Introduction
The removal of all pulp tissue, necrotic material and
microorganisms from the root canal is essential for
endodontic success. This can only be achieved if the
length of the tooth and the root canal is determined
with accuracy. The outcome of treatment of roots with
necrotic pulps and periapical lesions is influenced
significantly by the apical level of the root filling
(Sjo¨gren et al. 1990). Traditionally, the point of termination
for endodontic instrumentation and obturation
has been determined by taking radiographs. The
development of the electronic apex locator has helped
make the assessment of working length more accurate
and predictable (Fouad & Reid 2000). The aim of this
review is to examine the variety of apex locators
available and overview their development. Contemporary
endodontic texts were consulted and a database
search performed using Medline to identify general