Without dispute, determining and establishing the correct apical working length during root canal therapy has a profound and critical effect on the successful outcome of the procedure. However, this very thing has presented a challenge to endodontists and clinicians for many years, due to the fact that locating the apical constriction zone within a clinical perspective is very difficult—mostly because of its position and conformation, which are highly variable.
Methods of determining the working length include tactile sensation, knowledge of root canal lengths and anatomy, assessment of preoperative radiographs, and electronic apex locators. Traditionally, radiography has been the most used method in obtaining information on the anatomy of the root canal and its surrounding tissues. However, the working length measurement performed radiographically presents several limitations, namely radiation exposure, time expenditure, and difficulty of interpretation because it is a 2-dimensional image that is often overlapped with anatomic structures and is subject to the interpretation of the observer. Apex locators have been presented as valid instruments for identifying the apical foramen, helping to determine working length alternatively to the radiographic method. One published in vivo study states: “Underestimation of the WL [working length] can lead to insufficient debridement of the root canal, whereas overestimation can result in damage to the periapical tissues, which will delay or prevent healing…Furthermore, radiographs provide a two-dimensional image of a three-dimensional structure, which might affect the interpretation.”1
Another published study found that “working length ending radiographically 0–2mm short of the radiographic apex does not guarantee that instrumentation beyond the apical foramen will be avoided. Therefore radiographic working-length measurements should be combined with electronic working length determination using modern apex locators.”2
Third-generation apex locators detect the canal terminus by measuring the electrical properties of the apical part of the root canal, such as resistance and impedance, using multi-frequency measurement, like Ultradent Products, Inc.’s Endo-Eze® FINDTM apex locator. Endo-Eze FIND is a battery operated, portable device designed for foramen localization, using a multifrequency-dependent impedance method. FIND’s easy-to-read, full-color graphic display, audio feedback, and fully automatic measurements make foramen localization and working-length determination easy and convenient during root canal treatment. Thanks to its compact design and small footprint, FIND easily fits on any counter or treatment tray.
To learn more about, or purchase, the Endo-Eze FIND apex locator kit, please call 800.552.5512 or visit ultradent.com.
1. Stöber EK, Duran-Sindreu F, Mercadé M, Vera J, Bueno R, Roig M. An evaluation of root ZX and iPex apex locators: an in vivo study. J Endod. 2011;37(5):608-10.
2. ElAyouti A, Weiger R, Löst C. Frequency of overinstrumentation with an acceptable radiographic working length. J Endod. 2001;27(1):49-52.