Comparison Of Different Dentin Pretreatment Protocols On The Bond Strength Of Glass Fiber Post

Part Ι Effects of different dentin pretreatment protocols on the bond strength of glass fiber postObjective To compare three different dentin pretreatment protocols include 2% chlorhexidine(CHX), 2.5% sodium hypochlorite(Na OCl) and 35% phosphoric etching on the bond strength of glass fiber post by using push-out text. So that appropriate pretreatments to root canal dentin can be used for clinical selection and providing a theoretical basis for improvement bond strength of resin cement to root canal dentin.Methods Forty human new extracted non-caries signal-rooted canal anterior teeth were collected and post spaces were prepared:Group I:2% chlorhexidine(CHX)(n=10); Group II:2.5% sodium hypochlorite(Na OCl)(n = 10); Group III:35% phosphoric etching(n = 10);Group IV:saline solution(control)(n = 10).Fiber posts were then luted in the treated roots using self-etching adhesive and the push-out test was performed.Test piece following testing was placed under optical microscope to observe the breakage method.The data were recorded and analyzed(a=0.05).Results Group I showed no difference in the mean bond strength value(p>0.05),bond strength decreased in group II compared with saline solution(p<0.05),but the bonding strength of group III increased obviously(p<0.05).Conclusions The use of 2.5% sodium hypochlorite decreased the bond strength of glass fiber posts using a self-etching adhesive system, whereas 35% phosphoric etching increased it obviously.The use of 2% chlorhexidine show no significantdifference compared with saline solution.Part II Microscopic observation of adhesive interface by using different dentin pretreatment protocolsObjective To investigate the microstructure of different pretreatment of root canal wall interface and fiber post bonding interfaceMethods 44 intact extracted signal-rooted canal anterior were sectioned perpendicular to the long axis at a point of 2.00mm-occlusal to the buccal cement-enamel junction(CEJ) and post spaces were prepared,four radicular dentin treatments include 2% chlorhexidine(CHX), 2.5% sodium hypochlorite(Na OCl) and 35% phosphoric etching and saline solution were used to pretrement root canal and then were sectioned longitudinally to be observed.Four specimens were selected randomly for microscopic observation of fiber post bonding interface.Results No typical hybrid layer was found while the effects of radicular dentin pretreatments on penetration of resin tags into the dentinal tubules were clearly observed at the resin-dentin interfaces.Fiber post bonding interface observation:the resin tags of 35% phosphoric etching were forming, relatively dense, 2% chlorhexidine resin tags were short compared with the control group,2.5% Na OCl have not seen obvious resin tags.Conclusions Dentin pretreatment by using 35% phosphoric etching provided good resin infiltration,producing a three-dimensional interlocking micronetwork of resintags in the dentin tubules with multiple lateral branches that penetrate the intertubular dentin.