Teeth need calcium, phosphate and fluoride. Fluoride ions bond easily with calcium ions always present on tooth surfaces and in saliva. Saliva is the mouth’s primary defense against tooth decay.
Research has proven that fluoride works to prevent tooth decay by boosting the ability of saliva to return lost minerals to tooth enamel before cavities can develop. Saliva enhances protection of enamel by providing high levels of calcium and phosphate ions at the tooth surface. The best explanation of how fluoride, calcium and phosphate work is that they aid / enhance the natural properties of saliva.