Fluoride is a substance that strengthens the structure of the tooth for small children who are under seven years of age, and prone to caries due to habits like bottle feeding and too much sweets. If the right amount of fluoride is applied during this period, the actual structure of the enamel is strengthened and becomes more resistant to acids produced by the bacteria responsible for caries and decay. This means that, as the child grows, they will have teeth that are better protected right from the beginning.