Gelatin (denatured collagen), assumed to be a periodontal membrane, was insolubilized by glutaraldehyde in solution. DTA and IR analyses showed that gelatin can be insolubilized well by a glutaraldehyde solution. Gelation of 10wt% concentration had a maximum value of adhesive strength at the composite resin surface which was virtually independent of the type of commercial composite, although it depended strongly on the surface roughness. The adhesive strength in solution at 37℃ decreased to one-tenth in air, and was maintained for at least 2 weeks. A glutaraldehyde concentration below 5% was the most effective, but it was expected a treatment time longer than 1 hr would be required.

View full abstract

In attempt to improve the physical properties of dental resinous materials, tris (2-methacryloxyethyl) isocyanurate (TMEIC) was synthesized from tris (2-hydroxyethyl) isocyanurate and methacryloyl chloride. The relationship between the chemical structure of the synthesized methacrylate and physical properties of TMEIC-MMA copolymers and trimethylol propane trimethacrylate (TMPT)-MMA copolymers were investigated, and we found the following; 1) The compressive strength, elastic modulus and Knoop hardness were increased, but transverse strength decreased with an increase in the TMEIC concentration. 2) The amount of water sorption increased with an increase in the TMEIC concentration. 3) The physical properties of TMEIC-MMA copolymers were relatively higher than those of TMPT-MMA copolymers.

View full abstract

Authors have studied on the resin restorative materials which can adhere strongly to tooth structure. During these studies, various amino acid acrylate have been synthesized, among them, N, O-dimethacryloyl tyrosine (DMTY) was most favourable. Based on this composition, a bonding system which can polymerize with redox system was prapared and applied as an bonding agent between human dentin and composite resin. In the present investigation, the effect of concentration of DMTY and the kind and amount of catalyst on the adhesive strength was studied. From the observation, such an composition as DMTM (30)-HEMA (70) mol% monomer into which both 1.0wt% of BPO and sodium benzene sulfonic acid, showed the favourable adhesive strength of 44kg/cm² to the polished (by abrasive sand paper of JIS600) human dentin.

View full abstract

The tarnish test, wear test and morphological, compositional investigations were performed using Ion-plated specimens which plated Type IV gold alloy to non-precious alloys. Results 1. The resistance to tarnish of the Ag-In and Ag-Cu system alloys was improved by this Ion-plating preparation. 2. The amount of wear of the Ion-plated specimen was large to Type IV gold alloy, but small to the porcelain and enamel. 3. The amount of wear of Type IV gold alloy casts and the Ag-In system alloy was great to the Ion-plated specimen, while that of Ni-Cr system alloy, porcelain and enamel was small. 4. The structure of the Ion-plated film consisted of very fine crystals. 5. The composition of the Ion-plated film varied as compared with that of the original alloy, and the distribution of the component elements in the film was not uniform. It was assumed that the reason for this is the difference in the evaporation velocities of the component elements.

View full abstract

It is reported that methacrylates with both hydrophobic and hydrophilic groups promote the interpenetration of monomers into tooth substrates. 2-Hydroxy-3-phenoxypropyl methacrylate (HPPM) and 2-hydroxy-3-β-naphthoxypropyl methacrylate (HNPM) were only effective for adhesion to etched enamel. The bond strength was 18MPa when 5% 4-methacryloxyethyl trimellitate anhydride (4-META) in MMA, initiated by tri-n-butyl borane (4-META/MMA-TBB resin), was applied to dentin treated with 10% citric acid and 3% ferric chloride (10-3). The 10-3 solution did not have any adverse effects on the higher order structure of dentinal collagen during demineralization. It has been found that the adhesion promoting monomers, HPPM, HNPM and 4-META, are effective at increasing bond strength to dentin and enamel, and that there is a strong relationship between interpenetration and the bond strength. The affinity of HPPM and HNPM for hard tissues was weaker than that of 4-META and they could not promote monomer interpenetration deeply enough into the intact dentin. SEM observations of dentin side tensile fracture specimens showed cohesive failure of the demineralized dentinal region.

View full abstract

In attempting to establish a more accurate electronic method for measuring root canal length, a previous study by Usui has shown that resistance and frequency in an electronic apparatus had an influence on the meter indicating value. The purpose of this study was to examine clinically the influences of electrical resistance and frequency in the apparatus on the meter indicating value during the application of the “Endotape Method”. The results indicated that the meter indicating value increased in accordance with an increase in resistance and became slightly greater with an increase in frequency. Application of the “Endotape Method” allows measurement of the root canal length even if there are conductive substances in the root canal.

View full abstract

The purpose of this study was to investigate the effects of testing temperature(5〜50℃), absorbed water and thermal cycling on composite restorative materials. Three composite resins with different compositions (Isopast, Silar Clearfil-F) and two unfilled PMMA resins (Uni-Fast, Sevriton) which were used as controls, were chosen in order to examine their compression properties, and stress relaxation and surface characteristics. The resistance to compression of all materials tested decreased proportionately with an increase in the testing temperature. A high resistance was observed for two composite materials, Silar and Clearfil-F. Isopast, consisting of an MFR composite, had a resistance value which was lower than that of the unfilled resins. The effect of absorved water on the compression properties was less than that of temperature. However, a relatively larger absorbed water effect was observed for Isopast and Sevriton compared with the other materials. Although the rate of stress relaxation was hardly changed at temperatures below 37℃, it was greatly increased at temperatures above 37℃ in all materials except Silar. Thermal cycling (within 2, 000 times) had little affect on the compression properties, the rate of stress relaxation and the surface characteristics of the cured composite resins.

View full abstract

To develop a new elastomeric impression material “Themoplastic-elastomer impression material” which indicates reversible thermal change, polycaprolactone-poly (dimethylsiloxane) block copolymers were designed and synthesized as a base polymer of the material. A coupling method was adopted to link mono-and/or difunctional polycaprolactone and poly (dimethylsiloxane) α, ω-diol, using α, ω-bis (dimethylamino) octamethyltetrasiloxane as a coupling agent. Block copolymers were obtained which had rubber elasticity at room temperature and reproducibility above the temperature of 55℃, at which the caprolactone segments melted. The dynamic rigidity of the blockcopolymers ranged from 0.2MPa to 0.5MPa at 25℃ (20〜70Hz). Melting viscosities varied with the molecular weight. They were less than 900Pa・s for high molecular weight compounds and less than 200pa・s for low molecular weight compounds, respectively, at 70℃ and 2sec^-1.

View full abstract

Metallurgical and chemical properties of several Ti base Ti-V-Fe-Al system alloys and Ti-Mo-Al system alloys which exhibit the shape memory effect were studied, and their applicability to dentistry was discussed. Strip specimens were deformed to half circles with a diameter of 17mm at room temperature and heated. Ti-11V-2Fe-3Al and Ti-11.5V-2Fe-3Al alloys began to recover their shape at 90℃ and 60℃, respectively, which corresponds to their As temperatures. At 210℃ the recoveries had ratios of 97% and 63% respectively. The recovery was maintained even after cooling the specimen to 30℃. On the other hand, in the case of Ti-Mo-Al system alloys, two specimens of Ti-11.2Mo-3.4Al and Ti-14.1Mo-3.4Al were examined, but they showed insufficient shape recovery. Further studies on optimal concentrations are required for this alloy system. Anodic polarization behavior of Ti-Mo-Al system alloys, together with pure Ti, Ti-6Al-4V and typical shape memory alloy Ti-Ni, were measured in a 1% NaCl solution at 37℃. Up until 1, 100mV, all specimens showed a constant, small amount of current density which resulted from the formation of passive surface film. By further increasing the electric potential, however, an abrupt increase in current density was observed for Ti-Ni. On the other hand, in specimens such as pure Ti and Ti-base alloys, small peaks in current density were observed at about 1, 500mV, but by further increasing the potential to 2, 000mV, an almost flat current density curves was obtained. This suggests the reformation of the secondary passive film. Based on these results, it may be possible to use Ti-11〜11.5V-2Fe-3Al alloys for dental implants. Futher experiments on the mechanical and other properties will be carried out.

View full abstract