The main cause of tooth decay is not the amount of sugar in the diet, but how often it is eaten or drunk. The more often your child has sugary foods or drinks, the more likely they are to have decay. It is therefore important to keep sugary foods to mealtimes only. If you want to give your child a snack, try to stick to cheese, vegetables and fruit, but not dried fruit.
It is also worth remembering that some processed baby foods contain quite a lot of sugar. Try checking the list of ingredients: the higher up the list sugar is, the more there is in the product. Sometimes, these are shown as fructose, glucose, lactose or sucrose. Thorough brushing twice a day, particularly last thing at night, will help to prevent tooth decay.