| Summary: | 碩士 === 中山醫學大學 === 牙科材料研究所 === 92 === Porcelain fused to metal prostheses had been used for many years, while the biocompatibility and esthetic properties were still insufficiently. The all ceramic prostheses were developed for improving those disadvantages. The translucency and flexural strength are most important properties when choosing all ceramic materials.
The purpose of this study is to evaluate the translucency and biaxial flexural strength of all ceramic core materials, as well as the microstructure in different ceramic systems.
Three kinds of all ceramic core materials were chosen: IPS Empress(R) 2, VITA In-Ceram(R) Alumina and VITA In-Ceram(R) Zirconia. The specimens of IPS Empress(R) 2 were fabricated by heat-pressed method, named Em2 group, and the specimens of VITA In-Ceram(R) Alumina and VITA In-Ceram(R) Zirconia were fabricated by DCS(R) system, named InA group and InZ group. All disc specimens were prepared 0.5+0.05 mm and 0.8+0.05 mm in thickness and 14 mm in diameter ( n = 5 per group ). After grinding and polishing with sandpaper, simulate firing procedures (according to the manufacturer's recommend) were applied to all specimens.
The color meter was used to measure the translucency of specimens (0 = transparent, 1 = opaque), then the biaxial flexural test was used to measure the flexural strength of the specimens. The data of translucency, load (N) and flexural strength (MPa) were analyzed by one-way ANOVA followed by Tukey multiple comparison test for significant findings ( α = 0.05 ). Weibull statistics were also applied to all data for calculating the Weibull modulus (m). The fracture surface of these core materials were observed under scanning electron microscope ( SEM ).
The translucency values in order of most translucent to most opaque were as follows: Em2 0.5mm, Em2 0.8 mm, InA 0.5 mm, InA 0.8 mm, InZ 0.5mm, InZ 0.8 mm. The load (N) data in order of high to low were as follows: InZ 0.8mm, InA 0.8 mm, Em2 0.8 mm, InZ 0.5 mm, InA 0.5 mm, Em2 0.5 mm. The flexural strength of InZ were highest, follow by InA, and Em2, and there was a statistically significant difference among these 3 kinds of core materials. Weibull modulus in order of high to low were as follows: Em2 0.8mm, Em2 0.5 mm, InZ 0.8 mm, InA 0.5 mm, InA 0.8mm, InZ 0.5 mm. The SEM analysis of the fractured surfaces indicated that Em2 was mostly of transgranular fracture of lithium disilicate crystalls, InA and InZ was mostly of transgranular fracture of alumina platelets, the zirconia particles of InZ were also observed. IPS Empress(R) 2 can be used for anterior region because of higher translucency and lower flexural strength. VITA In-Ceram(R) Alumina and VITA In-Ceram(R) Zirconia can be used for posterior region because of lower translucency and higher flexural strength.
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