CALCIFICATION OF TEETH

II. COMPARISON OF SOME PROPERTIES OF HUMAN AND RAT TEETH

¹ Department of Biochemistry and the Pediatric Research Laboratory, The Jewish Hospital of Brooklyn, and the Department of Chemistry and the Division of Applied Physics, The Polytechnic Institute of Brooklyn, Brooklyn, N. Y.

1. The enamel and dentin of human and rat teeth, both before and after fluoride treatment, give apatite patterns in spite of the wide variations in composition that were encountered.

2. Where the Ca:PO₄ ratio was less than 1.50, namely in the rat dentin and enamel, -Ca₃ (PO₄)₂ was found in the ignited specimens. Where the Ca:PO₄ ratio was more than 1.60, namely in the human teeth and in both the rat and human teeth after sodium fluoride treatment, apatite was found after ignition.

3. Phosphate is lost in preference to carbonate under fluoride treatment at a pH of 7.1.

4. The PO₄:2CO₃ ratios of the enamels are higher in the human and lower in the rat than the corresponding dentins. (There is some evidence to indicate that more intensive investigation of human teeth may alter this conclusion.)

5. Enamel PO₄:2CO₃ ratios found in experimental animals were both higher and lower than those found hitherto in humans.

6. The Ca:PO₄ ratios of human enamel may be higher than, lower than, or equal to those of human dentin. The Ca:PO₄ ratios of rat enamel are always higher than those of rat dentin.

7. The Ca:PO₄ ratios of human dentin are usually higher than those of rat dentin. The range of Ca:PO₄ ratios of human enamel is smaller than that of rat enamel.