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Objective: To synthesize nano-hydroxyapatite (nano-HA) and evaluate its effect on the occlusion of dentinal tubules in vitro, and therefore provide evidence for the clinical application., Methods: (NH(4))(2)HPO(4) and Ca(NO3)2 were used to form nano-HA, which was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FTIR) and X-ray diffractometer (XRD) respectively. Twenty-four dentin slabs were obtained from 8 healthy third molars and randomly divided into 3 groups, which were control group, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) group, and nano-HA group. After the CPP-ACP and nano-HA were topically applied to the slabs of two study groups twice a day for 7 days, the surface of slab dentin was observed using SEM., Results: SEM, TEM, FTIR, and XRD tests showed that nano-HA was synthesized successfully. SEM observations revealed that the sealing of dentinal tubules of nano-HA group was extremely high when compared with those of control and CPP-ACP group., Conclusions: In comparison with CPP-ACP, nano-HA could occlude dentinal tubules more effectively in vitro.

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.

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.

Objective: The purpose of this study was to explore the preparation method of nanometer powders of dental alumina ceramics., Methods: The 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)., Results: The 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., Conclusion: With the proper preparation condition, weakly agglomerated powders of alumina in nanometer particle size could be obtained.