The removal of the smear layer using the Quantec system. A study using the scanning electron microscope

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Abstract
Aim The aim of this study was to determine the ability of the Quantec Series 2000 rotary nickel–titanium endodontic system to remove dentinal debris and smear layer produced during canal preparation.Methodology A first group (control) of 12 curved root canals was prepared using conventional manual instruments and the step‐back technique. A second group of 12 curved root canals was instrumented using the complete Quantec sequence according to the manufacturer’s instructions. In both groups, irrigation was performed using a 3% NaOCl solution. The canal walls were observed under a scanning electron microscope and the coronal, middle and apical thirds of each canal photographed at a magnification of 500.The views were divided into 10 subareas by overlaying a grid, and the absence or presence of a smear layer was rated and scored on three appearances using the scale described by Ciucchi et al. (1989) .Results The scores were higher (i.e. less debris was present) in the middle third (P 0.0001) and in the apical third (P 0.0001) of canals prepared with the Quantec system when compared with those prepared with K‐files. Nevertheless, in canals prepared with Quantec instruments, the scores were significantly higher in the coronal third compared with the apical third (P 0.005).Conclusions The Quantec rotary system produced cleaner canal walls than conventional manual instrumentation, particularly in the middle and apical thirds. This finding may imply that stresses applied to the cutting regions of Quantec instruments by accumulation and compression of the smear layer are minimized.