Titanium and titanium alloys were anodic oxidized to investigate the method reproducing color similar to that of the tooth, then weight loss and color changes of the metals after wear tests were investigated. Four kinds of metals, i.e. Ti, Ti-6 Al-4 V, Ti-6 Al-7 Nb and 50 at% Ni-Ti, were tested. The experimental conditions, i.e. surface finishing, cleansing, pickling in acid, anodic oxidization and heat treatment, were examined. After such treatment, the specimens underwent a wear test by tooth brushing, then weight loss and color changes of the metals after testing were measured and compared to values obtained before testing. It was found that all four kinds of metals could reproduce the tooth color. The oxide layers obtained by anodic oxidization were relatively thick even and were measurable in sum. All specimens maintained being sufficient wear resistance with the thickness of the oxide layer mainly affected by heat treatment. The color and composition of oxide layers was affected by the titanium content, presence of other metal elements, and their oxides. The maintenance of tooth color against wear was chiefly due to the original metal color itself.

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In the application of surface modification technology, nitrogen and oxygen are sealed in a vacuum furnace, while titanium casting specimens were heat-treated at reduced atmospheric pressure and at a temperature lower than titanium's transformation point. The samples formed solid-solution layers of functionally graded structures on the surfaces. cast specimens of titanium materials were made with commercial Pure titanium (CP titanium) and titanium alloy (Ti-6 Al-7 Nb). Experiments performed on processed specimens included tensile strength, elongation, Vickers hardness, deformation of the heat treatment test and SEM image observation. Surface hardening of titanium increased, but surface hardening did not influence tensile strength. Specimens did not deform due to the influence of the heat treatment. Elongation increased slightly, but the gap size could not be confirmed before or after the treatment. Reforming could be observed only in the limited surface of the specimens on SEM images of the metal surface.

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The castability, the cast surface property and mechanical characteristics of the experimental magnetic palladium-cobalt-silver alloy were compared with those of the commercial dental gold-silver-palladium alloy and type 3 gold alloy. And the metallograghic examination and measurement of the attraction force to the commercial magnetic material were executed. The conclusions were as follows 1. The castability of the experimental magnetic alloy was the same as that of the commercial alloys. 2. The roughness of the cast surface was greater than that of the commercial alloys when cast with a gas-blow pipe. However, surface roughness was similar when cast with a high frequency microwave and argon arc. 3. Hardness and elastic modulus of the casting were greater compared with those of the commercial alloys. Both were greater on average when casting with a high frequency microwave and argon arc. 4. Uniform dispersion of all component elements was noted. 5. The attraction force was 320 gf for EX 400 and 430 gf for EX 600.

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To evaluate the cushioning effects of petrolatum-painted casting ring liners on the hygroscopic expansion of investment materials, cushioning ability was determined for fifteen ceramic liners (A:rockwool type, B:ceramic fiber low temperature type, C:ceramic fiber standard type, D:ceramic fiber low temperature-standard type, E:kaolin type). Petrolatum-painted liners were seated inside the sliding frame of an apparatus for expansion measurement, and then the hygroscopic expansion was measured for 120 min. Cushioning effects were calculated by the difference between hygroscopic expansion with and without liner. The cushioning effect of liners increased with time and peaked at 20 min, then markedly decreased by 30〜45 min, and changed only slightly thereafter. In eleven liners, the cushioning effect showed a positive value by 120 min starting 15 min after the water was poured. The maximum cushioning effects of fifteen liners were noted in D group liners.

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