The addition of fluoride, typically in the form of sodium fluoride, fluorosilicic acid, or sodium fluorosilicate, helps prevent tooth decay by strengthening tooth enamel and making it more resistant to acid erosion caused by bacteria in the mouth.
Public health authorities regulate the concentration of fluoride added to water to ensure it provides dental benefits while minimising the risk of dental fluorosis, a condition characterised by enamel discolouration. Fluoridation has been widely implemented since the mid-20th century and is considered one of the most effective public health interventions for preventing dental cavities and promoting oral health across populations.