Decay is slow. It usually takes months, sometimes years, to go from the first mark on a tooth to real pain. The earlier it is caught, the smaller the treatment, and the first stage can even reverse.
How decay starts
Bacteria in plaque feed on sugar and give off acid. Each time you eat or drink something sugary, that acid draws minerals out of the enamel for about half an hour. Saliva then puts some of them back. Decay happens when the losses keep outrunning the repairs.
The five stages
- White spots. The first sign is a chalky white patch, often near the gum line, where enamel has lost minerals. There is no hole yet and no pain. At this stage, fluoride and better habits can harden the enamel again.
- Enamel decay. The surface breaks down and a small cavity forms, sometimes turning brown. It still rarely hurts. A small filling fixes it.
- Dentine decay. Under the enamel is softer dentine, and decay spreads faster there. Now teeth may feel sensitive to sweet, cold or hot. The filling needed is larger.
- Nerve involvement. Once decay reaches the pulp, the nerve and blood vessels in the centre of the tooth, it becomes inflamed. This is the throbbing pain that keeps people up at night. The tooth usually needs root canal treatment to save it.
- Abscess. If the infection spreads past the root tip, a pocket of pus forms in the bone. Signs include swelling, a pimple on the gum, a bad taste and sometimes a temperature. This needs treatment quickly. If your face is swelling, see our page on tooth pain.
How to prevent it
- Brush twice a day with fluoride toothpaste, last thing at night and one other time. Spit out the foam but do not rinse with water: the fluoride left behind keeps working.
- Count how often, not how much. Sugar sipped through the day in tea, juice or biscuits does more harm than the same sugar eaten at one meal. Keep sweet things to mealtimes.
- Clean between your teeth once a day with floss or interdental brushes. Decay between teeth is the kind you cannot see in a mirror.
- Come in for a check-up as often as we advise, usually every six months. White spots and small cavities are easy to miss at home, and easy to treat when found early.
- Children: a smear of fluoride toothpaste from the first tooth, a pea-sized amount from age three, and help with brushing until about seven or eight.
Read more about check-ups and everyday care.