Smear layer dissolution by peracetic acid of low concentration.

AIM To test the effect of a noncaustic concentration of peracetic acid (PAA) in a standardized smear layer model. METHODOLOGY The smear layer dissolution kinetics of 0.5% PAA on human dentine were compared to those of 2.25% PAA and 17% ethylenediaminetetraacetic acid (EDTA) solutions. Coronal dentine discs were prepared from six human maxillary molars. A standardized smear layer was produced on the pulpal side of each disc. The smear layer-covered surface was divided into three similar areas and then exposed to one of the three solutions tested. Co-site image sequences (around 40, 500 ×) of the specific areas were obtained after four cumulative demineralisation times (15, 30, 60 and 180 s). An image processing and analysis sequence measured sets of images, providing data of area fraction (AF, dentine-free area in % of total analysis area). A general linear model for repeated measures was used to verify the influence of time and solution type over the change in AF from baseline (ΔAF). RESULTS Overall, EDTA and 2.25% PAA produced higher ΔAF values than the 0.5% PAA solution (P < 0.05). No significant difference was observed in ΔAF between 15 s and 30 s (P > 0.05). After 60 s of etching, all tested solutions produced similar ΔAF (P > 0.05), whereas at 180 s, ΔAF of both EDTA and 2.25% PAA continued to increase (P > 0.05). CONCLUSIONS After 60 s of contact, the 0.5% PAA solution dissolved smear layer as well as 2.25% PAA and 17% EDTA.