Mouth Ulcers by Cause: Aphthous, Traumatic, Infective Guide

A mouth ulcer is a break in the thin lining (mucosa) of the mouth that exposes the tissue underneath. It usually looks like a round or oval sore with a yellow-white centre and a red border, and it hurts most when eating spicy, salty or acidic food, or while brushing the teeth.

Knowing why an ulcer formed changes how it is treated. An aphthous ulcer comes from the body's own immune response, a traumatic ulcer comes from a physical injury such as a sharp tooth edge, and an infective ulcer comes from a virus, bacterium or fungus. Sorting ulcers by cause helps the dentist pick the right medicine and catch warning signs that need a biopsy.

Key Concepts

• Aphthous ulcer (canker sore): not contagious. Three types: minor (under 10 mm, heals in 7–10 days), major (over 10 mm, lasts weeks and may scar), and herpetiform (many tiny 1–3 mm ulcers in a crop).
• Traumatic ulcer: a single sore sitting exactly where a sharp tooth, rough filling, hard food or denture rubs. It heals within about two weeks once the cause is removed.
• Infective ulcer: caused by microbes. Herpes simplex virus makes clustered ulcers (often on the lips or the hard palate), bacteria can superinfect a wound, and the fungus Candida causes creamy removable patches that leave raw areas.
• Useful terms: prodrome means the tingling felt before an ulcer appears; pseudomembrane is the yellow-white covering on the sore; erythema is the red halo around it.

How It Works

1. Aphthous: immune cells mistakenly attack the mouth lining after triggers such as stress, a small bite injury, vitamin B12, iron or folate deficiency, or sodium lauryl sulphate in some toothpastes.
2. Traumatic: repeated friction tears the surface; white blood cells clean the wound, and new lining grows across it in about 10–14 days if the rubbing stops.
3. Infective: the microbe invades lining cells, and the immune system destroys the infected cells, leaving a painful crater. Herpes often starts as tiny blisters that burst into shallow ulcers, sometimes with mild fever and swollen neck glands.

Worked Example

Meera gets minor aphthous ulcers 6 times a year, each lasting 8 days: 6 × 8 = 48 ulcer days per year, about 13 percent of the year (48 ÷ 365 ≈ 0.13). After correcting low vitamin B12, episodes drop to 2 per year, so ulcer days fall to 2 × 8 = 16 — a gain of 48 − 16 = 32 pain-free days from one simple fix.

Common Misconceptions

• "All mouth ulcers spread to other people." Only infective ulcers such as herpes are contagious. Aphthous and traumatic ulcers cannot spread by kissing or sharing food.
• "An ulcer that will not heal is just stubborn." Any ulcer lasting more than 2–3 weeks needs examination, because a long-standing ulcer can occasionally be an early sign of oral cancer.
• "Rubbing salt into an ulcer heals it fast." Salt stings and can irritate the sore. Gentle warm salt-water rinses soothe the area, but they do not greatly speed healing.

Real-World Applications

• Dentists match treatment to cause: topical steroids or numbing gels for aphthous ulcers, smoothing a sharp tooth or adjusting a denture for traumatic ulcers, and antivirals or antifungals for infective ones.
• Cause-based thinking decides when to biopsy: a single non-healing ulcer at one spot for over three weeks is biopsied to rule out cancer.
• It guides practical advice: switching toothpaste, correcting denture fit, and eating soft non-spicy food while the sore heals.

In short: aphthous ulcers recur and are immune-driven, traumatic ulcers heal once the injury is fixed, and infective ulcers involve microbes and sometimes fever. Matching cause to treatment brings faster relief and keeps dangerous mimics from being missed.