Effect Of Different Treatments Of Bonding Agent On The Bonding Strength Of Total-etching Resin Cement

The development of bonding dental technology makes the minimally invasive treatment and esthetics restoration being true. The bonding technology not only saved the teeth and pulp tissue on the maximum extent but aslo satisfied the people's pursuit of beauty. Therefore, the research of bonding dental science has become one of the most popular area in mordern oral medcine research.As a bonding material, resin cement was popular in clinical workers because of its good biological safety, superior aesthetic performance and cohesive propcrties with many restorative materials. Therefore, how to achieve the best adhesion of resin cement, as well as the in-depth study of adhesion of resin cement have gradually become the hot of the dental adhesive.According to different pre-treatment of tooth surface, resin cements could be divided into three groups as totol-ething, self-etching and self-adhesive ones.Being a recently appeared merchandise, self-adhesive lutings simplified many clinical restorative procedures.However, they have been reported to have lower bonding strength than the multi-step ones.The totol-etching resin cements are still be regarded as the first choice for esthetic restoration..Many studies have shown that the flowable resin can be used as bonding agent in the direct restoration and gain similar strength. Moreover, it has aslo been confirmed that the bonding strength between tooth and resin cement may be affected by the different themal expansion between cement and bonding agent, the oxygen inhibition to unfilled resin, etc. But whether the total-etching resin cement could be used without bonding agent in the indirect restoration and what effect would different treatment of bonding agent do to the bonding strength still need further research.The purpose of this study is to evaluate the total-etching resin cement's bonding strength with bonding agent treated with different ways(without bonding agent, with bonding agent but no light-curing, with bonding agent and light-curing ).Micro tensile bonging strength is used to evaluate the bonding strength of every group before and after thermocycling.The bonding interface between dentin/enamal and resin cement is also observed by SEM.The result of this study could provide some important references for clinical procedures of totol-ecthing resin cement.The main result of this study can be concluded as follows.1. As to the three resin cements, the dentin groups without bonding agent had no bonding strength; however, the tensile bond strengths of the dentin groups with bonding agent were all satisfactory, and the bonding strength of the group with no curing (15.534±2.099;22.827±6.968;10.736±3.199) was significantly higher than the other(13.476±2.710 ; 14.076±5.165 ; 7.736±3.052). SEM observation proved that there was no resin tag in the group without bonding agent, while the group with bonding agent and light-curing showed dense hybrid layer and resin tags although the fissures also exist and the group with bonding agent but no light-curing showed high density layer between dentin and cement. So, curing the bonding agent and the resin cement at the same time shoud be recommended in clinic.2.The influence of different treatment of bonding agent on the bonding strength of totol-etching resin cement to enamal was not so significantly as to dentin. SEM observation revealed that resin tags were obvious in all three groups while they were much more equality in the groups with bonding agent.3. As to the dentin groups, the bonding strength of the groups with bonding agent but no light-curing were still better than the other groups after 5000 times thermal cycling. SEM observation showed that there were still high density layer between dentin and cement in the groups with bonding agent but no light-curing. While the groups with bonding agent and light-curing showed more fissures than before.4. As to the enamal groups, the bonding strength of the groups with bonding agent but no light-curing were still better than the other two groups after 5000 times thermal cycling. SEM observation showed that the groups with bonding agent but no light-curing had no significantly changes between before and after thermal cycling. While the groups with bonding agent and light-curing appeared more fissures and the groups without bonding agent showed obvious fracture on the top of resin tags. This approved that using bonding agent and light-curing it at the same time with resin cement could gain better long-term durability.