A canker sore (aphthous ulcer) is a common, non-contagious lesion that forms on the soft tissues inside the mouth. These sores appear as a painful, shallow wound with a white or yellowish center surrounded by a bright red border. While they cause significant discomfort and irritation to the surrounding oral tissues, the intense, localized pain often leads to confusion about the actual source of the discomfort, making it feel like a deeper dental problem.
Can Canker Sores Directly Cause Tooth Pain
A canker sore does not directly cause structural pain within the tooth itself, as it does not affect the dentin or pulp where true toothaches originate. The primary pain mechanism is localized irritation of the sensitive mucosal lining where the open ulcer is present. However, the sensation of tooth pain can occur through two distinct mechanisms: referred pain and proximity irritation.
Referred Pain
Referred pain happens when the dense network of nerves in the mouth misinterprets the origin of the pain signal. Since the same trigeminal nerve pathways relay sensations from the ulcerated soft tissue and the teeth, the brain can mistakenly perceive the localized gum or cheek pain as originating from a nearby tooth. This neurological confusion is common in the head and neck area, making it seem like the tooth is throbbing when the true source is the surface lesion.
Proximity Irritation
Proximity irritation is a more direct cause, typically occurring when a canker sore forms directly on the gumline or the inner cheek tissue immediately adjacent to a tooth. Simple actions like chewing, brushing, or even speaking can press the inflamed, raw surface of the sore against the hard dental structure. This constant mechanical friction creates a sharp, localized pain that mimics a dental issue.
Common Triggers and Formation of Canker Sores
The exact cause of canker sores is not fully understood, but their formation is linked to a variety of internal and external triggers. Minor physical trauma to the oral lining is a frequent precursor, often resulting from accidentally biting the cheek, aggressive toothbrushing, or irritation from dental appliances. This initial injury may compromise the mucosal barrier, allowing an ulcer to develop.
Dietary factors are strongly implicated, with acidic foods like citrus fruits, tomatoes, and spicy dishes frequently causing flare-ups. Nutritional deficiencies (Vitamin B-12, iron, folate, or zinc) can weaken oral tissues. High levels of emotional stress or fatigue are known to suppress the immune system. Some people also react to chemical irritants like sodium lauryl sulfate (SLS), found in many commercial toothpastes.
Other Sources of Oral and Dental Pain
If the pain is deep, constant, throbbing, or persists after the canker sore has healed, the discomfort is likely rooted in a true dental or gum issue.
Dental caries (cavities) are a common source of sharp pain, especially when decay exposes the sensitive underlying dentin. If decay reaches the pulp, it can cause severe, lingering pain and potentially lead to an abscess near the tooth root. Cracked or fractured teeth also cause sharp discomfort when biting or chewing, as pressure irritates the internal pulp.
Gum health problems, such as gingivitis or periodontitis, can also manifest as perceived tooth pain. Inflammation and infection of the gum tissue can cause a dull ache around the base of the teeth. If the gums recede, the hypersensitive root surface can become exposed. Pain may also be referred from non-dental sources like temporomandibular joint (TMJ) disorders or sinus infections.
Treating Canker Sore Discomfort and Knowing When to See a Dentist
Managing the discomfort of a canker sore focuses on protecting the open wound and reducing inflammation while the tissue naturally heals, a process that typically takes 7 to 14 days.
Over-the-counter topical anesthetics containing benzocaine can be dabbed directly onto the sore for temporary numbness and pain relief. Rinsing the mouth with a solution of warm water and salt or baking soda can help soothe the ulcer and maintain cleanliness. Temporarily avoid abrasive, spicy, or highly acidic foods and beverages, as these can sting the ulcer and delay healing. Using a soft-bristled toothbrush and a toothpaste free of sodium lauryl sulfate prevents further physical and chemical irritation.
Professional attention is necessary if:
- The sore is unusually large.
- New sores appear before old ones heal.
- The lesion persists for more than three weeks.
- The pain is severe and unmanageable with home care.
- A high fever develops.
- The sore makes swallowing or drinking extremely difficult.