What Does a Cavity in Teeth Look Like, and What Happens If You Leave It?

The first sign is a dull, chalky white patch on the enamel, often near the gum line or beside a tooth. At this point the surface is intact and the mineral loss can still be reversed with fluoride and fewer sugar exposures, which is covered in how to stop tooth decay.

Next the patch turns light brown or grey and the surface feels rough or slightly soft. Then it breaks. You see or feel a pit, a dark groove that catches food, or a corner of tooth that has gone missing. A true cavity does not heal once the surface has broken, because the lost tooth does not grow back.

Many cavities cannot be seen at all. Decay between two teeth or under the edge of an old filling hides from the mirror and from your own eyes, which is why a dentist finds more of it on an X-ray than by looking.

Enamel has no nerve. A cavity can move through it with no pain at all. Sensitivity to sweet, cold or hot food usually starts once decay reaches the dentine beneath, which is softer and carries tiny channels to the nerve.

Pain that lingers after the stimulus is gone, or wakes you at night, usually means the pulp is inflamed. That is a later stage than most people expect. The point of knowing this is that no pain does not mean no cavity, and the window in which the fix is smallest is entirely painless.

It deepens. Decay in enamel is a small filling. Decay through dentine is a larger one, and the larger the filling, the less tooth is left to hold it. Once decay reaches the pulp, the choice is a filling or a root canal, and that is a longer and more expensive treatment than a filling.

Past the pulp the infection can spread to the tip of the root and form an abscess: a throbbing ache, a gum boil, or swelling of the face. A tooth that has broken down this far may not be restorable and may need to be extracted.

Swelling that spreads across the face or under the jaw, fever, or difficulty swallowing or breathing needs care the same day. If breathing or swallowing is affected, go to a hospital emergency department.

Examination with a mirror and probe, then an X-ray where decay is suspected between teeth, under a filling, or deep in a back tooth. In Lucknow in 2026 an examination and X-ray costs roughly ₹200 to ₹1,200.

The X-ray shows how close the decay is to the pulp, and that distance decides the treatment more than anything you can see or feel. It is the single most useful piece of information for choosing between a filling and a root canal.

A white-spot stage lesion with an intact surface can be watched and remineralised. A cavity that has broken the surface needs decay removed and the tooth restored with a filling. Which material suits which tooth is explained in types of dental fillings, and the process is set out on the tooth fillings page.

Dark marks do not always mean decay. If what you have noticed is a dark spot rather than a hole, see black spots on teeth for how to tell stain from cavity.