Oral health and healthy chewing for healthy cognitive ageing: A comprehensive narrative review

Abstract

Ageing involves physiological cognitive decline. The deterioration of processing speed and memory, language, visuospatial and executive functions, is normal as one ages. 1 However, the magnitude of this deterioration, the temporality and the rate at which it occurs throughout life differ. 1 Certain situations or modifiable external factors either protect against this deterioration or accelerate the underlying mechanisms. 2 In fact, about 10% of the levels of neurodegenerative biomarkers (such as amyloid beta) may decrease spontaneously. 3 Furthermore, some factors have been identified as modifiable and reversible causes of cognitive deterioration. 4 Besides normal ageing and the associated cognitive decline that does not affect daily normal activities, neurodegenerative diseases and dementia syndromes, such as Alzheimer's disease (AD), induce more aberrant forms of deterioration. 5 Dementia syndromes are among the most devastating of all mental illnesses related to cognitive decline and are the most significant age-related disorders. 6 The deterioration affects several functions including motivation, social behaviour and emotional control. 7 As a result, dementia syndromes

The impact of tooth loss on cognitive function

“…More interestingly, when analyzed independently by type of tooth missing, the only significant association between cognitive decline and tooth loss was observed when molars are absent. This could be channeled through the Locus Coeruleus that is activated, among others, by the periodontal fibers and proprioceptive jaw muscle spindles [18]. Even more, the activation of the most important and potent masticatory muscle related to the activity of the molar teeth, the masseter, could help release important neurotrophic factors, such as brain-derived neurotrophic factor (BDNF), through the release of cathepsin B and irisin [18].…”

“…This could be channeled through the Locus Coeruleus that is activated, among others, by the periodontal fibers and proprioceptive jaw muscle spindles [18]. Even more, the activation of the most important and potent masticatory muscle related to the activity of the molar teeth, the masseter, could help release important neurotrophic factors, such as brain-derived neurotrophic factor (BDNF), through the release of cathepsin B and irisin [18]. This effect might be similar as that of exercise [33].…”

“…The possible etiologic role of edentulism in the development of MCI and dementia has attracted the attention of researchers in recent years [15][16][17]. Possible mechanisms supporting this relationship, as reviewed elsewhere [18], include the following: (1) the inflammation/infection mechanism: Porphyromonas gingivalis, a well-known periodontopathogen, may induce the local release of proinflammatory cytokines [19] and subsequently increase both the peripheral circulation [20] and brain accumulation of amyloid-β [21]; (2) the masticatory mechanism: preclinical and clinical studies have demonstrated the negative effect of impaired masticatory function on the incidence of cognitive performance [22]; (3) the diet and nutrition mechanism: this is strongly related to the masticatory one, since tooth loss may influence dietary patterns, which can have a deleterious effect on intraoral food preprocessing before deglutition, leading to a reduction in the intake of nutritional components that have a neuroprotective effect and also promote obesity [23].…”

Evaluation of the Relationship Between Oral Health, Chewing Ability, and Degree of Disease in Alzheimer-Type Dementia Patients

“…The chewing ability of the participants was assessed using two-colored gum. The chewing scores were ranked according to mixing rates of the gum specimens according to Schimmel et al's study (15) (Figure 1). The chewing scores of the healthy and AD groups were comparatively evaluated, and the scores of the AD group showed significantly lower values than the scores of the healthy group (p<0.001; Table 4).…”

The Sedentary Lifestyle and Masticatory Dysfunction: Time to Review the Contribution to Age-Associated Cognitive Decline and Astrocyte Morphotypes in the Dentate Gyrus

“…Oral and cognitive health are interconnected [ 100 ] and the recovery of masticatory activity can prevent cognitive decline [ 101 , 102 , 103 ]. The use of dental human prostheses successfully reduces cognitive consequences of masticatory dysfunction [ 104 ].…”