Determination of H-file sizes being more suitable for measuring of working length in immature teeth using an EAL

Successful root canal treatments of immature permanent teeth require data on the exact working length (W.L.) for the preparation of root canal in the clinic. The author and colleagues have previously reported that root canal length of an immature tooth can be measured using an electronic apex locator (EAL; Apit 11®, Osada Electric Co., Ltd., Tokyo, Japan) in in vitro experiments. This study aimed to find the sizes of H-files that are more suitable for root canal length measurements of immature teeth using Apit 11®. Extracted human immature permanent teeth were prepared to have accesses to their pulp cavities, and the root canal length of each tooth was measured physically and electronically using H-files, rular and Apit 11® in the in vitro experimental system. Six types of file diameters that are generally utilised in the clinic were used to take measurements in order to observe the relationship between the position of the file tip and the meter-indicated area. The results suggest that, of the H-files of sizes No. 10 to No. 70, No. 15 is probably the most reliable to locate the apical foramen when it is used with Apit 11®.