Mouth sores that don't heal: when to get a biopsy

Canker sores are the most common cause of painful mouth sores, and they heal on their own. What doesn't heal, or an unexplained white or red patch, needs a closer look, often with a biopsy. I am an oral and maxillofacial surgeon (UNAM), certified by the Mexican Board of Oral and Maxillofacial Surgery, a professor in the Department of Diagnostic and Surgical Sciences at the University of Costa Rica School of Dentistry since 2006, and I see patients in Tower 1 of Hospital CIMA.

Anesthesia

Local

Length

Short: the sample takes a few minutes

Results

Days to a few weeks

Consultation

60,000 colones · by video, 20,000

When it's indicated

• An unexplained sore lasting more than 3 weeks.
• A sore with a likely cause — a broken tooth, a rubbing denture — that hasn't healed 2 weeks after removing it.
• A red or red-and-white patch (erythroplakia or erythroleukoplakia).
• A white patch that doesn't rub off and has no other explanation (leukoplakia).
• A lump on the lip or inside the mouth, or one in the neck that persists without explanation.
• A papilloma or another cauliflower-like lesion: it's benign, but some lesions that look like one can be cancer, especially on the gums and in older people.

Before surgery

• Take a dated photo when you notice it. I can guide you by video, but the exam and the biopsy are in person.
• If something rubs it — a broken tooth, a loose denture — tell me: sometimes the first step is fixing that.
• Bring a list of your medications. If you take blood thinners, don't stop them on your own: stopping is associated with a higher risk of blood clots. I coordinate with your doctor.
• If the result scares you, tell me: anxiety can make people put off the diagnosis, and the American Dental Association guideline stresses talking it through.

How I plan it

How I do it

1. 01ConsultationI examine the lesion and your whole mouth, and together we decide whether removing the cause is enough or a biopsy makes sense.
2. 02Local anesthesiaI numb only the area. You feel pressure, but it should not hurt; if you feel anything, I add more anesthetic.
3. 03The sampleI remove the whole lesion or a piece of it — a papilloma, with a margin of healthy tissue — and close with a few stitches. Taking the sample takes a few minutes.
4. 04PathologyA pathologist examines it under the microscope: what it is, whether there is dysplasia (cell changes) and what grade. Moderate or severe dysplasia carries a much higher risk of transformation than mild.

Recovery

• When the anesthesia wears off, expect mild discomfort that usually lasts a few days; we manage it with medication.
• For the first few days, soft, cool food, nothing spicy or acidic.
• A little blood in your saliva on the first day is normal: press with gauze. If pressure doesn't stop it, call the office or go to the emergency room.
• Brush gently around the wound and don't smoke while it heals. The stitches fall out on their own or are removed at the follow-up.
• Results come back in days to a few weeks. If it's leukoplakia or lichen planus, follow-up continues: in one review, their estimated annual transformation risk was 1.56% and 0.28%, so it is periodic and long term.

Risks and how I prevent them

Bleeding

It's usually mild and stops with pressure. With direct oral anticoagulants, bleeding after mouth procedures was similar whether people continued them (11.8%) or stopped them (13.5%), and all of it was controlled with local measures.

Changed sensation

Uncommon, near the nerves of the lower lip or the tongue, so I plan the incision based on where the lesion is.

Infection or the wound opening

As with any wound in the mouth; it's prevented with gentle hygiene and no smoking. If you notice pus or a fever, call the office.

Needing another procedure

If the result doesn't explain what's visible, another biopsy makes sense. A papilloma can come back: in one case series it recurred less with at least 3 mm of healthy tissue around it, which is why I remove it with a margin.

Putting off the biopsy

This is a risk too: early detection of potentially malignant lesions and mouth cancer can improve the outlook.

Other options

Removing the cause and waiting two weeks

If something is likely rubbing it and there are no warning signs, this is the right step: most sores from rubbing heal within two weeks once the cause is removed. If it doesn't heal, I biopsy it.

No biopsy, if it's a typical canker sore

Shallow and well defined, it heals on its own in one to two weeks. A topical steroid or low-level laser eases the pain and shortens healing, although they are not proven to keep it from coming back.

Lights, stains or brushings

None has shown enough accuracy to be used routinely as a screening tool. A biopsy remains the first choice; brush cytology is reserved for specific situations we agree on.

Frequently asked questions