Abstract
Purpose: While attention has been focused on the relationship between masticatory dysfunction or tooth loss and general health, the effects of masticatory dysfunction on brain function remain poorly understood. In this article, we discuss the effects of masticatory dysfunction on brain function based on our own animal experiments.
Research overview: Study 1. Eighteen rats were divided into a tooth extraction group that had their upper molars extracted at 4 weeks old, an anesthesia group administered an equivalent amount of anesthesia, and an untreated group that did not undergo any procedure or receive any anesthesia. Tetanic stimulation was administered by cerebral microdialysis and glutamate discharge was measured during hippocampus function. The tooth extraction group exhibited significantly lower glutamate discharge. Study 2. Sixteen 5-week-old rats were divided into a tooth extraction group that had their upper molars extracted at 5 weeks old, and a control group that only received an equivalent amount of anesthesia. Glutamate discharge in the hippocampus was measured during a passive avoidance learning experiment using a telemetry biosensor system. While the tooth extraction group had significantly lower discharge during acquisition trials, no group differences were seen during retention trials.
Discussion: In addition to causing masticatory disturbance, early loss of molars may also lower release from glutamate synapses in the hippocampus and potentially lead to impaired neurobiochemical functioning.
Conclusion: These studies indicate that early loss of molars may be one factor triggering impairments in learning and memory.
