Final answer:
Fluoride in drinking water and toothpaste helps protect teeth from decay by forming a more resistant compound. However, excessive fluoride intake can lead to a bone disease called skeletal fluorosis.
Step-by-step explanation:
Fluoride in drinking water and toothpaste helps to protect teeth from decay by reacting with hydroxylapatite in teeth to form fluorapatite, which is more resistant to acid attacks and less soluble. Regular dental cleanings, reducing sugar consumption, and using sugarless candies or gum with sugar alcohols can also prevent tooth damage from acidic drinks and the fermentation of sugars by oral bacteria. However, excessive fluoride intake can lead to skeletal fluorosis, a bone disease. The US Environmental Protection Agency sets a maximum level of 4 ppm (4 mg/L) of fluoride in drinking water to prevent fluorosis.