First and foremost, you need to understand why a tooth decays to better appreciate what has gone wrong and what could be the remedy, as the child is young and corrective measures are very important at this juncture. Tooth decay occurs when the bacteria found in plaque feed on the sugars in the food, thereby producing acids that damage the teeth. This acid eats away at the enamel of the teeth before decaying the dentin beneath. If left untreated, the acid will eventually reach and damage the nerves.