The Accuracy in the Control of the Apical Extent of Rotary Canal Instrumentation Using Root ZX II and ProTaper Instruments: An In Vivo Study

The accuracy of Root ZX II (J. Morita, Kyoto, Japan) to control the apical extent of rotary canal instrumentation in vivo was assessed. Twenty-four premolars with a single canal were selected. The roots were divided in two groups according to the calibration of the automatic apical reverse mechanism of Root ZX II, set at levels 1 and 2. After endodontic access, the preparation was performed with ProTaper instruments (Dentsply Maillefer, Ballaigues, Switzerland) connected to the device. Afterwards, the last file used was introduced into the canal and fixed in place with acrylic resin. The teeth were extracted and ground until exposure of the file. The distance from the instrument tip to the apical foramen was obtained. The percentage of acceptable measurements and the difference between means were submitted to statistical analysis. The differences of setting the reverse mechanism at 1 and 2 were not statistically significant. Both settings were not accurate for determining and controlling the apical extent of rotary instrumentation.