Shear peel bond strength of compomers veneered to amalgam

The practice of veneering compomers to amalgam restorations has not been studied.

This in vitro study was designed to assess the shear peel bond strength and fracture pattern of 3 currently available compomers veneered to amalgam.

Sixty cylindrical preparations were filled with amalgam. Half (30) had no surface treatment, whereas the other half were air abraded. In both groups, 10 specimens each were veneered with Dyract AP, Hytac, and F2000 according to the manufacturers' instructions. All samples were kept at 37 degrees C in 100% relative humidity for 48 hours. SPBS was assessed with a universal testing machine and fracture patterns with a stereomicroscope. The results were analyzed with 2-way ANOVA and Tukey's multiple comparison test.

Dyract AP veneered to air-abraded amalgam had the highest SPBS (5.78 +/- 1.30 MPa); F2000 veneered to non-air-abraded amalgam had the lowest (2.99 +/- 1.4 MPa). Sandblasting significantly influenced SPBS in the case of Hytac (P<.02) and F2000 (P<.01). Within the non-air-abraded group, Dyract AP had significantly higher SPBS than Hytac (P<.03) and F2000 (P<.015). F2000 air-abraded specimens exhibited adhesive bond failure only, whereas all other groups showed both adhesive and combined bond failures.

Of the 3 compomers tested for veneering to amalgam, Dyract AP showed the highest SPBS. Air-abrading the amalgam surface was found to improve the SPBS of Dyract AP, though not significantly. Low SPBS and poor adhesion indicated that F2000 is unsuitable for veneering amalgam.