The aim of this study is to evaluate the physical and mechanical properties of our homemade investment material for the IPS-Empress2 castable ceramic. The IPS specific investment material was taken as control. Results show that the setting time, density before heating, density after heating, rate of open hole, compressive strength at 2 hours after setting and the compressive strength after heating to 920 degrees C of the homemade investment material are 9 minutes, 1.813 g/cm3, 1.402 g/cm3, 38.1%, 5.42 MPa and 8.37 MPa respectively, which are comparable or even better than the specific material. Under the SEM, the crystals of the phosphate hydrate in our homemade material are smaller than those in the special material. Since the physical and mechanical properties of our homemade investment material are comparable or superior to those of the specific material, a conclusion is drawn that it has a promising prospect of future clinical application.
Aluminum Silicates ; chemistry ; Crowns ; Dental Casting Investment ; chemical synthesis ; chemistry ; Dental Materials ; chemical synthesis ; chemistry ; Dental Porcelain ; chemistry ; Lithium Compounds ; chemistry ; Microscopy, Electron, Scanning ; Shear Strength ; Surface Properties ; Tensile Strength

IPS-Empress2 is a successful all-ceramic restoration system. To lower its cost, and promote its application, a kind of homemade fast investment material has been developed. The aim of this study was to evaluate the expansion properties of this investment material. The setting expansion, thermal expansion and total expansion of the homemade fast investment material were tested. The same properties of the IPS special fast investment material were also tested as control. Then the SPSS statistics software was used to evaluate the differences between the homemade material and the special material. The results show that the setting expansion rate, thermal expansion rate and total expansion rate of the special investment material for IPS-Empress2 are 0.858%, 1.11% and 1.17% respectively, while the same parameters of the homemade investment material are 0.798%, 1.09% and 1.16% respectively. There is no statistically significant difference in these expansion properties between the two investment materials. In conclusion, the expansion properties of homemade fast investment material are comparable to those of the special fast investment material, so it can compensate for the cast contraction of IPS-Empress2 castable ceramic precisely.
Aluminum Silicates ; chemical synthesis ; chemistry ; Crowns ; Dental Materials ; chemical synthesis ; chemistry ; Dental Porcelain ; chemical synthesis ; chemistry ; Lithium Compounds ; chemical synthesis ; chemistry ; Surface Properties ; Tensile Strength

The appearance of dental porcelains is comparable to natural teeth. This study discusses the effect of Y2O3 addition to the fluorescent property of dental porcelains. The composition of dental porcelains contained Y2O3 as the fluorescent agent and base frit. The combinations of Y2O3 added consist of a series with 0.5, 1.0, 1.5, 2.0 and 2.5 wt% respectively, based on the total composition. In the extreme condition, fluorescent agents are added from 5.0 up to 10.0 wt%. In order to enhance the fluorescent property of dental porcelains, an opacifiying agent, cerium oxide (CeO2) was also added to dental porcelains composition. The fluorescent property was determined using Spectroline EF-1400C/F that emits 240 nm wavelength ultraviolet light. The microstructure was examined by Scanning Electron Microscope (SEM). The result shows that, the fluorescent properties displayed are similar to natural teeth when subjected to ultraviolet light. SEM micrograph was able to show the fluorescent agent dispersed in glass phase. Increasing additions of Y2O3 gave the fluorescent properties near to natural teeth.
*Biocompatible Materials ; *Cerium ; Dental Porcelain/*chemical synthesis ; *Esthetics, Dental ; Fluorescence ; *Yttrium

OBJECTIVEThe purpose of this study was to explore the preparation method of nanometer powders of dental alumina ceramics.

METHODSThe effects of concentration of inorganic precursors, pH value, calcination temperature and ageing time on the synthesizing process, phase composition and microstructure of the materials were studied. Aluminium nitrate with concentrations of 0.03 mol/L, 0.05 mol/L, 0.1 mol/L and 0.2 mol/L were used as inorganic precursors to prepare alumina powders via sol-gel method. Ammonia water was added into the solutions to adjust the pH values to 5, 9 and 11. The dried gel was then calcined under different temperatures, from 950 degrees C to 1200 degrees C. The prepared alumina powders were studied by using X-ray diffraction (XRD), and scanning electron microscope (SEM).

RESULTSThe alumina powder which was prepared with 0.1 mol/L aluminium nitrate, pH 9, and calcined at 1200 degrees C for 10 min showed good physical characteristics. The diameter of final powder was about 70 nm.

CONCLUSIONWith the proper preparation condition, weakly agglomerated powders of alumina in nanometer particle size could be obtained.

Aluminum Oxide ; chemistry ; Biocompatible Materials ; chemical synthesis ; Ceramics ; chemical synthesis ; Dental Materials ; chemical synthesis ; Dental Porcelain ; chemistry ; Gels ; Hydrogen-Ion Concentration ; Nanotechnology ; Particle Size ; Powders