Efficacy Of The Ethanol-wet Bonding Technique And Hydrophobic Layer On Bonding Property Of Total-etch Adhesives

The instantaneous adhesive strength of the fourth to seventh generationadhesives that widely used now can meet the clinical demand, but increasinglyreflected the problem of poor bonding interface quality and durability. The reason forthis is the increasing of hydrophilia，and the mixture of hydrophilic and hydrophobicmonomers, makes incomplete Infiltration of resin monomers and highpermeability of interface, influence the quality of interface and durability. Wetting theacid etched dentin with ethanol and coating with a hydrophobic resin layer afterbonding maybe a beneficial attempt for improving the bonding performanceObjective:This study use two commonly used two-step total etched adhesives, saturate withethanol after etching, or coating with hydrophobic layer, respectively. Test themicrotensile bond strength and observe the microstructure of interface with SEM, Theaim of this study were to investigate the effect of ethanol wet bonding technique andhydrophobic layer on the bond strength and quality of bonding interface of two-steptotal-etch adhesives,further to provide an experiment evidence for clinicalapplication．Meterials and Methods:40freshly extracted，caries—free human molars were selected．A flat dentinewas exposed by removing occlusal enamel,all teeth were randomly divided into twogroups According to the different adhesives used：Single Bond （SB）and GlumaComfort Bond（GB）, and then each group was divided into five subgroups Accordingto the different Bonding scheme: the control group was bonded with adhesiveaccording to manufacturer’S directions, the experimental group including ethanol-saturated1min，ethanol-saturated2min，ethanol-saturated1min+Hydrophobic layer（SE）,SE. applicating different Bonding scheme listed above afteretching，．Composite layers were built up incrementally．The specimens weresectioned longitudinally across the resin．dentin interface into0．9×0．9mm~2sticks， and were subdivided into two groups which were tested after24hours or6months ofwater storage.The24hours microtensile bonding strength(MTBS) was acquired andthe fractured style of each sample was examined by stereomicroscope．All data wasanalyzed by SPSS．Another10freshly extracted，caries—free human third molarswere selected and appllyed the different Bonding scheme，The specimens weresectioned longitudinally across the resin．dentin interface into5mm×6mm×1.5mmslices，observing the morphology of hybrid layer and resin tags.Result:One-way ANOVA analysis of SB and GB group showed, compared with thecontrol group, ethanol-saturated2min after etching can significantly improve theMTBS value of the two kinds of adhesives (P <0.01); But there was no significantdifference in value between ethanol-saturated1min group and the control group;Thevalue of ethanol-saturated1min+Hydrophobic layer group has improved, but therewas no significant difference; Value of Hydrophobic layer(SE) group in GBsignificantly increased(P <0.05) but in SB the value close to the control group.SEMresults showed that ethanol-saturated2min can significantly improve the quality ofhybrid layer、the number and length of resin tags；Ethanol-saturated1min and1min+SE increases length of resin tags, but had no significant effect on the number;Hydrophobic layer can significantly increase the number and length of resin tags inGB group but in SB group only significantly increased the length; The improvementof the uniformity of mixing layer in latter three groups is relatively slight, inferior toethanol-saturated2min.Conclusion:1Nowadays clinical commonly used two-step total-etch adhesive SB, GB usinga simplified ethanol-wet technology alone, has an influence on adhesive propertyrelated to saturating time,Improvement of ethanol-saturated2mim is significant;Improvement of hydrophobic layer alone on GB significant,maybe related to theirdifferent chemical composition;Combined use of simplified ethanol-wet bonding andhydrophobic layer can improve the adhesive property, but there was no significant.2The improvement of MTBS might be explained by the improve of the bondinginterface, including the improvement of compactness and uniformity of hybrid layer and the number and length of resin tags. in addition, the influence of number onbonding strength is bigger than length.3Simplify ethanol-wet bonding technology and hydrophobic resin layer appliedto the clinical commonly used two-step total-etch adhesive all get the higher or similar24h bond strength, at the same time the quality of hybrid layer and resin tags havedifferent degrees of improvement also, so it is necessary to evaluate their influenceon nanoleakage and durability continuely in the future.