Objective:

To assess precision of Raypex 6 to locate foramen and establish placement in the canal -dentin-cement (CDC) area in lower molar canals by means of diaphanization. Material and methods: 52 permeable canals from 20 extracted lower molars immersed in alginate were used. Crown opening, location, permeabilization and irrigation with 5.25% sodium hypochlorite were performed. Electronic conductometry was obtained with Raypex 6 electronic locator. A K #15/20 file type was inserted in all samples which had labial clip inserted in alginate. The device’s screen indicated position of the apical foramen in the red bar, K files position was readjusted in the first two yellow bars, the file was then fixated with acrylic resin. Teeth were diaphanized by means of the nitric acid technique; teeth were kept in methyl salicylate. Samples were analyzed with clinical microscope at 16x, they were subjectively assigned a value called precise when the tip of the file was located at 0-0.5 mm, external or positive (+), when the file was +0.1 mm or more, and short or negative (-) when it was -0.51 mm or less with respect to the apical foramen. Results: Of the 52 analyzed samples, 40 were found to be precise, seven long and five short. Descriptive statistics showed 76.9% precision. Conclusion: Electronic working length with Raypex 6 showed suitable precision in mesial canals of lower molars.