COMPARATIVE ANALYSIS OF APICAL EXTRUSION OF DEBRIS AND SHAPING ABILITY IN CURVED ROOT CANALS USING FOUR DIFFERENT NITI INSTRUMENTS

Introduction: The aim of this study was to evaluate the apical extrusion of debris, apical transportation (AT) and centering ratio (CR) after root canal preparation using Reciproc, ProTaper, ProTaper Next (PTN) and Revo-S. Materials and methods: Sixty extracted human mandibular premolars with a curvature angle of 25 degrees and the same length were randomly divided into four groups (n=15). All root canals were shaped to size of 25: ProTaper Next X2 (Dentsply Maillefer), Reciproc (R25; VDW, Munich, Germany), Revo-S SU (25#, .06; MicroMega, Besancon, France) and ProTaper F2 (25#, .08; Dentsply Maillefer, Ballaigues, Switzerland). All roots were sectioned perpendicularly at 1, 3, 5 and 7 mm from the apex and were scanned by a micro-CT before and after the preparation. During this process, collect the debris of each tooth and weigh it three times consecutively. The amount of apical debris extrusion, AT and CR of teeth were recorded and compared between the groups by using the Kruskal-Wallis test. Results: In terms of extruded debris, all specimens showed apical debris extrusion, and no statistically significant difference was obtained among them (P>.05). In terms of transportation, there was no significant difference among the four groups (P >0.05); in terms of centering ratio, PTN and Revo-S had significantly higher (closer to C=1) centreing ratios than Reciproc and ProTaper. There was a significant difference between PTN and ProTaper (P<0.05), PTN and Reciproc (P<0.05), ProTaper and Revo-S (P<0.05) at 3 mm and 5 mm from the apical surface, but there was no significant difference in the mean centering ratio at 1 mm or 7 mm from the apical surface among the four groups. Conclusion: ProTaper Next and Revo-S prepared a more centered root canal shapes. All instruments caused extrusion of debris through the apex.