The present study aimed to clarify the relationship between the palatal mucosa properties and the pressure-pain threshold in both young dentulous and elderly edentulous subjects. The palatal mucosa in 17 elderly edentulous subjects (8 men,9 women；mean age：78.4 years) were measured at three points：the median point of the palate, the midpoint between the median point of the palate, and the lateral point of the first molar. Parameters of palatal mucosa were thickness (T [mm]) and modulus of elasticity (E [MPa]). Parameters of pressure-pain threshold were subsidence (S [mm]), pressure (P [MPa]), and compressibility [C [%]). A group of 17 young dentulous subjects was included as control. A Mann-Whitney U-test and a Spearmanʼs rank correlation coefficient were used to determine correlations between the thickness and the pressure-pain threshold at each measurement point. The greatest T and the smallest E, P, and C were found in elderly edentulous subjects. In elderly edentulous subjects, S at the median part and lateral part remained comparable. T was not significantly correlated with the parameters of pressure-pain threshold (S, P, or C) in the elderly edentulous. The palatal mucosa of elderly edentulous subjects is thick and has low elasticity, and is thus prone to deformation at small loads, which resulted in comparable amounts of subsidence between young dentulous and elderly edentulous subjects.

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We found that a reduction in masticatory stimulation due to raising mice on powder feed, leads to an early decline in learning and memory ability, which is a core symptom of dementia. Therefore, we used the senescence-accelerated mouse P8 to histopathologically investigate how the hippocampus is affected by a restoration of masticatory stimulation changing from powder to solid feed during the feeding period. The experimental groups comprised a group raised up to age 5 months and a group raised up to age 7 months. The mice were divided into four groups: a group raised solely on solid feed, a group that was changed from powder to solid feed at age 3 months, a group that was changed from powder to solid feed at age 5 months, and a group raised solely on powder feed. After raising mice on these types of feed, brain slices of each mouse were obtained and Nissl staining was performed. The pyramidal cell count and cell surface area were then determined. Results suggested a trend in which changing from powder to solid feed and a restoration of masticatory stimulation prevents a reduction in the hippocampal pyramidal cell count. We consider that the restoration of masticatory stimulation in the early stage is important in the prevention of dementia.

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[in Japanese]

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Articulation and swallowing are functions that are mutually associated. However, few studies have investigated the association between these two functions in the elderly. The aim of this study is to investigate the association between articulation and the risk of swallowing in rural community-dwelling elderly Japanese individuals. Two-hundred and sixty-six independent elderly living in the northern area of Miyazaki and the Shiribeshi area in Hokkaido, Japan were investigated to clarify the risk of swallowing using the questionnaire "Dysphagia Risk Assessment for the Community-dwelling Elderly (DRACE)" and oral diadochokinesis using the syllables /pa/, /ta/, /ka/, and /pataka/. The diadochokinetic rates for all four syllables were significantly associated with the DRACE score. In the stepwise multiple regression analysis controlled for confounding factors, oral diadochokinesis for the syllable /pataka/ was a determinant factor for swallowing risk. Our study indicated that oral diadochokinesis associated with the compound syllable /pataka/ might be significant in the evaluation of swallowing risk in rural community-dwelling Japanese elderly.

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