Glycolic acid and ultrasonic activation: Effects on smear layer removal, dentin penetration, dentin structure and bond strength of the root dentin filling material.

Background: Glycolic acid (GA) has been tested as enamel and dentin etchant, and final irrigant for smear layer removal. This study evaluated the effects of GA and ultrasonic activation (US) on smear layer removal, dentin penetration, dentin structure and bond strength of the root dentin filling material.

Material And Methods: The root canals of 210 teeth were distributed into four test groups: smear layer removal (N=50), dentin penetration (N=50), dentin structure (N=10) and bond strength (N=100). In all tests, specimens were subdivided into five groups, according to the final irrigation protocols: G1:distilled water(DW)+US; G2:17% EDTA; G3:17% GA; G4:17% EDTA+US; G5:17% GA+US. Scanning electronic microscopy, confocal laser scanning microscopy, transmission electronic microscopy and the push-out test were performed to evaluate smear layer removal, dentin penetration, dentin structure and bond strength, respectively. Statistical analysis was performed for each evaluation (α=5%).

Results: Groups 4 (EDTA+US) and 5 (GA+US) were the most effective on smear layer removal, with no statistical differences from each other (>0.05). The maximum penetration depth into dentinal tubules was observed for group 5(GA+US), being statistically different from all other groups (p<0.05). Group 5(GA+US) showed the largest collagen dispersion area, being statistically different from groups 1(DW+US), 2(EDTA) and 3(GA) (p<0.05), and similar to group 4(EDTA+US) (>0.05). The highest BS values for filling and restorative material were observed for all experimental groups, being statistically different from control group (p<0.05), with higher predominance of cohesive failure.

Conclusions: The association of GA and US promotes better smear layer removal, dentin penetration and collagen dispersion, with no influence on bond strength of the root dentin filling/restorative material. EDTA, final irrigation, glycolic acid, ultrasonic activation.