CAD/CAM composite restorations occasionally require morphologic adjustment by building up additional
composite to counter excessive abrasion. However, it is difficult to achieve bonding between the CAD/CAM
composite and the additional composite, because the CAD/CAM composite is highly-cured. This study investigated
the effect of surface treatment on the bond strength between the CAD/CAM composite and the additional
composite, in order to establish an optimum surface treatment for the additional building-up.
A CAD/CAM composite Cerasmart (GC) was ground with #800 waterproof abrasive paper. The ground surface
was blasted with alumina and ultrasonically cleaned in distilled water. The surface was then processed using
Universal Primer (Tokuyama Dental, Up group), Universal Primer and G-Premio Bond (GC, UpG group), Ceramic
Primer II (GC) and G-Premio Bond (CpG group), or ScotchbondTM Universal Adhesive (3M ESPE, Sb group). A
composite, MI Fil (GC), was built up on the treated surfaces. The specimens were subjected to shear bond tests.
One-way ANOVA and Bonferroni correction were performed for statistical analysis (α = 0.01, n = 10).
The shear bond strength was significantly higher in the UpG, CpG, and Sb groups than in the Up group.
It was clarified that silane coupling treatment followed by application of bonding agent improved the bond
strength between the CAD/CAM composite and the additional composite.
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