Most of the problems associated with falling asleep with a bottle begin to emerge after a child is one year old.
Cavities result from the interaction between normal mouth bacteria and carbohydrates in the diet.
The sugars are converted to acids as they are fermented by the bacteria. The acid then etches the enamel of the teeth if there is prolonged contact. Saliva helps to prevent cavities by digesting the sugars and by washing the teeth. When one falls asleep, saliva production decreases rapidly. Swallowing also decreases, and liquids present in the mouth at the time of falling asleep tend to pool for long periods.