| Background:Zirconia has become a common prosthodontic material in dentistry due to its superior physical properties,stable chemical properties,and good biocompatibility.However,the opacity of zirconia cannot meet the anterior aesthetic requirements.Many scholars have introduced some translucent equalization methods to make zirconia more translucent by changing the content of alumina and increasing the sintering temperature,thus resulting in the appearance of translucent zirconia.Translucent zirconia retains considerable mechanical strength,but the bonding property is still unstable,and the bonding strength with resin cement remains to be explored.Objective:（1）to prepare a relatively stable SiO2-ZrO2 slurry by changing pH and molecular weight of dispersant（2）to evaluated different surface treatments on the morphology,surface roughness,silicon element distribution,and crystal phase structure of SiO2-ZrO2 coated translucent zirconia.（3）to evaluated different surface treatments on the shear strength bond of processed translucent zirconia and resin cement.Methods and materials:A mix of a certain proportion of zirconia powder,silica powder,polyethylene glycol,and deionized water by ultrasonic.Adjust pH with 20%Na OH solution to 12 and seal in a glass bottle for use.The 150 discs（14mm×14mm×2mm）of pre-sintered translucent zirconia were equally divided into five groups（n=30）and the surface was treated separately by the following methods:（1）CT:fully sintered then surface not treat.（2）SB:fully sintered,50μm of alumina particles blasting 10s.（3）C21:SiO2-ZrO2 coating with the ratio of Si:Zr=2:1coating treatment then fully sintered（4）C11:SiO2-ZrO2 coating with the ratio of Si:Zr=1:1 coating treatment then fully sintered（5）C12:SiO2-ZrO2 coating with the ratio of Si:Zr=1:2 coating treatment then fully sintered.After surface treatments,ultra-pure water ultrasonic cleaning was carried out for 10min.Ten samples were randomly selected from each group.The surface morphology and surface element composition and distribution were observed by scanning electron microscope.The crystal structure of the surface was analyzed by an X-ray diffractometer,and the surface roughness was measured by roughness meter.The other 20 specimens in each group were treated with 9.5%hydrofluoric acid etched on the surface,washed and dried,and then bonded to the translucent zirconia surface with resin cement for resin column prepared in advance.After all the samples were bathed in distilled water at37℃for 24 hours,each group was divided into two subgroups.The shear strength of translucent zirconia and resin cement was directly tested in one group.The other group was put into a thermal cycle between 5℃and 55℃to undergo 10,000 aging treatments.The shear strength of both samples was tested,and the failure modes of all samples were observed and recorded.Results:（1）Electron microscope observation results showed that the translucent zirconia surface of CT group was relatively flat at low magnification,and the zirconia grains were compact without gaps at high magnification.Irregular scratches were observed on the translucent zirconia surface of the SB group at low magnification and irregular particle structures on the uneven surface at high magnification.At low magnification,SiO2-ZrO2 coated specimens can be observed as irregularly arranged islands with gullies of varying depths between them.At high magnification,zirconium atoms can be seen embedded on the surface of molten silica.（2）Energy spectrum analysis showed that:the CT group zirconia surface only zirconium and oxygen elements exist,SB group zirconia surface in addition to zirconium,oxygen elements,can also be observed in a small number of aluminum elements.In addition to zirconium and oxygen elements,silicon elements in proportion to the formula can be observed on the coated translucent zirconia surface.（3）X-diffractometer analysis showed that the sandblasting treatment and coating treatment did not cause phase transformation of the translucent zirconia surface.（4）Surface roughness:the roughness values of SB group and coating group with different proportions（C21group,C11 group,and C21 group）were significantly different from those of CT group（P<0.05）.The roughness values of the coating group（group C21,group C11,and group C21）were significantly different from those of the SB group（P<0.05）.In the coating group,the roughness value of group C21 was significantly different from that of group C11 and C12（P<0.05）,while the roughness value of group C11 was not significantly different from that of group C12（P>0.05）.（5）the results of the shear strength bond:In 24h group,there was a significant difference between two groups with five different treatments（P<0.05）.The shear strength of CT group was the lowest 10.0±2.2MPa,and that of C11 group was the highest 19.7±3.0MPa.The shear strength of C21 and C11 in the coating treatment group was higher than that of the sb group（P<0.05）.The shear strength bond in the coating treatment group increased firstly and then decreased with the decrease of silica content.In TC group,the shear strength of sandblasting treatment and SiO2-ZrO2 coating treatment was significantly different from that of untreated treatment（P<0.05）.There was a significant difference in shear strength bond between the C11 group and the SB group in the coating treatment（P<0.05）,while there was no significant difference between the C21 and C12 groups and the SB group（P>0.05）.（6）The same surface treatment method was analyzed from different aging treatments.Compared with the treatment of 37℃for24 hours,the shear strength bond of each treatment group decreased to a certain extent after the treatment of 10,000 thermal cycles,and there were significant differences among CT group,SB group,C21 group,and C11 group.（7）Observation results of the failure mode:the treatment group is mainly mixed failure mode.No cohesion failure was found in 24h group and TC group.In TC group,the proportion of CT group,SB group,and C12 group with adhesive failure was significantly increased.Conclusion:（1）SiO2-ZrO2 coating can increase the roughness of translucent zirconia,at the same time,increase silicon element containing the coated translucent zirconia.（2）SiO2-ZrO2 coating surface treatment can improve the shear strength bond to translucent zirconia and resin cement,and SiO2-ZrO2 coating with the ratio of Si:Zr=1:1 have great performance. |
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