Question: Are radiographs enough to accurately determine working length in root canal therapy?
Electronic length determination is more accurate than radiographic localization of the apical constricture. (Vieyra, et al IEJ, 2010). Radiographs are two dimensional and are unable to determine where the apical foramen is in relation to the root apex. Another shortcoming is that film angulation has a significant impact on the distance between the file tip and the radiographic root apex.
It is important to note as well that the minor constricture (the actual canal terminus) can vary from the radiographic apex by as much as 3-4mm and the apical foramen coincides with radiographic apex in only 17-46% of cases (Green, OOOP, 1973 and Kuttler, JADA, 1955) Therefore basing your WL solely on the radiographic position of an endodontic file to an arbitrary choice of a radiographic root apex has clinical significance on endodontic success – YOU’RE ACTUALLY OVEREXTENDED AND “FILLING LONG”.
Dr. M (Board Certified Endodontist)