Why is water fluoridation, which is the controlled adjustment of fluoride to public water supply, done?

Explanation

Community water fluoridation adjusts fluoride in a water supply with the aim of reducing dental caries, or tooth decay. Fluoride helps make tooth enamel more resistant to acid attack and supports remineralisation. The question asks the intended dental purpose, not for a dosing recommendation or a claim that fluoride prevents the other listed conditions.