Oral helse og kognitiv funktion
Mus og rotter, som får molarer fjernet, har sværere ved at finde frem til mad i eksperimentelle labyrinter. Det har ført til spekulationer om en sammenhæng mellem tyggefunktion og kognitiv funktion. Undersøgelser på unge mennesker har vist øget blodgennemstrømning og øget neuronaktivitet i hjernen ved tygning af tyggegummi, og at hukommelse og enkelte andre kognitive funktioner bliver bedre. Dette har ført til teorier om, at manglende tyggefunktion kan have betydning for udvikling af demens. En række epidemiologiske undersøgelser viser da også, at tandtab og demens ofte optræder sammen. Nogle forskere har hævdet, at mangelfuld mastikatorisk stimulation bidrager til svækkelse af neuroner i hjernevæv, mens andre påpeger, at tandtab oftest skyldes en bakteriel sygdom som marginal parodontitis, hvor både infektiøse agenser og inflammatoriske værtsreaktioner kan inducere mikrogliaceller til reaktioner, som fører til neurondød. Inflammationsteorien synes for tiden at nyde mest støtte blandt forskerne; men det påpeges, at de mange oplysninger om en sammenhæng mellem oral sygdom og kognitivt svigt hos ældre mennesker ikke nødvendigvis er udtryk for en kausal sammenhæng, idet mange forhold hos demente mennesker kan svække den orale helse.
Oral health and cognitive function: Experiments using radial arm mazes show that mice and rats have difficulties finding food when their chewing capability is disturbed after molar extraction. Observations of this kind have indicated an association between mastication and cognition. Experimental evidence show increased blood stream and neuronal activity in young individuals using chewing gum. Some experiments also indicate that memory and other cognitive functions improve during chewing. Observations of this kind have led to the concept that inferior mastication also may have an impact on the development of age related dementia. A series of epidemiological investigations confirm the association between loss of teeth and dementia, although the causation is uncertain. Some researchers propose that loss of masticatory stimulus may induce failures of neuronal activity. Others point to the fact that tooth loss is most often caused by a bacterial disease such as periodontitis, causing infectious agents and inflammatory host reactions to induce the microglia cells of brain tissue to reactions ending with neuronal death. At present, the inflammation hypothesis has the most credibility in neurological and psychological research. However, it is underlined that the association between oral disease and cognitive failure among older people does not necessarily indicate a causal relationship, because many circumstances related to dementia may cause poor oral health.
