Precision influence of file sizes on Elements-Diagnostic apex locator measuring

Objectives: To evaluate how the effects of file sizes affect the accuracy of the Elements Diagnostic apex locator in determining the working lengths of root canals in alginate models with various water contents.

Methods: Fifteen extracted single-rooted teeth were prepared, cleaned, and shaped, with apical constriction up to size #30. Specimens were embedded in alginate models constructed by sequential alginate dehydration for up to 15 hrs. The distance from the incisor edge to the major foramen of the root apex indicated the actual tooth length (AL). The electronically determined length (EDL) was measured by a K-file inserted into the root canal to a point just beyond the major foramen, and then withdrawn counter-clockwise until a flashing bar appeared at the "0.0" of the Elements Diagnostic unit (Sybron Endo, Anaheim, CA, USA). Four different sizes of K-files (#10, #15, #20, and #25) were used for the measurements. The subtraction difference (SD) between AL and EDL was recorded for each tooth. The % of water content in alginate and the SD values at three measuring timepoints in each file-size group were then compared by Student's t test.

Results: There was an average SD (0.69 mm) (min, 0.67 mm; max, 0.70 mm) displayed in the size #15 file regardless of the change in alginate water content from 66.2% to 65.94%. However, variations of SD (0.68-0.74 mm) in size #10, 0.58-0.66 mm in size #20, and 0.52-0.65 mm in size #25 were found when the alginate water content (66.2%) decreased to 65.94%.

Conclusions: When file size increased, the EDL reading was shorter in specimens with the same alginate water content. The Elements Diagnostic apex locator provided a consistent 0.69-mm short to the actual tooth length in a 0.30-mm-diameter constriction of the canals, with a size #15 file, when the water content of alginate was within 66.2% to 65.94%.