Evaluation of the effect of different nickel titanium files on apical debris extrusion in curved canals

The pain after root canal treatment is an important issue in dental clinic. Several materials, including irrigants, dentine chips, pulp tissue and microorganisms can be extruded through the apical foramen into the periapical tissue. The extruded materials may cause complications, such as postoperative pain, swelling and flare-ups, during or after root canal treatment. The shaping techniques effect the postoperative pain. The amount of extruded debris may change due to the preparation techniques used, and the file system changes depending on the design shape and tip diameter. The tendency of flattening due to the memory property of nickel titanium files during canal forming in curved canals causes apical transport to enlarge by enlarging apex diameter. This will increase the likelihood of developing post-operative flare-up by causing debris to be excreted in greater amounts into periradicular tissue. The aim of our study was to compare the effects of different nickel titanium files on apical debris extrusion in curved canals. One hundred twenty human mandibular molar teeth were selected. The mesio-buccal roots of teeth with 20-40 degree were used in study. Teeth with a root angle less than 20 degrees and greater than 40 degrees, teeth with immature root apex, with caries, calcified root canals, crown or root fracture, and previously root canal treated were not included. The covers of eppendorf tubes were removed and tubes were weighed using an analytic balance with 10-4 accuracy A size 10 K-file wase inserted into the root canal until the tip was visible at the apical foramen to determine the real length, and the working length was determined as 1 mm less than this length. The teeth were randomly divided into 5 equal groups (n = 24). After the teeth were divided into groups, the mesial and distal roots were separated. Mesial roots were placed in the eppendorf tubes. The specimens were prepared with XP-endo Shaper (Group 1, 30/.04), Hyflex CM (Group 2, 25/.04), ProTaper Next (Group 3, 25/.06), TF Adaptive (Group 4, 25/.06), or 2Shape (Group 5, 25/.06). In groups 1, 2, 3 and 5 an endodontic motor with rotational motion, and in Group 4. an endodontic motor with adaptive motion were used. At the end of the preparation process, the debris on the root surface were irrigated into the eppendorf tube. Distilled water was used in all irrigation processes. After the preparation process completed, the tubes were stored in a dry incubator for 5 days to allow evaporation of all moisture before the dry debris weighed. The weight of the extruded debris was determined by subtracting the initial weight from the final weight. Groups were compared using the Kruskal-Wallis test. Debris extrusion was detected in all groups. In terms of the amount of debris extrusion, the groups were listed as 2Shape (Group 5), ProTaper Next (Group 3), XP-endo Shaper (Group 1), HyFlex CM (Group 2) and TF Adaptive (Group 4), respectively. No significant difference was found between the groups in terms of extruded debris (p˂.05). Keywords: Apical extrusion, curved canal, root canal treatment