Accuracy of an electronic apex locator in primary teeth with root resorption

AIM: To evaluate whether root resorption of primary molar teeth affects the accuracy of the Root ZX apex locator and to compare the Root ZX at different meter readings with direct canal measurement. METHODOLOGY: Sixty extracted primary molar teeth with root resorption affecting one sixth to one third of root length were used. The teeth were embedded in an alginate model. A K-type file was used in association with a Root ZX apex locator to measure canal length. Measurements were recorded using the Root ZX meter reading 'Apex' and '0.5 bar'. Actual tooth length was measured with a K-file to the major foramen. All measurements were read under a stereomicroscope at 15x magnification. The deviation of the Root ZX measurement from the actual canal length was determined. RESULTS: Mean differences between Root ZX length meter reading 'Apex' and actual length were 0.01 +/- 0.23 mm whereas mean differences between Root ZX length meter reading '0.5 bar' and actual length were -0.33 +/- 0.30 mm. The Root ZX was 96.7% accurate to within +/- 0.5 mm of the apical foramen when compared with the actual canal length of primary molars with root resorption. CONCLUSIONS: Using a criterion of +/- 0.5 mm, the accuracy of the Root ZX was high and not affected by root resorption. When compared with direct canal measurement, the error in locating the apical foramen was smaller with measurement at meter reading 'Apex' than meter reading '0.5 bar'.