What Does a Cavity Look Like? Signs, Stages, and Photos Explained

Medically reviewed by Dr. Sam Wood

A cavity looks different depending on how far it has progressed. In the earliest stage it is a chalky white or slightly brown spot on the enamel with no hole. As it advances it becomes a brown or black spot, then a visible pit or hole in the tooth, and in late stages a large dark area, a broken edge, or a swollen gum with an abscess. Many cavities, particularly between teeth and inside grooves, cannot be seen at all and are found only on a dental X-ray. Early cavities are painless; sensitivity and toothache appear once decay reaches the dentin or the nerve.

What a cavity is

A cavity (dental caries) is a hole in a tooth caused by bacteria. The bacteria in plaque feed on sugars and starches and produce acid, which dissolves the minerals in enamel. At first the enamel simply loses mineral and turns chalky. If the acid attacks continue, the surface breaks down, a hole forms, and decay moves into the softer dentin beneath, where it spreads faster. Left alone, it reaches the pulp, the nerve and blood supply, and causes infection.

What a cavity looks like at each stage

Where cavities hide

Most cavities are not on the smooth front surfaces where you would see them. The common locations:

• Chewing surfaces of molars. The grooves trap plaque. A cavity here can look like a dark line in a groove and be far larger underneath than it appears; the enamel over the top stays intact while the dentin below hollows out.
• Between teeth. Invisible from outside. Found on bitewing X-rays, or noticed when floss shreds or food packs in one spot.
• At the gum line. Common in older adults with receded gums, where the exposed root has no enamel. Root cavities look like a brown or tan softened area at the base of the tooth.
• Around fillings and crowns. Decay creeps in at the edge of a restoration. It looks like a dark shadow or gap next to the filling.
• Around braces. White spots form around brackets when plaque is not removed.

Is that dark spot a cavity?

Not always. Things that look like cavities and are not:

• Stain in the grooves of molars from coffee, tea, or tobacco. It is dark but the surface is hard and smooth, and it does not grow.
• Fluorosis: white or brown mottling from excess fluoride during tooth development; it is symmetrical and does not change.
• Enamel hypoplasia: pits or grooves present since the tooth formed.
• An old dark filling or the shadow of a metal filling showing through.
• Tartar at the gum line, which is hard, yellow-brown, and comes off with a professional cleaning.

A dentist distinguishes these with a probe, drying the tooth, and X-rays. A stain that has been there unchanged for years is stain. A dark spot that is new, growing, soft, or catches floss is decay until proven otherwise.

What a cavity feels like

Early cavities feel like nothing. The first symptom is usually a brief twinge with something sweet, cold, or hot. Then food starts to catch or a rough edge appears. As decay nears the nerve, sensitivity lasts longer, pain comes when biting, and eventually there is spontaneous, throbbing pain, often worse lying down. A cavity that has stopped hurting after being painful is often a dead nerve, not a cure.

How dentists find cavities you cannot see

• Visual exam with the tooth dried and good light.
• Explorer probe to feel for soft spots, though dentists now rely less on this for early lesions.
• Bitewing X-rays, typically every one to two years, which show decay between teeth and under fillings as a darker shadow.
• Laser fluorescence devices and transillumination lights that detect early decay in grooves.

This is why a checkup finds cavities you did not know you had. A cavity found on an X-ray while still small is a simple filling; the same cavity found because it hurts is often a root canal.

Can a cavity be reversed?

Only at the white-spot stage, before the enamel surface has broken. Fluoride, from toothpaste, varnish at the dentist, or prescription-strength toothpaste, can remineralize the enamel, and the spot may fade or stay as a harmless mark. Cutting sugar frequency and cleaning the area thoroughly are essential. Once there is a hole, the tooth cannot rebuild itself; the decay is removed and the hole filled.

Treatment and cost

Dental insurance typically covers fillings at 70 to 80 percent as a basic service. Our root canal and dental crown guides cover the later-stage treatments.

Preventing cavities

Brush twice daily with fluoride toothpaste, spit but do not rinse, floss once a day, limit how often you eat or drink sugar rather than only how much, drink water, chew sugar-free gum after meals, get sealants on children’s molars, and have a checkup with X-rays as your dentist recommends. Dry mouth, from medications or medical conditions, sharply raises cavity risk and is worth discussing with your dentist.

When to see a dentist

See a dentist if you notice a new white, brown, or black spot on a tooth, a hole or rough area you can feel with your tongue, food that consistently catches in one place, floss that shreds at one spot, or sensitivity to sweet, hot, or cold that is new or lasting longer. See a dentist promptly for a toothache, pain when biting, or a broken tooth. Seek same-day care for swelling of the gum or face, a pimple on the gum, or pain with fever; these indicate an abscess. If you have not had a checkup in over a year, book one regardless of symptoms; the cavities that matter most are the ones you cannot see.

Frequently asked questions

Sources

• National Institute of Dental and Craniofacial Research – Tooth decay
• Mayo Clinic – Cavities/tooth decay
• Cleveland Clinic – Cavities
• American Dental Association (MouthHealthy) – Decay

This article is for general information only and is not a substitute for professional dental advice, diagnosis, or treatment. Always consult a licensed dentist about your specific situation.