Pull-out bond strength of a fibre-reinforced composite post system luted with self-adhesive resin cements

Abstract

Objectives: Due to morphological differences along the root canal, serious structural damage, or extensive endodontic preparation, cement thickness of luted fibre-reinforced composite (FRC) post systems can largely vary. This study aimed at evaluating the effects of a self-etch (Multilink Automix, MLA) and various self-adhesive resin cements (G-Cem, GCM; Maxcem Elite, MXE; RelyX Unicem, RLX; SmartCem 2, SMC) on the pull-out bond strengths of FRC posts to root canal dentine, and to compare the effects of different cementation thicknesses.

Methods: 100 bovine incisor roots were embedded in acrylic resin and randomly assigned to two groups. Root canals of group 1 were prepared with RelyX Fiber Post drill size one (Ø 1.3mm), whereas in group 2 drill size three (Ø 1.9mm) was used to attain different cement thicknesses (thicknesses 1 and 2). Each group was then subdivided into five subgroups (n=10). RelyX Fiber Posts size one (Ø 0.70mm) were luted with the respective resin cements. All specimens were subjected to pull-out evaluation using a universal testing machine. Post surface areas covered with cement were measured by means of stereomicroscopy.

Results: RLX revealed the significantly highest pull-out bond strengths in both groups (p<0.05), while MXE exhibited the significantly lowest pull-out bond strengths in group 2 (p<0.05). Main failure modes were determined as adhesive at the cement-post surface for all examined groups (except for SMC, group 2).

Conclusions: The different resin cements influenced the pull-out bond strengths, whereas the cement thickness itself was not responsible for any differences.

Clinical significance: Self-adhesive resin cements can provide an acceptable retention of FRC posts even in case of use with wider post space conditions.

Keywords: Cement thickness; Fibre post; Pull-out test; Self-adhesive cement; Self-etch cement.