Methods: Sixty root canals of extracted human incisors, canines, lower premolars were divided into three equal groups and prepared with Lightspeed rotary instruments and H-file manual instruments by application of step-back technique, and with Flex Master rotary instruments using crown-down technique. Each root was cross-sectioned 2, 5 and 8 mm above the apex. Each cross-section was analyzed with light microscope under 12th magnification. In order to describe the quality of root canal preparation (quantity of the dentin/pulp debris) and root canal’s cross-section morphology (round, oval, with recesses) the special classification was applied. The data was tested with the Chi-square Pearson’s test.
Results: All tested instruments were highly efficient in preparation of round root canals (no debris). The best results in 2 mm distance from root apex for all cross-sections and in 5 mm distance for oval canals were achieved using the Flex Master instruments, whereas the best results in 5 mm distance for root canals with recesses and in 8 mm distance for and cross-sections were achieved the H-file (data statistically insignificant). Regardless of the root canal’s cross-section morphology and the distance from the root apex, the most efficient in preparing the root canals were H-file instruments (p=0,01).
Conclusions: All tested instruments were equally efficient for preparation of the round root canals. The best results in canal preparation were obtained using Flex Master in apical part and H-file in coronal part of the root canal.