What Really Causes Cavities?
It's common sense that limiting the amount of sugar your child eats will help prevent tooth decay. But this may surprise you: Letting your child suck on a bottle for an hour may do more harm to his teeth than eating a dish of ice cream. How so? Every time your child consumes something that contains sugar or starch, the bacteria in his mouth produce an acid that eats away at tooth enamel. The longer your child's teeth are in contact with the food, the more damage is done. That explains why you should never put your child down to sleep with a bottle -- and why the AAPD advises against at-will nighttime breastfeeding (which exposes a child to fermentable carbohydrates that can lead to decay).
To further reduce the risk of cavities, feed your child nutritious snacks (such as fruits and veggies) instead of sweets. If he's thirsty between meals, give him water instead of a sweetened beverage or juice. And don't share utensils with your child, since you could transfer cavity-causing bacteria through your saliva. If you need to taste his food -- or want him to try yours -- use separate spoons.