MITOTIC ACTIVITY IN THE PERIODONTAL TISSUES OF THE RAT MOLAR

¹ Division of Periodontology, School of Dentistry, and the Department of Physiology, University of Minnesota, Minneapolis, Minn.

Thirty-one black male rats 5 months of age were studied under standardized circumstances. Mitotic activity in certain periodontal structures was evaluated. Marked mitotic periodicities were noted for the retromolar epithelium and for the connective tissue of the periodontal membrane. These mitotic rhythms were compared with the twenty-four hour rhythms in number of circulating eosinophils and in rectal temperature. The findings seem to indicate that certain oral structures follow the twenty-four hour periodic pattern of function in the organism as a whole. The effect of a mechanism for mitotic periodicity at the organismic level may be modified by local factors. In the specimens collected at the times chosen for this study, significant differences in the number of mitoses were not detected for the interdental papillae. The role of the presence as well as that of the degree of leukocytic infiltration is considered in this connection. The incidental findings of definite distribution patterns of mitoses within the periodontal membrane and along the molar roots are presented and discussed.