Ex vivo comparison of three electronic apex locators to determine working length in endodontic treatment

Aim: This ex vivo study evaluated the accuracy of three electronic apex locators (Root ZX (R) II, Propex II (R) and Elements Diagnostic (R)) in determining working length by comparing their findings with direct measurements. Materials and methods: Forty single-rooted human teeth underwent coronal access and cervical preparation. To determine actual working length, a size 10 K-file was inserted to the point where its tip was visible at the apical foramen under 8x magnification; a rubber stop was placed at the level of the incisal edge, and working length was measured with a millimetre endodontic ruler. The teeth were then mounted on a piece of floral foam soaked in 0.9% sodium chloride, and electronic measurements were made using the foramen identification criterion for apex location of the Root ZX II, Propex II and Elements Diagnostic units. Results: Analysis of variance (ANOVA; P = 0.9987) showed no statistically significant differences between the three electronic apex locators at either tolerance level. Root ZX II had a 93% accuracy rate, Propex II 90% and Elements Diagnostic 91%. No statistically significant differences were found between the locators being tested (P > 0.05), with a safety margin of +/- 0.5 mm. Conclusion: The three locators had acceptable accuracy rates for clinical use.