Brushing removes plaque from accessible tooth surfaces. It cannot reach the spaces between teeth, which account for approximately 40 percent of tooth surfaces. Flossing targets exactly these areas. Decay and gum disease in interdental spaces are the most common sites and cannot be prevented by brushing alone.
Two minutes of brushing twice daily with fluoride toothpaste combined with once-daily flossing is the evidence-based minimum. Interdental brushes are an effective alternative to floss for people who find floss awkward to use.