The ultrastructure of dentine from rat incisors following exposure to sodium fluoride and potassium pyroantimonate staining.

Weanling rats were given a single intraperitoneal injection of sodium fluoride and control animals normal saline for four consecutive days. The fluoride produced a consistent response in the mineralizing dentine of the incisors in which a hypermineralized band was succeeded by a hypomineralized band. Potassium pyroantimonate staining for calcium ions showed that following injection of fluoride, in contrast to the controls, there were large amounts of calcium pyroantimonate in the pre-dentine and throughout the odontoblasts. This suggests that fluoride temporarily affects the membrane enzyme systems which maintain calcium concentration gradients between the odontoblasts and the matrix. The resultant influx of calcium is probably associated with the hypermineralization of the dentine matrix in which more hydroxyapatite crystallites are deposited. Upon recovery of the odontoblasts the matrix is relatively depleted of calcium resulting in matrix hypomineralization.