Effect of Hypophysectomy on the Molar of the Rat

The gross and microscopic anatomy of the molars was studied in 2 groups of rats:

A. Completely hypophysectomized. 22 animals. Age at operation: 36 to 64 days. Post-operative life: 63 to 459 days. B. Litter mate controls. Some were unoperated but most were unsuccessfully subjected to operation. Normal oestrous cycles and normal rate of growth. 15 animals.

Significant alterations were observed only in group A. The gross findings in these animals were (a) retarded eruption; (b) shorter length of roots. The histologic findings are summarized below.

1. The epithelial attachment is absent in a number of cases for varying lengths near the cemento-enamel junction so that the enamel is bounded directly by connective tissue or by a cementum spur of varying length and width. In 7 animals the enamel shows here some areas of resorption.

2. The enamel is normal in structure except for areas of resorption near which the organic matrix is sometimes seen in decalcified sections.

3. The dentin appears, as a whole, normal in structure. It is resorbed when the resorption of the enamel or cementum has extended beyond the dentin boundary.

4. The pulp usually shows a reduced blood supply. In some cases it shows advanced atrophic changes and contains calcified globules. The size of the pulp chamber and pulp canal appears to be larger than normal.

5. The cementum shows an abnormal frequency of resorption which is most prominent at the bifurcation level and least prominent at the apical portion of the root. In some of the animals of longest post-operative life a great number of globules of various sizes that stain like the cementum are seen at the cementum surface which faces the periodontal membrane. In some cases similar but larger globules are seen in the periodontal membrane.