Evaluation of working length determination methods: an in vivo / ex vivo study

This comparative study was done to determine the accuracy in measuring the working length of root canal using tactile method, electronic apex locator and radiographic method, in vivo and comparing the lengths so measured to the actual working length, ex vivo, after extraction. Thirty single-rooted teeth scheduled for extraction were selected for the study. After obtaining the consent from patients, a preoperative radiograph was taken and access opening was done. Working length was determined by tactile method, by using Ingle's radiographic method and by using a Foramatron-IV digital apex locator. The teeth were then extracted and the actual working length was determined by placing an endodontic file in the root canal 0.5 mm short of the apex. The results indicated that among the three methods, the electronic apex locator showed the highest accuracy and the highest reliability for working length determination.