Optimisation of interfacial bond strength of glass fibre endodontic post systems.

Abstract

Currently endodontically treated teeth are clinically restored using a post and crown system, where the elastic modulus of the post is similar to dentine. The proposed post system materials include glass fibre reinforced post and composite resin adhesive. The objective of this study was to evaluate the comparative bond strength of a resin adhesive and a glass ionomer cement with human, elephant and sperm whale dentine and glass fibre post systems, through a push out test. The push out test was carried out on extracted single rooted human teeth, and with elephant tusk and sperm whale dentine. The two types of glass fibre posts (Everstick® Post and RelyX™ Fibre Post) were placed into the dentine using two adhesives (RelyX™ Unicem self etch resin adhesive and AquaCem® glass ionomer luting cement). The fracture toughness of the RelyX™ Unicem composite adhesive was measured using the peel test. The push out test sample of human dentine and RelyX™ fibre post luted with RelyX™ Unicem adhesive was simulated using a finite element model with experimental load parameters. The push out test results showed that elephant dentine produced better interfacial bond strength with both post systems and adhesives. The Everstick® post with RelyX™ Unicem adhesive showed optimum bond strength compared to the other test groups. Glass ionomer luting cement showed poor bond strength with both post materials. The finite element simulation of the push out test suggested that the interfacial failure occurred between the post and adhesive interface, where high shear stresses were seen between the post and adhesive interface. The study concluded that the Everstick® post along with RelyX™ Unicem provides the best interfacial properties required under masticatory loads. It can be suggested that glass ionomer cements should not be used as a luting agent for customised glass fibre posts.