An in vitro study on the accuracy of two electronic root canal length meters

AIM: To evaluate the accuracy of Tri Auto ZX electronic apex locator and JUSTY Ⅱ electronic canal length meter and the influence of the size of apical foramen. METHODS; 42 root canals were measured in vitro. Electronic working length measurements ( EMLM) were recorded with Tri Auto ZX and JUSTY Ⅱ at the reading The deviation of EMLM from the anatomical apical foramen and the accuracy were determined. The relationship between the area and diameter of the apical foramen and to the deviation was analyzed. RESULTS: The deviation of Tri Auto ZX was lower than those of JUSTY Ⅱ (P 0. 01). Within ±0.5 mm and ±1.0 mm from the apical foramen , the accuracy of Tri Auto ZX was higher than the JUSTY Ⅱ ( P 0. 01). Both deviations caused by Tri Auto ZX and by JUSTY Ⅱ were positively related to the area of the apical foramen (P 0. 01) . The critical area of the apical foramen which controlled the deviation was within 0. 5 mm from the apical foramen for Tri Auto ZX,which was larger than that of the JUSTY Ⅱ. CONCLUSION; In this study, when the anatomical apical foramen is chosen as the reference point, Tri Auto ZX is more accurate than JUSTY Ⅱ at the reading APEX. Tri Auto ZX could locate the apex accurately at a wider extent of the area of the apical foramen.