Google Endoplaza

Length Determination, the Apex Locator




With an electronic apex locator the length of a tooth can be determinated very precisely. When the point of a file reaches the apex, the apex locator gives a signal (display and/or acoustic).

A file which has good contact with the dentin of the root canal is pushed slowly towards the apical foramen. When the file has reached the periapical tissue, the apex locator gives a constant acoustic signal. This is the only reliable length of the tooth. Other (shorter) measurements are relative and so less reliable.

The electronic apex locator is indispensible. However one has to know the limitations.

The advantages:

  • A file will not go through the apex "by accident".
  • The radiographic determination is only a confirmation from the determinated length and files will never enter the periapical tissue if the dentist does not want it to.

  • If there is any doubt about a perforation of a root canal, the apex locator gives a signal which you can not misinterprete.
  • The probable working length is known immediately.
  • Pressing debris through the apical foramen can not happen any more.
The limitations:

  • When a file touches metal (amalgam or gold) the apex locator gives the wrong signal.
  • Too much fluid in the pulp chamber or in the root canals can cause the wrong signal.
  • An accessory canal can cause the wrong signal.
  • When there are connected canals (mesial canals of lower molar) and much hypochlorite solution is in the canals you can get the wrong signal.
  • When the pulp chamber "leaks" to the oral cavity (caries or a nonfitting crown)this can cause the wrong signal.
  • When the battery of the apex locator has insufficient power it can influence the results.
  • When the connections of the apex locator or the connections in the mouth are not correct this can lead to a wrong measurement (it seemes that the locator does not work properly).
  • An old root canal filling can cause trouble. The filling (guttapercha)should be passed before you get a signal.
  • The patient should not have a pacemaker! This is a contra indication!
  • A radiograph always is necessary to determine the correct length and the curvatures of the root canals.

Tip:
Before measuring teeth with more than one root canal, the pulp chamber must be dried and paper-points are placed in the root canals drying the coronal part of the other root canals. When air has been used to dry the pulp chamber the paperpoints prevent air reaching in the periapex area.

Want to know more about the electronic apex locator? Read the FAQ document!

From this page you can order the following products in our web shop (catalogue)


  • Electronic apex locator
  • Paper-Points
  • Files
To former chapter: Cleaning and shaping of the coronal part of the root canals
To next chapter: Cleaning and shaping of the complete root canal system

©2005 Endoplaza.com  |  This page is best viewed in a resolution of at least 1024 x 768 pixels  |  Latest update on 21 November 2006