Mouth Sores & Oral Care During Cancer Treatment

This page covers the practical side of a sore mouth: seeing a dentist before treatment begins, the daily routine that keeps things manageable, eating when swallowing hurts, and the dental problems that follow radiation to the head and neck. For the clinical picture — what mucositis is and how long it lasts — see Mucositis During Cancer Treatment.

This is the single step most often skipped, and it is the one with the most leverage.

The National Cancer Institute is direct: "Before you start treatment, visit your dentist for a cleaning and check-up. Tell the dentist about your cancer treatment and try to get any dental work completed before starting treatment."

Timing matters. NCI's oral complications summary says "a checkup of your oral health at least a month before cancer treatment begins usually allows enough time for the mouth to heal if any dental work is needed." The National Institute of Dental and Craniofacial Research gives the same advice: see a dentist about a month before treatment begins.

The reason is infection. NCI explains that "problems such as cavities, broken teeth, loose crowns or fillings, and gum disease can get worse or cause problems during cancer treatment. Bacteria live in the mouth and may cause an infection when the immune system is not working well or when white blood cell counts are low."

The exam checks for mouth sores or infections, tooth decay, gum disease, poorly fitting dentures, problems moving the jaw, and salivary gland problems. NCI advises choosing "a dentist who has experience treating patients with oral complications of cancer treatment."

NCI's everyday oral care during chemotherapy and radiation therapy:

• Brushing. Use a soft-bristle brush two to three times a day for two to three minutes, including where the teeth meet the gums. Let the brush air-dry between brushings.
• Toothpaste. Use a fluoride toothpaste with a mild taste — NCI warns that "flavoring may irritate the mouth, especially mint flavoring." If toothpaste stings, brush with a quarter teaspoon of salt in a cup of water instead.
• Rinsing. "Use a rinse every 2 hours to decrease soreness in the mouth. Dissolve 1/4 teaspoon of salt and 1/4 teaspoon of baking soda in 1 quart of water."
• Flossing. Floss gently once a day.
• Lips. Use a lip cream with lanolin to prevent drying and cracking.
• Dentures. Brush and rinse them daily, and keep them moist when not worn — not in hot water, which makes them lose their shape.

Check your mouth every day for sores or white spots, and tell your team what you find.

If your platelet count is low you may worry about brushing. NCI's position: "Most patients can safely brush and floss while blood counts are low," because regular oral care prevents infections that make bleeding worse. Ask your dentist or doctor how to do it safely in your case.

NCI's advice for a sore mouth: "Choose foods that are soft, wet, and easy to swallow. Soften dry foods with gravy, sauce, or other liquids." Avoid foods that are crunchy, salty, spicy, or sugary, and avoid alcoholic drinks. NIDCR adds sharp or hot foods to the avoid list, along with tobacco and alcohol.

Serving food chopped, ground, or blended shortens the time it has to stay in your mouth. Because eating less is easy when it hurts, NCI recommends between-meal snacks, foods high in calories and protein, and meeting with a nutrition counselor. People having chemotherapy and head or neck radiation together often need tube feedings, and NCI notes that "patients do better if they begin these feedings at the start of treatment, before weight loss occurs."

For dry mouth, NIDCR suggests plenty of water, ice chips, and sugar-free gum or candy; artificial saliva may also be needed.

Radiation to the head and neck leaves a longer shadow than chemotherapy does. NCI: "Radiation can cause acute complications but may also cause permanent tissue damage that puts you at a lifelong risk of oral complications." Dry mouth, tooth decay, infections, and taste changes may continue or appear months to years after treatment ends.

Saliva is the link. NCI says the amount of saliva "usually starts to decrease within 1 week after starting radiation therapy to the head or neck," and though the glands "may partly recover during the first year," recovery "is usually not complete, especially if the salivary glands received direct radiation." Less saliva means more decay: "dry mouth and changes in the balance of bacteria in the mouth increase the risk of tooth decay." NIDCR advises asking your dentist about fluoride gel to help prevent it.

Two further points for any dentist you see afterwards. NCI warns that "oral surgery or other dental work can cause problems in patients who have had radiation therapy to the head or neck. Make sure that your dentist knows your health history and the cancer treatments you received." Radiation "can destroy very small blood vessels within the bone," which can kill bone tissue and lead to fractures or infection. And jaw stiffness from fibrosis usually begins around the time radiation ends; NCI says "treatment should begin as soon as possible to keep the condition from getting worse or becoming permanent." NIDCR's exercise is to open and close the mouth as far as possible without pain, 20 times, three times a day.

NCI's instruction, unchanged:

"It's important to call your doctor or nurse if you have pain in your mouth, lips, or throat that makes it difficult to eat, drink, or sleep or if you have a fever of 100.4 °F (38 °C) or higher."

Mouth sores together with a fever, in someone with low blood counts, need same-day attention rather than a wait-and-see. Other sources put that fever threshold at 100.4 °F (38 °C), so use the number your own team gave you.

• National Cancer Institute — Mouth and Throat Problems During Cancer Treatment: https://www.cancer.gov/about-cancer/treatment/side-effects/mouth-throat
• National Cancer Institute — Oral Complications of Cancer Therapies (PDQ), Patient Version: https://www.cancer.gov/about-cancer/treatment/side-effects/mouth-throat/oral-complications-pdq
• National Institute of Dental and Craniofacial Research — Cancer Treatments and Oral Health: https://www.nidcr.nih.gov/health-info/cancer-treatments