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15 myths and facts about cavities

WebMD Medical Reference
Medically Reviewed by Dr Rob Hicks

Only one of the following statements is true. Do you know which one?

  • Eating acidic foods like lemons causes cavities.
  • If you have a cavity, you’ll definitely know it.
  • Once you treat a cavity, the tooth decay stops.

Check the myths and facts below to find out how cavities are caused, prevented and treated.

1. Sugar is the prime cause of cavities

Myth and fact. In reality, it’s the acid produced by bacteria in your mouth that causes cavities. What the bacteria do, however, is digest carbohydrates - and sugar is one of these, as are rice, potatoes, bread, fruit and vegetables.

When you eat anything with carbs, the bacteria become active and produce acid that then eats into your tooth. They can then lurk in the cavity where the toothbrush and floss can’t reach. The bacteria continue to metabolise carbs, produce acids, and your cavity keeps getting bigger.

It’s not the amount of carbohydrates you eat that causes tooth decay, but the length of time your teeth are exposed. If you eat a lot of carbs for lunch, that’s a big exposure. But if you spend the day sipping sugary drinks, that’s continuous exposure - and much more dangerous for your teeth.

2. Exposure to acidic foods like lemons causes tooth decay

Fact. Acidic foods such as lemons, citrus juices, or soft fruit drinks don’t cause cavities, but they may be putting your enamel in danger. Acids can cause erosion of the tooth-protecting enamel, thus weakening the tooth. If you lose the enamel's protection and expose the underlying dentin, the tooth is more prone to decay.

3. Children are a lot more likely to get cavities than adults

Myth. With the help of fluoride in the water or toothpaste, preventative care and the judicious use of sealants, tooth decay in school age children has been dramatically reduced.

However, there’s been an increase in cavities in older people, for a number of reasons. For example, some medications dry out the mouth and reduce saliva. Saliva is vital in fighting tooth decay because it helps neutralise acids, has a disinfectant quality, washes away bacteria, and helps prevent food from sticking to the teeth.

4. Aspirin placed next to a tooth will help toothache

Myth. Swallowing aspirin is what helps relieve toothache pain. Since aspirin is acidic, placing it beside the tooth can actually burn your gum tissue, causing an abscess.

5. All fillings eventually need replacing

Myth. An amalgam or composite filling needs to be replaced if it breaks down or a cavity forms around it, or if the tooth fractures. If none of those problems occur, you may be able to keep the same filling for life.

Fillings do have a life expectancy, but much depends on things like tooth wear and oral hygiene habits. If you brush your teeth properly at least twice a day with a fluoride toothpaste, and floss or use an interdental cleaner at least once a day, you’ll have less tooth decay and your fillings may last longer.

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