In vivo measurement accuracy in vital and necrotic canals with the Endex apex locator.

Currently apex locators are being used to determine working length. This study was undertaken to see what is actually being measured and if the pulp status, i.e. vital or necrotic, makes a difference in the determination. In this in vivo study, 33 teeth, both vital and necrotic, were measured by the Endex apex locator and then radiographed. After the length determination, the file was cemented to place, the tooth extracted, and then shaved back until the file and the apex were exposed. The position of the file was measured in relation to the apical foramen. Results indicate that all measurements were within a narrow range (-0.86 mm to 0.50 mm). There was no statistical difference in measurements between vital and necrotic canals.