An In Vivo Comparison of Two Frequency-based Electronic Apex Locators

By Welk AR, Baumgartner JC, Marshall JG.

Date: 03/2004
Journal: JOE


•Purpose:  To compare the accuracy in detecting the minor diameter of a two-frequency (Root ZX) and a five-frequency (Endo Analyzer Model 8005) EAL under clinical conditions. 

• vRoot ZX is based on the “ratio method” for measuring canal length. This method simultaneously measures impedance values at two frequencies (8 kHz and 0.4 kHz) and calculates a quotient of the impedances.  v vEndo Analyzer Model 8005 that measures the phase-angle values of impedance in the canal over five signal frequencies (0.5, 1, 2, 4, and 8 kHz). The phase-angle test determines when the impedance changes from a primarily reactive impedance to a primarily resistive impedance.  v

•N=    32 teeth planned for extraction


  oAccess was made, orifices were flared. 2.6% NaOCl irrigation

oRoot ZX and Endo Analyzer Model 8005 were used to determine WL for each canal.

oIn four teeth from each both group, file was reinserted into the canal and cemented in place using GIC.

oTeeth were extracted, radiographed and viewed under a microscope. The apical 4 mm of the root was shaved  longitudinally.

oTwo blinded investigators marked the distance of the file position in relation to the minor diameter microscopically for each specimen.

Most highlighted Results:  

1. The mean distance between the EAL WL and minor diameter was 1.03 mm (range +0.21 to +4.58 mm) for the Endo Analyzer Model 8005 and 0.19 mm (with a range of -0.5 mm to +1.73 mm ) for the Root ZX. 

2.The minor diameter (±0.5 mm) was located 90.7% of the times for the Root ZX and 34.4% for the Endo Analyzer

3.Endo Analyzer had significantly longer readings beyond the minor diameter than the Root ZX  4.It was found that each brand of EALs consistently measured the same length with no deviation in values between similar devices.

Clinical significance

 The Root ZX was able to predictably locate the minor diameter (± 0.5 mm) (90.7% accuracy) more frequently than the Apex Finder AFA Model 8005 (34.4% accuracy).