Effect of reducing acid-etching duration time on compressive strength and bonding of a universal adhesive to calcium silicate cements.

Abstract

To assess the effect of acid-etching duration time on the compressive strength, microstructure and shear bond strength of All-Bond Universal adhesive to MTA-Angelus (AMTA), and Biodentine (BD). Forty-eight cylindrical specimens (4mm in diameter, 6mm in height) of AMTA in four groups and 48 specimens of BD in four groups (n=12) were prepared and stored for 72h. The control groups were unetched whilst the three experimental groups were acid-etched for 5, 10 and 15s, respectively, followed by compressive strength testing. The effect of the various acid-etching times on surface micromorphology was evaluated under a scanning electron microscope. Similar groups were bonded using All-Bond Universal and Aelite Flo and shear bond strength was tested. Data were analysed using two-way ANOVA and Tukey tests. 10-s and 15-s acid-etching reduced the compressive strength of AMTA and BD (P<0.001), while 5-s etching did not (P≤0.86). In all the groups, BD had greater compressive strength compared to AMTA. Contrary to BD, the three etched AMTA groups had significantly higher shear bond strength compared to the control group (P<0.001), with no significant differences between them. The etched groups of AMTA had shear bond strengths comparable to all the BD groups. Scanning electron microscope observations indicated variable surface morphologies such as remnant crystals and cracking/eroding in all our groups of AMTA; though these differences were less prominent for BD. Shortening the acid-etching time to 5s resulted in a beneficial effect in terms of resin bonding for AMTA while preventing the detrimental effect of 10-s and 15-s etching on the compressive strength of AMTA and BD. However, the three etching times had no effect on resin-BD bond.