[In vitro investigation of three NiTi rotary instruments]

The purpose of our study was to compare the shaping ability of three nickel-titanium rotary instruments (RaCe/FKG Dentaire/, ProTaper /Dentsply-Maillefer/ and M(two)/VDW/) by measuring the asymmetry that occurs in curved canals during instrumentation. Eight simulated canals in resin blocks (Morita Europe) were prepared in each group by the same operator according to the instructions of the manufacturers. We used M(two) direct (VDW-Sirona) contra-angle with torque control function. Copious irrigation of the canals was performed with the use of Chloramine B solution and File-Eze (Ultradent) was used for lubrication. We accomplished our measurements on the pre- and postoperatively scanned images of the resin blocks with the aid of Image Tool for Windows 3.0 (UTHSCSA). Measuring points were assigned along the curvature of the canal axis line to represent 1 millimeter distance from the apex and from each other. The centre of the curvature was edited and radius lines were drawn from the centre through the measuring points. We determined the value of the preparation asymmetry at the levels of these measuring points along the radius lines. RaCe prepared with the greatest asymmetry at the first, second, fourth and fifth measuring points, at the third level ProTaper produced the highest value of asymmetry. In general M(two) prepared with the lowest asymmetry while it proved as a safe instrument system. The main disadvantage about ProTaper was the high risk of fracture. The RaCe sequence used in this study showed great asymmetry values at the apical area.