Ex vivo comparison of radiographic and electronic root canal length measurements in primary molars

Aim The aim of the study was to evaluate the accuracy of root canal length measurements of primary teeth using an electronic apex locator (EAL) and digital radiography in comparison to stereomicroscopic measurement as gold standard. Materials and methods After preparation of access cavities of twenty extracted primary molars, the teeth were embedded in alginate blocks. Endodontic files were inserted in the root canals and the length was measured using ProPex II (Dentsply, Maillefer). When the reading was stable for 5s a silicone stop was used for reference. The true.lengths of the files were then measured using a micrometer. The gold standard was determined by observing the tip of the file at the apical foramen under a stereomicroscope. For radiographic measurements standard images were obtained at 30 cm source-to-object distance, and zero degrees vertical and horizontal angulations. Radiographic images of each experimental tooth were obtained with the Digora Storage Phosphor Plates (SPP) (Soredex, Orion Corporation, Helsinki, Finland) with the x-ray unit operating at 65 kVp and 10 mA for 0.16 seconds (Trophy Radiologie, Vincennes, France). The radiographic root lengths were measured with the measurement tool of the Digora for Windows software. The mean measurements of both methods were compared to the gold standard measurements using Repeated Measure ANOVA test with Bonferroni adjustments to identify the pair-wise differences (p=0.05). Results The mean measurements obtained with the EAL (14.06 +/- 1.89 mm) were significantly lower than measurements done with SPP images (14.24 +/- 1.98 mm) (p<0.05). However, when both root canal length measurement techniques were compared to stereomicroscopic measurements (gold standard), no statistically significant difference was found. Conclusions The EAL might be safer than digital radiography for the measurement of root canal length in primary teeth.