| Fluorosilicic mica glass-ceramic for dental CAD/CAM system has its proximity with the teeth of the semi-transparent and better mechanical properties. The basical sintering thermal treatment has been confirmed on amount of preliminary researches. But its mechanical strength is limited and the colour is pure. Our experiments is based on the preliminary researches, designing differnt annealing treatments and add distinct mass of fractions aluminum borate whisker to improving the mechanical strength, and adding composite pigment containing zirconium-praseodymium yellow pigment and Zirconium-iron pink pigment to ameliorate the quality of glass-ceramic colour, providing the condition for clinical application with homemade fluorosilicic mica glass-ceramic.Content and methods:1. Based on the result of DTA analyzing and using orthogonal experiment, design reasonable annealing treatment over the cooling time in sintering of glass-ceramic: annealing at 540℃,580℃,620℃for 1h,4h,7h respectly. With the help of three-point bending test, SEM and XRD, studing the different isothermal anneal effects on flexible strength and microstructure of machinable mica based glass-ceramics.2. Use aluminum borate whisker as a reinforcing agent, adding 0.5wt%,5.0wt%,10.0wt% of ABOw into basic glass system, studing the effects on flexible strength and microstructure of machinable mica based glass-ceramics.3. Using 0.05wt%,0.10wt%,0.15wt%,0.20wt% of Zirconium-iron pink pigment match pairs with 0.15wt%,0.30wt%,0.45wt%,0.60wt% of zirconium-praseodymium yellow pigment, adding the composite pigment into basic glass system. With the help of measurement of Chromaticity, SEM and XRD, studing the influence of the different mass fraction composite pigment on colour of mica based glass-ceramics by sintering.Results:1. After annealing at different temperatures for different hours, the transverse rupture strength has incresed from 117.56±6.86Mpa of control group to 125.39±6.35Mpa, Among the annealing groups and non-annealing group showed significant difference(P<0.05). Annealing at 540℃for 1h, 4h, 7h and annealing at 580℃, 620℃for 1h, 4h, these transverse rupture strength showed no significant difference(P>0.05), while annealing for 7h at each temperature had(P<0.05).The transverse rupture strength was up to maximum 125.39±6.35Mpa when annealing at 620℃for 7h. Compared with annealing groups, the micromorphology characteristics of non-annealing group showed grain size inconsistency, less concentration and less homogeneous. After anneling at 620℃for 7h, he micromorphology characteristics showed the reduction of grain size, and its distribution was more homogeneous. The result of XRD showed no difference in the main crystalline.2. After adding different mass fractions of aluminum borate whisker, the transverse rupture strength has dynamic decreased in pace with the increasing mass fraction and showed significant difference(P<0.05), from 115.96±7.37Mpa of control group fall off to 43.27±5.59Mpa of 10.0wt% group. The macro morphology appeared obvious porosity. The results of SEM and XRD shows the microstructure and the main crystalline of the glass-ceramic and ABOw has changed.3. The chroma of four groups sinter within distinct mass fractions of composite pigment shows, the value of a~*,b~* has increased,the scope was 1.19±0.04 ~ 6.95±0.01 and 14.29±0.03 ~ 24.79±0.11 respectly, and has covered the a~*,b~* value scope of Vita classical shade guide. The scope of the L~* value was 85.91±0.04 ~ 78.78±0.02, beyond the a~*,b~* value scope of Vita classical shade guide. The change tendency of C~* ab value was more similar with b~* value. The H~* ab value has slightly decreased. The chromaticity has directed to red and yellow. The results of SEM and XRD showed no changes in the microstructure and the main crystalline.Conclusions:1. The reasonable annealing treatment over the cooling time in sintering of glass-ceramic has improved the microstructure and flexible strength of machinable mica based glass-ceramics. The best annealing treatment in our experiment is annealing at 620℃for 7 hours, then furnace cooling.2. The mechanical strength has dynamic decreased after adding 0.5wt%~10.0wt% of aluminum borate whisker into basic glass system, the microstructure and the main crystal phase both has changed. we considered that the aluminum borate whisker was not appropriate for our dental machinable mica based glass-ceramic as a reinforcing agent.3. After adding the composite pigment containing 0.05wt% ~ 0.20wt% of Zirconium iron pink pigment and 0.15wt% ~ 0.60wt% of zirconium praseodymium yellow pigment, the relationship between the concentrations of the added composite pigment and the chroma values was accorded with the principles of pigmentation, the colour of machinable mica based glass-ceramics has been improved, the value of a~*,b~* has covered the a~*,b~* value scope of Vita classical shade guide. and the results of SEM and XRD shows no changes the microstructure and the main crystal phase.. |
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