Cavities: What Causes Them and Whether They Can Heal on Their Own

Your mouth naturally contains bacteria, and some of these bacteria feed on sugars and starches from food, producing acid as a byproduct. That acid gradually wears away at the mineral structure of your tooth enamel, and if this process continues unchecked, it eventually creates a hole, or cavity, in the tooth.

Cavities can develop on the smooth surfaces of a tooth, in the deep grooves of the chewing surfaces of back teeth, between teeth where a toothbrush can't easily reach, and along the root surface if gums have receded enough to expose that area, which is more common in older adults. Each location tends to be caused by slightly different risk factors, though the underlying acid-and-bacteria process is the same.

Frequent consumption of sugary or starchy foods and drinks feeds the bacteria responsible for producing the acid that causes decay. Inadequate brushing and flossing allows plaque, a sticky film of bacteria, to build up on teeth rather than being regularly removed. Dry mouth, whether from certain medications or medical conditions, reduces saliva's natural ability to help neutralize acid and wash away food particles. And insufficient fluoride exposure, whether from water, toothpaste, or other sources, can leave enamel more vulnerable to acid damage than it would otherwise be.

Early cavities often have no noticeable symptoms at all, which is exactly why they're frequently caught first on a routine dental X-ray rather than by the patient noticing something wrong. As a cavity progresses, symptoms can include sensitivity to hot, cold, or sweet foods, visible pits or holes in the tooth, dark spots on the tooth surface, and eventually, pain, particularly when biting down.

### When to See a Dentist

Any new tooth sensitivity, visible discoloration or pitting, or pain warrants a dental visit, ideally sooner rather than later, since cavities generally only grow larger and more expensive to treat over time rather than resolving on their own once they've formed.

### Children

Children are at meaningfully higher risk partly due to diet, including frequent snacking and sugary drinks, and partly because developing brushing habits aren't always fully effective without parental supervision and reinforcement.

### Adults

Adults can develop cavities on original tooth surfaces as well as around the edges of existing fillings or crowns, where a small gap can sometimes develop over years and allow new decay to start.

### Older Adults

Gum recession, which becomes more common with age, exposes tooth root surfaces that are softer and more vulnerable to decay than the harder enamel covering the rest of the tooth, making root-surface cavities a specific concern for many older adults.

This depends entirely on how advanced the cavity is. In the very earliest stage, sometimes called a white spot lesion, where the enamel has begun losing minerals but hasn't yet broken down into an actual hole, it's genuinely possible to reverse this early damage through improved oral hygiene, fluoride treatment, and dietary changes, effectively re-mineralizing the weakened enamel before a true cavity forms. Once decay has progressed to an actual hole in the tooth, however, that structural damage doesn't heal or reverse on its own, and a filling or other restorative treatment is needed to repair it and stop further progression.

Left untreated, a cavity continues growing deeper into the tooth, eventually reaching the inner pulp where the nerve and blood supply are located, which can lead to significant pain, infection, and the need for a root canal or extraction rather than the simpler filling that would have addressed the same cavity at an earlier stage. Untreated decay can also spread to neighboring teeth and, in more severe cases, contribute to a dental abscess that can affect surrounding tissue beyond the tooth itself.

Small to moderate cavities are typically treated with a standard filling, removing the decayed tissue and restoring the tooth with composite resin or another filling material. Larger cavities affecting more of the tooth structure may require an inlay, onlay, or crown instead, depending on the extent of damage.

### Deep Cavities

A cavity that's progressed close to or into the tooth's inner pulp may require a root canal in addition to restorative treatment, since simply filling the visible decay wouldn't address the deeper infection or inflammation that's occurred.

Brushing twice daily with fluoride toothpaste, flossing daily to clean between teeth where a toothbrush can't reach, limiting frequent snacking on sugary or starchy foods, drinking fluoridated water where available, and keeping up with regular dental checkups and cleanings all meaningfully reduce cavity risk over time.

For people without dental insurance or with limited resources, dental schools often provide reduced-cost care performed by supervised students, community health centers frequently offer sliding-scale fees based on income, and some areas have public health dental programs specifically aimed at improving access to preventive and restorative dental care for underserved populations.

A common misconception is that cavities only affect people who eat a lot of candy, when in reality, frequency of sugar and starch exposure throughout the day matters more than total quantity, meaning frequent snacking and sipping on sugary drinks can be more damaging than eating the same total sugar in one sitting. Another misconception is that cavities always hurt, when in fact many cavities, particularly in early stages, cause no noticeable symptoms at all, which is exactly why regular checkups and X-rays matter for catching them before pain develops. It's also sometimes assumed that adults with all their permanent teeth are past the point of cavity risk, when adults remain fully susceptible to new cavities throughout life, including around the edges of older dental work.

Cost varies based on the size of the cavity, the material used for the filling, and your geographic location, generally increasing with the extent of decay that needs to be addressed. Most dental insurance plans provide at least partial coverage for fillings, since treating cavities is considered standard, medically necessary dental care.

How fast do cavities grow? This varies significantly by individual and by the specific tooth surface affected, ranging from a slow process over years to a more rapid progression over months in some cases, depending on factors like diet, oral hygiene, and saliva composition. Regular checkups help catch cavities at whatever stage they happen to be found.

Can you see a cavity yourself? Sometimes, particularly once decay has progressed enough to create a visible dark spot or pit, but many cavities, especially those between teeth or in early stages, aren't visible without a dental exam and X-ray, which is why professional checkups catch far more cavities than self-examination alone.

Do kids' cavities matter if the tooth is going to fall out anyway? Yes, generally. Untreated cavities in baby teeth can cause pain and infection just as they can in permanent teeth, and severely decayed baby teeth that are lost too early can affect the proper spacing and eruption of the permanent teeth coming in later.

Is it true that cavities can be contagious? The bacteria responsible for causing cavities can be transmitted between people, most commonly documented from caregivers to young children through shared utensils or similar close contact, which is part of why some pediatric dental guidance discourages this kind of sharing with infants and toddlers. Having those bacteria present doesn't automatically mean a cavity will form, though, since diet and oral hygiene remain major factors in whether decay actually develops.

Why do I keep getting cavities even though I brush regularly? This can stem from a combination of factors beyond just brushing frequency, including diet, flossing habits, dry mouth, the specific bacteria present in your mouth, and even genetics affecting enamel strength. If you're getting frequent cavities despite consistent brushing, it's worth discussing your specific risk factors with your dentist, since they may identify something specific worth addressing.