at 4℃ for 3 min and at 60℃ for 3 min. Adhesive strength to etched dentin : P-30 diluted with Enamel Bond showed the highest values of 64kg/cm² after 24-hour immersion in water, and 63kg/cm² after 300 thermal cycles. Adhesive strength to composite resin inlay : CR Inlay Cement showed the highest values of 310kg/cm² after 24-hour immersion in water, 306kg/cm² after 300 thermal cycles, and 297kg/cm² after 1000 thermal cycles. Adhesive resin cements other than CR Inlay Cement, showed a decrease in adhesive strengths to tooth substance and composite resin inlay after thermal cycling. Especially, Dual Cement and Duo Cement showed considerable decreases.

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