Generally, dental technicians clinically decide the sintering temperature of zirconia artificial teeth to mach the color of the teeth. However, the sintering temperature influence the microstructure and mechanical strength of ceramic body. In this study, to evaluate the free choice of sintering temp...
Generally, dental technicians clinically decide the sintering temperature of zirconia artificial teeth to mach the color of the teeth. However, the sintering temperature influence the microstructure and mechanical strength of ceramic body. In this study, to evaluate the free choice of sintering temperature lead to the problem of zirconia false teeth, the variation of microstructure, mechanical strength, and colortone of zirconia ceramics according to the change of sintering temperature were investigated. Bar type specimens were prepared from commercial zirconia block by cutting and polishing into 0.8㎝(L) × 1.0㎝(W) × 4.8㎝(H). Specimens were fired from 1,400 to 1,700℃ at 50℃ intervals and hold for 1hour at highest temperature. Apparent porosity, water absorption, firing shrinkage, bulk density, bend strength, whiteness were tested. Microstructures were observed by SEM. When fired above 1450℃, all specimens showed 0% of apparent porosity and water absorption, 20% of firing shrinkage, and 6.1g/㎤ bulk density regardless of firing temperatures. SEM photomicrographs showed grain growth of zirconia occurred above 1,600℃. Whiteness was also largely changed above this temperature. Maximum bend strength of 1,050MPa was obtained fired at 1,550℃. Bend strength slightly lowed above this temperature and showed 950MPa at 1,700℃. In order to fit the colortone of zirconia artificial tooth, arbitrary choice of higher firing temperature than 1,500℃ was not influenced on the mechanical strength up to 1,700℃.
Generally, dental technicians clinically decide the sintering temperature of zirconia artificial teeth to mach the color of the teeth. However, the sintering temperature influence the microstructure and mechanical strength of ceramic body. In this study, to evaluate the free choice of sintering temperature lead to the problem of zirconia false teeth, the variation of microstructure, mechanical strength, and colortone of zirconia ceramics according to the change of sintering temperature were investigated. Bar type specimens were prepared from commercial zirconia block by cutting and polishing into 0.8㎝(L) × 1.0㎝(W) × 4.8㎝(H). Specimens were fired from 1,400 to 1,700℃ at 50℃ intervals and hold for 1hour at highest temperature. Apparent porosity, water absorption, firing shrinkage, bulk density, bend strength, whiteness were tested. Microstructures were observed by SEM. When fired above 1450℃, all specimens showed 0% of apparent porosity and water absorption, 20% of firing shrinkage, and 6.1g/㎤ bulk density regardless of firing temperatures. SEM photomicrographs showed grain growth of zirconia occurred above 1,600℃. Whiteness was also largely changed above this temperature. Maximum bend strength of 1,050MPa was obtained fired at 1,550℃. Bend strength slightly lowed above this temperature and showed 950MPa at 1,700℃. In order to fit the colortone of zirconia artificial tooth, arbitrary choice of higher firing temperature than 1,500℃ was not influenced on the mechanical strength up to 1,700℃.
Keyword
#sintering temperature grain growth bend strength
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