Time and frequency
Brushing twice a day for about two minutes is generally recommended. Taking your time and giving every surface attention works better than brushing fast and hard.
Using a fluoride toothpaste is a widely recommended step in preventing decay. Ask your dentist which toothpaste suits you.
Regular, not rough
A soft-bristled brush and light pressure protect gums and tooth surfaces. Placing the brush at a slight angle to the gumline and using short, gentle movements is a good start.
The spaces between teeth are where a brush cannot reach. Floss or interdental brushes should therefore be part of the daily routine.
Replace your brush
A brush with splayed bristles loses its effect. The general advice is to replace it every few months, or sooner if the bristles wear out.

