the influence of instrument application frequency on apical extrusion of debris in three instrumentation techniques

introduction various kinds of hand-held or rotary techniques are used for mechanical preparation of the canal. the purpose of this study was to assess the influence of the number of applications on apical extrusion of debris in conventional and two rotary instrumentation techniques (profile, flex master). methods and materials in this in vitro study, 75 extracted single-rooted human mandibular premolars with curvature between 0-10 degrees were selected and divided into three groups of 25 teeth each. all teeth were shortened to length of 15 mm by cutting the crown. group h was prepared by hand step back technique, group p was prepared by profile system and group f was prepared by flex master system. the number of applications was according to manufacturer recommendation. for collection of debris, vials of distilled water were used that were weighed before preparation by 0.0001 weighing machine. at the end of canal preparation, vials were completely dried and weighed again. the difference between the weights of vials in two stages was the weight of debris extruded from apical foramen. the mean weight of debris in various numbers of applications within each system was compared by one–way variance analysis. results comparing the various numbers of applications in each system, it was noted that only in profile group, with increasing the number of applications, the quantity of debris extrusion was reduced. discussion unused profile instruments induce more extrusion of debris from apical foramen, rather than used ones. key words canal preparation, application number, debris extrusion.