THE EFFECTS OF BETA-AMINOPROPIONITRILE UPON THE MOLAR TEETH OF THE RAT

¹ The Department of Pathology and the Department of Dentistry and Dental Research, School of Medicine and Dentistry, University of Rochester, Rochester, N. Y.

1. The effects of a diet containing 0.2 per cent beta-aminopropionitrile on the molar teeth of weanling male and female rats were studied. The following observations were made:

a. In the apical regions of the first and second molars of the experimental rats killed after the thirteenth day on the diet, an abnormal type of dentin (osteodentin) was deposited, a recognizable epithelial diaphragm was absent, and the apex of the root was formed by the cementum only. The rate of root elongation and the thickness of cementum appeared to be decreased.

b. In the coronal parts of the roots and in the crown of the first and second molars of the experimental rats, the structure of the dentin, and the number, appearance, and arrangement of the odontoblasts, pulpal fibroblasts, and argyrophilic fibers of the pulp were found to be normal. At the level of the cementoenamel junction, the thickness of the dentin and predentin was the same in both groups of animals.

c. The dentin, cementum and epithelial diaphragm, the odontoblasts, and argyrophilic fibers of the pulp, and the collagen fibers and fibroblasts of the periodontal membrane of the third molars of the experimental rats did not present any abnormality.

2. The significance of these observations in relationship to the effects of beta-aminopropionitrile on cell differentiation and fiber formation in the connective tissues is discussed.