Occlusion and brain function: mastication as a prevention of cognitive dysfunction

Abstract

Research in animals and humans has shown that mastication maintains cognitive function in the hippocampus, a brain area important for learning and memory. Reduced mastication, an epidemiological risk factor for the development of dementia in humans, attenuates spatial memory and causes hippocampal neurons to deteriorate morphologically and functionally, especially in aged animals. Active mastication rescues the stress-attenuated hippocampal memory process in animals and attenuates the perception of stress in humans by suppressing endocrinological and autonomic stress responses. Active mastication further improves the performance of sustained cognitive tasks by increasing the activation of the hippocampus and the prefrontal cortex, the brain regions that are essential for cognitive processing. Abnormal mastication caused by experimental occlusal disharmony in animals produces chronic stress, which in turn suppresses spatial learning ability. The negative correlation between mastication and corticosteroids has raised the hypothesis that the suppression of the hypothalamic-pituitary-adrenal (HPA) axis by masticatory stimulation contributes, in part, to preserving cognitive functions associated with mastication. In the present review, we examine research pertaining to the mastication-induced amelioration of deficits in cognitive function, its possible relationship with the HPA axis, and the neuronal mechanisms that may be involved in this process in the hippocampus.

To see bruxism: a functional MRI study

“…It is important to understand masticatory function, and also parafunction that has crucial effects on whole-body health as well as To see bruxism: an fMRI study S Yılmaz cognitive functions. 18 By the end of the 20th century, non-invasive measurements of brain function were developed. 19 The fMRI technique was first used in a study published in 1991, which showed how a standard MRI scanner can be used to track where oxygenated and deoxygenated blood flows in the brain.…”

Oral health for an ageing population: the importance of a natural dentition in older adults

“…Periodontal pathogens could provide inflammatory mediators due to daily, transient bacteremias, which in return increase the oxidative stress in Alzheimer's disease (AD) 57 . Animal models have tried to avoid these confounding factors and confirm that introducing poor mastication experimentally or administering a soft diet in mice may inhibit learning and memory performance 53,58,59 . Whether the relationship between mastication and cognition is observational or causal is still under discussion, and evidence of the effect of restorative dental measures is still scarce.…”

Occlusal Disharmony in Mice Transiently Activates Microglia in Hippocampal CA1 Region but Not in Dentate Gyrus

“…The transient increase of microglial areas in the CA1 after the increase in occlusal vertical dimension may belong to these acute reactions. Although the underlying mechanisms of the transient increase of microglial area in the CA1 are unclear, possible pathways, such as neuronal and humoral pathways from the oral cavity to the hippocampus, were recently reviewed (Ono et al 2010). One possibility is that the increased plasma corticosterone after increasing the vertical dimension is detected by corticosteroid receptors localized in neurons of the hippocampal formation (Han et al 2005;Galeeva et al 2006;Sarabdjitsingh et al 2009) and that such neurons affect microglia.…”