ABSTRACT
It is of great importance to set up the Dental Equipment courses in the stomatology edu-cation for the undergraduates to cultivate new practical talents. In this paper, the teaching reform of Dental Equipment course and experience in teaching in China Medical University was proposed and discussed, especially the physical principles and practice classes was introduced. The physical principles of the equip-ment were introduced in the class to clarify the working mechanism and applications of the relative dental equipment, followed by the practice class for the operation of the equipment. The results demonstrated that the basic principles and cutting-edge technologies related to the equipment were also necessary parts of the dental equipment courses besides the instruction of the equipment widely applied in clinics. Content of practice class should cover the operation of both the basic dental equipment and digital equipment, which enables the students to expand the knowledge base on dental equipment for clinics. The reasonable cur-riculum design makes it easy for the teaching of the interdisciplinary subject, and the students can benefit from the curriculum. Besides, it is also favorable for the improvement of the equipped environment. The teaching method and experience herein are worth to be popularized.
ABSTRACT
BACKGROUND: There are many studies on the effect of different experimental parameters on the tetragonal phase of zirconia, but it is unclear whether pH values have effects on the tetragonal phase in hydrothermal reactionOBJECTIVE: To prepare two zirconia systems via hydrothermal method and to regulate the tetragonal phase purity and control the grain size of zirconia (ZrO2) crystal by pH values.METHODS: Analytical reagents Zr(NO3)4?5H2O and Y(NO3)3?6H2O were adopted as reactors, and nano-sized neat ZrO2 and yttria-stabilized tetragonal ZrO2 polycrystal (Y-TZP) powders were synthesized using the hydrothermal method. X-ray diffraction was adopted to characterize the influence of pH values and pH regulators (NaOH solution and ammonium hydroxide/NaOH solution) on phase purity and grain size of tetragonal zirconia.RESULTS AND CONCLUSION: Pure zirconia samples with a grain size lower than 20 nm were obtained through the hydrothermal method, and samples with higher tetragonal phase content compared to monoclinic phase could be derived when the pH value was higher than 10. The optimal pH values for neat zirconia and Y-TZP were 13 and 12,respectively. Furthermore, the ammonium hydroxide/NaOH solution was more favorable to enhance the content of tetragonal zircona. Therefore, the control of pH values and rational choice of pH regulators can improve the tetragonal phase purity and grain size of zirconia.
ABSTRACT
BACKGROUND:Zirconia is considered to be one ofthe promising prosthodontics materials because of its high strength, high hardness, excelent wear resistance and excelent corrosion resistance. However, the development of zirconia is hindered owing to the uncertainty in long-term stability of zirconiaal-ceramic crowns such as the cracking (chipping) of veneering porcelain and deterioration of mechanical properties of zirconia dental crowns under intraoral conditions. OBJECTIVE:To summarize the preparation of zirconia bioceramic and its application progress in the field of prosthodontics. METHODS:The properties, crystal structure, preparation and use of zirconia in prosthodontics were reviewed. Reasons that affected the stability of zirconia were also discussed. The future development of zirconia was forecasted. RESULTS AND CONCLUSION:Preparation of zirconia bioceramics involves the folowing aspects:powder synthesis, biscuit molding, and ceramic sintering.To improvethe istability of zirconia al-ceramic crowns,we optimize the preparation of zirconia powder topromotethe purity, mechanical properties, biological properties and stability. Furthermore, it is necessary to explore the effects of crystal nucleation, growth, second phase and grain size on crystal stability and biomechanical propertiesof thetooth abutment, as wel astoconduct an in-depth theoretical analysis on the effect oftooth abutmentand lattice matching of porcelain crowns on the interface.