Anesthetics
Simply put, pain is detected by pain receptors. These pain receptors generate pain signals that are transported through nerves to the brain. Once in the brain, the signals are registered as pain. An anesthetic is a drug that blocks this pathway, either at the pain receptor, the nerve, or both. Because canker sores can be very painful, anesthetics are sometimes used to control this pain and make patients more comfortable.
The two main anesthetics that are used as treatment for canker sores are benzocaine and lidocaine. Both medications come in a variety of preparations such as gels, ointments, sprays, pastes, and viscous (thick and sticky) suspensions. They are used topically (right on the canker sore) to stop pain signals from reaching the brain.
Anesthetics usually need to be applied with an applicator. If they are applied with a bare finger, the finger will become numb along with the treated area. While benzocaine and lidocaine could be injected under the skin, as canker sore treatments they are usually just placed topically. They may need to be reapplied four times a day or more (up to the maximum allowed).
Antiseptics
While it is not at all clear why they would help, certain antiseptic agents seem to reduce the symptoms of canker sores. This benefit is unexpected because canker sores are not contagious and do not seem to be caused by an infectious organism. Nevertheless, chlorhexidine gluconate and (dilute) hydrogen peroxide can shorten the duration that a person has an active canker sore and can also reduce pain. These antiseptics do not change whether the disease will recur, however.
Surgical care
The surgical treatment of canker sores is somewhat controversial. Directly removing the canker sore with a scalpel is not practical. This is because canker sores that are bad enough to warrant surgery would require too much tissue to be removed from the mouth. While some practitioners take a “biopsy” of the canker sore, essentially removing the whole lesion, this approach is not always favorable to patients. Instead, the main goal is to destroy (“burn”) the canker sore tissue rather than cutting it out.
Silver nitrate is one method for the surgical treatment of canker sores. The silver nitrate sticks are freely available. They are commonly used to cauterize mouth or nose bleeds that will not stop bleeding, but are less often used as a medicine for canker sores. Silver nitrate sticks work by causing a chemical burn when applied to mucous membranes (like the inside of the mouth). A physician that can see the aphthous ulcer could quickly treat it by touching the sore with the end of the stick. This converts the lesion from an ulcer into a burn. While this may make a less painful sore, the burn takes as long to heal as the aphthous ulcer.
Laser therapy may have a role in the surgical treatment of canker sores. Not only does laser treatment lessen patients’ pain and heal canker sores faster, some studies indicate that aphthous ulcers do not return as frequently with this treatment. Laser treatment for canker sores is not available everywhere. Moreover, not every physician that uses lasers in medical or surgical practice necessarily to uses it to heal canker sores.
Incidentally, cryotherapy (freezing the canker sore) does not appear to be an effective treatment for canker sores.
References
Arikan OK, Birol A, Tuncez F, Erkek E, Koc C. A prospective randomized controlled trial to determine if cryotherapy can reduce the pain of patients with minor form of recurrent aphthous stomatitis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;101:e1-e5.
Tezel A, Kara C, Balkaya V, Orbak R. An evaluation of different treatments for recurrent aphthous stomatitis and patient perceptions: Nd:YAG laser versus medication. Photomed Laser Surg 2009;27:101-106.
Zand N, Ataie-Fashtami L, Djavid GE et al. Relieving pain in minor aphthous stomatitis by a single session of non-thermal carbon dioxide laser irradiation. Lasers Med Sci 2009;24:515-520.
