Resumen: The aim of the study was to quantify and compare apical debris extrusion in two systems of continuous and reciprocating rotary instrumentation with, and without, the use of a patency file. An experimental study was carried out in 120 mesial roots of lower first molars, which were randomized in the following 4 groups: Group A. Reciproc (VDW) R25 without a patency file, Group B Mtwo (VDW) without a patency file, Group C Reciproc (VDW) R25 with a patency file and Group D Mtwo with a patency file. Groups A, B and C presented statistically significant differences in comparison to group D, Mtwo with the use of a patency file (p<0.008 to 95% reliability). In conclusion, the greater amount of debris extruded through the apex occurred in roots instrumented with the reciprocating rotary system; this difference was statistically significant in relation to teeth treated with the Mtwo continuous rotary system with the use of a patency file.