Takashi Horibe

Properties of test metal ceramic titanium alloys

Four test alloys were prepared using a high frequency centrifugal casting machine and a ceramic crucible for the development of titanium bonding alloys that can be cast in the ordinary atmosphere. Of these alloys, 10.06% Ti, 78.79% Ni, 9.02% Pd, 1.77% Sn and 9.91% Ti, 78.56% Ni, 9.07% Pd, 1.86% Sn, 0.65% Ir could be cast by the conventional high frequency centrifugal method; however, 89.18% Ti, 8.75% Ni, 1.03% Pd, 0.28% Sn and 89.81% Ti, 8.15% Ni, 1.01% Pd, 0.18% Sn, 0.67% Ir could be cast only by the argon are melting method. The alloys 10.06% Ti, 78.95% Ni, 9.02% Pd, 1.77% Sn and 9.91% Ti, 78.56% Ni, 9.07% Pd, 1.86% Sn, 0.65% Ir showed excellent physical and mechanical properties and bonding strengths, surpassing those of the commercial alloys TPW and Unimetal. Concerning the elution of component elements, the amounts of titanium eluted from these alloys were far smaller than those from pure titanium or a Ti-6Al-4V alloy, and nickel elution, which has become an issue in relation to metal allergy, was almost nil in contrast to Unimetal (Ni-Cr alloy). The alloy 9.91% Ti, 78.56% Ni, 9.07% Pd, 1.86% Sn, 0.65% Ir showed properties that indicated its favorable use as an alloy for the bonding of dental porcelain.

Correlation between air-drying duration and bond strength of composite resins to teeth

Cavity preparations involve both enamel and dentinal walls, but moisture contamination of these surfaces adversely influences the effectiveness of bonding interface. This in vitro study investigated the relationship between air-drying time and the bond strength to bovine enamel and dentin for two types of composite resins and their bonding agents. Comprehensive shear bond tests were performed with a universal testing machine, and mean bond strengths were computed by an analysis of variance and by Scheffés multiple comparison test. No statistical differences were noted between the bond strength to the unetched and etched enamel and air-drying duration for bondings. The bond strengths to the etched dentin was comparable despite the time of air drying, but the bond strengths to unetched dentin were dependent upon the length of air drying.

Firing Behavior of Titanium and Titanium Alloy.

To use titanium alloys with excellent properties as prosthetic materials, the amount of the oxide film produced after firing and its physical properties, which have major effects on their binding with porcelain, were studied in pure titanium and Ti-6Al-4V alloy.The following results were obtained:1. The amount of the oxide film was related to conditions of firing. It was greater as the rate of the increase in the temperature was slower, the duration of firing was longer, and the final firing temperature was higher.2. The color of the oxide film was also related to conditions of firing. Pure titanium became whiter, and Ti-6Al-4V alloy became browner, as the amount of film produced was greater.3. The hardness was similarly related to the amount of film produced. The materials were harder as the film was thicker.4. At 1, 000°C the expansion rate of Ti-6Al-4V alloy was about twice that of pure titanium. The coefficient of expansion of the alloy was also slightly greater at 200-700°C. Pure titanium has a transition point near 885°C at which the crystalline structure changes from α-phase to β-phase, but this transition point was not observed in Ti-6Al-4V alloy.

Studies on photopolymerized crown and bridge resin. Part 1. Physical properties of Dentacolor.

Light activated composite resin, Dentacolor, was examined on chemical composition, polymerization characteristics and bonding to a metal and adhesive resin cement in order to confirm the dental application of it. For bonding, the surface of metal, Au-Ag-Pd alloy, was treated as follows; a) retention beads added, b) retention beads+alumina sand blasting+tin electroplated+adhesive resin cement (Panavia EX), c) alumina sand blasting+tin electroplated+adhe sive resin cement.The results were summarized as follows;1) Dentacolor consists of 31 wt% of urethane dimethacrylate with a small amount of other methacrylate (unknown) and 69 wt% of composite filler (inorganic phase 47 wt%).2) The surface hardness of the cured product of Dentacolor was little affected by a position of a specimen in a photo-irradiation apparatus (Dentacolor XS) and a shade of Dentacolor, however, conversion of polymerization, which was presumed by its hardness of a vertical plane, was relatively high in the center of a flask.3) Compared with heat cured composite resin (Isosit), the surface hardness, wear resistance and solubility in water of Dentacolor were nearly equal, but the bending strength and water sorption were slightly lower than those of Isosit.4) The bonding strength of Dentacolor when another layer was put on the surface of its cured product was comparatively high (170 kg/cm2) and its value was little affected by the irradiation time to the first layer.5) The bonding strength of Dentacolor to the metal was increased with the surface treatment of the metal except for the method a)(170-180 kg/cm2).6) After thermal cycling, a good improvement of marginal sealing was shown by the surface treatment of the metal except for the method a)