Accuracy of root length determination using Tri Auto ZX and ProTaper instruments: an in vitro study.

The accuracy of the electronic apex locator feature of Tri Auto ZX was assessed. Twenty distobuccal roots were selected and, after endodontic access, placed in plastic cylinders filled with 2% agar until completely covered. The roots were divided in two groups according to the calibration of the automatic apical reverse mechanism of Tri Auto ZX, at 1 and 2 mm from the apical foramen. Preparation was performed with ProTaper instruments connected to the device. Afterwards, the last file used was introduced into the canal and fixed in place with acrylic resin. The roots were removed from the agar and ground until exposure of the file. The distances between file tip and apical foramen were submitted to statistical analysis. The distances reached were actually shorter than the preset distances in every case, however, they were considered clinically acceptable. Setting the reverse mechanism at 1 mm was more reliable than at 2 mm.