Comparison of working length determination with radiographs and four electronic apex locators

To evaluate the accuracy of the Root ZX, Elements-Diagnostic, Precision AL and Raypex 5 electronic apex locators when compared to radiographs for locating the apical constriction.

The apical constriction of 693 canals in 245 maxillary and mandibular teeth was located in vivo with four electronic apex locators (EALs) and radiographically. After extraction the actual location of the apical constriction was determined visually and with magnification. A paired samples t-test, X2 test and a repeated measure anova at the 0.05 level of significance were used to determine differences between the groups.

For anterior teeth, the Root ZX, Elements, Precision AL, Raypex 5 and radiographs located the apical constriction 89.09%, 83.63%, 85.45%, 81.81% and 32.72% of the time, respectively. For premolar teeth, the Root ZX, Elements, Precision AL, Raypex 5 and radiographs located the apical constriction 75%, 61.60%, 64.28%, 61.60% and 32.14% of the time, respectively. For molar teeth, the Root ZX, Elements, Precision AL, Raypex 5 and radiographs located the apical constriction 69.01%, 50.49%, 65.40%, 43.93% and 14.59% of the time, respectively. There was no statistically significant difference between the four EALs (P = 0.05).

Measuring the location of the apical constriction using the four apex locators was more accurate than radiographs and would reduce the risk of instrumenting and filling beyond the apical foramen.