Adiguzel, MehmetOzeken, FurkanCapar, Ismail DavutArslan, HakanDummer, Paul Michael Howell2026-01-312026-01-3120251329-19471747-4477https://doi.org./10.1111/aej.70043https://hdl.handle.net/20.500.12662/10725This clinical study evaluated four diagnostic approaches for locating the orifice of the second mesiobuccal canal (MB2) during root canal retreatment of maxillary molars: direct visual inspection, the Micro Hole Negotiator electronic device, the dental operating microscope, and their combined use. A stepwise protocol was used in 124 retreatment cases, applying each method sequentially. Detection rates of MB2 canals increased progressively, with the combined use of the microscope and electronic device yielding the highest adjusted diagnostic efficiency, followed by the microscope alone, the electronic device alone, and direct visual inspection. These findings suggest that optical magnification and impedance-based electronic feedback can enhance canal identification, particularly under complex retreatment conditions. The electronic device outperformed direct visual inspection and may enhance the detection of MB2 canals in clinical settings where a microscope is unavailable.eninfo:eu-repo/semantics/openAccessdental operating microscopesendodonticsmaxillaroot canal therapysecond mesiobuccal canalArticle10.1111/aej.700432-s2.0-10502352218341327840Q2WOS:001628205600001Q3