effect of etching time duration on the push out strength of self adhesive cement to root dentin

Introduction: Post debonding is one of the most important causes restoration failure in endodontically treated teeth restored with fiber-post. The weakest connection post-cement-dentin complex cement-dentin bonding surface. In this study we evaluated effect etching phosphoric-acid and its duration on push-out strength self-adhesive resin cement to dentin. Materials Method: Root canal therapy was done for fifty intact one-canal premolars then crown cut from CEJ. Fiber-post space prepared root by FGM special drill. were randomly divided into five groups ten teeth. Group without any intervention considered as control-1 other etching. Three etched 37%phosphoric-acid 15seconds, 60seconds 90seconds. last group, after preparation, protocol wasn't performed which control-2. all samples, White post fiber-ost(FGM) size2 cemented TheraCem (Bisco) two 4mm pieces mounted acryl. Push-out test Instron machine each sample shear bond obtained MPa.