In vitro evaluation of the accuracy of several electronic apex locators.

This study describes two tests of the in vitro accuracy of several models of electronic canal length measuring devices (ECLMDs) using a gelatin test model and extracted human teeth with fully formed apices. In part 1, four previously untested ECLMDs were used in dry canals after access and pulpectomy. File lengths with wth file tip just visible at the foramen were compared to ECLMD lengths. Clinically significant ECLMD measurements of > or + 0.5 mm than visual length were noted with two ECLMDs 16.6% and 10% of the time. The other two ECLMDs had no measurements >0.5 mm than the visual measurement. The gelatin test model proved highly accurate with 4 of 6 ECLMDs tested thus far. Part 2 compared the accuracy of a previously tested ECLMD using the gelatin model when taking length measurements with canals both dry and wet with distilled water in them. There was no difference between measurements in wet or dry canals. Irrigation with distilled water may be a clinical aid when using resistance ECLMDs.