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

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.

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.

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).

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

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