Etiology
Excessive fluoride ingestion during tooth development is the sole cause. Sources include fluoridated drinking water at concentrations above optimal (>1 ppm), fluoride supplements, swallowing of fluoride toothpaste in young children, and high fluoride foods (marine fish, tea) or beverages.
The critical period for permanent incisors is primarily ages 15-30 months; for molars, the first 3-4 years of life. Primary teeth are affected during the third trimester of pregnancy through age 2.
The severity of fluorosis is dose-dependent: mild cases from slightly elevated fluoride (2-3 ppm), severe cases from chronically high fluoride (>4-6 ppm) during tooth development.
Endemic fluorosis occurs in areas with naturally high geological fluoride in groundwater — a major public health issue in parts of India, East Africa, China, and Central Asia.