THE DISTRIBUTION OF LEAD IN HUMAN ENAMEL

¹ Eastman Dental Dispensary and School of Medicine and Dentistry of the University of Rochester, Rochester, N. Y.

1. The distribution of lead was determined in pooled ground samples of successive layers of enamel from unerupted and erupted teeth of different ages. A group of mottled teeth was also included.

2. Lead was found to be present in the enamel of both unerupted and erupted teeth.

3. There was an increase in the lead concentration of the surface enamel in fully formed unerupted teeth. compared to that of incompletely formed ones. The amount of lead in the outer enamel of erupted teeth was greater than that of unerupted teeth and showed an increase with age. The greatest concentration in the outermost enamel, 550 ppm, was found in the over 50 years' group.

4. In all groups of teeth, the greatest amount of lead was found in the outermost enamel layer, and decreasing amounts were found in the subsurface layers until a fairly constant level was reached which represented the lead concentration in the bulk of the enamel. This concentration was about 30 ppm in teeth from young persons and about 90 ppm in teeth from persons over 50 years of age.

5. The lead content of the enamel of mottled teeth was less than that of normal erupted teeth, showing either that the amount of lead in the enamel may vary in different geographical regions or that presence of fluorine in large amounts may interfere with lead uptake.

6. Since lead occurs in relatively high concentrations in the outer enamel, its presence may be important, but, as yet, its significance has not been established.

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