What are canker sores? And what arent they?

Feb. 1, 2000
Patients frequently call all sores in and around the mouth "canker sores." To add to the confusion, "canker sore" and "cold sore" seem to be interchangeable terms. For purposes of our discussion here, canker sores will be defined as aphthous ulcers and cold sores will be herpes lesions.

Canker sores are aphthous ulcers and cold sores are herpes lesions.

Trisha E. O`Hehir, RDH, BS

Patients frequently call all sores in and around the mouth "canker sores." To add to the confusion, "canker sore" and "cold sore" seem to be interchangeable terms. For purposes of our discussion here, canker sores will be defined as aphthous ulcers and cold sores will be herpes lesions.

We all know what herpes lesions look like, especially on the lip. First, they are bubbly, then crusty. But what about lesions just inside the lip and other intraoral lesions? Ever get confused between herpes lesions and aphthous ulcers? What is the real difference between the two? In the early days of my career, I found this question very confusing. I asked many clinicians and educators to get an answer.

Years ago, a graduate student explained it to me this way. "It`s simple. Canker sores are bacterial and cold sores are viral. Canker sores always occur on mucous membranes and cold sores occur on keratinized tissue." That oversimplified explanation provided a good starting point on my journey to learn the difference.

From my reading, it`s clear that much is still unknown about aph-thous ulcers. Many theories have been presented, along with lots of anecdotal treatments. Some authors think that aphthous ulcers and herpes are the same entity. This is most likely due to the fact that both lesions share several characteristics. They both are recurrent, painful, superficial oral lesions that persist for seven to 14 days. They usually heal spontaneously, leaving no scar. Sometimes, lymph nodes in the area are affected. In advanced cases, aphthous ulcers look more like herpes.

Among specialists in the area of oral medicine, it now is agreed that recurrent aphthous ulcers (RAU) and herpes simplex virus (HSV) are two distinct and separate entities. Some important differences should be noted.

Herpes lesions are contagious, while aph-thous ulcers are not. Herpes are secondary lesions produced by the herpes virus and are a counterpart of herpes labialis. The virus is stored in nerve ganglions.

Upon careful inspection, the lesions have different characteristics. Aphthous ulcers occur on nonkeratinized tissue, such as buccal mucosa, mucobuccal fold, floor of the mouth, under and on the sides of the tongue, and on the soft palate. Herpes lesions occur on keratinized tissue, such as the lips, hard palate, gingiva, and alveolar ridge. Aphthous ulcers generally are limited to a few in the mouth at one time (RAU Minor). The center is ulcerated with a yellow or gray pseudomembrane and is encircled by a thin red rim or halo.

Herpes consists of several small vesicles that rupture, forming a crust, especially on the lips. In many cases, the lesions recur in the exact same place. Inside the mouth, multiple small lesions often run together or coalesce to form a single large lesion.

The actual cause of aphthous ulcers is unknown, making them impossible to prevent and difficult to treat. They are the most common oral lesion, affecting 20 percent of the population. RAU Minor constitutes more than 70 percent of all canker sores, with RAU major and herpetiform RAU seen much less

frequently. RAU Major involves one to 10 lesions - each larger than the typical canker sore - and they persist for weeks or months. Herpetiform RAU usually occurs in the posterior of the mouth, with 10 to 100 small lesions forming in clusters. These lesions look similar to HSV, thus the name.

Aphthous ulcers are considered bacterial, not because bacteria cause the lesions, but because once the lesions appear, bacteria are attracted to the necrotic tissue. Speculation is that the immune system triggers these lesions, in concert with stress, nutritional deficiencies, oral trauma from a toothbrush or crusty French bread, hormones, or certain systemic diseases. Some people seem to have allergies to certain foods, dyes, or preservatives that trigger the lesions.

On the other hand, smoking seems to be protective, probably due to increased keratinization of the mucosa. Nicotine replacement used in smoking cessation programs also seems to reduce the incidence of canker sores. There does seem to be some genetic link, since half of first-degree relatives of aphthous ulcer sufferers also have the condition.

With the cause of aphthous ulcers unknown, treatment is limited to pain control and reducing healing time. A long list of over-the-counter products for aphthous ulcers exists. Many ointments or rinses contain topical anesthetics, such as benzocaine. Some products are anti-inflammatory or antimicrobial. Topical steroids also are frequently used as a treatment.

Systemic drugs have been tried, in particular prednisone. This drug works to reduce the number and frequency of lesions, but as soon as the drug is withdrawn, the ulcers recur. Several other systemic drugs have been tried, including thalidomide. Thalidomide has been shown to be helpful in advanced cases, especially those involving HIV infections. Most systemic drugs provide some relief for some patients, but not for all patients and not for extended periods of time.

In addition to the over-the-counter topical products, only one prescription topical agent is available for the treatment of aphthous ulcers - Aphthosol® from Block Drug. This drug contains amlexanox, a potent inhibitor of inflammatory medicators. The prescription paste is mucoadhesive, covering the aphthous ulcer and forming a protective layer.

Don`t confuse Aphthosol® with another prescription topical ointment for the treatment of herpes labialis on the face and lips. That drug is Denavir®. Penciclavir is the active ingredient and is for viral lesions. It works by inhibiting cellular replication of the virus. It can be applied directly to a lesion or even when just a tingling in the lip tells the patient a herpes lesion is eminent.

Treating patients with recurrent oral lesions requires patience and good communication. Distinguish between aphthous ulcers and herpes lesions, and then select an appropriate treatment.

Trisha E. O`Hehir, RDH, BS, is a senior consulting editor of RDH. She also is editor of Perio Reports, a newsletter for dental professionals that addresses periodontics. The Web site for Perio Reports is www.perioreports.com. Her e-mail address is trisha@perioreports. com.