Effects Of Different Sintering Systems On The Properties Of Alumina Doped With Zirconia

Objective:Master the zirconia preparation process that meets the mechanical performance requirements of dental zirconia.The effect of speed sintering system on the density,porosity,hardness,flexural strength,surface morphology and crystal structure of 0.25 wt%Al₂O₃doped 3Y-TZP was investigated.Methods:In the pre-experiment,the specimens which meet the mechanical properties requirements of dental zirconia were prepared by conventional sintering method.The pre-experiment was repeated three times,and the specimens prepared by conventional final sintering could meet the relevant national standards,and the relevant parameters of the pre-experiment process were recorded and used in the formal experiment.The relative effect of different sintering systems on the properties of zirconia was explored and summarized.The specific process is as follows.Firstly,0.25 wt%Al₂O₃and 3Y-TZP were fully mixed in a ball mill,and then the strips and discs were grown by dry pressing and cold isostatic pressing.After that,the specimens were pre-sintered in a vacuum hot pressing sintering furnace,After heating to 800℃at 3℃per minute,keep it at this temperature for 2 h,and then cooled in the furnace to prepare pre-sintered zirconium blocks.The pre-sintered zirconium blocks were randomly divided into two groups:chairside rapid sintering（SS group）and conventional pressureless sintering（CS group）.Two different sintering procedures were used to perform secondary sintering on the two groups of test pieces.The test piece needs to comply with the relevant standards,exclude the test pieces that do not meet the relevant standards,and replenish the loss test pieces.Ensure that each group of two different final sintering methods prepare 15 test pieces that meet the quality control standards.The specific test items are as follows.1.The density and apparent porosity of zirconia samples of two different sintering systems were measured by Archimedes drainage method.2.The surface hardness of CS group and SS group was measured by digital microhardness tester,three specimens in each group.3.Three point bending test was used to detect the flexural strength of two groups of specimens,3 specimens in each group.4.X-ray diffraction（XRD）and Standard Electronic Microscope（SEM）were used to detect the crystal structure of a typical sample in each group and to characterize the surface morphology of the two groups of samples.The effects of two sintering methods on the density,porosity,hardness,flexural strength,surface morphology and crystal structure on the results were investigated.Results:The experimental parameters of this study can be used to prepare specimens that meet the mechanical properties of dental zirconia.The performance comparison results of the specimens prepared by two different sintering procedures are as follows.1.The crystalline structure and composition of the two sets of test specimens meet the requirements of dental zirconia,and the crystalline structure and composition of the two are similar.2.Compared with the conventional sintering（CS）group,the density of chairside speed sintering（SS）had no significant difference.3.The hardness of SS group was slightly higher（P<0.05）.4.The apparent porosity of SS group was higher than that of CS group（P<0.05）,but the flexural strength of SS group was slightly lower than that of CS group（P<0.05）.5.And the results show that the grain size of SS group is smaller and denser than that of CS group,but the grain arrangement is not uniform and pores are visible.6.The fracture surfaces of the specimens prepared by the two sintering methods are all composite of transgranular fracture and intergranular fracture.Conclusions:The zirconia preparation process used in this study can prepare specimens that meet the mechanical properties of dental requirements.The speed sintering process has some influence on the mechanical properties of 3Y-TZP doped 0.25 wt%Al₂O₃,but mechanical properties of the material can meet the clinical requirements.