Relationship between texture perception and oral function: A preliminary study in young, healthy adults.

BACKGROUND: Oral frailty, characterised by reduced oral function, is associated with systemic health issues in older adults. Although the criteria for diminished oral function often focus on motor and secretory abilities, texture perception also plays a crucial role in health due to its impact on food intake and palatability. OBJECTIVE: This study aimed to explore the relationship between thickness discrimination ability (TDA) and oral motor and secretory functions in healthy young individuals. METHODS: Twenty-eight adults were assessed for texture perception using eight concentrations of aqueous xanthan gum solutions to determine TDA scores. Measurements of occlusal force, masticatory performance, tongue pressure, stimulated salivary flow rate and tongue-lip motor function were conducted. Spearman's correlation analysis was used to evaluate the relationship between TDA scores and oral functions. Participants were divided into high-sensitivity and low-sensitivity groups based on their TDA scores to compare oral function test results. RESULTS: The TDA scores varied among the participants, with higher scores correlating with higher masticatory performance (r = 0.41, p < .05). Masticatory performance in the high-sensitivity group was significantly higher than in the low-sensitivity group (211.9 ± 59.2 mg/dL vs. 157.9 ± 43.0 mg/dL, p = .013), with no significant differences in other oral functions. CONCLUSION: Masticatory performance was correlated with TDA, suggesting a link between the selection function of mastication and thickness discrimination. These findings highlight the potential relevance of texture perception in oral function and indicate the need for further exploration, particularly in older adults with declining oral health.

Number of teeth and functional disability in community-dwelling older adults.

INTRODUCTION: This study determined whether tooth loss was associated with the development of functional disability and estimated the population attributable fraction (PAF) of functional disability due to tooth loss, along with risk factors for functional disability such as physical function and cognitive impairment. METHODS: The participants were 838 community-dwelling older adults aged ≥70 years living in the Tsurugaya district in Japan in 2003. The exposure variable was the number of remaining teeth (counted by trained dentists). Other variables were age, sex, depressive symptoms, cognitive impairment, educational attainment, physical function and social support. The Cox proportional hazards model was applied to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of the incidence of functional disability for each risk factor, such as tooth loss. The functional disability PAF due to tooth loss was estimated, and risk factors for functional disability were identified. RESULTS: In total, 619 (73.9%) participants developed functional disability during follow-up. A multivariable model showed that those with <20 teeth (HR, 1.28; 95% CI, 1.08-1.53) were more likely to develop functional disability than those with 20 teeth or more. PAF estimation for functional disability was shown to have decreasing values in the following order: age, female sex, tooth loss and reduced physical function. CONCLUSIONS: Tooth loss was associated with the development of functional disability in community-dwelling older Japanese adults. While retaining teeth may be a potential strategy for avoiding functional disability, clinical studies on the effect of dental treatment on preventing functional disability are warranted.

Expression of matrix metalloproteinase-3 and -10 is up-regulated in the periodontal tissues of aged mice.

OBJECTIVE: The present study was designed to investigate the whole transcriptome of periodontal tissues of both young and aged mice to identify the characteristic up-regulation of protease genes with aging and to localize their translated protein products in the periodontal tissues. BACKGROUND: The metzincin protease superfamily is composed of matrix metalloproteinases (MMPs), a disintegrin and metalloproteinases, and a disintegrin and metalloproteinases with thrombospondin motifs. Up-regulation of these extracellular matrix-degrading proteases has been implicated in senescence of tissues and organs, including the skin. However, few studies have investigated the expression profiles of these proteases and potential involvement in aging of periodontal tissues. METHODS: Periodontal tissues with the surrounding mandibular bones were collected from 50- and 10-week-old mice. Total RNA was extracted from the periodontal tissue and analyzed by cap analysis of gene expression (CAGE) to identify differentially expressed genes encoding the metzincin proteases. Furthermore, quantitative real-time polymerase chain reaction (qRT-PCR) was performed to validate the CAGE results, and the phenotypic expression of proteases involved in aging was localized via immunohistochemical analysis. RESULTS: The CAGE results showed that the expression levels of MMP-3, -10, and -12 were up-regulated at 50 weeks. Subsequent qRT-PCR analysis showed that the gene expression levels of MMP-3 and -10 were significantly increased with age. MMP-10 immunoreactivity was localized exclusively in the cementum and alveolar bone adjacent to the periodontal ligament and was stronger and broader in aged mice than young mice. MMP-3 immunoreactivity was localized in the periodontal ligaments at both 10 and 50 weeks. CONCLUSION: In the present study, we demonstrated that the expression of MMP-3 and -10 increased with aging and identified their characteristic localizations in aged periodontal tissues.

Regular dental visits, periodontitis, tooth loss, and atherosclerosis: The Ohasama study.

OBJECTIVE: We aimed to explore the association between regular dental visits and atherosclerosis and between periodontitis, number of remaining teeth, and atherosclerosis among community dwellers in Japan. BACKGROUND: Few studies have examined the association between regular dental visits, periodontitis, tooth loss, and atherosclerosis in community dwellers in Japan. METHODS: The participants of this cross-sectional study included community dwellers aged ≥55 years and residing in Ohasama. Exposure variables were regular dental visits; periodontitis, defined as radiographic alveolar bone loss (BL); the Centers for Disease Control/American Academy of Periodontology (CDC/AAP) classification; and number of remaining teeth. The primary outcome was atherosclerosis, defined as maximum carotid intima-media thickness ≥1.1 mm or confirmation of atheromatous plaque. RESULTS: Of 602 participants, 117 had atherosclerosis. In the multivariate model, compared to those with regular dental visits, the odds ratio (OR) (95% confidence intervals [CIs]) of atherosclerosis among those with the absence of regular dental visits was 2.16 (1.03-4.49). Regarding BL-max, compared with those in the first quartile, ORs (95% CIs) of those in the second, third, and fourth quartiles were 1.15 (0.65-2.30), 0.65 (0.32-1.35), and 1.57 (0.81-3.01), respectively. Regarding CDC/AAP classification, compared to those with no or mild periodontitis, ORs (95% CIs) for those with moderate and severe periodontitis were 2.48 (0.61-10.1) and 4.26 (1.01-17.5), respectively. Regarding the number of remaining teeth, compared to those with ≥20 teeth, ORs (95%CIs) for those with 10-19 and 1-9 teeth were 1.77 (1.004-3.12) and 0.96 (0.52-1.80), respectively. CONCLUSION: The absence of regular dental visits and presence of periodontitis are associated with atherosclerosis among community dwellers in Japan.

Oral health-related quality of life is associated with the prevalence and development of depressive symptoms in older Japanese individuals: The Ohasama Study.

OBJECTIVE: This prospective study investigated the cross-sectional association between impaired oral health-related quality of life (OHRQoL) and the prevalence of depressive symptoms, and the longitudinal association between impaired OHRQoL and development of depressive symptoms among older adults. BACKGROUND: Previous studies have shown a relationship between poor oral health and depression among older adults; however, findings are inconsistent. MATERIALS AND METHODS: Participants were 669 community-dwelling older Japanese individuals aged≥55 years (mean: 67.8 ± 7.2 years). Data of 296 participants were used for longitudinal analyses. OHRQoL was evaluated using the Oral Impacts on Daily Performances scale. Impaired OHRQoL was defined as the presence of at least one impact on the scale. Depressive symptoms were assessed using the Japanese version of the Zung self-rating depression scale with a cut-off score of 40. RESULTS: The cross-sectional logistic regression model demonstrated that impaired OHRQoL was significantly associated with depressive symptoms (odds ratio [OR], 5.17; 95% confidence interval [CI], 2.99-8.95) independent of age, sex, body mass index, hypertension, cerebrovascular/cardiovascular disease, smoking, drinking alcohol, education, cognitive function, objective oral health (dentition status) and oral health behaviour (dental visit within 1 year). Similarly, impaired OHRQoL predicted the development of depressive symptoms within 4 years in a fully adjusted longitudinal model (OR, 6.00; 95% CI, 1.38-26.09). CONCLUSION: Impaired OHRQoL was identified as a potential comorbidity of depressive symptoms and a predictor for depressive disorder later in life. OHRQoL may be a useful clinical outcome for elder patients with regard to their mental and oral health.

Dental Status is Associated With Incident Functional Disability in Community-Dwelling Older Japanese: A Prospective Cohort Study Using Propensity Score Matching.

BACKGROUND: A growing number of epidemiology studies have shown that poor oral health is associated with an increased incidence of functional disability. However, there are few studies in which the confounding bias is adjusted appropriately. In this study, we examined whether dental status is associated with functional disability in elderly Japanese using a 13-year prospective cohort study after elimination of confounding factors with propensity score matching. METHODS: Participants were community-dwelling Japanese aged 70 years or older who lived in the Tsurugaya district of Sendai (n = 838). The number of remaining teeth (over 20 teeth vs 0-19 teeth) was defined as the exposure variable. The outcome was the incidence of functional disability, defined as the first certification of long-term care insurance (LTCI) in Japan. The variables that were used to determine propensity score matching were age, sex, body mass index (BMI), medical history (stroke, hypertension, myocardial infarction, cancer, and diabetes), smoking, alcohol consumption, educational attainment, depression symptoms, cognitive impairment, physical function, social support, and marital status. RESULTS: As a result of the propensity score matching, 574 participants were selected. Participants with 0-19 teeth were more likely to develop functional disability than those with 20 or more teeth (hazard ratio 1.33; 95% confidence interval, 1.01-1.75). CONCLUSIONS: In this prospective cohort study targeting community-dwelling older adults in Japan, having less than 20 teeth was confirmed to be an independent risk factor for functional disability even after conducting propensity score matching. This study supports previous publications showing that oral health is associated with functional disability.

The Association between Number of Remaining Teeth and Maintenance of Successful Aging in Japanese Older People: A 9-Year Longitudinal Study.

With population aging, an increasing attention has been paid to quality of life rather than mere longevity. Now, it is urgently needed to clarify predictors of well-being in later life, i.e., "successful aging (SA)." The aim of this study is to investigate whether the number of remaining teeth impacts on maintenance of SA among Japanese older people. The present study was conducted in Tsurugaya district, a suburban area of Sendai, in northern Japan, and included older people aged ≥ 70 years who had met the criteria for SA at a 2003 baseline survey. At the baseline survey, dentists obtained data for the number of remaining teeth. We obtained information about Long-term Care Insurance certification, including the dates of incident functional disability and death between 2003 and 2012. Data pertaining to health-related quality of life (HRQOL) were collected at the 2003 baseline survey and the 2012 follow-up survey. Maintenance of SA was defined in terms of survival, disability-free status and high HRQOL in both 2003 and 2012. Among 450 participants, 108 (24.0%) were considered to have maintained a state of SA. When participants were classified into three groups according to previous studies, in comparison with participants who retained 0-9 teeth, the multivariate prevalence ratios (95% confidence intervals) were 1.39 (0.81-2.36) for those who retained 10-19 teeth and 1.58 (1.002-2.50) for those who retained ≥ 20 teeth (p trend = 0.046). The present results suggest that retaining ≥ 20 teeth is associated with maintenance of SA among Japanese older people.

Contribution of systemic inflammation and nutritional status to the relationship between tooth loss and mortality in a community-dwelling older Japanese population: a mediation analysis of data from the Tsurugaya project.

OBJECTIVES: To assess whether systemic inflammation and nutritional status contribute to a relationship between tooth loss and mortality in community-dwelling older Japanese individuals using mediation analyses. MATERIALS AND METHODS: This longitudinal study targeted community-dwelling older Japanese individuals (N = 891). The exposure variable was the number of teeth (edentulous, 1-9, 10-19, ≥ 20), while the outcome was all-cause mortality from 2003 to 2016. Nutritional status and systemic inflammation were evaluated as mediators and based on serum albumin and high-sensitivity C-reactive protein levels, respectively. Covariates included age, sex, smoking, alcohol consumption, medical history, educational level, depressive symptoms, cognitive impairment, and physical function. The Cox proportional hazards model was applied to calculate hazard ratios (HRs) for the association between tooth loss and mortality and the contributions of systemic inflammation and nutritional status to this association. RESULTS: Edentulous participants (HR, 1.84; 95 % confidence interval [CI], 1.30-2.59) and those with 1-9 teeth (HR, 1.75; 95% CI, 1.28-2.40) groups exhibited a significantly higher risk of mortality than did those with ≥ 20 teeth. Mediation analyses showed that nutritional status contributed to the association between tooth loss and mortality in participants with 1-9 teeth, whereas systemic inflammation played no role in this association. CONCLUSIONS: Nutritional status may contribute to the association between tooth loss and mortality in community-dwelling older Japanese individuals with fewer remaining teeth. CLINICAL RELEVANCE: The data from this prospective cohort study help in elucidating parts of the biological mechanism underlying tooth loss and all-cause mortality in older individuals.

Verification of the criteria for reduced occlusal force to diagnose oral hypofunction in older Japanese people: A prospective cohort study on incident functional disability.

In 2016, the Japanese Society of Gerodontology (JSG) proposed the concept of "oral hypofunction (OHF)," and recommended two initial criteria for reduced occlusal force (ROF): <200 N of maximum occlusal force (MOF) and < 20 remaining teeth. However, the JSG stated that these criteria need to be reviewed by accumulating further evidence. To examine the validity and equivalence of the two criteria for ROF in the diagnostic criteria for OHF by using the incidence of functional disability as the outcome. This study enrolled 815 community-dwelling Japanese individuals ≥ 70 years. They underwent examinations for physical, mental and social functions; MOF; and number of teeth at baseline. The incidence of functional disability (a condition that requires at least partial assistance with daily activities) based on the first certification of long-term care insurance was followed up. The Cox proportional hazard model revealed that MOF < 200 N (hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.04-1.72) and < 20 teeth (HR, 1.40; 95% CI, 1.07-1.84) were significantly associated with increased risk of functional disability. Receiver operating characteristic curve analyses revealed that the optimal cut-off values of MOF and number of teeth that best predicted incident functional disability were 264.6 N and 19 teeth, respectively. Twelve teeth were the optimal threshold that best predicted < 200 N of MOF. The two criteria for ROF in the diagnostic criteria for OHF had some degree of validity. However, further studies are needed to develop appropriate and reliable criteria for a decision of ROF.

Association between tooth loss and cognitive impairment in community-dwelling older Japanese adults: a 4-year prospective cohort study from the Ohasama study.

BACKGROUND: Numerous prospective studies have investigated the association between the number of remaining teeth and dementia or cognitive decline. However, no agreement has emerged on the association between tooth loss and cognitive impairment, possibly due to past studies differing in target groups and methodologies. We aimed to investigate the association between tooth loss, as evaluated through clinical oral examinations, and the development of cognitive impairment in community-dwelling older adults while considering baseline cognitive function. METHODS: This 4-year prospective cohort study followed 140 older adults (69.3% female) without cognitive impairment aged ≥65 years (mean age: 70.9 ± 4.3 years) living in the town of Ohasama, Iwate Prefecture, Japan. Cognitive function was evaluated with the Mini-Mental State Examination (MMSE) in baseline and follow-up surveys. Based on a baseline oral examination, the participants were divided into those with 0-9 teeth and those with ≥10 teeth. To investigate the association between tooth loss and cognitive impairment, we applied a multiple logistic regression analysis adjusted for age, sex, hypertension, diabetes, cerebrovascular/cardiovascular disease, hypercholesterolemia, depressive symptoms, body mass index, smoking status, drinking status, duration of education, and baseline MMSE score. RESULTS: In the 4 years after the baseline survey, 27 participants (19.3%) developed cognitive impairment (i.e., MMSE scores of ≤24). Multiple logistic regression analysis indicated that participants with 0-9 teeth were more likely to develop cognitive impairment than those with ≥10 teeth were (odds ratio: 3.31; 95% confidence interval: 1.07-10.2). Age, male gender, and baseline MMSE scores were also significantly associated with cognitive impairment. CONCLUSIONS: Tooth loss was independently associated with the development of cognitive impairment within 4 years among community-dwelling older adults. This finding corroborates the hypothesis that tooth loss may be a predictor or risk factor for cognitive decline.

Contribution of each masticatory muscle to the bite force determined by MRI using a novel metal-free bite force gauge and an index of total muscle activity.

PURPOSE: To develop a metal-free bite force gauge that can monitor the bite force in a strong magnetic field and to analyze the correlations between bite-force and total T2 shift of the mastication muscles. MATERIALS AND METHODS: The gauge used a micro-pressure sensor made of optical fiber. Ten subjects performed a 60-s isometric bite task at 40% of maximum clenching in various occlusal support conditions (intact dentition, right molar loss, or left molar loss). Spin-echo images were taken with a 1.5 Tesla scanner before and immediately after the task to correlate the bite force with the mean voxel count, mean shift in transverse relaxation time (ΔT2), and total T2 shift of each masticatory muscle. RESULTS: Measurements of total T2 shift identified significant correlations between the bite force and activities of the superficial layer of the bilateral masseter muscle, regardless of the occlusion condition (intact dentition: left, P = 0.007 and right, P < 0.001; right molar loss: left, P = 0.02 and right, P = 0.021; and left molar loss: left, P = 0.022 and right, P = 0.049). In contrast, significant correlations were not detected between the bite force and mean ΔT2 (intact dentition: left, P = 0.102 and right, P = 0.053; right molar loss: left, P = 0.393 and right, P = 0.868; and left molar loss: left, P = 0.531 and right, P = 0.92). CONCLUSION: Measurement of total T2 shift using a metal-free bite force gauge is a more sensitive index of individual muscle activity than mean ΔT2 during a bite task. J. MAGN. RESON. IMAGING 2016;44:804-813.

Relationship between tooth loss and progression of frailty: Findings from the English longitudinal study of aging.

OBJECTIVE: The objective of the present study was to investigate the relationship between indicators of oral health status (number of teeth; denture use) and the progression of frailty amongst adults in England. METHODS: The subjects were participants of the English Longitudinal Study of Aging [ELSA] aged 50 years and older. We used panel data from three waves of the study (Waves 7-9). Indicators of oral health comprised the number of teeth (≥20; 10-19; 1-9; 0) and combination of removable denture usage and the number of teeth. Frailty was assessed by the 32-item Frailty Index (FI). Covariates were age, sex, education, marital status, smoking, alcohol, and physical activity. The longitudinal relationship between oral health indicators and change in FI were investigated using linear mixed-effect models considering frailty as a time-varying variable. RESULTS: Among the 7,557 participants, compared to those people with 20 or more teeth, change in frailty over time was significantly higher among those with less than 20 teeth: 10-19 teeth (ß: 0.249, 95 %CI: 0.116 to 0.382), and 1-9 teeth (ß: 0.238, 95 %CI: 0.053 to 0.423) and being edentate (ß: 0.286, 95 %CI: 0.106 to 0.465) when adjusting for co-variates. The rise in frailty over time was significantly higher among those with fewer teeth (<20 teeth), including those using dentures. CONCLUSIONS AND IMPLICATIONS: This longitudinal analysis suggests that tooth loss is associated with accelerated progression of frailty and utilizing dentures did not reduce the trend in frailty. Thus, maintaining a functional natural dentition is important in healthy ageing.

Association between oral health and nutritional status among older patients requiring long-term care who received home-visit dental care.

PURPOSE: This study examined the association between oral health and nutritional status among older patients receiving home-visit dental care. METHODS: This study enrolled 110 older patients (age ≥65 years) requiring long-term care who received home-visit dental care. The oral health indicators evaluated included number of teeth, occlusal support, number of functional teeth, tongue pressure, tongue coating index (TCI), and rinsing ability. Nutritional indicators included skeletal muscle mass index (SMI) and the mini-nutritional assessment short-form (MNA-SF). A multivariate modified Poisson regression analysis (adjusted for age, sex, medical history, care level, and housing type) was used to calculate prevalence ratios and 95% confidence intervals (CIs). RESULTS: The prevalence ratio for low SMI was not significantly higher for patients with ≥20 teeth than for those with 1-19 or no teeth. Number of teeth was not significantly associated with MNA-SF score. A high TCI score (2.15, 95% CI: 1.07-4.32) and poor rinsing ability (2.32, 95% CI: 1.25-4.30) were significantly associated with low SMI. High TCI scores were associated with low scores in MNA-SF categories (1.25, 95% CI: 1.01-1.55). CONCLUSION: TCI and rinsing ability, rather than number of teeth, were associated with nutritional status in older patients requiring long-term care.

Actual state of the diurnal masseteric electromyogram: Differences between awareness and non-awareness of awake bruxism.

PURPOSE: This study aimed to elucidate the relationship between diurnal masseter muscle activity and awareness of diurnal awake bruxism (d-AB) by conducting a comparative analysis of electromyographic (EMG) data from individuals with and without awareness of diurnal awake bruxism (d-AB), utilizing EMG data gathered from multiple subjects. METHODS: Unilateral masseter electromyography (EMG) recordings were performed during the daytime using an ultraminiature wearable EMG device. A total of 119 participants (59 with awareness of diurnal tooth clenching [d-TC] and 60 without awareness of d-TC) were included. Waveforms longer than 0.25 s with the two amplitude conditions, exceeding twice the baseline and >5% of maximum voluntary clenching, were extracted. In addition, the number of bursts and episodes (groups of bursts), burst duration, and burst peak amplitude were calculated for each participant. RESULTS: There were no significant differences in the EMG parameters between the groups with and without awareness of d-TC. Additionally, the frequency distribution of the number of EMG waveforms exhibited wide ranges and substantial overlap between the two groups. CONCLUSIONS: The variability in the number of bursts and episodes, burst peak amplitude, and burst duration among subjects suggests the need for an objective classification of d-AB severity based on EMG values. The absence of significant differences and large overlap in frequency distributions between the groups with and without awareness of d-TC indicate difficulty in predicting muscle activity solely based on awareness of d-AB.

Associations of Dental Health With the Progression of Hippocampal Atrophy in Community-Dwelling Individuals: The Ohasama Study.

BACKGROUND AND OBJECTIVES: Although tooth loss and periodontitis have been considered risk factors of Alzheimer disease, recent longitudinal researches have not found a significant association with hippocampal atrophy. Therefore, this study aimed to clarify a longitudinal association between the number of teeth present (NTP) and hippocampal atrophy dependent on the severity of periodontitis in a late middle-aged and older adult population. METHODS: This study included community-dwelling individuals aged 55 years or older who had no cognitive decline and had undergone brain MRI and oral and systemic data collection twice at 4-year intervals. Hippocampal volumes were obtained from MRIs by automated region-of-interest analysis. The mean periodontal probing depth (PD) was used as a measure of periodontitis. Multiple regression analysis was performed with the annual symmetric percentage change (SPC) of the hippocampal volume as the dependent variable and including an interaction term between NTP and mean PD as the independent variable. The interaction details were examined using the Johnson-Neyman technique and simple slope analysis. The 3-way interaction of NTP, mean PD, and time on hippocampal volume was analyzed using a linear mixed-effects model, and the interaction of NTP and time was examined in subgroups divided by the median mean PD. In all models, dropout bias was adjusted by inverse probability weighting. RESULTS: Data of 172 participants were analyzed. The qualitative interaction between NTP and the mean PD was significant for the annual SPC in the left hippocampus. The regression coefficient of the NTP on the annual SPC in the left hippocampus was positive (B = 0.038, p = 0.026) at the low-level mean PD (mean -1 SD) and negative (B = -0.054, p = 0.001) at the high-level mean PD (mean +1 SD). Similar results were obtained in the linear mixed-effects model; the interaction of NTP and time was significant in the higher mean PD group. DISCUSSION: In a late middle-aged and older cohort, fewer teeth were associated with a faster rate of left hippocampal atrophy in patients with mild periodontitis, whereas having more teeth was associated with a faster rate of atrophy in those with severe periodontitis. The importance of keeping teeth healthy is suggested.

Relationship between maximum occlusal force and gastrointestinal cancer in community-dwelling older Japanese adults.

Globally, the cancer burden is expected to increase as populations are ageing. Therefore, cancer prevention among older age groups is important. This prospective cohort study examined the relationship between the number of remaining teeth, maximum occlusal force, and incidence of gastrointestinal cancer in community-dwelling older Japanese individuals using data from the Tsurugaya project; 847 participants were included. The exposure variables were the number of remaining teeth and the maximum occlusal force, with the outcome being the incidence of gastrointestinal cancer. Covariates were age, sex, medical history, smoking, alcohol consumption, educational attainment, and physical function. The Cox proportional hazard model was used to examine the relationship between the number of remaining teeth, maximum occlusal force, and incidence of gastrointestinal cancer. With a median follow-up of 7.6 years, 63 participants were confirmed to have gastrointestinal cancer. The risk of gastrointestinal cancer was significantly higher in those with an occlusal force lower than the median (hazard ratio, 2.80; 95% confidence interval, 1.54-5.10). No significant risk difference was found according to the number of remaining teeth. Low maximum occlusal force was associated with the incidence of gastrointestinal cancer in community-dwelling older Japanese adults.

Statistical parametric mapping of three-dimensional local activity distribution of skeletal muscle using magnetic resonance imaging (MRI).

Analysis of the internal local activity distribution in human skeletal muscles is important for managing muscle fatigue/pain and dysfunction. However, no method is established for three-dimensional (3D) statistical analysis of features of activity regions common to multiple subjects during voluntary motor tasks. We investigated the characteristics of muscle activity distribution from the data of ten healthy subjects (29 ± 1 year old, 2 women) during voluntary teeth clenching under two different occlusal conditions by applying spatial normalization and statistical parametric mapping (SPM) to analysis of muscle functional magnetic resonance imaging (mfMRI) using increase in transverse relaxation time (T2) of the skeletal muscle induced by exercise. The expansion of areas with significant T2 increase was observed in the masticatory muscles after clenching with molar loss comparing with intact dentition. The muscle activity distribution characteristics common to a group of subjects, i.e., the active region in the temporal muscle ipsilateral to the side with the molar loss and medial pterygoid muscle contralateral to the side with the molar loss, were clarified in 3D by applying spatial normalization and SPM to mfMRI analysis. This method might elucidate the functional distribution within the muscles and the localized muscular activity related to skeletal muscle disorders.

Relationship Between Oral Health and Fractures in Community-Dwelling Older Japanese Adults.

OBJECTIVE: To investigate the relationship between poor oral health and the incidence of fall-related fractures in older Japanese individuals. DESIGN: A 9-year prospective cohort study. SETTING AND PARTICIPANTS: Participants comprised 937 community-dwelling older Japanese adults aged 70 years or older. They all lived in the Tsurugaya district, a suburban area of Sendai city, and underwent comprehensive geriatric assessment, including an oral examination, in a public facility. MEASUREMENTS: The exposure variables were related to oral health status (posterior occlusal support, number of remaining teeth, and occlusal force). The outcome measure was the incidence of fall-related fractures, which was determined by National Health Insurance data. Analyzed covariates included age, sex, medical history, smoking, alcohol drinking, educational level, depressive symptoms, cognitive impairment, physical function, body mass index, and history of falls. Statistical relationships were examined by calculating hazard ratios (HRs) at 95% confidence intervals (CIs) using the Cox proportional hazard model. RESULTS: In the multivariate analysis, the HRs of fall-related fractures were significantly higher in those with unilateral posterior occlusal support (HR, 2.72; 95% CI, 1.13-6.55) and no posterior occlusal support (HR, 2.58; 95% CI, 1.29-5.15) than in those with bilateral posterior occlusal support. The HRs (95% CIs) of fall-related fractures in individuals with 10-19 and 1-9 teeth and edentulous individuals were 1.77 (0.81-3.89), 2.67 (1.24-5.75), and 2.31 (1.01-5.28), respectively, compared to those with ≥20 teeth. CONCLUSIONS AND IMPLICATIONS: Poor oral health status is a risk factor for the incidence of fall-related fractures in community-dwelling older Japanese individuals. The findings suggest that attention should be focused on oral health status to further understand the risk of fall-related fractures among community-dwelling older adults.

Caregiver-reported dementia as a predictor of oral health among patients receiving home-visit dental treatment: A retrospective cohort study.

OBJECTIVE: To assess caregiver-reported dementia as a risk factor for retained roots, an indicator of poor oral hygiene, among patients receiving home-visit dental treatment in Japan. METHODS: The medical records of 231 dentate patients who received home-visit dental treatment (covered by public medical insurance) for more than 2 years were retrospectively analyzed. The number of teeth and retained roots at the initial and final examinations were obtained from the dental charts, and the "change in the number of retained roots from initial to final examination" was determined. The presence or absence of caregiver-reported dementia, diabetes, and osteoporosis, as well as the level of long-term care needed, were used as indicators of general health condition at the initial interview. Multiple regression analyses were conducted in five models that tested the association of independent variables (age, gender, observation period, general health, presence or absence of caregiver-reported dementia at the initial interview) with changes in the number of retained roots. RESULTS: In all models, the presence of caregiver-reported dementia at the initial interview was significantly associated with the change in the number of retained roots (p < .05). The adjusted coefficient of determination (R2 ) of model 5, which included all the predetermined independent factors, was .168. CONCLUSIONS: Caregiver-reported dementia may be a risk factor for an increase in the number of retained roots among patients who receive home-visit dental treatment and may serve as an indicator of the need for regular and proactive oral hygiene management.

Masticatory motion is controlled in humans by a limited set of muscle synergies.

The masticatory motion, whereby food introduced into the mouth is processed into a bolus suitable for swallowing, can be divided into successive masticatory cycles, each comprising downward and subsequent upward movements of the mandible. The present study deals with the problem of the existence of muscle synergies in mastication, that is whether some of the muscles involved in mastication receive common motor drives, rather than controlled individually. Evidence for muscle synergy during mastication is scarce, partly due to the difficulties in simultaneous recording of the electromyographic (EMG) activities from all the muscles involved. Thus, we analyzed the variability of the mandibular motion during mastication rather than to examine the EMG patterns, based on the hypothesis that a motion elicited by a limited set of muscle synergies can be approximated as a superposition of the same number of independent motions. Mandibular motion paths were recorded from 8 healthy males (25-31 years), who chewed gum or gummy candy. A morphometric technique, which describes the shape of a closed curve by using normalized elliptic Fourier descriptors and reduces the variance of the shape by using principal component analysis, was applied to analyze the variability of the mandibular motion paths. We found three independent variations of the motion paths, whose linear combinations accounted for an average of 93% (range, 88-96%) of the total variance. The extracted variations were similar among the subjects. These findings provide indirect evidence for the existence of a limited set of muscle synergies for mastication in humans.