| Ceramic materia ls have been important dental crown and brid ge materia ls inclinica l applica tion more widely, because of the excellent aesthetic properties,physica l and chemica l stability. Since all-cera mic materia ls have quite similar optica lproperties as the natural tooth structure and can eliminate the problems associa tedwith the meta l substrate of meta l-ceramic restorations.W ith excellent biocompatihilityand light obstruction, various all-cera mic systems are preva iling the marketnowada ys. To satis fy the patients and dentists of the aesthetic requirements, scholarshave developed heat-pressed ceramic (IPS–Empress,E-ma x), the alumina ceramic (In-Ceram, Procera AllCera m),a nd the zirconia ceramic(Cercon,La va)and other allceramicrestoration system. The aesthetic properties of heat-pressed ceramic arebetter, but it was limited by the bending strength, just suitable for anterior teeth.Aluminum and zirconia ceramic system has higher flexural strength, but due to itstransparency, the defective influe nce of the aesthetic effect limits the applica tion indental restoration. However, its processing methods combined with computer-aideddesign and computer-aided ma nufacture(CAD / CAM) technology, pre-sintering ofmachinable ceramics can be cut by CAD / CAM technology to process, through thefina l sintered to fully dense. Produced by the technical support of all-cera mic crownand brid ge can be easily processed with high strength and accuracy. Therefore, a newdental machinable ceramic of high strength, high toughness, easily processing inprosthodontics clinica l with particularly translucency simultaneously will have greatpractica l value. The ceramics with outsta nding flexibility and machinability has been the objective to overcome the defect such as the brittleness, fracture of ceramics andlarge shrinkage, while nano-ceramic is considered to be a strategic way to solve thisproblem.The subject of this paper was selecting diatomite as raw materia ls, preparation ofa new type of dental machinable ceramic materia ls, using the framework of its loosestructure and the addition of nano flexibilizers such as nano zirconia, nano alumina,nano titanium dioxide whisker to improve the mecha nical properties. Study theeffects of sintering temperature and calefactive velocity on the properties ofdiatomite-based dental ceramic materia ls, It was also screened the sintering process ofthe new type of dental ceramics. Its mecha nical and aesthetic properties of dentalceramic materia ls basica lly meet the requirements, with its excellent machinability itwill have broad prospects. The results can be used as the basis of the further research. Objective:To study the effects of sintering temperature on the properties ofDia tomite-based dental ceramic, It was screened the temperature for the developmentof the new type of dental ceramics on research.Methods:Based on the composition of diatomite, the new dental machinable ceramicwas added with nanometer materia ls and obtained through the treatment of ballmilling,dry-pressing and sintering Dia tomite-based dental ceramic was prepared bydry press method and sintered at different temperatures from 600℃to 950℃at per50℃. The physica l properties (three-point bending strength, fracture strength andmicroha rdness) and machinability were measured.Results:The materia l after sintering had smooth surface, no crack ivory in it andoyster white.W ith the rising of sintering temperature,microha rdness and fracturetoughness of the Dia tomite-based ceramic increased. The best machinability of theceramic appeared at the temperature of 750℃(P <0.05).In this sinteringtemperature ceramic materia l linear shrinkage rate reached to 3.06±0.27,the densityreached to1.96±0.07.Conclusion:By controlling the sintering temperature, the properties of Dia tomitebasedceramic could be changed to fit the requirments of dental CAD/CAM allceramic. Objective:To study the effects of calefactive velocity on the properties of Dia tomitebaseddental ceramic,the relationship between the structure and properties of themateria l was studied.It provided basis for the development of the new type of dentalceramics on research.Methods:Based on the composition of diatomite, the new dental machinable ceramicwas added with nanometer materia ls and obtained through the treatment of ballmilling,dry-pressing and sintering. Dental ceramic was sintered at different velocityfrom 50℃/h to 400℃/h at per 50℃/h. X-ray diffractometer (XRD) and scanningelectron microscope (SEM) were used to characterize the crysta l form andmicrostructure. The mecha nical properties (three-point bending strength, fracturestrength and microha rdness) of diatomite-based ceramic were recorded.Results:The internal structure of the materia l observed in SEM presentedpolycrysta lline structure and the grain boundary clarity. Sintered diatomite-basedceramic materia l formed quartz crysta l (SiO2), tetragona l ZrO2,α-phase Al2O3 andTiO2 anatase crysta ls before sintering.Sintering temperature is 750℃, calefactivevelocity of 200℃/ h of ceramic with better machinability (P<0.05).Conclusion:The mecha nical and esthetic properties of the new type ofDia tomite-based dental machinable ceramic were basica lly qualified but the flexuralstrength still needs to be increased. |
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