Effect Of Different Pretreatments To Dentin On Bonding Strength Of Fiber Post With Self-etching System

Experiment One:Observation of Fracture interfaces between fiber post and dentinObjectives:To evaluate the interfaces of fiber post-luting cement and root dentin-luting cement after fracture.Method:10 adult central incisors were pulled out for periodontal disease and saved in 0.1%thymol solution.Two weeks after endodontical treatment,the post space preparation of all teeth were made,the fiber posts were then cemented using Panavia F self-etching resin bonding cement according to the instructions.Each cemented tooth was embedded and serially cut into 6 sections.The fracture load of each section was measured with push-out test using a universal testing machine.The fractured samples were then observed by using stereomicroscope and scanning electron microscope (SEM)Result:Regardless of the different portions of root canal,the bonding fracture mainly located at dentin-cement interface,especially-between top of hybrid layer and dentin.Conclusion:Dentin-cement interface is the weak area of dentin-bonded fiber posts, especially at the top of hybrid layer.Improving the stability of hybrid layer might promote the bonding strength of fiber post to dentin.Experiment Two:Effect of different dentinal surface treatments on bonding strength of self-etching luting system.Objective:To investigate the effect of different pretreatments to root canal dentin on bonding strength of fiber post to dentin after post space preparation.Method:Thirty adult central incisors were pulled out for periodontal disease and saved in 0.1%thymol solution.Two weeks after endodontical treatment,the post space preparation of all teeth were made,the teeth were assigned into three groups randomly with 10 teeth each.The teeth of three groups were irrigated with 14%EDTA,5.25% NaOCl and 0.9%NaCl for 60s respectively.Panavia F self-etching resin bonding cement was imported into post space according to the instructions.Then the sample will be embedded and cut into 6 section.Each cemented tooth was embedded and serially cut into 6 sections.The fracture load of each section was measured with push-out test using a universal testing machine and its bonding strength was calculated. Kruskal-Wallis H test Mann-Whitney U test were used for statistical analyses.Result:At cornal 1/3 of root canal,there were highly significant differences of bonding strength between EDTA group and other groups(p＜0.01).At middle 1/3,the bonding strength of EDTA group was significantly higher than those of others(p＜0.05). At apex 1/3,the bonding strength of EDTA group is significantly higher than NaOCl group(p＜0.05).Conclusion:EDTA irrigation to post space before bonding could enhance the bonding strength between resin cement and dentin.