Accuracy of Working Length Determination Using Tri Auto Zx & Protaper Instruments: An In Vitro Study

Aim and objectives: To assess the accuracy of Tri Auto ZX as an apex locator and its automatic apical reverse mechanism (AAR) set at 0.5, 1 and 1.5mm using Pro-Taper instruments. Materials and Methods: Forty-five freshly extracted single rooted human teeth were used and divided into three groups: (1) Teeth prepared using AAR set at 0.5mm (2) Teeth prepared using AAR set at 1mm (3) Teeth prepared using AAR set at 1.5mm.Tri Auto ZX (J. Morita, Kyoto, Japan) was activated to auto mode and biomechanical preparation was carried out using protaper instruments till size F3 for each group. The F3 instrument was stabilized at the position and roots were ground longitudinally until exposure of the instrument. Under stereomicroscope the distance between the file tip and apical foramen was measured. Results: The results showed the mean value for Groups was 0.4617mm, 0.8976mm and 1.5277mm respectively. Statistical analysis between the groups revealed that Groups I and III showed no statistical difference i.e (p<0.05). Group II showed the significance at 5% significance level. Conclusion: Tri Auto ZX showed to be an acceptable device for determining root canal length and instrumentation. Using a preset distance set at 0.5 and 1.5mm were more accurate than set at 1mm.