Effects of fluoride, calcium, and phosphate administration on mineralization in rats

Seven days before a fluoride injection of 20 mg sodium fluoride per kg body weight, 3-month-old rats grown on a standard pellet diet containing 0.8% calcium and 1.4% phosphate were given a diet of rice with only 0.025% calcium and 0.1% phosphate. Microradiographs of the continuously growing incisors showed a hypermineralized and subsequent hypomineralized zone. Blood analysis demonstrated a decrease and a subsequent reestablishment of plasma calcium concentration. In some experiments calcium and phosphate were administered to compensate the hypocalcemia which prevented the hypomineralized zone from arising. A delay of calcium and phosphate administration led to formation of a mineralized band within the hypomineralized zone. The results are discussed with reference to calcium homeostasis.