THE LIPIDE CONTENT OF ENAMEL AND DENTIN

¹ Department of Biological Chemistry, Georgetown University Schools of Medicine and Dentistry, Washington, D. C., and the U. S. Naval Dental School, Bethesda, Md.

The data on both enamel and dentin are summarized in Table I. Dentin contains 0.024 per cent cholesterol and 0.36 per cent total lipide other than cholesterol. Enamel contains only 0.008 per cent cholesterol and the noncholesterol total lipide content is 0.60 per cent. Pincus³ has reported the isolation of a fatty substance approximating 1 per cent of the organic fraction of enamel. His data are difficult to evaluate since his interest was primarily in the protein rather than the lipide fraction but it would appear that he found, associated with the protein, less than 0.004 per cent of the enamel as lipide.

The fatty acids in dentin lipide, based upon their saponification and iodine numbers, resemble those found in bone lipide, 200 and 50, respectively. The fatty acids in enamel lipide are less saturated and contain longer chains than those in bone lipides.

Krasnow⁴ has reported that enamel contains more phospholipide phosphorus than dentin and our results are in agreement with this. It must be noted, however, that the values given by Krasnow in his abstract are based upon 100 mg. of enamel and dentin and unless this is a typographical error and should be based upon 100 Gm., his results are one thousand times higher than ours and would account for more than the total organic content of enamel.

Human enamel contains 0.008 per cent cholesterol. Total lipides other than cholesterol have been found in dentin to the extent of 0.36 per cent and 0.60 per cent in enamel. The iodine and saponification numbers of these lipides have been determined. Phospholipide contents of enamel and dentin, 0.075 and 0.014 per cent, respectively, were found, based upon the phosphorus content of the total, noncholesterol lipide.