Bonding self-adhesive resin cements to glass fibre posts: to silanate or not silanate?

To evaluate the bond strength of self-adhesive resin cements (SARCs) to glass fibre posts with or without a silane coupling agent.

The SARCs tested were: Maxcem Elite (MXE; Kerr), RelyX Unicem clicker (UNI; 3M ESPE), seT capsule (SET; SDI), and SmartCem 2 (SC2; Dentsply Caulk). The conventional cement RelyX ARC (ARC; 3M ESPE) was evaluated as a reference. Rectangular-shaped flat posts were obtained (Angelus). After silanizing or not the posts, resin cement cylinders were built on the post surfaces. The cylinders were tested in shear after 24 h. Bond strength data were submitted to two-way anova and Student-Newman-Keuls' test (5%). Failure modes were classified under magnification as adhesive failure, mixed failure involving the cement or mixed failure involving the post.

For ARC, MXE and SET, the silanated groups had higher bond strengths. For SC2 the silane had no influence, while for UNI silanization decreased the bond strength. The conventional ARC had the lowest bond strength when the posts were not silanated; UNI showed the highest values. When the posts were silanated, SET had the highest values, followed by MXE, ARC and SC2; UNI had the lowest values. A predominance of adhesive failures was detected for all groups, with higher number of mixed failures when the posts were silanated.

As the silane impaired or generally had no effect on the bond strength of SARCs to the glass fibre posts, and also as the bond strength of all SARCs was higher than the conventional cement when the posts were not silanated, it seems that silanization of glass fibre posts is not necessary when SARCs are used.