AUTORADIOGRAPHIC VISUALIZATION OF IN VITRO EXCHANGE IN TEETH, BONES, AND OTHER TISSUES, UNDER VARIOUS CONDITIONS

¹ Department of Histology and Embryology, University of Ottawa, Canada

1. Autoradiograms of in vitro exchanged P₃₂, Ca₄₅, and S₃₅, in teeth and bones have been obtained.

2. Exchange behavior of young bones and teeth in vitro is comparable to the early autoradiographic patterns after injections of P₃₂ or Ca₄₅ in vivo.

3. Young normal tissues exchange at a greater rate than older tissues.

4. Areas of new growth in a bone tumor and around a bone graft exchange more than normal bone.

5. Recent calcified lesions of hyaline cartilage and muscular arteries exchange at a higher rate than older lesions.

6. In adult human teeth, cementum exchanges more than dentin. Dentin exchanges more than enamel.

7. In the enamel of certain adult human teeth, caplike regions proximal to the dentinoenamel junction exchange heavily but show no difference in radiopacity.

8. Following hyaluronidase incubation, there is a progressive increase in exchange over dentin.

9. The process of dentinal caries is accompanied by progressively increased exchange in the dentin of the diseased tooth.

10. P₃₂, Ca₄₅, and S₃₅, exchange at a great rate in the vicinity of carious lesions.