Comparative Study of 6 Rotary Nickel-Titanium Systems and Hand Instrumentation for Root Canal Preparation in Severely Curved Root Canals of Extracted Teeth

Introduction: Some improvements have been developed with new generations of nickel-titanium (NiTi) rotary instruments that led to their successful and extensive application in clinical practice. The purpose of this in vitro study was to compare the root canal preparations performed by using GT Series X and Twisted File systems produced by innovative manufacturing process with Revo-S, RaCe, Mtwo, and ProTaper Universal systems manufactured directly from conventional nitinol and with stainless steel K-Flexofile instruments. Methods: The mesiobuccal root canals of 140 maxillary first permanent molars that had between 30 degrees-40 degrees curvature angle and 4- to 9-mm curvature radius of the root canal were used. After root canal preparations made by using GT Series X, Twisted File; Revo-S, RaCe, Mtwo, and ProTaper Universal NiTi rotary systems and stainless steel K-Flexofile instruments, transportation occurred in the root canal, and alteration of working length (WL) was assessed by using a modified double-digital radiographic technique. The data were compared by the post hoc Tukey honestly significant difference test. Results: NiTi rotary systems caused less canal transportation and alteration of WL than K-Flexofile instruments (P < .05). There was no significant difference between NiTi rotary system groups at any levels (P > .05) except 2:5 mm from the WL. At this level ProTaper Universal system caused significant canal transportation (P < .05). Conclusions: GI Series X and Twisted File rotary systems produced with innovative process were concluded to shape the curved canals to result in minimal canal transportation, similar to Revo-S, RaCe, Mtwo, and ProTaper Universal rotary systems manufactured by traditional methods. (J Endod 2013;39:278-282)