Effect Of Thermal-cycling On The Bond Strength Of Titanium And Porcelain After Micro-arc Oxidation Of Different Electrolytes

Objective:To study the effect of thermal-cycling on the bonding strength of titanium-ceramics after micro-arc oxidation treatment with 20g/L Na2SiO3 solution and20g/LMgSiF6 solution as electrolyte.Methods:78 pieces of cut pure titanium specimens（25mm×3mm×0.5mm）were randomly divided into three groups A,B and C,each group with 26 pieces,then three groups were sand blasted.After that,B and C were processed with micro-arc oxidation.The electrolyte solutions were 20g/LMgSiF₆ solution and 20g/L Na2SiO₃ solution.The next,2 samples were randomly selected from each group to observe the morphology of the film formed by scanning electron microscopy（SEM）.The remaining 24 pieces of each group were sintered according to the ISO9693 standard.After that,the test pieces of each group were randomly divided into three groups:A1,A2,A3,B1,B2,B3,C1,C2and C3,with 8 pieces in each one.The group 2 and 3 carry on 3000 and 6000thermal-cycling respectively.Each group was randomly selected 6 pieces for three-point bending experiment.Calculate the strength of titanium porcelain bonding.Analyze the differences in bonding strength between groups with the statistics.The remaining two specimens in each group were embedded in epoxy resin to reveal the interface of titanium and porcelain.The morphology and element diffusion distribution of the bonding interface were observed by scanning electron microscopy（SEM）and energy dispersive spectroscopy（EDS）.Two specimens were randomly drawn from 6 specimens after three-point bending in each group,and the titanium substrate after titanium-ceramic separation was observed.Results:Bonding strength of titanium porcelain in each group measured by three-point bending:27.86±1.70MPa（Group A1）,25.58±2.20MPa（Group A2）,25.03±1.92MPa（Group A3）,38.93±2.14MPa（Group B1）,25.73±4.00MPa（Group B2）,25.68±1.80MPa（Group B3）,38.05±3.00MPa（Group C1）,35.30±0.59MPa（Group C2）,31.73±1.93MPa（Group C3）,There was a significant difference in A1,B1,C1 without cold-heat cycle（P=0.00,P<0.05）.After 3000 cycles of cold and heat,the bonding strength of B2 group was decreased,which was significantly different from that of B1group(P_B2=0.00,P<0.05).There was no significant difference between A2 group and C2 group(P_A2=0.072,P_C2=0.052,P>0.05).After 6000 cycles of cold and heat,there was a significant difference between group A3,B3,C3 and A1,B1,C1(P_A3=0.022,P_B3=0.00,P_C3=0.001,P<0.05).The decrease of C3 group was 16.6%than that of C1 group,which was far smaller than that of B3 and B1 by 65.96%.Scanning electron microscopy（SEM）and energy dispersive spectroscopy（EDS）analysis showed that the number and range of pores in the interface increased with the increase of the number of cycles of cold and heat.Compared with the control group,the diffusivity of O element to titanium substrate decreased in both groups.Observe the residue of ceramic powder on the surface of titanium substrate after the separation of titanium porcelain,the residue ceramic powder of group C3 was the most.Results:Micro-arc oxidation technology can effectively improve the bonding strength of titanium porcelain.A certain number of thermal-cycling will reduce the bonding strength of titanium porcelain.The microarc oxidation treatment of 20g/L Na₂SiO₃solution can withstand the complex and changeable oral environment and is more suitable for clinical application.