A COMPARISON OF TWO METHODS OF ASHING ENAMEL AND DENTIN

¹ Division of Dental Research and Division of Pharmacology and Toxicology, University of Rochester School of Medicine and Dentistry, Rochester 7, N. Y.

1. About fifty teeth were separated into enamel and dentin. An aliquot of each tissue was then ashed by incineration (heat ash) and another by extraction with 3 per cent KOH in ethylene glycol (glycol ash). Calcium, magnesium, and phosphorus analyses were made on every ashed aliquot.

2. Incineration drives off CO₂ so that the heat ash always was a smaller percentage of the dry weight than was the glycol ash which contained all of the CO₂. The percentages of calcium, magnesium, and phosphorus in the heat ash were therefore higher than in the glycol ash.

3. In the enamel samples, the glycol-ashing procedure apparently removed about 1 per cent of unidentified extractables presumed to be inorganic constituents.

4. In the dentin samples, a larger loss of extractables occurred, amounting to about 2 per cent of the dry weight. Calculations were made to show that a small loss of calcium (of the order of 0.5 per cent) and a larger loss of phosphorus (of the order of 1.5 per cent) would give a glycol ash having the composition actually found.