How Do You Get Cavities Between Your Teeth? Key Facts

Cavities between your teeth, often called interproximal cavities, form when plaque builds up in the tight spaces where your toothbrush bristles cannot reach. These areas are the most common spot for decay in adults, and they develop when acid-producing bacteria feed on sugar and starch left behind from food. Unlike cavities on the chewing surfaces, decay between teeth can progress for a long time without any symptoms, which is why regular dental checkups with X-rays are so important.

What Causes Cavities Between Teeth?

Decay between teeth happens through the same basic process as any other cavity, but the location makes it harder to prevent. Your mouth naturally contains hundreds of types of bacteria. Some of these bacteria form a sticky film called plaque on your teeth. When you eat carbohydrates — especially sugars and refined starches — the bacteria feed on those particles and produce acid as a waste product.

That acid attacks the hard outer layer of your tooth, called enamel. Enamel is the hardest substance in your body, but it is not indestructible. Repeated acid attacks weaken the enamel and eventually create a tiny hole, or cavity. Between teeth, this process is accelerated because food gets trapped in the contact point where two teeth touch. Saliva, which normally washes away acid and helps repair early damage, has a hard time reaching that narrow space.

The anatomy of the area matters too. The point where teeth touch is a natural trap. Floss is specifically designed to clean this area because toothbrush bristles simply cannot fit between tight teeth. If plaque sits in that space for extended periods, the acid concentration stays high and the enamel breaks down faster than it can repair itself.

How Do You Know If You Have a Cavity Between Your Teeth?

Early cavities between teeth usually cause no symptoms at all. You cannot see them in the mirror because they form in the hidden space between adjacent teeth. The first sign is often nothing. This is why dentists rely on bitewing X-rays to detect interproximal decay. These X-rays show the sides of the teeth that face each other, revealing decay long before it becomes visible or painful.

As the cavity grows deeper, symptoms eventually appear. You might feel sensitivity to cold drinks, hot foods, or sweets. You might experience pain when biting down or chewing. Some people notice food getting stuck between the same two teeth more often than before. By the time pain develops, the cavity has typically reached the dentin — the softer layer beneath the enamel — and treatment will require a filling at minimum.

If decay reaches the pulp, the innermost chamber containing nerves and blood vessels, you will likely feel severe pain. At that stage, a root canal may be necessary. Waiting for symptoms is never a good strategy with interproximal cavities. The damage progresses silently, and the longer it goes untreated, the more invasive and expensive the treatment becomes.

What Are the Biggest Risk Factors?

Several factors increase your chances of developing cavities between your teeth. Understanding these helps you target your prevention efforts where they matter most.

• Poor flossing habits — The single most direct risk factor. If you do not floss daily, plaque accumulates in the spaces between teeth where brushing cannot reach.
• Frequent snacking — Every time you eat, your mouth produces acid for about 20 to 30 minutes afterward. Constant snacking means your teeth are constantly bathed in acid.
• Sugary and acidic drinks — Sodas, sports drinks, juices, and sweetened coffee or tea deliver sugar directly to the spaces between teeth.
• Dry mouth — Saliva is your mouth’s natural defense system. It neutralizes acid and washes away food particles. Medications, certain medical conditions, and mouth breathing can reduce saliva flow.
• Tight teeth — Some people have teeth that touch very closely, leaving almost no room for floss to slide through. This makes cleaning harder and traps food more easily.
• Receding gums — As gums pull away from teeth, the root surface becomes exposed. Root surfaces are softer than enamel and decay faster.

Some of these factors are within your control. Others, like the shape of your teeth or genetics, are not. What matters is focusing on the habits you can change.

How Are Cavities Between Teeth Treated?

Treatment depends entirely on how far the decay has progressed. The earlier it is caught, the simpler and less expensive the treatment.

If the cavity is caught very early, before it has broken through the enamel, fluoride treatment may be enough to stop the process. High-concentration fluoride varnish applied by a dentist can help remineralize weakened enamel. Some research suggests that fluoride can reverse very small lesions entirely.

Once the decay has created an actual hole in the tooth, a filling is required. The dentist removes the decayed material and fills the space with a composite resin, amalgam, or other restorative material. For cavities between teeth, the filling often needs to extend into the chewing surface so the dentist can access the decay. This is sometimes called an MO or DO filling, referring to the surfaces involved.

If the cavity is large and too much tooth structure has been lost, a crown may be needed. If the decay reaches the pulp, a root canal becomes necessary. The dentist removes the infected nerve tissue, cleans the root canals, and seals them. The tooth then typically requires a crown to protect it.

No home remedy can fix a cavity that has already formed. Once enamel is destroyed, your body cannot regenerate it. Only a dentist can remove the decay and restore the tooth.

How Can You Prevent Cavities Between Teeth?

Prevention is straightforward, but it requires consistency. The steps are well established and supported by decades of dental research.

Floss daily. This is the single most important step for preventing interproximal cavities. Floss removes plaque from the surfaces your toothbrush cannot reach. If traditional floss is difficult for you to use, try floss picks, interdental brushes, or a water flosser. The best tool is the one you will actually use every day. Some studies suggest interdental brushes may remove plaque more effectively than floss, but the most important factor is regular use.

Use fluoride toothpaste. Fluoride strengthens enamel and helps repair early damage. Look for a toothpaste with fluoride as an active ingredient. If you are at high risk for cavities, your dentist may recommend a prescription-strength fluoride toothpaste.

Limit sugar intake. The bacteria in your mouth need sugar to produce acid. The less sugar you consume, the less acid your mouth produces. Pay attention to hidden sugars in sauces, breads, and processed foods, not just obvious sweets.

Drink water throughout the day. Water helps rinse away food particles and keeps saliva flowing. If you drink sugary or acidic beverages, try to consume them with meals rather than sipping them throughout the day.

See your dentist regularly. Professional cleanings remove tartar, which is hardened plaque that you cannot remove at home. Regular X-rays catch interproximal cavities early, when they are still small and easy to treat.

Does a Water Flosser Work as Well as String Floss?

Water flossers have become popular, and they do work. Research shows they are effective at removing plaque and reducing gum inflammation. Some studies have found that water flossers are at least as effective as string floss for reducing plaque between teeth, and some people find them easier to use consistently.

The best evidence supports using whatever tool helps you clean between your teeth every day. If you hate string floss and avoid it, a water flosser is better than not cleaning at all. If you are comfortable with string floss and use it correctly, it remains a proven, inexpensive option. The key is cleaning the contact points between teeth daily, regardless of which tool you choose.

One honest caveat: water flossers require proper technique. Simply running water over your teeth does not do much. You need to aim the stream directly at the space between teeth and hold it there for a few seconds. If you are unsure whether you are using it correctly, ask your dentist or hygienist to demonstrate at your next appointment.

Can Cavities Between Teeth Heal on Their Own?

No. Once a cavity has formed — meaning the enamel has broken and created a hole — it will not heal on its own. The tooth cannot regenerate lost enamel. Without treatment, the cavity will continue to grow larger and deeper.

What can happen is that very early enamel damage, called a white spot lesion, can be reversed. At this stage, the enamel is weakened but not yet broken. Fluoride and good oral hygiene can help the enamel remineralize and repair itself. This is why catching problems early matters so much. By the time a cavity is visible or painful, it is too late for remineralization.

If you suspect you have a cavity between your teeth, schedule a dental appointment. Only a dentist can determine whether the decay is still reversible or whether it requires a filling.