Background and Aim: Mechanical preparation of canal is one of the most important stages in root canal therapy. Various kinds of hand or rotary techniques are used for mechanical preparation of canal and each of them has advantages and disadvantages. During canal preparation, extrusion of debris from the apical foramen can result in periapical inflammation and increased pain and edema. The aim of this study was to compare hand instrumentation technique with three rotary systems (Profile, Race, Flex Master) regarding the amount of extruded debris from apical foramen during canal preparation.

Materials and Methods: In this experimental in vitro study, one hundred human extracted single rooted mandibular premolars with curvature between 0-10 degrees were selected and divided into four groups of 25 teeth each. All teeth were shortened to 15 mm length by cutting the crown. Group H was prepared by hand step back technique, group P by Profile system, group R by Race system and group F by Flex Master system. For debris collection, vials containing distilled water were used which were weighed before preparation. After the end of canal preparation, vials were completely dried and weighed again. The difference between weights of vials in two stages was the weight of debris extruded from apical foramen. The groups were compared by One-way ANOVA with p<0.05 as the level of significance.

Results: Group H had the highest mean weight of debris which showed significant difference with all three rotary groups (P<0.001). The lowest mean weight of debris was observed in group R (Race) which was significantly different from group F (Flex Master) but not significantly different from group P (Profile).

Conclusion: Based on the results of this study, race rotary system caused less debris extrusion from apical foramen compared to hand step back technique and Flex Master rotary system.