Electronic determination of root canal working length in primary molar teeth: an in vivo and ex vivo study

P>Aim To evaluate in vivo and ex vivo the accuracy of an electronic apex locator in primary molar teeth with or without root resorption. Methodology Fifteen primary molar teeth with 30 root canals were divided into two groups: roots without resorption (n = 13) and roots with resorption (n = 17). Root canals were measured with the Root ZX apex locator in vivo, and then after tooth extraction, each canal was measured electronically ex vivo. The actual root canal length was measured visually, with the placement of a K-file into the most cervical edge of either apical foramen or resorption. The Student's t-test was applied for statistical analysis at a 5% significance level. Results The electronic apex locator was precise in 69% and 65% of the cases with and without root resorption, respectively (tolerance = +/- 0.5 mm), in vivo and 69% and 77%ex vivo. When the tolerance was +/- 1 mm, however, these figures increased to 92% and 94% for root canals with and without resorption, respectively, in vivo and ex vivo. No significant difference was observed between the resorbed and non-resorbed root canals measured using the Root ZX. Conclusion The Root ZX apex locator was accurate in determining in vivo and ex vivo the working length +/- 1 mm in primary molar teeth in over 90% of roots regardless of the presence of root resorption.