An electronic apex locator is an electronic device used in
endodontics
Endodontics (from the Greek roots ''endo-'' "inside" and ''odont-'' "tooth") is the dental specialty concerned with the study and treatment of the dental pulp.
Overview
Endodontics encompasses the study (practice) of the basic and clinical ...
to determine the position of the
apical constriction Apical constriction is the process in which contraction of the apical side of a cell causes the cell to take on a wedged shape. Generally, this shape change is coordinated across many cells of an epithelial layer, generating forces that can bend or ...
and thus determine the length of the
root canal
A root canal is the naturally occurring anatomic space within the root of a tooth. It consists of the pulp chamber (within the coronal part of the tooth), the main canal(s), and more intricate anatomical branches that may connect the root c ...
space. The apex of the root has a specific
resistance to electrical current, and this is measured using a pair of
electrodes
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
typically hooked into the lip and attached to an
endodontic file
Endodontic files and reamers are surgical instruments used by dentists when performing root canal treatment. These tools are used to clean and shape the root canal, with the concept being to perform complete chemomechanical debridement of the root ...
.
The electronic principle is relatively simple and is based on electrical resistance; when a circuit is complete (tissue is contacted by the tip of the file), resistance decreases markedly and current suddenly begins to flow. Various devices signal this event by a beep, a buzz, a flashing light, digital readouts, or a pointer on a dial.
History and uses
The original electronic apex locators operated on the direct current principle. A problem with these devices was that conductive fluids such as hemorrhage, exudate, or irrigant in the canal would permit current flow and therefore a false reading. Newer devices are impedance-based, using alternating current of two frequencies;these measure and compare two electrical impedances that change as the file moves apically. The benefit is that these devices are much less affected by fluid
conductive media in the canal. The impedance type apex locators have been demonstrated to be 80 to 95% accurate in identifying the apical foramen. Therefore after obtaining a reading, 1 to 2 mm is subtracted as the corrected working length.
Electronic apex locators have been shown to be more accurate than
radiography
Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...
when determining the position of the apical foramen.
Adaptive Apex Locators
Adaptive Apex Locator overcomes as the disadvantages of the popular apex locators 4th generation – low accuracy on working in wet canals, as well the disadvantages of devices V th generation – difficulty on working in dry canals and necessarily of compulsory, additional wetting.
Adaptive Apex Locator continuously defines humidity of the canal and immediately adapts for dry or wet canal. On this way is possible to be measured as in dry and in additional wetted canals as well, canals with blood or exudates, canals with still not-extirpated pulp.
See also
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Apex location
Apex location is a method of determining the length of the root canal of a tooth - manually or with a mechanical canal instrument that passes a low intensity electric current through the tooth.
The electrical characteristics of the tooth structur ...
External links
The use of apex locators in the diagnosis of perforations Dr. Yosef Nahmias, Endodontic Magazine
Dental equipment
Dentistry
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