Methods: A total of 20 ProTaper nickel-titanium files (10 S1 and 10 F2), were divided in 5 groups: no immersion, immersion in 5.25% NaOCl for 5 or 10 minutes and immersion in 17% EDTA gel for 5 or 10 minutes. Twenty areas of the surface along 3-mm section at the tip of the files (perfect squares of 1µm x 1 µm) were analyzed by atomic force microscopy (AFM Perception, Assing, Italy) operating in contact mode under ambient condition. Three-dimensional images (400 × 400 lines) were processed by Gwiddion software and the roughness average (Ra) and the root-mean-square value (Rms) of the scanned surface profiles were recorded (nm). Student t Test was used to determine if the means were equal when comparing immersed sample respect to controls (p<0.05).
Results: Mean Ra and Rms values of S1 files (0.77±0.08; 1.10±0.14) were significantly higher than Ra and Rms of F2 files (2.31±0.22; 2.89±0.26). Moreover, 10 minutes of NaOCl immersion, 5 and 10 minutes of EDTA immersion increased surface roughness of both instruments. The greater values were found for F2 files immersed 10 minutes in EDTA, showing a Ra of 5.8 ±1.66 and a Rms of 7±3.12.
Conclusions: NaOCl and EDTA significantly increased the surface roughness of Protaper files. Nevertheless, the effect on clinical performance should be studied since fracture of these instruments can occur without any visible defect.