Abstract
The effects observed by Erdheim 1 and later by Toyofuku 2 in the teeth of parathyroidectomized white rats led Erdheim to emphasize the relation of the parathyroids to calcium metabolism. The uncertainty as to the mode of action of the parathyroids caused us to undertake a similar study of the teeth of some thyroparathyroidectomized rats which had been produced for another purpose.
The two rats whose teeth were studied were males and had been kept, like the others, on a standard diet of 60% cracked corn, 20% powdered milk, 16% powdered casein, 3% alfalfa meal, 0.5% sodium chloride, and 0.5% calcium carbonate. Both showed typical tetany after the operation, and both showed gross dental defects before death. Rat 1 had a brown line along the anterolateral edge of the right upper incisor when it died on the 29th day; rat 2 had suffered a spontaneous fracture of both lower incisors and marked elongation of the opposing upper incisors before it died on the 82nd day. Microphotographs, with detailed descriptions, of the transverse sections of the teeth of these rats will be published elsewhere. 3 The following is a brief summary of the findings:
RAT 1. Pulp and odontoblasts well preserved, dentine well calcified. The greatest disturbance occurred in the enamel epithelium and in the bone adjacent to one of the teeth. The ameloblasts were disorganized in places, and there was proliferation of the outer layer of the enamel epithelium. These layers showed some folding. At one level a striking exostosis of the alveolar bone had taken place. This abnormal bone growth obliterated the peridental membrane as it progressed inwards towards the tooth, and it finally lay in contact with the enamel itself. In so doing it either pushed aside or induced atrophy of the enamel epithelium in its path.
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