Tooth decay develops when a child’s teeth and gums are exposed to any liquids or foods other than water for long periods. The most common way this happens is when parents put their children to bed with a bottle of formula, milk, juice, soft drinks, sugar water, or sugared drinks. It can also occur when children are allowed to drink from a sippy cup, suck on a bottle, or breastfeed for long periods during the day or night.To prevent tooth decay:
Keep your baby’s mouth clean by gently brushing the gums and teeth with water and a soft infant toothbrush or gauze. Once your baby has 8 teeth, you can start using a child-sized toothbrush for daily cleanings.
Brush your child’s teeth 2 times a day. Start by using a fluoride-free toothpaste. When your child is able to spit and not swallow the toothpaste (usually around 2 to 3 years old), you should continue brushing his or her teeth using a pea-sized amount of fluoride toothpaste.
(from American Academy of Paediatrics)