Effect of enamel etching time on roughness and bond strength

The current study examined the effect of different enamel conditioning times on surface roughness and bond strength using an etch-and-rinse system and four self-etch adhesives. Surface roughness (Ra) and composite to enamel shear bond strengths (SBS) were determined following the treatment of flat ground human enamel (4000 grit) with five adhesive systems: 1) Adper Single Bond Plus (SBP), 2) Adper Prompt L-Pop (PLP), 3) Clearfil SE Bond (CSE), 4) Clearfil S³ Bond (CS3) and 5) Xeno IV (X4), using recommended treatment times and an extended treatment time of 60 seconds (n=10/group). Control groups were also included for Ra (4000 grit surface) and SBS (no enamel treatment and Adper Scotchbond Multi-Purpose Adhesive). For surface roughness measurements, the phosphoric acid conditioner of the SBP etch-and-rinse system was rinsed from the surface with an air-water spray, and the other four self-etch adhesive agents were removed with alternating rinses of water and acetone. A ProScan 2000 non-contact profilometer was used to determine Ra values. Composite (Z100) to enamel bond strengths (24 hours) were determined using Ultradent fixtures and they were debonded with a crosshead speed of 1 mm/minute. The data were analyzed with ANOVA and Fisher's LSD post-hoc test. The etch-and-rinse system (SBP) produced the highest Ra (μm) and SBS (MPa) using both the recommended treatment time (0.352 ± 0.028 μm and 40.5 ± 6.1 MPa) and the extended treatment time (0.733 ± 0.122 μm and 44.2 ± 8.2 MPa). The Ra and SBS of the etch-and-rinse system were significantly greater (p<0.05) than all the self-etch systems and controls. Increasing the treatment time with phosphoric acid (SBP) and PLP produced greater surface roughness (p<0.05) but did not result in significantly higher bond strengths (p>0.05).