Filling of the root canal should be completed within a millimeter of the root tip or apex. Short fills exceeding 2 millimeters, predispose to bacterial contamination of the underfilled root canal with resulting abscess or chronic inflammation necessitating retreatment, surgical endodontics or extraction.

Filling of the root canal should end at the root tip apex. Overextended filling materials can penetrate the underlying main sensory nerve in the lower jaw or into the sinus in the upper jaw causing a chemical burn to sensitive nerve tissue. Persistent numbness and/or pain in the lip and chin is symptomatic of overfill of lower posterior teeth. A posttreatment xray will show the overfill. If overfill impinges the lower jaw nerve, a 3D xray should be taken and referral to a maxillofacial microsurgeon to evaluate for immediate decompression surgery to remove the overfill before the nerve becomes irreversibly injured from chemical toxicity and inflammatory compression which compresses blood supply and causes sensory nerve death or necrosis. Microsurgery beyond 48 hours decreases the likelihood of reversibility, and increases the likelihood of permanent burning pain or numbness of the lip, chin, and gums.

If numbness persists 6 hours after root canal therapy, the patient should telephone the treating dentist or endodontist for re-evaluation and consultation for immediate referral to a microsurgeon for surgical removal of any overfill into the inferior alveolar nerve canal. Literature shows complete numbness reversal if microsurgical removal of root canal overfill materials inside the inferior alveolar nerve canal are surgically removed within the first 48 hours and partial numbness improvement if microsurgically removed within 3 months. Furthermore, if microsurgical inferior alveolar nerve decompression is treated in the first three months, improvement has been shown in two thirds of endodontic overfill cases. Thus time is of the essence for immediate microsurgery for surgical removal of root canal overfills located inside the inferior alveolar nerve canal.

Some root canal filling pastes are not FDA approved and contain harmful toxic paraformaldehyde and lead which mummify sensory jaw nerves. No U.S. dental school has recommended these pastes for over a decade. Nevertheless the American Endodontic Society (AES), which is not ADA (American Dental Association) affiliated, advocates these paraformaldehyde containing pastes which are notorious for causing permanent lip and chin numbness and/or pain. These unnecessarily toxic root canal filling pastes are known as Sargenti paste, N2 and RC2B. By contrast, the American Association of Endodontists, which is the ADA recognized speciality group, regards the use of paraformaldehyde containing root canal fillers or paste as substandard practice. See Sargenti Opposition Society and our article Ethics and Informed Consent for more information.

Filing instruments or placement of posts on completion of root canal treatment may penetrate the root side and cause an abscess or endodontic failure. Midtreatment xrays can avoid this mishap with careful measurements ensuring instruments are placed inside the root canal space and not off angled and out the root side. Three-dimensional xrays, known as Cone Beam CT, will aid in diagnosis if a perforation has occurred. The best 3D imaging for endodontic diagnosis is the J. Morita Corporation's Accuitomo CBCT machine. The Accuitomo is the least expensive to the patient, offers the least radiation and provides the highest resolution.

American Association of Endodontists. Maxillary Sinusitis of Endodontic Origin. April 2018.
American Association of Endodontists. Colleagues for Excellence, The Standard of Practice in Contemporary Endodontics. Fall 2014.
Gluskin, A. Double-edged sword of calcium hydroxide in endodontics. JADA. May 2020.
Gluskin, A. Anatomy of an Overfill: a reflection on the process. Endodontic Topics. 2009, 16, pp. 64-81.
Gluskin, A. Mishaps and serious complications in endodontic obturation. Endodontic Topics. 2005, 12, pp. 52-70.
Pogrel, A. Nerve damage in dentistry. General Dentistry. March/April 2017, 65 (2): pp. 34-41