292 W. V. MAYER AND S. BERNICK 



In addition to the effects of hibernation on caries and its effects on 

 bone and dentinogenesis, animals in hibernation for periods of from 

 3 weeks to 3 months exhibit various degrees of periodontal involve- 

 ment. Osteoporosis of bone was shown in Fig. 4 in an animal which 

 had been hibernating for 3 months. Figure 12 represents the inter- 

 proximal region of two premolars of an animal hibernating for 3 

 weeks. There is a loss of trabeculation, although less than that ob- 

 served in Fig. 4. There is, however, a pocket formation on both the 

 mesial and distal surfaces of the two adjacent teeth, and the distal 

 surface of the second premolar exhibits a deep pocket that extends 

 to the lower half of the root. In addition, the presence of calculus is 

 obvious. In still another hibernating squirrel the distal region of 

 the first upper molar exhibits a degeneration of the surface epithe- 

 lium and the presence of calculus on the cementum ( Fig. 13 ) . There 

 is also a noticeable loss of interseptal bone and a further downgrowth 

 of the epithelial attachment. 



After 3 months in hibernation a section of the interproximal region 

 between two molars of a squirrel shows an epithelial attachment 

 which has proliferated to the apex of the root ( Fig. 14 ) . The crest 

 of the bone has been lowered to the apical region. The cemental 



Fig. 13. Interproximal region between two molars of a hibernating animal. 

 Further downgrowth of the epithelial attachment and loss of interseptal bone 

 are common during hibernation. 



Fig. 14. Interproximal region between two molars of an animal in hiberna- 

 tion. The epithelial attachment has proliferated to the apex of the root. The 

 crest of the bone has been lowered to the apical region. Cemental tears on the 

 distal surface of the molariform tooth, a periodontal pocket in the gingiva of 

 the same surface, and the pulpal abscess indicate the deleterious effects of 

 hibernation on teeth. 



Fig. 15. Interproximal region bet\^een two molars of an animal in hiberna- 

 tion. The presence of epithelium in the interradicular region, the lowering of 

 the crest of the bone, and the carious lesion in the dentin further attest to the 

 stresses of hibernation. 



Fig. 16. Upper first molar of an animal in hibernation for 3 months. The 

 bifurcation involvement with loss of attachment fibers and bone, the periapical 

 abscess, and the cemental tears indicate further deterioration in the oral cavity 

 during hibernation. 



Fig. 17. Upper first molar of a hibernating animal. The complete encapsula- 

 tion of a root fragment by epithelium is a response to the degeneration of tooth 

 structure during hibernation. 



