Take note, missing teeth are no longer just a problem that affects aesthetics and chewing function. Epidemiological studies have shown that missing teeth also increase the risk of dementia. Although the exact mechanism by which missing teeth increase the risk of dementia is not yet known, it is still possible to comb through the literature to find clues that missing teeth increase the risk of dementia.
Impaired chewing movement affects cerebral blood flow
People have different cerebral blood flow rates and blood flow before and after chewing. The blood flow rate in the middle cerebral artery is significantly increased after mastication exercise, and the blood supply to the corresponding brain regions is increased.
Missing teeth will increase the bite burden of surrounding teeth, and long-term absence will cause jaw teeth elongation and tilting of teeth on both sides, resulting in masticatory function disorder. Therefore, when an elderly person is missing teeth, normal chewing movements cannot be completed successfully.
Compared to people with healthy teeth, the blood flow to the brain is significantly slower and the volume of blood supply to the brain is significantly reduced in people with missing teeth. This contributes to the structural and functional degeneration of the corresponding neural tissues.
Studies have found abnormal changes in cerebral blood flow in Alzheimer’s patients, with significantly lower blood flow rates and volumes in the bilateral frontal lobe, hippocampus, temporal cortex and basal nucleus of the brain than in healthy older adults.
Absence of teeth affects cerebral neuromediators
After removing unilateral molars from aged rats for 2 months, the researchers found that tooth loss caused a decrease in cholinergic fibers in the prefrontal cortex and hippocampus of aged rats.
Tooth loss induced memory impairment through a pathway unrelated to amyloid myelin and reduced neuronal activity, presynaptic and postsynaptic protein levels in the cortex and hippocampus.
Tooth loss induces glial cell activation, which in turn leads to upregulation of the expression levels of neuroinflammatory cytokines tumor necrosis factor and interleukins in the hippocampus.
Tooth loss activated the stress-activated protein kinase JNK and increased heat shock protein 90 (HSP90) levels in the hippocampus, which may lead to glial cell activation.
Hippocampal glutamate release is also reduced after tooth loss, leading to decreased neuronal excitability and further exacerbating the onset of dementia and cognitive impairment.
Inflammation can affect the brain through neural pathways
When you see the reason for this, you may also be puzzled. We are talking about missing teeth and dementia, what does it have to do with periodontitis? Actually, the main cause of tooth loss in the elderly is chronic periodontitis.
Periodontitis is a chronic infection of the periodontal supporting tissues caused by microorganisms in plaque, resulting in the destruction of periodontal supporting tissues and eventually loosening and extraction of teeth.
High levels of pathogenic bacteria and inflammatory mediators can be detected in the composition of the gingival sulcus fluid of patients with periodontitis. Serum levels of C-reactive protein and leptin are also high in patients with periodontitis.
These inflammatory factors and oral microbiota may affect the brain through circulatory or neural pathways contributing to the development of dementia. A case-control study has shown a correlation between inflammatory cytokine levels and periodontitis in patients with Alzheimer’s disease, mild cognitive impairment.
