Surface Treatment Methods For Removing Saliva Contamination Of Zirconia Ceramic And Its Influence On Bonding Strength Of 2 Resin Adhesives

Introduction:Zirconia ceramics are widely used in dental clinical applications due to their excellent physical properties,aesthetic properties and good biocompatibility.However,due to the stable physical and chemical properties of zirconia ceramics,the limited surface treatment methods,the bonding quality of zirconia restorations to dental tissue is not ideal.Resin adhesives are often used to bond zirconia restorations.At present,10-MDP containing adhesives are generally considered to be the most suitable resin adhesives for zirconia ceramics.During the clinical operation,the surface of the prosthesis is unavoidably contaminated by saliva,and these contaminations will adversely affect the bonding effect of zirconia restorations.The research on the effect of removing saliva contamination of zirconia ceramics mainly focuses on the surface treatment of zirconia ceramics.Sand blasting,as a more commonly used surface treatment for zirconia ceramics,has the ability to remove saliva contamination while roughening the ceramic surface.The cleaning product,Ivoclean,is capable for cleaning protein contamination on the tissue surface of all-ceramic restorations and increasing the bonding strength.Other studies have shown that phosphoric acid and sodium hypochlorite can remove saliva contamination on the surface of zirconia ceramics.Objectives:To study the effect of saliva contamination on the bonding strength between zirconia ceramics and Clearfil Sac,RelyX?Unicem adhesives.And the effect of saliva contamination removal methods such as Ivoclean,sandblasting,1%sodium hypochlorite,and phosphoric acid,and their effect on the bonding strength of two resin adhesives.This will provide a clinical theoretical basis for the adhesion of zirconia restorations.Methods:126 pieces of 10mm×10mm×2.5mm ground and sandblasted LAVA zirconia ceramic specimens were randomly divided into 6groups according to different surface treatment methods:no contamination（NC）,sodium hypochlorite（SHC）,phosphoric acid Acid（PA）,Ivoclean（IC）,air abrasion（AB）,saliva contamination（SC）.One specimen from each group was used for X-ray photoelectron spectroscopy detection.The remaining test specimens were divided into two subgroups,which were bonded with Valux^TMPlus resin cylinders by Clearfil Sac and RelyX?Unicem resin adhesives.Then each divided into two parts,ones after 24 hours and others after 5000 thermocycling,the shear bond strength（SBS）were measured using a universal testing machine.The fracture surfaces were observed with a stereo microscope,and the fracture mode and percentage of each group were recorded.The data were analyzed by multivariate analysis of variance using SPSS 21.0 software.LSD-t method was used to compare the statistical differences between different groups.Results:1.The average short-term adhesive strength of Clearfil Sac adhesive is between 9.27-24.94MPa,the adhesive strength is NC≈IC≈AB>SHC≈PA>SC,NC≈IC≈SHC≈AB,AB≈PA≈SC,and the average strength after aging is between 8.23-2.71MPa.Connection strength NC,IC,SHC>SC,PA<NC.2.The average short-term adhesive strength of RelyX?Unicem adhesive is between 7.95 to 1.97 MPa,the adhesive strength is NC>PA,SHC,SC,AB>SHC,SC,NC≈AB≈IC,IC≈PA≈SHC≈SC;the average strength after aging is between 0-4.34MPa,Adhesion strength NC,AB,IC>SC,NC≈IC≈AB≈PA,PA≈SHC≈SC.2.No cohesive fracture mode was observed by stereomicroscope,and both were adhesive fracture mode and mixed fracture mode.3.Fracture mode analysis shows that the proportion of adhesive fracture mode of RelyX?Unicem adhesive is greater than that of Clearfil Sac adhesive,and the proportion of adhesive fracture mode increases after 5000 thermocycling.4.XPS analysis shows obvious peaks of oxygen,carbon,and zirconium on the six groups of zirconia ceramics.The content of C,N,O,P,S elements on the surface of the IC group is closest to that of the NC group.Conclusions:1.Clearfil Sac resin adhesive has stronger bonding strength to zirconia ceramicS than RelyX?Unicem adhesive.2.Saliva contamination has a significant negative impact on the bonding strength and durability of zirconia ceramics.3.Ivoclean has obvious effect on saliva contamination removal on zirconia surface.Sand blasting has obvious effect on removing saliva contamination on the surface of zirconia ceramics,but it cannot guarantee the long-term bonding effect of Clearfil Sac adhesive.37%phosphoric acid,1%sodium hypochlorite has a poor removal effect on saliva contamination on the surface of zirconia.