TOOTH CONDITION, A FACTOR IN EXPERIMENTAL ISOTOPE ABSORPTION

¹ Division of Oral Histology, School of Dental and Oral Surgery, Columbia University, New York, N. Y.

The amount of radio-active phosphorus defined in dental tissues as a result of experiments designed to determine the degree of their metabolic activity is dependent largely upon the age of the tooth, type of the animal, secondary dentin formation, protective metamorphosis, degree of attrition and pulp vitality. All of these factors affect the permeability of teeth, a quality closely related to physiological phenomena. If protective metamorphosis has occurred due to ageing, attrition, and secondary dentin formation, permeability of the dentin is reduced greatly; hence, very little radio-active phosphorus can pass from the pulp into the dentin and enamel. The teeth of animals used for purposes of defining metabolic activity should be examined as to their permeability because this factor will affect the results of the experiment.

The degree of pulp activity also plays a rôle in the degree of metabolic activity in dentin and enamel. Pulp extirpation leads to a vast temporary increase in permeability in recently erupted teeth, causing the absorption of radio-active phosphorus from channels other than the dental pulp. Thus a confusion results, suggesting that the dental pulp is unimportant in effecting metabolic changes in the tooth.