Effects of Tooth Loss and Aging on Memory in Rats

Objectives: The impairment of spatial memory by tooth loss has not yet been well understood in relation to aging. The purpose was to test the interactive effect of tooth loss and aging on spatial memory and the hippocampal cell density in rats.

Methods: 96 male Wister rats, seven weeks old, were divided into four groups (n=24 each) based on the number of teeth extracted: bilateral first molar teeth; the first and second molar teeth; and the first, second, and third molar teeth. A control group was also given anesthesia without extraction of teeth. The spatial memory was assessed by means of an eight arm radial maze, which was conducted on days of 1, 4, 7, 40, and 92 weeks after the tooth extraction. Following each test, six rats randomly selected from each group were donated to calculation of the pyramidal cell densities in CA1, CA3, and CA4 of the hippocampus. ANOVA test was conducted to determine the significant effects of the number of tooth loss and aging on the spatial memory and the cell densities, followed by the Fisher's PLSD (p=.05).

Results: Both the number of tooth loss and the aging significantly accelerated the maze performances and the cell densities; however, the interactive effect was insignificant. After 7w, the number of tooth loss was inversely proportional to the performances and the hippocampal cell densities. The average weight of rats slightly increased by controlled feeding throughout the experiment without showing a significant difference between the control and experimental groups.

Conclusion: The results indicated that, in rats, the spatial memory-linked hippocampal cell densities were reduced in association with both the tooth loss and aging, but their interaction was not significant. This suggests that teeth have an independent role in the prevention of spatial memory impairment.