Ex vivo evaluation of the capacity of the Tri Auto ZX to locate the apical foramen during root canal retreatment

Aim To evaluate ex vivo the capacity of the Tri Auto ZX to locate the apical foramen during root canal retreatment. Methodology The root canals of 62 maxillary and mandibular canines were prepared to a length 1 mm short of the apical foramen, to an apical size 35 using 1% sodium hypochlorite as an irrigant. Once prepared, the length of each tooth was measured directly using a size 15 K‐Flexofile introduced in the canal until the tip was visible at the apical foramen. After the file was removed, its length was recorded to a precision of 0.01 mm using a calliper. These direct lengths (DL) became the ‘gold standard’ for comparison with the electronic lengths (EL) derived from the Tri Auto ZX. After direct measurement, the tooth was measured electronically (EL1) and the canals were filled using lateral condensation of gutta‐percha cones and sealer. Seven days later the root filling was removed using solvent, Gates‐Glidden burs, and K‐files, and new electronic lengths determined (EL2). The electronic lengths (EL1 and EL2) were compared with the DL, and the differences were analysed statistically using the proportions test and Student's t‐test. Results At a tolerance limit of ±0.5 mm, EL1 coincided with the DL in 76% of cases. Lengths obtained in the presence of remnant of filling material (EL2) coincided in 81% of cases. The proportions test used to compare these percentages showed no statistically significant difference between EL1 and EL2 (P > 0.05). The Student's t‐test revealed a statistically significant difference (P