2018 Volume 61 Issue 3 Pages 178-189
Purpose: We studied the early bond strengths of various resin cements to the following: 1) CAD/CAM resin block (C-RC), 2) Dentin (D-RC), and 3) Both CAD/CAM resin block and dentin (D-RC-C). The effects of applying one-step self-etch adhesives to dentin surfaces prior to luting were also investigated.
Methods: Flat dentin surfaces (#800 finished) of bovine teeth and flat surfaces [#800 finished/sandblasting/silanization (Ceramic Primer Plus, Kuraray Noritake Dental)] of the CAD/CAM resin blocks (Cerasmart, GC) were prepared. As for the C-RC specimens, only the resin cement paste [RelyX Unicem2 Automix (UN, 3M ESPE), RelyX Ultimate Resin Cement (UL, 3M ESPE), SA luting plus (SA, Kuraray Noritake Dental)] was applied to the pretreated resin blocks. As for the D-RC specimens, UN, UL or SA paste was also applied to the dentin substrates both with and without the adhesive, Scotchbond Universal Adhesive (SBU, 3M ESPE) or Clearfil Universalbond Quick (CUQ, Kuraray Noritake Dental) [SBU−/UN (UN group), SBU+/UL (UL group), CUQ−/SA (SA− group), CUQ+/SA (SA+ group)]. As for the D-RC-C specimens, the substrates of the dentin and resin block were butted together with and without the adhesive. The micro-tensile bond strengths (μ-TBS) and fractomorphology were evaluated (Tukey’s test, α=0.05).
Results: The μ-TBSs of the C-RC in the UN or UL group were approximately 66 or 68 MPa respectively, showing excellent bonding of the resin cements to the resin blocks. The D-RC or D-RC-C in the UN group was approximately 5 or 10 MPa respectively with adhesive failure, while the same groups when using SBU (UL group) demonstrated values of approximately 31 or 33 MPa respectively accompanied by cohesive failure in SBU, UL or dentin, leading to significant adhesion-promoting effects to dentin substrates (p<0.05). The C-RC in the SA group was around 41 MPa with adhesive failure. The μ-TBSs of D-RC or D-RC-C were 27 or 14 MPa respectively in the SA+ group, demonstrating the efficacy of the adhesive, however the level could not be quantified in the SA− group.
Conclusion: This study revealed that the promotion of adhesion of the resin cement to dentin substrates by using the one-step self-etch system might be indispensable for securely bonding resin blocks and dentin substrates. The findings also indicated the need for a butt bonding test of various adherents from a clinical point of view.
