RESUMO
The aim of this study is to evaluate the effect of various disinfection protocols on the cutting efficiency and chemical composition of ProTaper, Twisted File, Twisted File Adaptive, and Hedström files. Four experimental groups (n = 10) were presoaked in either enzymatic solution or 1% sodium hypochlorite for 30 min, followed by either 5 or 15 min of ultrasonic cleaning and then autoclaved. Resin-simulated canals with a single curvature of 38-40° were prepared by each instrument system. Cutting efficiency of each instrument was analyzed by subtracting the final weight from the initial weight of the resin blocks. Chemical compositions were studied by field emission scanning electron microscopy and X-ray energy-dispersive spectrometry. The cutting efficiency of Hedström, ProTaper, and Twisted File instruments decreased compared to their control groups (p < 0.05) whereas it did not change for Twisted File Adaptive. More corrosion was detected with longer ultrasonication time. No difference was observed regarding the pre-soaking media. Disinfection protocols exerted a significant overall effect on the performance of Hedström, ProTaper, and Twisted File instruments. Corrosion, microcracks, and crevices were evident on all tested instruments after disinfection protocols applied. All disinfection protocols, regardless of the pre-soaking media used or the ultrasonic cleaning time applied, have some effect on the cutting efficiency and the surface characteristics of the files.
