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.
