Final answer:
Fluoride added to water is an effective method for reducing tooth decay across populations by strengthening enamel and inhibiting bacteria that cause cavities.
Step-by-step explanation:
Adding fluoride to water is an effective way of reducing dental cavity formation. Community water fluoridation is recognized as the most cost-effective method of delivering fluoride to all, leading to a reduction of tooth decay by about 25% in children and adults. Not only does fluoride strengthen tooth enamel and promote remineralization by enhancing the uptake of calcium and phosphate ions, but it also possesses bacteriostatic properties that help inhibit the proliferation of plaque-forming bacteria, thus reducing the production of harmful acids that contribute to tooth decay.