Baby bottle tooth decay or syndrome is a form of tooth decay that can destroy the teeth of an infant. This decay may even enter the underlying bone structure, which can hamper development of the permanent teeth. The teeth most likely to be damaged are the upper teeth. Baby bottle decay is caused by frequent and long exposure of a child's teeth to liquids containing sugar such as milk, formula, fruit juices, pop and other sweetened liquids. These liquids fuel the bacteria in a child's mouth, which produces acids that attack enamel.