THE DESTRUCTIVE EFFECT OF CITRATE VS. LACTATE IONS ON RATS' MOLAR TOOTH SURFACES, IN VIVO

¹ Dental Research Section, Division of Physiology, National Institute of Health, U. S. Public Health Service, Bethesda, Md.

A study was made of the effect of citrate and lactate anions on rats' tooth surfaces, in vivo. Citrate and lactate drinking fluids adjusted to pH 5.5-7.2 were consumed in place of drinking water by young growing rats, and under these practically neutral conditions the citrate ion had a marked local decalcifying action on lingual tooth surfaces. No such action was caused by the lactate ion.

The action of citrate is explained as due to the binding of the calcium of the dentin and enamel by citrate to form a soluble calcium citrate complex. This in vivo action by citrate was predicted in certain fundamental studies of the chemistry of calcium and citrate ions.

The destruction of dental tissue by citrate, in itself, bears no gross similarity to ordinary dental caries. The process is believed to be a non-acid decalcification brought about by a specific organic anion, i.e., citrate, under practically neutral conditions. The suggestion is made that in considering the etiology of dental caries less emphasis be placed on acid-decalcification, and that the possibilities of a non-acid decalcification brought about by bacterial metabolites, be given more attention in dental caries research.

The destructive action of citrate on dentin and enamel surfaces suggests certain similarities with erosion observed in human teeth.

The results suggest further studies in vivo regarding surface effects of other anions in addition to citrate, as well as effects of certain foods and beverages on tooth surfaces.