Tooth decay is often due more to what, and how often you eat or drink, than to how you brush your teeth. As far as possible, avoid acidic and sugary foods and drinks (such as fizzy drinks, fruit juice, squash and sports drinks) between meals - Very early decay can heal, as long as your mouth has a few hours between each acid attack. Drink water where possible, and look for sugar-free sweets or chewing gum (remember to dispose of in a bin!).