[Influence of zirconia content on translucency of zirconia-toughened alumina glass-infiltrated ceramic].

OBJECTIVE: The objective of this study is to investigate the influence of zirconia content which is 0-30.0% weight percentage of matrix on translucency of zirconia-toughened alumina glass-infiltrated ceramics. METHODS: Seven groups were divided according to different weight percentage of zirconia (0, 2.5%, 5.0%, 7.5%, 10.0%, 20.0% and 30.0%). After sintering, infiltrating and polishing, spectral transmittance was determined with spectrophotometer under D65 standard source. Contrast ratio was also tested by whiteness colorimeter. RESULTS: With mass fraction of zirconia increasing from 0 to 30.0%, spectral transmittance reduced from 0.406% to 0.058%, while contrast ratio value increased from 0.849 +/- 0.005 to 1.015 +/- 0.006. When zirconia content was 10.0%, contrast ratio was 0.990 +/- 0.008. When it was more than 10.0%, transmission rate of the downward trend and contrast ratio of the rising trend became flat. CONCLUSION: Zirconia content has a direct impact on translucency of zirconia-toughened alumina glass-infiltrated ceramic, which is essentially opaque when zirconia content is 10.0%. When mass fraction of zirconia is more than 10.0%, the influence of zirconia content is reduced.

[Microstructure analysis of the machinable infiltrated ceramic fracture surface].

OBJECTIVE: To compare the fracture surface of the machinable infiltrated ceramic (MIC) prepared in different conditions, and to relate its strength and toughness to the differences in their microstructures. METHODS: The Al2O3 matrix were prepared, infiltrated by the machinable glass and crystallized. Based on sintering and infiltrating time and conditions, the specimens were divided into three groups: Perfect group, insufficiently infiltrated group, mal-sintered substrate group. Specimens were fabricated, three point flexural strength and elastic modulus were tested, and the microstructure of the MIC fracture surfaces was analyzed by means of scanning electron micrograph (SEM) observation. RESULTS: The strength of the insufficiently infiltrated group and mal-sintered substrate group were lower than that of the perfect group, and faults in the microstructure of these two groups also proved this. The foreland of glass infiltrating in the Al2O3 and the interface of glass and complex demonstrated that the Al2O3 surface was smoother than the complex and there was a big crack in the glass but not in the complex which proved the crack resistibility of glass and Al2O3 were smaller than that of the complex (MIC). CONCLUSION: Correct preparing process could make the glass infiltrate into properly sintered Al2O3 sufficiently which ensured best mechanical properties of the complex.

[Investigation of the function of the glass colorant on the machinable infiltrated ceramics color].

OBJECTIVE: To investigae the function of the glass colorant on the color of the machinable infiltrated ceramics(MIC). METHODS: Five kinds of glass with different colorant were infiltrated through the aluminous matrix by heating the components to 1 100 degrees C for 2 hours. The specimens surface was polished, and their thickness was 0.5 mm. RESULTS: The refractive index of the MIC infiltration glass was 1.59691 (587.6 nm, nd) . The most different parameter of the MIC color were L*, then a*, and b* had little difference . The parameters of the color space of MIC were: L*(64.55-71.46), a*(3.35-7.38), b*(10.00-12.41), Ca*b*(11.38-13.95), ha*b*(54.07-73.00). These were almost close to the color parameters of Vita In-ceram. CONCLUSION: This experiment proved that the glass colorant was changed the MIC color parameters, and the main function was on L*, then a*. The ceramic color was up to the requirement of clinic.

[Investigation of machinable-infiltrated-ceramic glass infiltrating through the aluminous matrix].

This investigation was amied at the infiltrative capability of the machinable-infiltrated-ceramic(MIC) glass and the color of the composite after the MIC glass infiltrated through the aluminous matrix with different packing densities. By heating the components to 1100 degrees C for 2 hours, the MIC glass was made to infiltrate through the aluminous matrix with different packing densities. We measured the infiltrative depth and the color parameter and observed the rupture surface of the composite by means of SEM. There was a linear relation between the square of infiltrative depth and the packing density of aluminous matrix. The minimal depth was 3.092 mm. No relationship was noted between the composite's color coefficient and the packing density of aluminous matrix. In the rupture process of the composite, crack deflexion, crystal evulsion, and rupture through crystal could be observed. This experiment proved that the infiltrative characters of MIC glass meet the clinical requirement, the composite's color is steady and the mechanical intensity is stable.