15 Facts about Teeth. (WebMD exclusive)

Myths and Facts About Cavities

WebMD Feature

By Wendy C. Fries

Reviewed By Alfred D. Wyatt Jr., DMD
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, but it’s almost a fact.

The truth is, acid produced by bacteria in your mouth is the cause of cavities, says Kimberly A. Harms, DDS, an American Dental Association consumer advisor and former president of the Minnesota Dental Association. However, these bacteria are triggered to make acid when you eat anything with carbohydrates — and sugar is a carb.
Rice, potatoes, bread, fruits, and vegetables are also carbs.

Once the acid eats into your tooth, the bacteria “have a nice little hole to live in where your toothbrush and floss can’t reach,” says Harms. The bacteria continue to metabolize carbs and produce acids — and your cavity just keeps getting bigger.

Here’s an important fact. It’s not the amount of carbs 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 one big exposure. But if you spend the day sipping sugary drinks, that’s continuous exposure — and much more unhealthy for your teeth.

“We have a saying,” says Harms. “Sip all day and get decay.”

2. Exposure to Acidic Foods, Like Lemons, Causes Tooth Decay
Fact. Acidic foods such as lemons, citrus juices, or soft drinks don’t cause cavities, but they may be putting your enamel in danger.

“Acids can tear down your enamel and weaken your tooth,” says Harms. “If you lose the enamel’s protection and expose the underlying dentin, your tooth is now more prone to decay.”

3. Kids Are a Lot More Likely to Get Cavities Than Adults
Myth. With the help of sealants, fluoridated water, and preventive care, “we’ve actually cut decay in school-aged children by half in the last 20 years,” says Harms.

However, there’s been an increase in cavities in senior citizens “because they have some unique circumstances,” she says. Some medicines dry out the mouth, for example, reducing salvia. Saliva is vital in fighting tooth decay because it helps neutralize acids, has a disinfectant quality, washes away bacteria, and helps prevent food from sticking to your teeth.

4. Aspirin Placed Next to a Tooth Will Help a Toothache
Myth. Swallowing aspirin is what helps reduce toothache pain. Since aspirin is acidic, placing it beside the tooth can actually burn your gum tissue, causing an abscess. “So don’t do it,” says Harms. “Always swallow the aspirin!”

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, says Harms. If none of those problems occur, you can keep the same filling for life.

“Fillings do have a life expectancy,” says Harms, but it depends on things like tooth wear and oral hygiene habits. If you brush your teeth twice a day with a fluoride toothpaste and floss and use a mouth rinse once a day, you’ll have less tooth decay and your fillings may last longer.
6. If You Have a Cavity, You’ll Know It
Myth. “That’s a big, big, bad myth,” Harms says. Mild tooth decay doesn’t cause symptoms. The pain we associate with cavities comes when tooth decay is more advanced and causes damage to the nerve.

Allowing tooth decay to advance can “lead to much more expensive procedures, like root canals,” says Harms. That’s why regular dental checkups are so important.

Also, once a cavity starts, it doesn’t repair itself. A cavity “will always grow once you get to a point where you can’t clean it out any longer.” Once decay gets into the dentin of the tooth — below the enamel — it just continues to grow.

7. Once a Tooth Is Treated, the Decaying Stops
Fact. “You can get decay later on in other areas of the tooth, but the particular decay that was taken out is gone.”

Once you get a cavity filled — and if you maintain good brushing, flossing, and rinsing habits — you typically won’t get decay in that spot again.

Harms adds one caveat: “Sometimes a filling gets old and the margins where it meets the tooth begin to break down or pull away, and because you can’t reach it to clean it out, bacteria can get in there and decay can begin again.”

8. Cavities Are More Likely Between Teeth
Fact. “Anywhere bacteria can hide that you can’t, or aren’t able to, reach with a toothbrush or floss is a likely place for decay,” says Harms. The deep grooves on the back of your front teeth are a good place for tooth decay, for example. “And yes, it can happen between teeth because the toothbrush won’t get in there and a lot of people have trouble flossing.” This is where using a mouth rinse with fluoride (also called an anti-cavity rinse) can give you extra protection.

9. Gaps in Teeth Encourage Cavities
Fact. If you have a small gap between your teeth and can’t clean it, you’re more likely to develop tooth decay there.

“Bigger gaps are easier to keep clean,” says Harms. So as long as they are free of bacteria, big gaps are less likely to develop tooth decay.

10. Chips and Cracks in Teeth Lead to Decay
Fact. If cracks and chips create a hiding place for bacteria, a spot where your toothbrush can’t reach, those areas are more prone to tooth decay. Using a fluoride mouth rinse can reduce the risk of decay since it can flow into places your brush can’t reach.

“Lately we’re seeing more and more cracks in teeth because people are grinding,” Harms says. “Stress, worries about the economy, it makes some people grind their teeth more. … Stress [management] can play an important role in tooth health.”

11. Sensitivity in Teeth Means You Have Decay
Myth. Tooth sensitivity could just mean you have hypersensitive teeth, or you have gum recession that’s exposed some root.

You could also have a cracked or broken tooth or could need a root canal. “There are many things, including decay, that could lead to sensitive teeth,” Harms says.

12. Cavities Are the Only Reason for Root Canals
Myth. You need a root canal if the nerve inside a tooth is damaged. Untreated cavities may eventually lead to nerve damage, but there other causes, too.

“Cracks, fractures, or other types of trauma to the tooth can also cause nerve damage,” says Harms. In many cases “clenching and grinding can traumatize the tooth severely enough to need root canal therapy.”

13. Clenching and Grinding May Lead to Cavities
Fact. “Clenching and grinding is one of the most destructive things you can do to your teeth,” says Harms. With normal chewing, teeth touch for mere milliseconds, suffering very little stress. But clenching and grinding puts tremendous pressure on your teeth for extended periods.

That strain “can eventually cause damage and cracks and fractures of your teeth,” says Harms. If those fractures expose the weaker dentin, tooth decay can form at a faster rate. “Typically grinding and clenching lead to the need for crowns to restore the fractured tooth or root canal therapy to treat the traumatized nerve.”

14. You Don’t Need to Worry About Cavities in Baby Teeth
Myth. Baby teeth hold the space for permanent teeth. “If cavities are left untreated in baby teeth, they can develop into serious pain and abscesses. Occasionally the infection can spread to other areas of the body, and in rare occasions can even result in death,” says Harms.

15. Brushing, Flossing, and Rinsing Is the Best Way to Prevent Cavities
Fact. “Absolutely! Prevention is the key,” says Harms. You need to remove bacteria from teeth. Brush twice a day with a fluoride toothpaste, and floss and rinse daily. Antimicrobial rinses target bacteria, reducing plaque, bad breath, and the severity of gingivitis. Rinses with fluoride make teeth more resistant to decay. If bacteria are removed daily from every area of your tooth, “you won’t get cavities,” says Harms.