Endodontic overfilling involving the mandibular canal may cause an injury of the inferior alveolar nerve (IAN). We report a case of disabling dysesthesia and paresthesia of a 70-year-old man after endodontic treatment of his mandibular left third molar that caused leakage of root canal filling material into the mandibular canal. After radiographic evaluation, extraction of the third molar and distal osteotomy, a surgical exploration was performed and followed by removal of the material and decompression of the IAN. The patient reported an improvement in sensation and immediate disappearance of dysesthesia already from the first postoperative day.