The relation of calcium in the saliva to dental caries

Abstract

Calcium was estimated by the method of Clark [1921] with the modification, suggested by Stanford and Wheatley [1925], of washing the calcium oxalate precipitate with a saturated solution of calcium oxalate instead of distilled water. Before precipitation of calcium as oxalate the mucin in the saliva was removed as far as possible; a drop of 10 % acetic was added; the saliva was shaken for half an hour and then filtered through an ash-free paper. The most likely sources of error in this method are the contamination of the calcium oxalate precipitate with organic matter and the loss of calcium with the precipitated mucin. To check this, estimates were also made on 27 samples by incinerating without removing mucin, dissolving the precipitate in dilute HCl, neutralising to methyl red and continuing the estimation on this solution. On the average the results by the incineration method were 01 mg. per 100 cc. higher than those by the direct method; the difference between the two methods was 0-6 mg. on one occasion and 0 3 mg. on another, otherwise the difference did not exceed 0x2 mg. Duplicates by the direct method agreed well. The subjects sucked acid drops in order to stimulate the flow of saliva.