A canker sore, medically known as an aphthous ulcer, can cause a sensation of pain in your teeth. This discomfort often feels like a genuine toothache, even though the sore is a soft tissue injury. These common, painful lesions develop inside the mouth, and their proximity to the gums and complex oral nerves results in a misleading sensation of dental pain, even though the tooth structure remains entirely healthy.
What Exactly Is an Aphthous Ulcer?
An aphthous ulcer is characterized by a distinct appearance: a round or oval lesion with a white or yellowish center surrounded by a bright red, inflamed border. These non-contagious sores form on the movable, soft tissues of the mouth, such as the inside of the cheeks, lips, the tongue, or the delicate tissue at the base of the gums. They are the most common type of mouth ulcer, affecting about 20% of the population at least occasionally.
Their appearance is often linked to triggers that disturb the immune system’s balance in the mouth. Common factors include minor physical trauma, such as an accidental cheek bite or aggressive toothbrushing, alongside emotional stress. Certain nutritional deficiencies, specifically low levels of iron, folate, or vitamin B-12, are also known to precipitate outbreaks.
Dietary factors can also play a role, as consuming acidic or spicy foods can irritate the sensitive oral lining and contribute to ulcer formation. Certain toothpastes containing the foaming agent sodium lauryl sulfate (SLS) may also increase the frequency or duration of the sores. The ulcer typically begins with a tingling sensation before developing into a painful open lesion, which lasts about one to two weeks for minor cases.
The Mechanism of Referred Dental Pain
The sensation of a toothache originating from a soft-tissue sore is an example of referred pain. This is a neurological event where the brain interprets pain signals as coming from a different location than the actual source of injury. In the mouth, this misinterpretation occurs due to the dense and highly interconnected nature of the sensory nerves in the head and face.
Pain signals from the mouth, jaw, and teeth are primarily carried to the brain by the trigeminal nerve, which has multiple overlapping branches. When a canker sore forms near the gum line or adjacent to a tooth, intense inflammatory signals travel along these shared nerve pathways. The brain has difficulty pinpointing the exact origin of the irritation because nerve fibers from the soft tissue and tooth structures converge.
Because the brain is accustomed to receiving pain signals from the tooth pulp, it defaults to interpreting the strong inflammatory signal from the sore as a problem with the nearest tooth. This misdirection can make the teeth feel sensitive, tender, or cause a dull, throbbing ache, even though a dental examination would show the tooth is healthy.
Managing Pain and Promoting Healing
Managing the discomfort from an aphthous ulcer focuses on reducing inflammation and protecting exposed nerve endings. Immediate relief can be found by performing a simple saltwater rinse several times a day, which helps cleanse the area and create a less acidic environment. Avoiding spicy, highly acidic, or abrasive foods is also helpful, as these substances can directly irritate the sore and worsen the pain.
Many people find relief using over-the-counter topical anesthetics, such as gels or liquids containing benzocaine, which temporarily numb the surface of the lesion when applied directly. Other products, like milk of magnesia, can be dabbed onto the sore to create a protective coating and neutralize the area’s acidity. For more persistent or painful sores, a healthcare provider may prescribe medicated mouth rinses or topical steroid preparations to reduce the inflammation and accelerate recovery.
While most canker sores heal on their own within one to two weeks, professional intervention may be necessary in certain cases. You should seek medical or dental attention if the sore is unusually large, lasts longer than two weeks without healing, or causes severe difficulty with speaking, eating, or drinking. These prolonged or severe cases may indicate an underlying condition or require stronger prescription treatments to manage the associated pain.