Effect of Multiple Enamel Surface Treatments on Micro-Shear Bond Strength

Abstract

Objectives: The aim of this study was to evaluate the effect of different enamel surface treatments on the micro-shear bond strength. Materials and methods: Sixty-four approximal surfaces from freshly extracted molars were randomly assigned to eight groups, according to combinations of the following enamel surface treatments: ground or unground, 37.5% phosphoric acid etching time of 15 or 30 s, and with or without primer application. The same bonding agent (Optibond FL™ Adhesive, Kerr) was then used for all groups, and a 1.8 mm diameter resin composite (Harmonize™, Kerr) cylinder was built up on the bonded surface. Samples underwent a shear force test at a crosshead speed of 1 mm/min until failure. Bond strength was calculated, and failure modes were inspected under an optical microscope. Results: Bond-strength values ranged from 8.2 MPa for 15 s etched unground enamel with primer application to 19.6 MPa for 30 s etched ground enamel without primer application. ANOVA and Fisher's LSD post hoc tests revealed significant differences between the groups. Conclusions: Etching time and grinding have a statistically significant effect on the micro-shear bond strength of a three-step etch-and-rinse adhesive system on enamel. Primer application does not seem to be beneficial for enamel adhesion.

Keywords: adhesion; bonding; etching time.

Figure 1

Photographs of the experimental setup (a) and of one specimen (b).

Figure 2

Group means comparison (vertical bars denote 95% confidence intervals).

Figure 3

SEM images of different enamel surface treatments. (a) (Group U15) Enamel prisms are hardly detectable. (b) (Group U30) Enamel prisms are more visible. (c) (Group G15) Enamel prisms are more prominent. (d) (Group G30) Enamel prisms are very detectable, and bonding area appears to be larger.