The effect of lead acetate on dentine formation in the rat

The intravenous injection of lead acetate produces a response in dentine by formation of the so-called lead line. This is associated with a rapid but temporary rise in serum calcium and phosphorus. Previous studies have suggested that lead replaces calcium and phosphorus in the apatite lattice. In this study the lead line was investigated in the scanning electron microscope using backscattered electron imaging and was shown to consist of continuous hypomineralized interglobular spaces within the dentine. Dentine formation was disrupted for at least a week after injection of lead ions. With energy dispersive analysis by X-rays, no localized concentration of lead was detectable within the 'lead line'. It is suggested that the lead line results from a direct effect of lead on the odontoblasts and other hard tissue-forming cells producing a rapid loss of intracellular calcium temporarily displaced by lead ions and a subsequent disturbance of local calcium metabolism.