Study On The Ltd And The Crown Fitness Of Microwave Sintered Nano-Zirconia Ceremic For Dental Use

Objective:1. To compare the LTD of dental zirconia by sintering in the microwave furnace and conventional furnace;2. To compare the fitness of dental zirconia ceramic crown by sintering in the microwave furnace and conventional furnace and provide a reference for oral clinical application.Materials and Methods:1.48 zirconia wafer specimens were fabricated and randomly divided equally into two groups. One group was sintered in a microwave furnace (M group). The other group was sintered in a conventional furnace(C group). The samples from two groups were divided into 2 groups respectively according to the different processing time (A group:LTD Oh, B group:LTD 5h) and received different period of artificial aging in autoclave at 134? with 0.2 MPa. After aging, the m phase fraction was determined by X-ray diffraction analysis. The biaxial flexural strength was performed by universal testing machine. The fracture cross section was scanned by SEM.2. The mandibular premolar teeth in vitro were used to prepare full ceramic crowns.Ten resin die was impressed by silica gel.Ten zirconia ceramic crowns were fabricated by CAD/CAM and randomly divided equally into two groups. One group samples were sintered in microwave oven and the other group was sintered in conventional oven. All crowns and dies were cut along the centre line after adhered to the die. The gaps of crowns were observed under SEM and compared that sintered by two sintering methods.Results:1.The m phase of zirconia from group CA,CB,MA,MB were (0.20±0.07)%, (16.38±0.11)%,(0.19±0.05)%,(16.93±1.17)%.Group CA and group CB, group MA and group MB have significant differences (P<0.05). The grain size of zirconia sintered by microwave method was uniform. The fracture surface of zirconia showed no obvious crack and the grain size lager after LTD 5 h.2.The biaxial flexural strength of zirconia from group CA,CB,MA,MB were 1061.4±57.43Mpa,1033.9±86.32Mpa,1005.30±56.39Mpa,1004.90± 84.00Mpa. Each group have no no significant differences (P>0.05).3. Marginal fit and axial plane of zirconia ceramic crowns sintered by two methods have no significant differences (P>0.05). Shoulder suitability and occlusal surface have significant differences (P<0.05).Conclusion:1.the LTD m phase contents of zirconia performance of zircinia sintered by microwave method were similar to the zirconia sinrered by conventional method.2. Microwave sintered cercon zirconia crowns appeared to have clinically acceptable marginal fit.