What is the required concentration of fluoride in water for a 5-year-old to avoid the need for additional supplementation?

A concentration of 0.75 ppm of fluoride in water is considered optimal for children, particularly around the age of five. This level helps in promoting dental health and preventing tooth decay while minimizing the risk of dental fluorosis. The American Dental Association and the Centers for Disease Control and Prevention have recognized that maintaining fluoride in this concentration range supports healthy enamel formation, which is especially vital during the years when permanent teeth are developing.

In contrast, concentrations below this level might not provide sufficient fluoride for caries prevention, potentially necessitating additional fluoride supplementation. On the other hand, concentrations that exceed this optimal level could increase the risk of adverse effects, such as dental fluorosis, particularly in children whose teeth are still developing. Therefore, 0.75 ppm strikes an important balance, making it the most appropriate answer.