Objective: Mandibular first molars typically have two roots and three root canals. However, the presence of an additional distolingual root, known as radix entomolaris, is a rare but clinically significant anatomical variation. Failure to recognize this variation may lead to endodontic failure. This case report presents the retreatment of tooth #47 exhibiting radix entomolaris, along with a detailed 28-month follow-up.

Case: A 32-year-old female patient presented to our clinic with no symptoms but reported a history of failed root canal treatment on tooth #47. Radiographic examination revealed a wide periapical radiolucency, and the diagnosis was established as asymptomatic apical periodontitis. The presence of radix entomolaris was confirmed through radiographic evaluation, and retreatment was indicated. Following the removal of previous filling materials, an access cavity was prepared under local anesthesia and rubber dam isolation. All canal orifices, including the additional distolingual root canal, were carefully located. Working lengths were determined using an electronic apex locator and confirmed radiographically. Canal shaping was performed with the ProTaper Next NiTi file system up to X4. Irrigation was carried out using 2.5% NaOCl and 17% EDTA. Calcium hydroxide was used as an intracanal medicament. After confirming the absence of clinical symptoms, the canals were obturated using the lateral condensation technique.

Conclusions: Identifying rare anatomical variations such as radix entomolaris is critical for successful endodontic treatment. In this case, careful treatment planning and execution led to complete healing of the lesion and functional preservation of the tooth during the 28-month follow-up.

Keywords: Radix entomolaris, Root canal retreatment, Apical periodontitis