Cracked tooth: how to spot it, and how it's treated.

A cracked tooth is exactly that — a crack in the hard structure of the tooth, ranging from a harmless surface line in the enamel (a "craze line") to a deep fracture that reaches the nerve or splits the tooth in two. The trouble is that many cracks are invisible to the eye and even to X-rays, and the symptoms are intermittent. What matters is how deep the crack goes and whether it is stable — which is why a tooth that hurts only sometimes still deserves a proper look.

Common causes are biting something hard (ice, a popcorn kernel, a bone), grinding or clenching that fatigues the tooth over time, a large old filling that leaves less natural tooth to resist force, sudden temperature changes, and simply age, as years of chewing add up. A tooth that has had a root canal can also become more brittle. Often a crack is the result of a weak spot meeting an unlucky bite rather than one dramatic event.

The classic sign is sharp pain on biting that disappears when you release — especially on a specific tooth or food. You may also get sensitivity to hot, cold or sweet that lingers, pain that comes and goes rather than staying constant, and discomfort that is hard to locate. Unlike a cavity, a crack often gives no constant ache until it is advanced, which is why the on-and-off biting pain is the clue worth acting on.

Treatment depends entirely on the depth. A shallow craze line in enamel often needs nothing beyond monitoring. A crack within the tooth is usually restored with a bonded filling or, more often, a crown that holds the tooth together and stops the crack spreading. If the crack has reached the nerve, a root canal followed by a crown can save it. A crack that extends below the gum or splits the root, however, usually means the tooth cannot be saved and needs removal — which is exactly why earlier is better.

See a dentist promptly if biting pain is becoming frequent or severe, if a piece of tooth has broken off, or if there is sensitivity that lingers well after the trigger — these suggest the crack is deepening towards the nerve. Swelling, a constant throb, or signs of infection (a bad taste, fever) mean it has reached the nerve and need urgent care. Meanwhile, chew on the other side and avoid hard or very hot/cold foods on that tooth.