You often can't tell you have a cavity until it's already growing, because early decay in the enamel doesn't hurt. Common signs include sensitivity to hot, cold, or sweets, a toothache, a visible hole or dark spot, and pain when you bite — but the only way to know for sure is a dental exam and X-rays.
What is a cavity?
A cavity is a small hole in a tooth caused by decay. It starts when plaque — a sticky film of bacteria — feeds on sugars and releases acids that dissolve the tooth's outer layer, the enamel. Left alone, that decay moves deeper into the tooth.
Signs and symptoms of a cavity
- Sensitivity to hot, cold, or sweet foods and drinks
- A toothache, either constant or when you bite down
- A visible hole or pit in a tooth
- White, brown, or black spots on the tooth surface
- Food regularly getting stuck in the same spot
- Persistent bad breath or a bad taste
None of these is a sure sign on its own. Tooth pain can come from a cracked tooth, gum problems, or sensitivity, and natural grooves can look like holes. That's why an exam matters.
How a cavity progresses
- Demineralization: acids start pulling minerals out of the enamel, often showing up as a chalky white spot. There's no pain yet.
- Enamel decay: the enamel breaks down and a small cavity forms. It may look brown or dark.
- Dentin decay: decay reaches the softer layer under the enamel, which has nerve connections. This is when sensitivity and pain usually begin.
- Pulp involvement: decay reaches the tooth's nerve and blood supply, often causing significant pain.
- Abscess: an infection can form at the root, with swelling and pain that needs prompt care.
Can a cavity be reversed?
Only at the very earliest stage. When decay is limited to demineralization — before a hole forms — fluoride, good brushing and flossing, and cutting back on sugary snacks and drinks can help the enamel remineralize and stop the spot from becoming a cavity. Once decay has broken through the enamel and formed a hole, it can't heal on its own and needs treatment. Catching it early is one of the biggest reasons to keep up with regular checkups.
How cavities are treated
- Fluoride treatment for very early demineralization.
- A filling for most cavities: the decay is removed and the tooth is rebuilt.
- A crown when decay has weakened a large part of the tooth.
- A root canal when decay reaches the nerve.
- An extraction when a tooth can't be saved.
The earlier a cavity is treated, the simpler and less costly the fix usually is. For what a small cavity costs to treat, see our guide to small cavity signs, treatment, and cost.
What causes cavities?
- Plaque left on teeth from inconsistent brushing and flossing
- Frequent sugary or starchy snacks and drinks
- Sticky foods that cling to teeth
- Dry mouth, often from certain medications
- Acid reflux, which exposes teeth to stomach acid
- Deep grooves in back teeth that trap food
How to prevent cavities
- Brush twice a day with fluoride toothpaste and floss daily.
- Limit sugary snacks and drinks, especially between meals.
- Drink water throughout the day.
- Ask about dental sealants for cavity-prone back teeth.
- See your dentist for regular checkups and cleanings.
Frequently asked questions
How do I know if I have a cavity?
Common signs include sensitivity to hot, cold, or sweets, a toothache or pain when biting, a visible hole, or dark spots on a tooth. Early cavities often cause no symptoms, so a dental exam and X-rays are the only way to know for sure.
Can you reverse a cavity?
Only at the earliest stage. Before a hole forms, fluoride, good brushing and flossing, and less sugar can help weakened enamel remineralize. Once decay has formed a hole, it can't heal on its own and needs treatment, usually a filling.
Do cavities always hurt?
No. Early cavities in the enamel usually don't hurt because enamel has no nerves. Pain often starts once decay reaches the dentin underneath, which is why regular checkups catch many cavities before you feel them.
What happens if a cavity isn't treated?
It keeps growing. Decay can reach the tooth's nerve and cause pain or an infection, which may then need a root canal or an extraction instead of a simple filling.
How are cavities treated?
Very early decay may be treated with fluoride. Most cavities are treated with a filling. Larger cavities may need a crown, and decay that reaches the nerve may need a root canal.
Think you might have a cavity?
A quick exam will tell you what's going on and what, if anything, needs to be done. New guests can start with a $39 new-guest exam and X-rays, and many offices offer same-day care if you're in pain. Find your nearest Ideal Dental.