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  | OCLC =  

  }}</ref> has provided further evidence in support of the interaction between masticatory processes, learning and memory, focusing on the function of the hippocampus that is essential for the formation of new memories.  

  }}</ref> has provided further evidence in support of the interaction between masticatory processes, learning and memory, focusing on the function of the hippocampus that is essential for the formation of new memories.  

An occlusal disharmony, such as loss of teeth and increases in the vertical occlusal dimension, causes bruxism or pain to the mastication muscles and temporomandibular disorders (TMDs). <ref>Christensen J., Effect of occlusion-raising procedures on the chewing system. Dent Pract Dent Rec. 1970 Mar;20(7):233-8. https://www.ncbi.nlm.nih.gov/pubmed/?term=Effect+of+occlusion-raising+procedures+on+the+chewing+system.</ref><ref name=":2">Ichihashi, Y., et al., ''Occlusal disharmony attenuates glucocorticoid negative feedback in aged SAMP8 mice.'' Neurosci Lett, 2007. 427(2): p. 71-6. https://www.ncbi.nlm.nih.gov/pubmed/?term=Occlusal+disharmony+attenuates+glucocorticoid+negative+feedback+in+aged+SAMP8+mice.+Neurosci+Lett%2C+2007.</ref>. Hence, to describe the impaired function of the hippocampus in a reduced situation or abnorme asticatory function. Tthe authors employed an animal model (mice) called ‘Molarless Senescence-Accelerated Prone’ (SAMP8) in order to make a parallelism on man. In mice, SAMP8, to which the occlusion was modified, increasing the occlusal vertical dimension of about 0.1 mm with dental materials showed that the occlusal disharmony disrupts learning and memory. These animals showed an age-dependent deficit in space learning in the mice at Morris’s water. <ref>Arakawa, Y., et al., ''Duration-dependent effects of the bite-raised condition on hippocampal function in SAMP8 mice.'' Okajimas Folia Anat Jpn, 2007. 84(3): p. 115-9. https://www.ncbi.nlm.nih.gov/pubmed/?term=Duration-dependent+effects+of+the+bite-raised+condition+on+hippocampal+function+in+SAMP8+mice.+Okajimas+Folia+Anat+Jpn%2C+2007</ref><ref name=":0">Kubo, K.Y., et al., ''Occlusal disharmony induces spatial memory impairment and hippocampal neuron degeneration via stress in SAMP8 mice.'' Neurosci Lett, 2007. 414(2): p. 188-91 https://www.ncbi.nlm.nih.gov/pubmed/?term=Occlusal+disharmony+induces+spatial+memory+impairment+and+hippocampal+neuron+degeneration+via+stress+in+SAMP8+mice.+Neurosci+Lett%2C+2007</ref>  

An occlusal disharmony, such as loss of teeth and increases in the vertical occlusal dimension, causes bruxism or pain to the mastication muscles and temporomandibular disorders (TMDs). <ref>{{Cite book

| autore = Christensen J

  | titolo = Effect of occlusion-raising procedures on the chewing system

| opera = Dent Pract Dent Rec

| anno = 1970

| oaf = <!-- qualsiasi valore -->

| OCLC =  

}}</ref><ref name=":2">{{Cite book

| autore = Ichihashi Y

| titolo =  Occlusal disharmony attenuates glucocorticoid negative feedback in aged SAMP8 mice

| opera =  Neurosci Lett

| anno = 2007

| DOI = 10.1016/j.neulet.2007.09.020

| OCLC =  

}}</ref>. Hence, to describe the impaired function of the hippocampus in a reduced situation or abnorme asticatory function. Tthe authors employed an animal model (mice) called ‘Molarless Senescence-Accelerated Prone’ (SAMP8) in order to make a parallelism on man. In mice, SAMP8, to which the occlusion was modified, increasing the occlusal vertical dimension of about 0.1 mm with dental materials showed that the occlusal disharmony disrupts learning and memory. These animals showed an age-dependent deficit in space learning in the mice at Morris’s water. <ref>Arakawa, Y., et al., ''Duration-dependent effects of the bite-raised condition on hippocampal function in SAMP8 mice.'' Okajimas Folia Anat Jpn, 2007. 84(3): p. 115-9. https://www.ncbi.nlm.nih.gov/pubmed/?term=Duration-dependent+effects+of+the+bite-raised+condition+on+hippocampal+function+in+SAMP8+mice.+Okajimas+Folia+Anat+Jpn%2C+2007</ref><ref name=":0">Kubo, K.Y., et al., ''Occlusal disharmony induces spatial memory impairment and hippocampal neuron degeneration via stress in SAMP8 mice.'' Neurosci Lett, 2007. 414(2): p. 188-91 https://www.ncbi.nlm.nih.gov/pubmed/?term=Occlusal+disharmony+induces+spatial+memory+impairment+and+hippocampal+neuron+degeneration+via+stress+in+SAMP8+mice.+Neurosci+Lett%2C+2007</ref>  

Increasing the vertical dimension of the bite in SAMP8 mice decreases the number of pyramidal cells<ref name=":0" /> and the numbers of their dendritic spines.<ref>Kubo, K.Y., et al., ''The bite-raised condition in aged SAMP8 mice induces dendritic spine changes in the hippocampal region.'' Neurosci Lett, 2008. 441(2): p. 141-4. https://www.ncbi.nlm.nih.gov/pubmed/?term=The+bite-raised+condition+in+aged+SAMP8+mice+induces+dendritic+spine+changes+in+the+hippocampal+region.+Neurosci+Lett%2C+2008.</ref> It also increases the hypertrophy and hyperplasia fibrillar protein acid in astrocytes in the regions of the CA1 and CA3 hippocampus. <ref>Ichihashi, Y., et al., ''The bite-raised condition in aged SAMP8 mice reduces the expression of glucocorticoid receptors in the dorsal and ventral hippocampus.'' Okajimas Folia Anat Jpn, 2008. 84(4): p. 137-42. https://www.ncbi.nlm.nih.gov/pubmed/?term=The+bite-raised+condition+in+aged+SAMP8+mice+reduces+the+expression+of+glucocorticoid+receptors+in+the+dorsal+and+ventral+hippocampus</ref>. In rodents and monkeys, occlusal disharmonies induced through an increase in the vertical dimension with acrylic increases on the incisors <ref name=":3">Areso, M.P., et al., ''Occlusal disharmonies modulate central catecholaminergic activity in the rat.'' J Dent Res, 1999. 78(6): p. 1204-13. https://www.ncbi.nlm.nih.gov/pubmed/?term=%2C+Occlusal+disharmonies+modulate+central+catecholaminergic+activity+in+the+rat.+J+Dent+Res%2C+1999</ref><ref>Yoshihara, T., Y. Matsumoto, and T. Ogura, ''Occlusal disharmony affects plasma corticosterone and hypothalamic noradrenaline release in rats.'' J Dent Res, 2001. 80(12): p. 2089-92. https://www.ncbi.nlm.nih.gov/pubmed/?term=Occlusal+disharmony+affects+plasma+corticosterone+and+hypothalamic+noradrenaline+release+in+rats.+J+Dent+Res%2C+2001</ref> or the insertion of bite-plane in the jaw are associated with increased urinary cortisol levels and elevated plasma levels of corticosterone, suggesting that occlusal disharmony is also a source of stress.

Increasing the vertical dimension of the bite in SAMP8 mice decreases the number of pyramidal cells<ref name=":0" /> and the numbers of their dendritic spines.<ref>Kubo, K.Y., et al., ''The bite-raised condition in aged SAMP8 mice induces dendritic spine changes in the hippocampal region.'' Neurosci Lett, 2008. 441(2): p. 141-4. https://www.ncbi.nlm.nih.gov/pubmed/?term=The+bite-raised+condition+in+aged+SAMP8+mice+induces+dendritic+spine+changes+in+the+hippocampal+region.+Neurosci+Lett%2C+2008.</ref> It also increases the hypertrophy and hyperplasia fibrillar protein acid in astrocytes in the regions of the CA1 and CA3 hippocampus. <ref>Ichihashi, Y., et al., ''The bite-raised condition in aged SAMP8 mice reduces the expression of glucocorticoid receptors in the dorsal and ventral hippocampus.'' Okajimas Folia Anat Jpn, 2008. 84(4): p. 137-42. https://www.ncbi.nlm.nih.gov/pubmed/?term=The+bite-raised+condition+in+aged+SAMP8+mice+reduces+the+expression+of+glucocorticoid+receptors+in+the+dorsal+and+ventral+hippocampus</ref>. In rodents and monkeys, occlusal disharmonies induced through an increase in the vertical dimension with acrylic increases on the incisors <ref name=":3">Areso, M.P., et al., ''Occlusal disharmonies modulate central catecholaminergic activity in the rat.'' J Dent Res, 1999. 78(6): p. 1204-13. https://www.ncbi.nlm.nih.gov/pubmed/?term=%2C+Occlusal+disharmonies+modulate+central+catecholaminergic+activity+in+the+rat.+J+Dent+Res%2C+1999</ref><ref>Yoshihara, T., Y. Matsumoto, and T. Ogura, ''Occlusal disharmony affects plasma corticosterone and hypothalamic noradrenaline release in rats.'' J Dent Res, 2001. 80(12): p. 2089-92. https://www.ncbi.nlm.nih.gov/pubmed/?term=Occlusal+disharmony+affects+plasma+corticosterone+and+hypothalamic+noradrenaline+release+in+rats.+J+Dent+Res%2C+2001</ref> or the insertion of bite-plane in the jaw are associated with increased urinary cortisol levels and elevated plasma levels of corticosterone, suggesting that occlusal disharmony is also a source of stress.