Cavities are among the most common health problems people of any age deal with, and they are also among the most preventable. A cavity does not appear overnight. It is the end point of a slow process that, caught early, can sometimes be stopped or even reversed. This guide explains how tooth decay starts, how it progresses, how dentists find and treat it, and what actually helps prevent it.
What is a cavity?
MedlinePlus describes dental cavities as holes, or structural damage, in the teeth (MedlinePlus: Dental cavities). The process that creates them is called tooth decay, or caries. According to the National Institute of Dental and Craniofacial Research (NIDCR), people can get tooth decay at any age once they have teeth, from early childhood through the senior years (NIDCR: Tooth Decay).
How tooth decay starts
Your mouth always contains bacteria. When those bacteria come into contact with sugars and starches from food and drink, they produce acid. MedlinePlus explains that bacteria, acid, food debris and saliva combine to form plaque, a sticky film that clings to teeth. Plaque is most common on the back molars, just above the gumline and around the edges of fillings. If it is not removed, it hardens into tartar (also called calculus).
Each acid attack pulls minerals out of the enamel. Saliva and fluoride help put minerals back. Decay develops when, over time, more minerals are lost than restored.
What raises the risk
- Frequent sugar and starch. MedlinePlus notes that sticky foods are more harmful than non-sticky ones because they stay on the teeth, and that frequent snacking keeps acid in contact with enamel longer.
- Sipping sugary drinks throughout the day or constantly sucking on candy or mints.
- Not enough fluoride from toothpaste, water or professional treatments.
- Dry mouth. Saliva helps neutralize acid and supplies minerals. See our guide to dry mouth and your teeth.
- Receding gums. NIDCR explains that many older adults have gum recession, which exposes root surfaces that can decay.
- Tobacco use, which NIDCR recommends avoiding.
The stages of a cavity
Dentists describe decay in a range of ways, but in plain terms it tends to move through these stages:
- Early mineral loss. NIDCR says a white spot may appear where minerals have been lost. This is the earliest sign of decay, and at this point it can still be stopped or reversed with fluoride and good habits.
- Enamel breakdown. If mineral loss continues, the enamel weakens and breaks down, forming a hole. Once a true cavity forms, it will not heal on its own.
- Decay in the dentin. The layer under the enamel is softer, so decay can spread faster. This is often when sensitivity to sweets, heat or cold begins.
- Reaching the pulp. MedlinePlus explains that untreated decay can destroy the inside of the tooth, the pulp, which contains nerves and blood vessels. This usually means more extensive treatment, such as a root canal, or removal of the tooth.
- Infection. An untreated cavity can lead to a tooth abscess, a pocket of pus that causes pain, swelling and sometimes fever. Read our guide to tooth abscess signs.
Symptoms to watch for
One of the trickiest things about cavities is that early decay usually causes no symptoms at all. MedlinePlus notes that cavities often do not hurt unless they grow large, reach the nerve or cause a fracture. When symptoms do appear, they can include:
- A toothache or achy feeling, especially after sweet, hot or cold foods and drinks
- Visible pits, holes or dark spots on the teeth
- White, brown or black staining, which NIDCR lists among the signs of decay
- Pain when biting down
If you have tooth pain now, our article on common toothache causes and when it is urgent can help you decide how quickly to be seen.
How dentists find cavities
According to MedlinePlus, most cavities are discovered in their early stages during routine checkups. The dentist may find a soft area on the tooth surface, and dental X-rays can reveal some cavities before they are visible. NIDCR adds that a dentist may check for soft or sticky areas. This is a big part of why regular exams matter: catching decay before it hurts usually means a smaller, simpler repair. Our guide to how often to see the dentist covers checkup timing.
Treatment options
Fluoride for early decay
NIDCR explains that if decay is caught before a hole forms, a dentist can apply fluoride to help reverse it.
Fillings
For an actual cavity, the usual treatment is a filling. The dentist removes the decayed material and restores the tooth. MedlinePlus lists composite resin, glass ionomer and amalgam as filling materials, and notes that composite resin is widely preferred today because it closely matches natural tooth color and is strong enough for back teeth. For pricing factors, see our page on dental filling costs.
Crowns
When decay is extensive and not much healthy tooth remains, a crown may be recommended. MedlinePlus explains that large fillings and weakened teeth are more likely to fracture, so the damaged part is removed and a crown is fitted over the rest of the tooth. Our guide to dental crowns explains the materials and what affects cost.
Root canal treatment
If decay reaches the pulp or the nerve dies, MedlinePlus describes root canal treatment: the pulp and decay are removed, the roots are filled and sealed, and in most cases a crown is placed afterward to protect the tooth. See our root canal guide.
Extraction
When a tooth is too damaged to save, removing it may be the only option. That opens a separate discussion about whether and how to replace it.
MedlinePlus makes an important point about timing: treatment is less painful and less expensive when it is done early. If you are anxious about dental work, it also notes that nitrous oxide with local anesthetic or other medicines may be an option. Our guide to sedation options at the dentist explains the choices.
How to prevent cavities
NIDCR and MedlinePlus agree on the core habits:
- Use fluoride. NIDCR recommends fluoride toothpaste, fluoridated tap water where available and fluoride mouth rinse.
- Brush twice a day and clean between your teeth daily with floss or another interdental cleaner.
- Limit sugary drinks and snacks. MedlinePlus suggests eating sticky foods such as dried fruit or candy as part of a meal rather than alone, then brushing or rinsing with water.
- Ask about sealants. Sealants are thin protective coatings on the chewing surfaces of back teeth. MedlinePlus notes they are often placed on children’s molars soon after they come in, and that adults may benefit too.
- Keep up with checkups and cleanings so early decay can be found while it is still reversible or easy to fix.
- Avoid tobacco, including smokeless tobacco.
Finding a dentist
If it has been a while since your last exam, our dentist directory lets you search by city and specialty. If cost is a barrier, our guide to low-cost dental care and our article on dental school clinics cover lower-cost options.
Frequently asked questions
Can a cavity heal on its own?
Very early decay, before a hole forms, can be stopped or reversed with fluoride and good habits, according to NIDCR. Once a cavity has formed, it needs treatment from a dentist.
Do cavities always hurt?
No. Early cavities usually cause no pain. That is why routine exams and X-rays are useful: they can find decay before it becomes painful.
What is the most common filling material?
MedlinePlus notes that composite resin is the preferred material today because it matches tooth color and is strong enough for back teeth. Amalgam and glass ionomer are also used.
Can adults get cavities?
Yes. NIDCR says tooth decay can affect people of all ages, and older adults can develop decay on root surfaces exposed by gum recession.
Sources
By the Dentist Review Editorial Team.
This article is for general information only and is not medical advice. Talk to a licensed dentist about your own situation. See our disclaimer.
Featured image: “Rock-Candy-Sticks” by Evan-Amos, via Wikimedia Commons, licensed CC BY-SA 3.0. Resized and compressed for the web.
Our guides are written and reviewed by the Dentist Review editorial team. We research each topic using public, authoritative sources such as the CDC, the National Institutes of Health (NIH/NIDCR), the American Dental Association (ADA) and CMS, and we update guides when guidance changes. Guides are for general information only and are not dental or medical advice; please read our disclaimer and learn more about us.