Ex Vivo Evaluation of the Accuracy of Electronic Foramen Locators in Root Canals with an Obstructed Apical Foramen

• Because of the importance of maintaining a correct working length during preparation of the root canal system, it is essential to know the accuracy of the electronic foramen locator (EFL) devices in all situations. It could help to determine the best protocol for the use of the equipment. Until now, no study devoted itself to evaluate nonpatent foramens.
• It was observed that, depending on the operating mechanism, each EFL presented a different behavior when used in canals without patent foramens. The results for the Root ZX II were significantly lower than those observed for other EFLs. The Propex II offered values very close to those found for −1.0. In turn, the Apex ID in this condition provided results similar to those observed at 0.0, suggesting that its mechanism is not interfered with the inability to access the apical foramen.
• It was also noted that without the obliteration of the foramen, all EFLs tested (Root ZX II, Propex II, and Apex ID) were accurate and reliable considering the measurements performed at the major foramen.
• When the lengths were established to a position short of the apical foramen (−1.0 mm), inferior results were observed, suggesting that, at this level, the use of these devices could produce inferior results, obligating the clinicians to make some confirmative procedures.
• Up to now, no study evaluated the accuracy of the Apex ID foramen locator. In the present research, this device produced quite accurate values.
• The findings of this study may help clinicians who use this type of equipment or encourage new supporters to define more security protocols of their usage procedures.

IntroductionThe objective of the present study was to evaluate the accuracy of electronic foramen locators (EFLs), Root ZX II (RZX; J. Morita, Tokyo, Japan), Propex II (Dentsply Maillefer, Ballaigues, Switzerland), and Apex ID (AID; SybronEndo, Glendora, CA), in root canals with an obstructed apical foramen (OAF) and to compare them with those 1.0 mm short of the apical foramen (AF; −1.0) and at the AF (0.0).MethodsThirty human mandibular molars had their coronal and cervical preparations accessed. Then, the AFs were standardized (250 μm). Electronic root canal measurements were performed for the −1.0 and 0.0 working lengths, and the canals were obstructed with dentinal debris. The distance to the AF displayed by the EFLs was then recorded. The last instrument used was fixed with a cyanoacrylate-based adhesive; the apical portions of the roots were scraped, allowing for the determination of the distance between the tips of the instruments and the AFs.ResultsThe precision rates at 0.0, −1.0, and the OAF were 94.7%, 43.9%, and 1.8% (RZX); 93.0%, 54.4%, and 54.4% (Propex II); and 93.0%, 68.5%, and 75.4% (AID), respectively (±0.5 mm). No significant differences were found between the devices at 0.0; however, for the measurements at −1.0 and the OAF, the AID offered significantly better results than RZX (P < .05).ConclusionsThe absence of foraminal patency caused by dentin debris obstruction affects the accuracy of the EFLs differently, suggesting distinctive interactions with their operating mechanisms.