A 24-year-old patient complains of aching pain in the 11 tooth that is getting worse during biting down on food. Two days ago the tooth was filled for pulpitis. Objectively: the 11 tooth is filled. The thermal test causes no pain, vertical percussion is slightly painful. X-ray picture of the 11 tooth shows that the endodontic filling is 1 mm above the root apex. Which of the following methods will be most effective for eliminating this complication?