To evaluate the effect of
different factors on the push-out bond strength of glass fiber posts
luted in simulated (standard) root canals using different composite
Three types of glass-fiber root-canal
posts with a different matrix, namely an epoxy resin (RelyX post, 3M
ESPE), a proprietary composite resin (FRC-Plus post, Ivoclar-Vivadent),
and a methacrylate resin (GC post, GC), and three types of composite
cements, namely an etch-and-rinse Bis-GMA-based (Variolink II,
Ivoclar-Vivadent), a self-etch 10-MDP-based (Clearfil Esthetic Cement,
Kuraray) and a self-adhesive (RelyX Unicem, 3M ESPE) cement, were
tested. Posts were either left untreated (control), were treated with
silane, or coated with silicated alumina particles (Cojet system, 3M
ESPE). Posts were inserted up to 9-mm depth into composite CAD-CAM
blocks (Paradigm, 3M ESPE) in order to solely test the strength of the
cement–post interface, while excluding interference of the cement–dentin
interface. After 1-week storage at 37°C, three sections (coronal, middle, apical) of 2-mm thickness were subjected to a push-out bond-strength test.
three variables, namely the type of post, the composite cement and the
post-surface pre-treatment, were found to significantly affect the
push-out bond strength (p<0.001).
Regarding the type of post, a significantly lower push-out bond
strength was recorded for the FRC-Plus post (Ivoclar-Vivadent);
regarding the composite cement, a significantly higher push-out bond
strength was recorded for the self-adhesive cement Unicem (3M ESPE); and
regarding the post-surface treatment, a significantly higher push-out
bond strength was recorded when the post-surface was beforehand
subjected to a Cojet (3M ESPE) combined sandblasting/silicatization
surface pre-treatment. Many interactions between these three variables
were found to be significant as well (p<0.001). Finally, the push-out bond strength was found to significantly reduce with depth from coronal to apical.
testing revealed that different variables like the type of post, the
composite cement and the post-surface pre-treatment may influence the
cement–post interface, making clear guidelines for routine clinical
practice hard to define. Further long-term durability testing may help
to clarify, and should therefore be encouraged.