Effect Of Polishing Treatments On Bond Strength Of Dentine With Self-adhesive Resin Cement

The underlying mechanism of adhesion to dentin is based on the infiltration of resin monomers into partially demineralized dentine,a process called hybridization.But the existence of the so called "smear layer"(SL)might impede hybridization.According to previous studies,different rotary polishing methods would result in different SLs and consequently make influence on dentine bond effectiveness.With these years'efforts on dentine bond,the original commend to remove SL has been changed to keep and modify them to form a hybrid layer.And with the improvement of components and properties of dentin adhesive systems,the steps are simplified and effectiveness are enhanced.Self-adhesive resin cements,with the lowest technique sensitivity and well aesthetic characteristics,has been quite popular among dentinsts,but their clinical performance remain to be explored.Thus,the aim of this study is to measure the micro-tensile bond strength(?TBS)of different self-adhesive resin cements luted to dentine surface prepared with 3 different polishing methods.[Object]To determine the effect of polishing treatments on self-adhesive resin cements luted with human dentine.[Methods]99 human dentin plats were made of none-carious h?man third molars.96 of them were divided into eight groups,12 each.Every 12 plats were grouped into three subgroups,named group A,group B,and group C.Group A was polished with coarse diamond burs(105-125?m).Group B was polished with fine diamond burs after polished with coarse diamond burs(25?m).And group C was further polished with Sof-Lex polishing discs following the steps of group B.4 of the subgroups were then cemented to composite blocks with the following 6 self-adhesive resin cements:SA CEMENT,RelyX U200,Multilink Speed,G-Cem,Bis-Cem,Perma Cem-Dual,named as group SC,group RX,group MS,group GC,group BC and group PC.The other 2 groups were set as control groups,and cemented with Syntac primer+ Syntac adhesive+ heliobond+ Variolink N and Primer A&Primer B+ Multilink N,named as group VL and group MN.In all the groups,micro tensile bond strength(microTBS)was evaluated of each subgroup after water storage for twenty-four hours(n=20).The fracture patterns of samples were defined under stereomicroscope.The other 3 dentine plats were treated with methods like group A,group B,and group C.The smear layer's(SL)thickness and tubule plugs were observed with scanning electron microscope(SEM)of the remained dentine plats.[Results]1.Smear layer characteristics:as the polishing procedures were taken,dentin SL was getting thinner and denser.The proportion of blocked tubules was getting higher.2.Micro-tensile bond strength:because over half of the micro tensile test samples occurred pre-testing failure,group BC and group PC were not tested for ?TBS.In group VL and group RX,?TBS values show no difference among group A,group B,and group C(P>0.05).Except group VL,all the other groups show a tendency that ?TBS drops and rises among group A,group B,and group C,and no significant difference was found between group A and group C(P<0.05).?TBSs of all the self-adhesive resin cements groups are significantly higher or comparable with group VL with all the 3 polishing methods,except the value of group GC in group B.3.Failure types:in group VL and group MN,most of the fractures were happened on dentin-cement interface.The rate of failure type happened within resin cements rises when it comes to self-adhesive cements.[Conclusion]Polishing dentine using fine diamond burs after preparation with coarse diamond burs reduces the ?TBS of self-adhesive resin cements.Yet the ?TBS is enhanced after the following polishing step with Sof-Lex polishing discs.