Radioactive Phosphate Absorption By Dentin and Enamel

Studies have frequently been made on dentin in an attempt to clarify problems relating to the structure and physiological behavior of this tissue. Thus far, 3 principal methods have been used: 1. Dyes have been used by Beust (1), Fish (2, 3), Bodecker (4), Lefkowitz (5), and others in studies of the rate and degree of penetration through the dentin. 2. Roentgen ray absorption studies, to determine the relative absorption of different parts of the tooth, were made by Van Huysen, Hodge and Warren (6). 3. Radioactive isotopes have also been used extensively in studies relating to the absorption of dentin and other tissues. Hevesy, Holst and Krogh (7) administered radioactive phosphorus to rats, cats and humans, and found that phosphorus atoms of the blood plasma exchange with those of the teeth and other tissues. They also state that actively growing teeth, such as the incisor of the rat, show a higher rate of absorption than mature teeth of the rat and other animals. They further state that the absorption of P32, in the rat incisor, is much more pronounced in the rapidly-growing proximal part than in the distal region of the tooth. This situation was also found to be true in rat incisors in which the pulps had been removed. They conclude from these and other observations that the circumpulpal region of the tooth shows the highest degree of phosphorus absorption. Manly and Bale (8) measured the relative amount of radioactive pohosphorus absorbed by the glycocol extracted dentin of the rat incisor and observed results similar to those reported by Hevesy, Holst and Krogh. Observations regarding the differential absorption of radioactive phosphorus in the rat incisor have also been recorded by Erbacher and Wannenmacher (9). The original observations of Hevesy, Holst and Krogh have also been confirmed in part by several other investigators. Wasserman, Blayney, Groezinger and DeWitt (10) observed in the dog that teeth with pulps removed take up radioactive phosphorus throughout the entire tooth at a rapid rate but to a lesser degree than in the intact tooth. Slight differences in the amount of absorption were noted by Volker and Sogannaes (11), and Sogannaes and Volker (12), who separated dentin into apical and coronal samples and also according to 'density' fractions. Finally, McCauley (13), and Scott and Marshall (14) noted in their radioautographs, that the circumpulpal dentin revealed a greater absorption of P32 than other parts of the tooth.