Dental Cavities

Decay starts when the bacteria in plaque turn the sugar left on a tooth into acid. The acid dissolves minerals out of the enamel, and once enough has gone the surface collapses into a soft hole.

While the hole is only in enamel you will feel nothing. It becomes sensitive when it reaches the softer dentine underneath, and it becomes painful when it reaches the nerve at the centre. A tooth that has started to ache at night has usually been decaying for months.

Your dentist looks at each tooth under a bright light and dries it, because early decay shows as a chalky white patch that only appears on a dry surface. A blunt probe is run over suspicious spots to feel whether the enamel has softened.

An X-ray is taken where a cavity is suspected between two teeth, since those surfaces cannot be seen or reached with a probe. The X-ray also shows how close the decay has come to the nerve, which is what decides whether the tooth can still be filled.

You can eat and drink as soon as the numbness wears off, which takes two to three hours. Chew on the other side until then, because a numb lip and cheek are easy to bite.

Some sensitivity to cold for a week or two is normal after a deep cavity has been cleaned out. Pain that builds over several days, or that wakes you, means the nerve has been affected and you should go back.