Effect Of Different Silanization On The Shear Bond Strength Of Fiber Posts In Vitro

With the development of prosthodontics and dental materials, as well as enhanced awareness of dental reservations, fiber post and core have been widely used in dental practice for its superior performance. The main failure mode for fiber post and core repairing the tooth is the post debonding. Therefore, the bonding of the fiber post is the key point of the research. In this study, Micro push-out tests were carried out to investigate the shear bond strength between the fiber post and core materials. And scanning electron microscope was used to observe the micro-structural morphology, to approach the internal mechanism of the different shear bond strength.The study was devided into two parts, which are summarized respectively as below.PartΙEffect of silanization on the shear bond strength of composite resin core materials to fiber postsObjective: To investigate the influence of different silanization and thermal cycling on the shear bond strength of composite resin core materials to fiber posts.Methods: Forty glass fiber posts were devided into 4 groups: (1) no treatment, (2) chair-side silane application, (3) industrial silane treatment, (4) industrial silane treatment followed by chair-side silane application. Each group was further divided into 2 subgroups and stored in distilled water, either for 24 hours without thermal cycling or for 150 days with 15,000 thermal cycles between 5°C and 55°C, with a dwell time of 30 seconds. Composite resin core buildup was formed (12mm in length and 4 mm in diameter) by a PTFE tube. Following water storage, the specimens were sectioned into 1-mm-thick segments using a water-cooled low speed diamond blade. Micro push-out tests were performed with a universal testing machine at a crosshead speed of 0.5 mm/min. The data was recorded and analyzed with one-way ANOVA and Post Hoc Tests (α=0.05).Results: The treatment groups showed higher shear bond strengths than that of the control group (P<0.001). Industrial silane treatment group showed higher bond strengths than that of chair-side silane application group(P<0.001). No significant difference was found between the group (3) and group (4). After water storage and thermal cycles, the shear bond strengths decreased significantly all of the groups.Conclusion: Within the limitations of this study, either chair-side silane application or industrial silane treatment enhanced the shear bond strength of composite resin core material to glass fiber posts. Industrial silane treatment showed better result than that of chair-side silane application. Long-term water storage and thermal cycling significantly decreased the bond strength between composite resin core material and glass fiber posts.PartΙΙEffect of silanization on the surface morphology and bonding interface of fiber postsObjective: To investigate the influence of different silanization on the surface morphology and bonding interface of fiber posts to core materials.Methods: Eight glass fiber posts were devided into 4 groups: (1) no treatment, (2) chair-side silane application, (3) industrial silane treatment, (4) industrial silane treatment followed by chair-side silane application. After surface treatment, one post from each group was examined with an SEM to study their surface conditions, while the other was formed a composite resin core by a PTFE tube. The specimens were sectioned into 1-mm-thick segments using a water-cooled diamond blade. Each specimen was sputter-coated with gold-palladium alloy and examined with an SEM.Results: Fiber post without industrial treatment shows a relatively smooth surface and less fibers are exposed. While fiber post with an industrial silane treatment seems relatively rough and more fibers are exposed. No defects are detectable between fiber post and core materials interface in all the groups. Industrial silane treatment group and industrial silane treatment followed by chair-side silane application group could found microretentive morphological changes.Conclusion: SEM analysis revealed the presence of microretentive morphological changes, which certainly increase post-retentive properties. Industrial silane treatment should increase fiber posts mechanical retention and chemical retention.