Mouth care and preventing tooth decay

Looking after your mouth and teeth is very important to help prevent dental problems. You may be at higher risk of dental problems because of your treatment for head and neck cancer.

Even if you only have a few teeth, it is important to have a good mouth care routine. You need regular check-ups with a dentist or dental hygienist every 3 to 6 months. This will help find early signs or tooth decay and look after your gums. It also reduces the risk of developing jaw problems.

Saliva is important in keeping your mouth clean. If you have a dry mouth, you are more likely to get mouth infections, such as thrush. Saliva also protects your teeth against decay. A dry mouth also means you are at much higher risk of tooth decay.

Saliva allows the tongue, lips and cheeks to slide easily over the teeth. If you have any rough, chipped or sharp teeth or dentures it is important to get them fixed. This prevents them rubbing inside your mouth and causing ulcers to develop.

Protecting your teeth

Things you can do to help protect your teeth include the following:

  • Follow a mouth care routine agreed with your dentist or dental hygienist.
  • Do not smoke.
  • Use fluoride products (see below) prescribed by your dentist.
  • Avoid sugary drinks.
  • Only have acidic foods or drinks at mealtimes.
  • Check your mouth daily for ulcers, red, white or dark patches or signs of tooth decay. When you have a dry mouth, decay is often at the top or bottom of the tooth near the gum line.
  • If you notice a change in your mouth or teeth, see your dentist straight away.


Thrush is a fungal infection which causes redness and white patches in the mouth. Other symptoms include:

  • a sore mouth or a burning feeling on the tongue
  • an unpleasant taste in your mouth
  • difficulty eating or drinking.

Tell your doctor if you have any of these symptoms. They can prescribe medicine to help. If you have dentures, you are more likely to get oral thrush. Take them out at night and brush your dentures every day.

Using fluoride

Your dentist or dental hygienist will advise you on how to brush your teeth and keep your gums healthy. They will also prescribe a specialised fluoride toothpaste called Duraphat® 5000ppm. This strengthens the hard, outer layer (enamel) on your teeth and helps protect them from decay. It can also help reduce tooth sensitivity.

This toothpaste is not available over the counter. Your dentist or doctor will prescribe this for you to use if you have any of your own teeth.

You can use a fluoride mouthwash at a different time to tooth brushing. For example, you can use mouthwash 30 minutes before you brush your teeth or another time of day.

Your dentist may also recommend:

  • wearing mouth guards containing fluoride overnight
  • having fluoride painted on your teeth once every 3 months.

Some dentists may also advise using a calcium tooth mousse to use before brushing your teeth. After cancer treatment, you may not have enough calcium in your mouth to help fluoride toothpaste work as well as possible. This product is not available on prescription but can be bought online.

Reduce sugary and acidic foods and drinks

When you eat sugary foods, the bacteria in your mouth quickly turns the sugar into acid. This damages your teeth and gums by breaking down the enamel on the outside of your teeth. This makes your teeth more sensitive and can cause tooth decay.

Here are some tips to reduce tooth decay:

  • Eat and drink fewer acidic things

    These include fizzy drinks, orange juice, oranges, other citrus fruits and tomatoes. The more times you eat or drink something acidic or sugary, the more acid attacks there are on your teeth. Limit these foods and drinks to meal times, no more than 4 times a day.

  • Choose sugar-free drinks

    Avoid those with phosphoric acid or citric acid which are harmful to the teeth. Check the list of ingredients to see if these are in your drink. Fizzy sugar-free drinks are often acidic. Sparkling water can damage teeth as it contains carbonic acid. The safest drink for your teeth is still water. Or you could have plain milk, tea or coffee without added sugar.

  • Try to avoid or reduce foods with refined sugar

    These include chocolate, sweets, biscuits, cakes and pastries, fruit pies, dried fruit, sweet sauces, sponge puddings, breakfast cereals, ice cream, jams, honey and fruit in syrup.

  • Check food labels to see how much sugar they contain

    Look out for glucose, sucrose, maltodextrin, dextrose, lactose, caramel, fructose, maltose, toffee, molasses, honey, syrup, corn sugar and hydrolysed starch. These are all alternative names for sugars.

If you need to gain weight after treatment you may need some high-energy foods as part of your diet. You can see a dietitian for further advice. Try to make sure you look after your mouth and teeth to limit any possible damage.

Brushing your teeth

Following a regular mouth care routine is very important to protect your teeth. You can agree this with your dentist or dental hygienist.

Here are some tips:

  • Brush your teeth for 2 to 3 minutes every morning and night before going to sleep, using a high-fluoride toothpaste.
  • Choose a toothbrush with a small head and soft bristles. Or use an electric toothbrush with a small head that moves in circles. Some electric brushes have a gentle setting and use a soft or sensitive brush head.
  • Brush each tooth slowly and gently. This is enough to clean plaque from a tooth without hurting your gums. Gently massage the gum around the base of each tooth with your toothbrush.
  • Move your toothbrush around the mouth, brushing the outside surface of each tooth. Repeat on the inside surface of each tooth. Repeat on the biting surface of each tooth.
  • After brushing spit out any excess but do not rinse with mouthwash or water. The fluoride in the toothpaste stays around your teeth and keeps protecting them, especially at night.

It is also important to clean between your teeth with dental floss or interdental brushes at least once a day. Move the floss in gentle circles between the teeth, instead of pulling back and forth. A dentist or dental hygienist can show you how to do this and advise you on the best products for you.

If you wear dentures

Here are some tips to help with mouth care if you wear dentures:

  • Use a different toothbrush from the one to brush your teeth and use a denture cleaning cream.
  • Clean and rinse your dentures after eating, as well as every night and morning.
  • Remove any denture fixative which has stuck to the inside of the mouth. A tissue and warm water should help with this.
  • Remove and clean your dentures at night. Soak them in a cleaning solution recommended by your dentist. This gives your mouth a rest and reduces the chance of mouth infections such as thrush.
  • Gently brush the inside of your mouth with a small, soft toothbrush. This is because food may collect between the cheek and gums.

You may wear a special type of denture called an obturator. Your dentist may advise you to keep it in and only take it out to clean it. You should follow the advice you are given.

About our information

  • References

    Below is a sample of the sources used in our late effects of head and neck cancer treatment information. If you would like more information about the sources we use, please contact us at

    Nilsen M L, Belsky MA et al. Late and long term treatment-related effects and survivorship for head and neck cancer patients. Current treatment options in oncology. 2020. Volume 21. Issue 12.

    Machiels J.-P, Leemans C. R. et al. Squamous cell carcinoma of the oral cavity, larynx, oropharynx and hypopharynx. EHNS-ESMO-ESTRO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Annals of Oncology, 2020. Volume 31, Issue 11, Pages 1462-1475.

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Chris Alcock, Consultant Clinical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 01 April 2022
Next review: 01 April 2025
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

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