Ongoing mouth ulcers, what to look for? Oral Hygiene and what kinds of other problems?

The short version: most mouth ulcers are harmless canker sores, but the ones that matter are the ones that don't heal, grow, or bleed.

Ongoing mouth ulcers deserve a checklist, not a shrug. The most common cause is recurrent aphthous stomatitis, the medical name for canker sores. A 2022 study of 215 patients found that the worse the ulcers, the higher the body's inflammation markers: the immune-inflammation index correlated strongly with ulcer severity (r=0.80), as did the neutrophil-to-lymphocyte ratio (r=0.74) [1]. That tells you these sores are not just a local problem. They track with systemic inflammation.

What to look for matters more than what to do. A 2013 study of 223 patients validated a severity score based on six features: number of ulcers, size, duration, ulcer-free period, pain, and site [2]. That is your checklist. A single small sore that heals in a week is nothing. Multiple large sores that last over two weeks, recur constantly, or appear on the tongue or gums deserve real attention.

Oral hygiene is part of the picture but not the whole story. A 2024 study of 96 HIV patients found that poor oral hygiene was significantly associated with oral lesions (p=0.02) [6]. But hygiene alone will not fix an immune problem. The same study found smoking, alcohol, and low CD4 counts all tracked with lesions [6]. If you smoke, that is the single biggest modifiable risk: tobacco use is strongly linked to oral cancer, with smokers showing far higher rates of floor-of-mouth and tongue cancers than never-smokers [31].

The dangerous conditions to rule out are oral lichen planus and cancer. A 2016 study found that about 1 in 3 clinically diagnosed lichen planus cases were actually something else on biopsy, including one squamous cell carcinoma [9]. A 2021 study of 271 lichen planus patients found a malignant transformation rate of about 0.7%, all in erosive tongue lesions [15]. That is rare but real. Any ulcer that persists beyond three weeks, feels hard, or bleeds easily needs a biopsy, not another mouthwash.

My call: if ulcers are small, few, and heal within two weeks, treat them as canker sores and focus on stopping tobacco and alcohol. If any ulcer lasts over three weeks, grows, or feels hard, get a biopsy. Confidence: high on the checklist, moderate on the cancer risk because the transformation rate comes from one retrospective study.