A canker sore, medically known as an aphthous ulcer, is a common, painful lesion that develops inside the mouth. These ulcers form on the soft, movable tissues, yet the discomfort often feels like it is coming from a hard structure, leading many people to suspect a dental problem. Whether this minor injury can truly cause tooth pain depends less on the tooth itself and more on how the nervous system processes pain signals. Understanding this soft tissue injury is the first step toward accurately identifying the source of the discomfort.
What Exactly Is a Canker Sore?
A canker sore is a small, shallow ulcer characterized by a distinct physical appearance. The typical lesion is round or oval, presenting with a whitish or yellowish center surrounded by a pronounced red, inflamed border. These ulcers develop exclusively on soft mucosal tissues, such as the inside of the cheeks, lips, tongue, or at the base of the gums.
Minor canker sores are generally less than one centimeter in diameter and usually heal without scarring within one to two weeks. Common triggers include minor injuries from aggressive brushing or dental work, emotional stress, and consuming highly acidic or spicy foods. The pain is localized to the ulcer itself, intensifying when the tissue is moved or irritated by contact.
Understanding Referred Pain and the Nerve Connection
The sensation of tooth discomfort from a canker sore stems from referred pain, a neurological phenomenon. All sensation in the mouth and face is transmitted through the trigeminal nerve (the fifth cranial nerve). This nerve acts as the main sensory pathway, supplying the teeth, gums, jaw, and surrounding soft tissues.
When a canker sore irritates nerve endings, the intense signal travels along this shared nerve trunk toward the brain. Because the pathway is shared with the teeth and jaw, the brain can misinterpret the signal’s location, assigning the pain to a nearby structure like a tooth. A sore located high on the gum line or near the back teeth may generate a dull ache that feels like a toothache.
Distinguishing Canker Sore Pain from True Dental Issues
Accurately identifying the source of pain requires distinguishing the characteristics of the discomfort. Canker sore pain is typically a constant, dull ache or burning sensation highly sensitive to movement, talking, or contact with acidic foods. The pain generally remains localized to the visible sore, even if the sensation is perceived in an adjacent tooth.
In contrast, pain originating from a true dental issue, such as a deep cavity or abscess, presents with specific features. Dental pain is often sharp, throbbing, and localized within the tooth structure. It is frequently triggered by temperature changes, especially cold, or the pressure of biting down. If the pain persists after the canker sore heals, or if it is accompanied by facial swelling, fever, or pus drainage, professional dental attention is required.
Managing Pain and Promoting Healing
Immediate relief focuses on reducing irritation and soothing exposed nerve endings. Over-the-counter topical anesthetics containing benzocaine can be applied directly to the lesion to temporarily numb the area, allowing for more comfortable eating and speaking. Creating a protective barrier with specialized oral adhesive pastes can also shield the ulcer from external friction.
Simple home remedies promote healing and reduce inflammation. Rinsing the mouth several times a day with a warm saltwater solution or a baking soda and water mixture helps clean the area and neutralize irritating acids. Patients should avoid spicy, highly acidic, or abrasive foods, as these substances irritate the ulcerated tissue. If a canker sore is unusually large, causes severe difficulty eating, or fails to heal within two weeks, professional consultation is recommended.