| Objective:In this experiment,the effect of different thermal acid etching time on the bonding strength of transparent zirconia to resin was studied,which laid a foundation for the further popularization and clinical application of thermal acid etching treatment of zirconia.Methods:A domestic transparent zirconia was selected as the research object in this experiment.The square specimen(8 mm×8 mm×1.5 mm,n=350)and the rectangular specimen(12 mm×5 mm ×1.5 mm,n=112)were prepared.The square and rectangular specimens were randomly divided into 14 groups:control group and alumina sandblasting group(50 μm,0.2 Mpa,20 s),Group A was 9.5%hydrofluoric acid thermal etching group,and A1-A6 groups were 5 min,10 min,20 min,30 min,60 min and 90 min hot acid etching group;Group B was 40%hydrofluoric acid thermal etching group,and B1-B6 were 5 min,10 min,20 min,30 min,60 min and 90 min hot acid etching group.And the following experiments were conducted:1.One sample was randomly selected from each square specimen,and the surface morphology of transparent zirconia was observed by scanning electron microscope.Two samples were randomly selected,and the surface roughness of two transparent zirconia surfaces were measured by optical profiler.Two samples were randomly selected and the surface crystal phase transition was observed by X-ray diffractometer.The three-point bending strength of the rectangular specimen was measured by the universal testing machine.2.Each group of square specimens was bonded with double curing resin cement MultilinkSpeed(n=20),and then randomly divided into 2 subgroups(n=10).The shear bond strength of one group was tested immediately after soaking in distilled water at 37℃ for 24 hours,and the shear bond strength of the other group was tested after soaking in distilled water at 37℃ for 24 hours and aging for 5000 times between 5℃ and 55℃.3.The statistical analysis of the above results was conducted using One-Way Analysis of Variance(ANOVA)and Boferroni test,when p<0.05 is considered statistically significant.Results:1.After thermal etching transparent zirconia with 9.5%hydrofluoric acid,no monocline phase transition was detected when the treatment time was less than 30 min,and the bending strength was not significantly different from that of blank control group and sandblasting group(p>0.05).When the treatment time was 60 min,monoclinic phase transformation occurred and bending strength decreased,which was significantly different from that of blank control group(p<0.05),but not significantly different from that of sandblasting group(p>0.05).When the treatment time was 90 min,the monoclinic phase transition was detected,and the bending strength was significantly decreased compared with blank control group and sandblasting group(p<0.05).2.The surface roughness of transparent zirconia can be increased by both 9.5%and 40%hydrofluoric acid etching.When 40%hydrofluoric acid thermal etching reaches 60 minutes,the roughness value is the highest(2.06±0.082 μm).The adhesive strength of transparent zirconia resin cements can also be increased by using 9.5%and 40%hydrofluoric acid hot acid etching.The maximum bonding strength was 18.08±0.56 MPa(9.5%hydrofluoric acid)for 60 min and 17.28±0.73 MPa(40%hydrofluoric acid)for 5 min.However,the bonding strength decreased when 9.5%hydrofluoric acid was etched for 90 min(p>0.05),and significantly decreased when 40%hydrofluoric acid etched for 5 min(p<0.05).After cyclic aging,the shear bond strength of hot acid etching group did not decrease significantly(p>0.05).Conclusion:Under the conditions of this experiment,the mechanical properties of transparent zirconia were not significantly affected by the appropriate concentration and treatment time(such as 40%hydrofluoric acid for 5 minutes)when hydrofluoric acid was used to corrode transparent zirconia.The adhesive strength of transparent zirconia-resin cements can be improved effectively,which provides a new strategy for improving the adhesive strength of transparent zirconia in clinic. |
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