What Causes Cavities?

Key takeaways

• Cavities start when bacteria in plaque turn sugars and starches into acid that wears down enamel.
• How often teeth are exposed to sugar and acid matters as much as how much you eat or drink.
• A deep cavity or infected tooth can cause pain that feels like a headache.
• A night guard does not cause cavities, but it needs regular cleaning.
• Early cavities are quiet, so routine exams help catch them while treatment is simple.

What causes cavities?

Cavities are caused by acid made by bacteria in plaque, the sticky film that builds up on teeth. When you eat or drink sugars and starches, those bacteria feed on them and release acid that slowly dissolves tooth enamel.

Four things usually need to come together: a tooth surface, bacteria, a food source for those bacteria, and enough time. If plaque stays on a tooth and sugars keep arriving, the acid attacks keep repeating. Saliva and fluoride can repair early damage, but when the attacks outpace the repair, the enamel weakens and eventually breaks down into a hole, which is what a dentist calls a cavity. Cavities are also called tooth decay or dental caries, and they are among the most common health conditions people deal with. The process is gradual, which gives you many chances to slow or stop it.

How does plaque turn into a hole in a tooth?

It happens in stages. Acid first removes minerals from enamel, leaving a chalky spot, and if the cycle continues the surface breaks and a hole forms.

The usual progression looks like this:

1. Demineralization. Acid pulls calcium and phosphate out of the enamel. You may see a white, dull patch but feel nothing.
2. Enamel breakdown. The weakened surface collapses into a small cavity. Early on it can be hard to notice without an exam and X-rays.
3. Dentin involvement. Beneath enamel is softer dentin, and decay moves faster through it. Sensitivity to sweets, cold or heat often begins here.
4. Pulp involvement. If decay reaches the nerve and blood vessels inside the tooth, it can cause lasting pain, swelling or infection.

Because the early stages are quiet, many people do not know they have a cavity until it grows. That is normal, and it is why routine exams matter.

Which habits and risk factors make cavities more likely?

Frequent snacking and sipping, skipped cleaning, and low saliva are the most common contributors. Anything that keeps teeth bathed in sugar or acid for long periods raises risk.

• Frequent sugary or starchy snacks. Each snack starts a new acid attack that lasts a while, so grazing all day is harder on teeth than eating the same food at one meal.
• Sipping sodas, juice, sports drinks or sweetened coffee. Slow sipping keeps sugar and acid on your teeth.
• Inconsistent brushing and flossing. Plaque left between teeth and along the gumline is where many cavities begin.
• Dry mouth. Saliva rinses away food and neutralizes acid, so a dry mouth from medications, medical conditions or mouth breathing can raise risk.
• Not enough fluoride. Fluoride helps enamel rebuild itself after acid attacks.
• Deep grooves and crowded teeth. Back teeth with deep pits are hard to clean, and crowding creates spots a brush misses.
• Worn or older fillings. Decay can form at the edge of an existing restoration.

Genetics, gum recession that exposes tooth roots, and certain medical treatments can play a part too. Plenty of careful brushers still get cavities.

Can cavities cause headaches?

Sometimes, indirectly. A deep cavity or an infected tooth can cause pain that spreads to the jaw, temple or face and feels like a headache.

When decay reaches the inner pulp, the nerve can become inflamed or infected. That pain may throb, get worse with chewing or hot and cold, and radiate to nearby areas. An abscess may also bring swelling, a bad taste or fever. A small, shallow cavity rarely causes headaches on its own.

Headaches have many causes, so a cavity is not always the reason. Clenching and grinding, sinus problems and tension can all mimic tooth pain. If a headache comes with tooth sensitivity, a toothache on one side or facial swelling, it is worth having a dentist take a look. Our team offers same-day emergency care for severe pain and infection, and walk-ins are welcome.

Do night guards cause cavities?

A night guard does not cause cavities on its own, but a dirty one can contribute. Guards are made to protect teeth from grinding, and they are generally safe when they are cleaned and fitted well.

The concern is hygiene. If you put a guard over teeth that were not brushed, or the guard itself is not cleaned, bacteria and plaque can sit against your teeth for hours. A poorly fitting guard can also trap food. To prevent this, brush and floss before wearing it, rinse and brush the guard each morning with a gentle cleanser, let it dry in a ventilated case, and bring it to checkups so it can be checked for fit and wear. Grinding without protection can wear enamel and leave teeth more vulnerable, so a clean, well-fitted guard usually helps. You can read more about custom night guards if you are curious.

Why do some people get cavities even when they brush?

Cavity risk depends on more than brushing. Timing of meals and snacks, saliva, tooth shape, medications and acid exposure all matter.

Acid from other sources can soften enamel and make decay easier. Acid reflux, frequent vomiting and acidic drinks all bring acid into contact with teeth, and weakened enamel is more likely to develop cavities. Some medications reduce saliva. Braces and aligners can make cleaning harder, and exposed root surfaces from gum recession decay more easily than enamel does. Technique matters too: a quick scrub can miss the same spots every day. Using a soft brush, fluoride toothpaste and cleaning between teeth daily covers the areas most often missed. If you keep getting cavities despite good habits, tell your dentist. There is usually a pattern that can be found and addressed.

How can you lower your chances of getting cavities?

Brush twice a day with fluoride toothpaste, clean between teeth daily, and limit how often sugar and acid touch your teeth. Regular checkups catch problems while they are small.

• Brush for two minutes, morning and night, with fluoride toothpaste.
• Floss or use another between-teeth cleaner once a day.
• Keep sweet and starchy foods near mealtimes instead of spreading them across the day.
• Drink water between meals, especially after sweet or acidic drinks.
• Chew sugar-free gum if dry mouth is an issue, since it can help saliva flow.
• Ask about professional fluoride treatment at your cleaning.
• Ask about sealants. The CDC notes that "Dental sealants on the back teeth prevent 80% of cavities."

Very early spots can sometimes be strengthened with fluoride and better habits before they ever need a filling, which is another reason it helps to be seen sooner rather than later.

What happens if you find out you have a cavity?

Most cavities are treated with a simple filling, and very early ones may only need monitoring. The earlier a cavity is found, the smaller and simpler the treatment tends to be.

A dentist removes the decayed part of the tooth and restores it. Many people choose tooth-colored fillings because they blend in with the natural tooth. Larger damage may need a crown, and decay that reaches the nerve may need a root canal. Treatment is planned around your tooth and your budget. We accept most major dental PPO plans, and for people without insurance we offer CareCredit, in-house payment plans and the Ultra Discounts plan. No matter how long it has been since your last visit, there is no judgment here. Our offices in Peoria, North Phoenix and Metro welcome new patients, and our team speaks Spanish. This article is general education, not a diagnosis. A dentist can look at your teeth and advise on your own situation.

Sources

1. Cavities, American Dental Association (MouthHealthy)
2. Tooth Decay, National Institute of Dental and Craniofacial Research (NIH)
3. About Cavities (Tooth Decay), Centers for Disease Control and Prevention
4. Tooth erosion and acid reflux, American Dental Association (MouthHealthy)