Effect of chemical surface treatment of contaminated CAD-CAM resin composite blocks on surface free energy and bond strength.

Purpose: To evaluate the effects of four chemical treatment methods on the contaminated surfaces of VITA ENAMIC (EN) and CERASMART (CS) resin composite computer-aided design-computer-aided manufacturing blocks (RCBs).

Methods: Each RCB was contaminated with a handpiece oil for 1 minute. These contaminated surfaces were then chemically treated by Gel Etchant (PA), Ivoclean (IC), Monobond Etch & Prime (MB), or Ceramics Etch (HF) reagents (n= 12), after which their shear bond strengths, morphologies, failure modes, and surface free energies were examined.

Results: The shear bond strengths of the HF-treated surfaces significantly exceeded those of the specimens treated with the other reagents. Adhesive fractures were observed for both the EN and CS blocks after 24 hours of treatment with lubricating oil, PA, and IC. The largest numbers of mixed and cohesive fractures were detected for the MB- and HA-treated specimens. The HF-treated EN and CS blocks possessed the highest surface free energies. The bonding strengths of the resin composites decreased after the contamination of their surfaces; however, the adhesion properties of both blocks were considerably improved by chemical treatment.

Clinical Significance: The lubricating oil contamination of dental handpieces significantly reduces the adhesion between the CAD-CAM resin composite block and the resin composite. Therefore, it is necessary to remove contamination and improve the adhesiveness using an optimal chemical surface treatment.