STUDIES ON THE DIFFERENT PATHWAYS OF EXCHANGE OF MINERALS IN TEETH WITH THE AID OF RADIOACTIVE PHOSPHORUS

¹ Walter G. Zoller Memorial Dental Clinic and Department of Anatomy, University of Chicago, Chicago, Ill.

1. Measurement was made of the intake of phosphorus by the teeth of adult dogs within 24 hours after an intravenous injection of an aqueous solution of radioactive sodium-phosphate. 2. The methods applied in this study are described. 3. Both normal teeth and the corresponding teeth on the opposite side of the jaw of which the pulp was either removed or injured were studied. 4. It was shown by this method that pulpless teeth continue to take up phosphorus by the way of the cemento-dentinal junction. About one-tenth of the amount of phosphorus taken up by normal teeth in 24 hours enters the pulpless teeth through the cementum. 5. The rate of phosphorus intake was the same in both pulpless teeth and teeth with pulp injured by a slight trauma. 6. When crown and root parts of the teeth were separatedly measured, no difference was found as to the amount of phosphorus contained within the dentin. 7. Since this is true of pulpless teeth where the phosphorus enters the dentin only on the root part via cementum, a quick distribution of the phosphorus throughout the dentin must take place. 8. By separating the 3 hard tissues of the tooth from each other, phosphorus was shown to have also entered the enamel. 9. If covered by an impermeable cap, the enamel nevertheless takes up the same amount of phosphorus. Therefore, the amount of phosphorus taken up by the enamel from the saliva which contains radioactive phosphorus, is negligible compared with the uptake from the dentin even in pulpless teeth. 10. The question is discussed whether the intake of minerals by the tissues of pulpless teeth is the same process as the metabolic exchange of the same substances in normal teeth or if it is a purely physical adsorption or simple chemical combination.