Chewing Ability and Tooth Loss: Association with Cognitive Impairment in an Elderly Population Study

Chewing ability and its associated factors among community-dwelling older adults in Chengdu, China: A cross-sectional study

AIM

To investigate the current status of chewing ability and analyze the risk factors among Chinese community-dwelling older adults.

METHODS

In this cross-sectional study, color-changeable gum and a color difference meter were used to assess chewing ability in the population. The statistical analysis employed multivariate logistic regression models to identify and quantify the factors influencing chewing ability.

RESULTS

A total of 373 community-dwelling adults aged 65 and older in Chengdu, in the west of China, were included in this study; 64 individuals (17.2%) exhibited signs of poor chewing ability. Female (odds ratio [OR]: 0.124, 95% CI: 0.057-0.268, p < .001), education level with college degree and above (OR: 0.114, 95% CI: 0.030-0.434, p = .001), number of teeth less than 20 (OR: 5.401, 95% CI: 2.509-11.626, p < .001), and decreased oral diadochokinesis (OR: 4.445, 95% CI: 1.775-11.132, p = .001) were significant factors in chewing ability in this study, after adjustment for potential variables.

CONCLUSIONS

The prevalence of decreased chewing ability among Chinese community-dwelling older adults was 17.2% and decreased chewing ability was associated with men, lower education level, less than 20 teeth and decreased oral diadochokinesis.

Masticatory Function, Sex, and Risk of Dementia Among Older Adults: A Population-Based Cohort Study

BACKGROUND

A decline in masticatory function may indicate brain dysfunction related to dementia, but the relationship between masticatory function and dementia risk remains unclear. This study aimed to investigate whether masticatory function is associated with the risk of cognitive decline and dementia.

METHODS

Data were obtained from the nationwide prospective cohort study of randomly sampled community-dwelling Koreans aged ≥ 60 years. The 5,064 non-demented participants, whose number of chewing cycles per bite was assessed by clinical interview, were followed for 8 years with biennial assessments of cognitive performance and clinical diagnoses of all-cause dementia and Alzheimer's disease (AD). Structural brain magnetic resonance imaging was collected from a subset of cohort participants and their spouses for imaging analyses.

RESULTS

Males who chewed ≥ 30 cycles/bite had faster decline in global cognition and memory function and were at higher risk for incident all-cause dementia (hazard ratio [HR], 2.91; 95% confidence interval [CI], 1.18-7.18) and AD (HR, 3.22; 95% CI, 1.14-9.11) compared to males with less than 10 cycles/bite. Additionally, increased chewing cycles in males were associated with reduced brain volume, particularly in regions involved in compensatory cognitive control of mastication. There was no significant association between chewing cycles and the risk of dementia or brain volume in females.

CONCLUSION

Older men who frequently chew their meals could be considered a notable population at risk for dementia who should be carefully assessed for their cognitive trajectories.

Association between oral health and cognitive impairment in older adults: Insights from a Six-year prospective cohort study

OBJECTIVE

This study aims to investigate the relationships between four baseline oral conditions (periodontal status, dental caries, tooth wear, and dentition) and repeated global cognition or domain-specific cognition (memory, executive function, attention, and verbal fluency) in non-demented older adults over time.

METHODS

This prospective cohort study (2011-2019) enrolled 516 non-demented community-dwelling older adults (age ≥ 65) to explore the association between oral health and cognitive function. Global and domain-specific cognition were assessed biennially (four repeats) using a battery of neuropsychological tests. The baseline oral health conditions were examined, including periodontal status, dental caries, tooth wear, and dentition. The association of these oral conditions with cognition was evaluated by generalized linear mixed models. Stratified analyses were performed by important covariates.

RESULTS

Over time, dental caries was associated with poor memory in two different logical memory tests (β^= -0.06 and β^= -0.04). Incomplete dentition with less than 28 teeth was associated with poor performance in attention (β^= -0.05) and verbal fluency (β^= -0.03). These associations became more evident in those with an elevated inflammatory marker (IL-6, β^= -0.11 to -0.08). In contrast, tooth wear was associated with better memory in two different logical memory tests (β^= 0.33 and β^= 0.36) and better executive function (β^= 0.06) over time, and this association became more evident in those with the lowest inflammatory marker (IL-6, β^= 0.10).

CONCLUSIONS

Dental caries and incomplete dentition were associated with poor memory, attention, and verbal fluency performance. Conversely, tooth wear was associated with better memory performance and executive function.

CLINICAL SIGNIFICANCE

For early prevention of dementia, an evaluation of multiple dental and periodontal status in older adults helps predict the risk of dementia in the preclinical phase. Maintaining intact tooth structure without caries progression and eventually tooth loss may help prevent the worsening of memory, attention, and verbal fluency over time.

Relationship between the number of teeth, occlusal force, occlusal contact area, and dietary hardness in older Japanese adults: The SONIC study

PURPOSE

Individuals with impaired masticatory function tend to prefer soft foods, which results in decreased masticatory muscle activity. This study examined the association between the oral condition (number of teeth, occlusal force, and occlusal contact area) and dietary hardness using a daily dietary questionnaire.

METHODS

This cross-sectional study evaluated 1841 participants aged 69-71 and 79-81 years. Registered dentists examined the number of teeth, occlusal force, and occlusal contact area. Dietary hardness was defined as the estimated masticatory muscle activity required for a habitual diet. Habitual diet during the preceding month was assessed using a brief self-administered diet history questionnaire. Confounding factors, such as age, sex, socioeconomic status, smoking habits, history of chronic diseases (hypertension, hyperlipidemia, and diabetes), and cognitive function were also evaluated. Multivariate linear regression analyses were performed to assess the association between dietary hardness and each oral condition.

RESULTS

Occlusal force (standardized regression coefficients [β]=0.08, P < 0.01) and occlusal contact area (β=0.06, P < 0.01) were significantly associated with dietary hardness after adjusting for the confounding factors. Number of teeth was not significantly associated with dietary hardness. In addition, the associations between dietary hardness, sex, and a history of diabetes were stronger than those between dietary hardness and oral factors.

CONCLUSIONS

Occlusal force and contact area were significantly associated with dietary hardness as estimated from the masticatory muscle activity using a daily diet questionnaire.

Periodontitis and brain magnetic resonance imaging markers of Alzheimer's disease and cognitive aging

INTRODUCTION

We examined the association of clinical, microbiological, and host response features of periodontitis with MRI markers of atrophy/cerebrovascular disease in the Washington Heights Inwood Columbia Aging Project (WHICAP) Ancillary Study of Oral Health.

METHODS

We analyzed 468 participants with clinical periodontal data, microbial plaque and serum samples, and brain MRIs. We tested the association of periodontitis features with MRI features, after adjusting for multiple risk factors for Alzheimer's disease/Alzheimer's disease-related dementia (AD/ADRD).

RESULTS

In fully adjusted models, having more teeth was associated with lower odds for infarcts, lower white matter hyperintensity (WMH) volume, higher entorhinal cortex volume, and higher cortical thickness. Higher extent of periodontitis was associated with lower entorhinal cortex volume and lower cortical thickness. Differential associations emerged between colonization by specific bacteria/serum antibacterial IgG responses and MRI outcomes.

DISCUSSION

In an elderly cohort, clinical, microbiological, and serological features of periodontitis were associated with MRI findings related to ADRD risk. Further investigation of causal associations is warranted.

Chewing ability and associated factors in older adults in Germany. Results from GEDA 2019/2020-EHIS

BACKGROUND

Oral well-being is an important component of general well-being and quality of life, as it is greatly influenced by the ability to chew and speak, and thus by central factors of social interaction. Because quality of life and participation are important factors for health in older age, the aim of this article was to examine the chewing ability, including associated factors, for the older population in Germany on the basis of a nationally representative sample.

METHODS

Database is the German Health Update (GEDA 2019/2020-EHIS), a population based cross-sectional survey of the Robert Koch Institute. In the telephone interview, participants aged 55 years and older were asked: "Do you have difficulty biting and chewing on hard foods such as a firm apple? Would you say 'no difficulty', 'some difficulty', 'a lot of difficulty' or 'cannot do at all/ unable to do'?" Prevalences and multivariate prevalence ratios (PR) were calculated with 95% confidence intervals (95% CI) from log-Poisson regressions. Sociodemographic, health-, behavioral- and care-related characteristics were investigated as associated factors.

RESULTS

The analyses were based on data from 12,944 participants (7,079 women, 5,865 men). The proportion of people with reduced chewing ability was 20.0%; 14.5% had minor difficulty, 5.5% had major difficulty. There were no differences between women and men. The most important associated factors for reduced chewing ability were old age (PR 1.8, 95% CI 1.5-2.1), low socioeconomic status (PR 2.0, 95% CI 1.7-2.5), limitations to usual activities due to health problems (PR 1.9, 1.6-2.2), depressive symptoms (PR 1.7, 1.5-2.1), daily smoking (PR 1.6, 95% CI 1.3-1.8), low dental utilization (PR 1.6, 95% CI 1.4-1.9), and perceived unmet needs for dental care (PR 1.7, 95% CI 1.5-2.1).

CONCLUSIONS

One fifth of adults from 55 years of age reported reduced chewing ability. Thus, this is a very common functional limitation in older age. Reduced chewing ability was associated with almost all investigated characteristics. Therefore, its prevention requires a holistic view in the living environment and health care context of older people. Given that chewing ability influences quality of life and social participation, maintaining or improving chewing ability is important for healthy aging.

White matter abnormalities mediate the association between masticatory dysfunction and cognition among older adults

BACKGROUND

Masticatory parameters, such as reduced number of teeth and posterior contacts, have been shown to be associated with reduced cognitive status. The underlying mechanisms that affect these associations, are however, not well understood.

OBJECTIVES

The study aims to investigate the association between masticatory dysfunction and cognition and explore the mediating effect of brain structure.

METHODS

In this cross-sectional study, 45 older adults with subjective masticatory dysfunction (mean age 72.3 ± 4.0 years) were included. Mini-Mental State Examination score <25, brain trauma, neurological disease, neurodegenerative disorders, depression or poor Swedish language skills were criteria for exclusion. Cognitive functions (executive function and episodic memory) and masticatory dysfunction defined by functional occluding status (FOS; the number of occluding units and number of remaining teeth) were analysed with partial correlation models. Structural magnetic resonance imaging was performed on 28 feasible participants. Multiple regression analyses were performed to evaluate the predictive value of brain structure and white matter hypointensities (WM-hypo) on cognitive functions. A mediation analysis was applied to assess significant predictor/s of the association between FOS and cognition.

RESULTS

Both episodic memory and executive functions were positively correlated with FOS. WM-hypo predicted cognitive status (executive function, p ≤ .01). WM-hypo mediated 66.6% (p = 0.06) of the association between FOS and executive functions.

CONCLUSION

Associations between FOS and cognitive functions are reported, where FOS, a potential modifiable risk factor, was related to both episodic memory and executive functions. The mediating effect of WM-hypo on the association between FOS and executive functions highlights the impact of the vascularisation of the brain on the link between mastication and cognition. The present study provides increased knowledge that bridges the gap between masticatory dysfunction and cognition.

The relationships between mastication and cognitive function: A systematic review and meta-analysis

Masticatory function such as chewing is expected to modify human cognitive function, and/or the possibility of improving cognitive function is also predicted. This systematic review investigated whether masticatory function affects cognitive function for older/young adults. Full articles written in English from January 2000 to April 2022 were collected using PubMed and Cochrane Library. Target outcomes were cognitive function test scores, cognitive processing speed (reaction time), and masticatory function. For each research question, two independent reviewers conducted the search and screening, data extraction, quality assessment, and risk of bias assessment. The reviewers resolved any disagreements by discussion. From 226 articles retrieved, 20 were included in this review. Older adults with lower scores on the cognitive function test had lower masticatory performance, lower chewing ability, chewing difficulty, and decreased number of teeth. An increased risk of cognitive impairment was found in older adults with masticatory dysfunction. For young adults, gum chewing significantly reduced the processing speed of cognitive tasks compared to no gum chewing. Although most of the evidence included had a low level of evidence and a high risk of bias because of the research designs, the results still suggest that mastication may be a factor in improving cognitive function.

Chewing difficulty and frailty trajectories in Chinese nursing home residents: A prospective cohort study

AIM

To investigate frailty trajectories in nursing home residents, and to test whether chewing difficulty was a significant factor associated with frailty trajectories.

METHODS

This is a 1-year prospective cohort study. Data were collected from 27 nursing home residents in China at baseline, 6 months, and 12 months. Latent class growth modeling was used to identify frailty trajectories. Multilevel multinomial logistic regression was used to test the relative risk ratios (RRRs) with 95% confidence intervals (CIs) of the chewing difficulty assessed at baseline on frailty trajectories.

RESULTS

In total, 269 nursing home residents were included in the analysis. Three frailty trajectories identified were non-frailty trajectory (n = 181, 67.3%), stable frailty trajectory (n = 52, 19.3%), and progressive frailty trajectory (n = 36, 13.4%). Chewing difficulty was found among 138 (51.3%) nursing home residents. With the non-frailty trajectory group as the reference, residents with chewing difficulty were more likely to demonstrate stable frailty trajectory (RRR = 2.55, 95% CI [1.28-5.11]) or progressive frailty trajectory (RRR = 3.46, 95% CI [1.47-8.15]).

CONCLUSIONS

Changes in the frailty of nursing home residents are heterogeneous and chewing difficulty should be assessed and addressed on a routine basis in nursing homes to prevent the deterioration of frailty or reverse it. Geriatr Gerontol Int 2023; 23: 803-808.

Lower masticatory function relates to cognitive health and intrinsic brain network in older adults

OBJECTIVES

Mastication is associated with brain activation at the primary somatosensory cortex (S1) and the primary motor cortex (M1). Masticatory functions differ between patients with cognitive impairment (CI) and cognitively healthy older adults (non-CI). The association between cognitive health, brain network of functional connectivity, and mastication has remained unknown. The study investigated the association between masticatory performance (MP) and the topological feature of the functional network at the M1 and S1 in the CI and non-CI groups.

SUBJECTS AND METHODS

Forty-nine non-CI and 15 CI subjects received resting-state (rs) fMRI and assessment of MP. The topological feature of the M1 and S1 was quantified by eigenvector centrality (EC), an index that reflects a brain region as a functional "hub" of brain network.

RESULTS

In the non-CI group, MP was significantly correlated with EC of the left M1 and the right M1. The correlation was not statistically significant in the CI group. Cognitive status (CI or non-CI) and EC of the left M1 and the right M1, respectively, were statistically significant predictors to individual MP.

CONCLUSION

Cognitive status and the topological feature of the M1 in the intrinsic functional network may contribute to the individual difference in masticatory function.

Treponema denticola Has the Potential to Cause Neurodegeneration in the Midbrain via the Periodontal Route of Infection-Narrative Review

Alzheimer's disease (AD) is a neurodegenerative disease and the most common example of dementia. The neuropathological features of AD are the abnormal deposition of extracellular amyloid-β (Aβ) and intraneuronal neurofibrillary tangles with hyperphosphorylated tau protein. It is recognized that AD starts in the frontal cerebral cortex, and then it progresses to the entorhinal cortex, the hippocampus, and the rest of the brain. However, some studies on animals suggest that AD could also progress in the reverse order starting from the midbrain and then spreading to the frontal cortex. Spirochetes are neurotrophic: From a peripheral route of infection, they can reach the brain via the midbrain. Their direct and indirect effect via the interaction of their virulence factors and the microglia potentially leads to the host peripheral nerve, the midbrain (especially the locus coeruleus), and cortical damage. On this basis, this review aims to discuss the hypothesis of the ability of Treponema denticola to damage the peripheral axons in the periodontal ligament, to evade the complemental pathway and microglial immune response, to determine the cytoskeletal impairment and therefore causing the axonal transport disruption, an altered mitochondrial migration and the consequent neuronal apoptosis. Further insights about the central neurodegeneration mechanism and Treponema denticola's resistance to the immune response when aggregated in biofilm and its quorum sensing are suggested as a pathogenetic model for the advanced stages of AD.

Association between Dietary Hardness and Cognitive Dysfunction among Japanese Men in Their 60s: A Cross-Sectional Study

We aimed to examine the cross-sectional association between dietary hardness and cognitive dysfunction among Japanese men in their 60s. Participants were 1494 men aged 60-69 years from the baseline survey of Hitachi Health Study II (2017-2020). Dietary hardness was defined as an estimate of masticatory muscle activity involved in consuming solid foods. Habitual intake of these foods was assessed using a brief-type, self-administered diet history questionnaire. Cognitive dysfunction was defined as a score ≤ 13 points on the test battery for screening for Alzheimer's disease (MSP-1100). The mean (SD) age of participants was 63.5 (3.5) years. The prevalence of cognitive dysfunction was 7.5%. The ORs (95% CIs) for cognitive dysfunction in the second and third tertiles were: 0.77 (0.47, 1.26) and 0.87 (0.54, 1.41), respectively, after adjustment for socio-demographic factors (p for trend = 0.73). After further adjustment for protective nutrient intake against cognitive dysfunction, the corresponding figures were 0.72 (0.43, 1.21) and 0.79 (0.43, 1.46), respectively (p for trend = 0.57). Dietary hardness was not associated with the prevalence of cognitive dysfunction among Japanese men in their 60s. Future prospective studies are necessary to investigate the association between dietary hardness estimated by a validated questionnaire and cognitive dysfunctions.

Influence of Age on Associations of Occlusal Status and Number of Present Teeth with Dementia in Community-Dwelling Older People in Japan: Cross-Sectional Study

While occlusal status has been reported to be related to cognitive function, little is known about the influence of age on that relationship. The present study examined the associations of tooth loss and occlusal status with dementia in the older people, as well as the effects of age on those relationships. A total of 196 older participants (median age: 84 years) were enrolled. Occlusal status was assessed using functional tooth units (FTU), calculated based on the number of paired natural or artificial teeth. Logistic regression analysis was then performed using dementia as the objective variable, and FTU or number of teeth as explanatory variables. The results showed that higher FTU was associated with lower risk of dementia. Furthermore, when stratified by median age, the association was greater for those aged less than 84 years. On the other hand, there was no significant association of number of present teeth with dementia. These results suggest that the risk of dementia is lower for individuals with better occlusion and that occlusal factor may have a greater effect on dementia onset in younger older people. It is thus recommended that both occlusal function and age be incorporated as factors in programs developed for dementia prevention.

Tooth loss and the risk of cognitive decline and dementia: A meta-analysis of cohort studies

Introduction

Epidemiological studies have shown that tooth loss may be associated with an increased risk of cognitive decline and dementia. However, some results do not show a significant association. Therefore, we performed a meta-analysis to evaluate this association.

Methods

Relevant cohort studies were searched in PubMed, Embase, Web of Science (up to May 2022), and the reference lists of retrieved articles. The pooled relative risk (RR) and 95% confidence intervals were computed using a random-effects model (CI). Heterogeneity was evaluated using the I 2 statistic. Publication bias was evaluated using the Begg's and Egger's tests.

Results

Eighteen cohort studies met the inclusion criteria. Original studies with 356,297 participants with an average follow-up of 8.6 years (ranging from 2 to 20 years) were included in this study. The pooled RRs of tooth loss on dementia and cognitive decline were 1.15 (95% CI: 1.10-1.20; P < 0.01, I 2 = 67.4%) and 1.20 (95% CI: 1.14-1.26; P = 0.04, I 2 = 42.3%), respectively. The results of the subgroup analysis showed an increased association between tooth loss and Alzheimer's disease (AD) (RR = 1.12, 95% CI: 1.02-1.23) and vascular dementia (VaD) (RR = 1.25, 95% CI: 1.06-1.47). The results of the subgroup analysis also showed that pooled RRs varied by geographic location, sex, use of dentures, number of teeth or edentulous status, dental assessment, and follow-up duration. None of the Begg's and Egger's tests or funnel plots showed evidence of publication bias.

Discussion

Tooth loss is associated with a significantly increased risk of cognitive decline and dementia, suggesting that adequate natural teeth are important for cognitive function in older adults. The likely mechanisms mostly suggested include nutrition, inflammation, and neural feedback, especially deficiency of several nutrients like vitamin D.

Food Hardness Modulates Behavior, Cognition, and Brain Activation: A Systematic Review of Animal and Human Studies

Food hardness is one of the dietary features that may impact brain functions. We performed a systematic review to evaluate the effect of food hardness (hard food versus soft food diet) on behavior, cognition, and brain activation in animals and humans (PROSPERO ID: CRD42021254204). The search was conducted on 29 June 2022 using Medline (Ovid), Embase, and Web of Science databases. Data were extracted, tabulated by food hardness as an intervention, and summarized by qualitative synthesis. The SYRCLE and JBI tools were used to assess the risk of bias (RoB) of individual studies. Of the 5427 studies identified, 18 animal studies and 6 human studies met the inclusion criteria and were included. The RoB assessment indicated that 61% of animal studies had unclear risks, 11% had moderate risks, and 28% had low risks. All human studies were deemed to have a low risk of bias. The majority (48%) of the animal studies showed that a hard food diet improved behavioral task performance compared to soft food diets (8%). However, 44% of studies also showed no differential effects of food hardness on behavioral tests. It was also evident that certain regions of the brain were activated in response to changes in food hardness in humans, with a positive association between chewing hard food, cognition performance, and brain function. However, variations in the methodologies of the included studies hindered the meta-analysis execution. In conclusion, our findings highlight the beneficial effects of dietary food hardness on behavior, cognition, and brain function in both animals and humans, however, this effect may depend on several factors that require further understanding of the causality.

Locus Coeruleus Dysfunction and Trigeminal Mesencephalic Nucleus Degeneration: A Cue for Periodontal Infection Mediated Damage in Alzheimer's Disease?

Alzheimer's disease (AD) is a leading neurodegenerative disease with deteriorating cognition as its main clinical sign. In addition to the clinical history, it is characterized by the presence of two neuropathological hallmark lesions; amyloid-beta (Aβ) and neurofibrillary tangles (NFTs), identified in the brain at post-mortem in specific anatomical areas. Recently, it was discovered that NFTs occur initially in the subcortical nuclei, such as the locus coeruleus in the pons, and are said to spread from there to the cerebral cortices and the hippocampus. This contrasts with the prior acceptance of their neuropathology in the enthorinal cortex and the hippocampus. The Braak staging system places the accumulation of phosphorylated tau (p-tau) binding to NFTs in the locus coeruleus and other subcortical nuclei to precede stages I-IV. The locus coeruleus plays diverse psychological and physiological roles within the human body including rapid eye movement sleep disorder, schizophrenia, anxiety, and depression, regulation of sleep-wake cycles, attention, memory, mood, and behavior, which correlates with AD clinical behavior. In addition, the locus coeruleus regulates cardiovascular, respiratory, and gastrointestinal activities, which have only recently been associated with AD by modern day research enabling the wider understanding of AD development via comorbidities and microbial dysbiosis. The focus of this narrative review is to explore the modes of neurodegeneration taking place in the locus coeruleus during the natural aging process of the trigeminal nerve connections from the teeth and microbial dysbiosis, and to postulate a pathogenetic mechanism due to periodontal damage and/or infection focused on Treponema denticola.

Assessment of subjective and objective masticatory function among elderly individuals with mild cognitive impairment

BACKGROUND

Masticatory function is known to be related to cognitive ability; therefore, factors for improving masticatory function should be identified.

AIMS

This study aimed to identify factors influencing masticatory function associated with mild cognitive impairment (MCI) in elderly individuals.

METHODS

A total of 123 elderly participants [mean age: 76.5 ± 6.5 years; 82 females (66.7%), 41 males (33.3%)] were included. Cognitive function was evaluated by the Korean version of the Mini-Mental State Examination (KMMSE). Questionnaires for subjective evaluation were administered, and dynamic objective masticatory function evaluations, including chewing tests and bite force measurements, were performed. Intergroup differences were evaluated by the Wilcoxon rank-sum and chi-square test, and correlations between cognitive ability and masticatory function were evaluated by multilinear logistic regression.

RESULTS

The number of teeth, number of posterior teeth, bite force, masticatory ability index (MAI) and posterior support status showed significant differences between the normal (KMMSE > 23) and MCI (KMMSE ≤ 23) groups. However, only the MAI, representing dynamic masticatory performance, was significantly associated with MCI regardless of age, sex and removable prostheses. The number of teeth and posterior teeth, bite force, subjective masticatory ability and posterior occlusal support showed no significant association with MCI.

DISCUSSION

These results suggested the importance of chewing function for preventing the progression of cognitive impairment.

CONCLUSIONS

Considering that only the MAI was significantly associated with MCI, it is more important to improve chewing efficiency by harmonizing therapeutic prosthetics with the surrounding masticatory system than simply increasing the number of teeth to prevent or delay cognitive impairment in elderly individuals.

Relationship Between Cognitive Function, Oral Conditions and Systemic Metabolic Function in the Elderly

Systemic metabolic disorders, including lifestyle-related diseases, are known risk factors for dementia. Furthermore, oral diseases such as periodontal disease and tooth decay are also associated with systemic metabolic disorders such as lifestyle-related diseases, and have also been reported to be indicators of risk factors for developing dementia. In this study, we investigated the relationship between cognitive function, oral conditions and systemic metabolic function in the elderly. We investigated the number of healthy teeth, the number of prosthetic teeth fitted, the number of missing prosthetic teeth, etc., in 41 elderly patients (69.7 ± 5.6 years old). Cognitive function was evaluated by the Mini Mental State Examination (MMSE). We also estimated MMSE scores for each subject using deep learning-based assessment of MMSE scores. This deep learning method enables the estimation of the MMSE score based on basic blood test data from medical examinations and reflects the systemic metabolic state including lifestyle-related diseases. The estimated MMSE score correlated negatively with age (r = -0.381), correlated positively with the number of healthy teeth (r = 0.37), and correlated negatively with the number of missing prosthetic teeth (r = -0.39). This relationship was not found in the measured MMSE scores. A negative correlation (r = -0.36) was found between age and the current number of teeth and a positive correlation (r = 0.37) was found between age and the number of missing prosthetic teeth. A positive correlation was found between the number of teeth requiring prosthesis and lifestyle-related diseases. The deep learning-based estimation method of cognitive function clearly demonstrated the close relationship between oral health condition, systemic metabolic function and the risk of cognitive impairment. It was determined that the smaller the number of existing teeth and the larger the number of missing prosthetic teeth, the higher is the risk of cognitive impairment. Systemic metabolic function is presumed to affect oral health and cognitive function. Interestingly, no such relationship was found in the measured MMSE scores. There are two possible reasons for this. The first is that MMSE is a subjective test and is less accurate in assessing cognitive function. The second is that because the MMSE estimated based on blood data using deep learning is calculated based on the metabolic function, it has a stronger correlation with the oral health condition affected by the metabolic function. In conclusion, oral health condition may predict cognitive impairment in the elderly.

Associations Between Abdominal Obesity, Chewing Difficulty and Cognitive Impairment in Dementia-Free Chinese Elderly

OBJECTIVE

To investigate the independent and synergistic associations between abdominal obesity, chewing difficulty and cognitive impairment in a community-dwelling older adults sample in China.

METHODS

Cognitive function was measured by the 5 min- Montreal Cognitive Assessment (5 min-MoCA) and abdominal obesity was measured by A Body Shape Index (ABSI) in 572 participants recruited from local communities. Chewing difficulty was assessed via a self-report questionnaire. Linear regression and general logistic regression were performed to investigate the association of chewing difficulty and abdominal obesity with cognition.

RESULTS

Chewing difficulty score [β (95% CI) = -.30 (-.49, -.11)] and ABSI [β (95%CI) = -.30 (-.55, -.05)] were independently associated with worse performance on the 5 min-MoCA. Whilst ABSI was not associated with cognitive impairment, the co-existence of chewing difficulty and abdominal obesity [OR (95% CI) = 2.22 (1.18, 4.17)] was found associated with the presence of cognitive impairment.

CONCLUSION

Chewing difficulty and abdominal obesity were independently associated with cognition. Abdominal obesity and chewing may have an additive effect on cognitive function.

Use of handgrip strength measurement as an alternative for assessing chewing function in people with dementia

Background

Chewing ability and handgrip strength can be independent explanatory factors of physical fitness. The usability of measurement procedures for assessing chewing function in people with dementia seems to be limited. This study aimed to show an association between handgrip strength and chewing function to enable the use of handgrip strength measurement as an alternative for determining chewing parameters in people with dementia. 

Methods

The data analysed here are part of the OrBiD (Oral Health, Bite Force and Dementia) pilot study. A total of 120 participants were assigned to five evaluation groups based on their cognitive abilities using the Mini-Mental State Examination (MMSE). The MMSE groups in this data analysis were “no dementia” (noDem, MMSE 28–30), “mild cognitive impairment” (mCI, MMSE 25–27), and “mild dementia” (mDem, MMSE 18–24). Handgrip strength, maximum occlusal force, and chewing efficiency were measured. 

Results

The Mini-Mental State Examination scores among all participants (n = 71) resulted in a median of 27 and a range of 18–30. An association between maximum handgrip strength and the cognitive impairment of the participants was shown. Nevertheless, the use of handgrip strength measurement as an alternative for determining chewing function was not verified in this study.

Conclusions

The feasibility and reliability of chewing function measurements in people with dementia should be investigated. Existing measurement procedures may need to be adapted or new assessments may need to be developed to be usable in people with dementia.

Trial registration

ClinicalTrials.gov NCT03775772.

The Impact of Masticatory Function on Cognitive Impairment in Older Patients: A Population-Based Matched Case-Control Study

PURPOSE

The aim of this study was to investigate the association between the changes in masticatory function and cognitive impairment by analyzing longitudinal data of older Korean patients.

MATERIALS AND METHODS

Patients aged over 60 years with dental records between 2005 to 2010 (baseline; T1) and 2014 to 2020 (follow-up; T2) were selected in a single medical center. Based on the dementia diagnosis after T2, the cohort was classified into two groups, the dementia group (n=122) and the control group (n=366). Changes in masticatory function were calculated using the total functional tooth unit (T-FTU) in both groups. The incidence of tooth extraction (%) and the subsequent rehabilitation during the observation period were also evaluated.

RESULTS

In the dementia group, T-FTU significantly decreased from T1 to T2 (9.81±2.78 to 9.11±3.16, respectively, p=0.008), while no significant change was observed in the control group. During the mean observation period of 9 years, significantly more teeth were extracted and neglected to be prosthetically restored in the dementia group than in the control group. Regression analysis revealed that the number of missing teeth neglected [odds ratio (OR)=1.195, 95% confidence interval (CI)=1.025-1.393, p=0.023] and previous alcohol consumption (OR=4.445, 95% CI=1.831-1.795, p=0.001) were the most significant risk factors of dementia.

CONCLUSION

There might be a causative relationship between the neglected missing dentition and the onset of dementia.

Does reduced chewing ability efficiency influence cognitive function? Results of a 10-year national cohort study

A growing body of literature suggests that oral health can influence cognitive function during aging. However, it is currently unclear whether reduced masticatory efficiency influences cognitive impairment in longitudinal studies.This study sought to investigate the effects of reduced chewing ability on the incidence of cognitive impairment using national representative data from 10 years of follow-up in Korea. Among the 10,254 people recruited in 2006 (1st wave), 7568 with normal cognitive function were selected. The participants were followed up every 2 years. The number of participants followed up until the 6th wave was 5020 in 2016. Chewing ability and scores on the Mini-Mental State Examination were recorded using self-reported questionnaires. Risk factors for dementia taken from systematic literature reviews were used as covariates. We performed logistic regression and created general estimating equation models after controlling for all covariates to assess the relationship between chewing ability and cognitive decline. Decreased chewing function was associated with mild cognitive impairment after controlling for confounding variables.The odds ratio for cognitive impairment was about 1.28 times higher than in people with poor chewing function as in those with good chewing function. We identified changes in chewing function from the 1st wave to the 6th wave; the odds ratios were 2.21 (95% confidence interval = 1.90-2.58) in the good-poor group and 2.11 (95% confidence interval = 1.74-2.55) in the poor-poor group.We identified an impairment in cognitive function in the poor (poor-poor and good-poor) chewing ability group. Therefore, we have confirmed that reduced mastication efficiency may contribute to a deterioration in cognitive function. People with deteriorated chewing ability must be given additional attention to aid in the prevention of cognitive decline.

Oral hypofunction and association with need for daily assistance among older adults in long-term care

BACKGROUND

Oral hypofunction (OHF) is related to occlusal status and bite force. It has specific symptoms and varying degrees of severity.

OBJECTIVES

OHF was determined with five signs. The relationships between OHF and need for assistance in oral hygiene, moving, eating, and occlusal status in older adults living in long-term care (LTC) were examined.

METHODS

A comprehensive clinical oral examination was conducted on 393 residents who lived in LTC in Helsinki, Finland. The five signs to determine OHF were mouth dryness, visible food residue on oral or denture surfaces, ability to keep the mouth open during examination, clearness of speech, and diet of pureed or soft food. Score points of 0-2 were given for each sign and the sum was categorized as mild, moderate, or severe OHF. Participants were divided into three groups accordingly, and occlusal status was determined based on contact units. In addition, nurses collected background information on number of medications and level of cognition. Need for assistance was based on oral hygiene, moving, and eating.

RESULTS

Of participants (n=319), 21% showed severe and 41% moderate OHF. Occlusal status differences between the OHF groups were significant. OHF severity associated linearly with increased severity of cognitive impairment and increased need for assistance in oral hygiene, eating, and moving.

CONCLUSIONS

OHF score based on the five signs can be used to determine OHF severity. OHF was common and associated with occlusal status, cognitive impairment, and need for assistance in oral hygiene, moving, and eating in older adults living in LTC.

Tooth Loss Suppresses Hippocampal Neurogenesis and Leads to Cognitive Dysfunction in Juvenile Sprague–Dawley Rats

Background

Both animal studies and prospective observational studies on patients with neurodegenerative disease have reported a positive link between oral diseases and cognitive function. However, the effect of early tooth loss on hippocampal morphology remains unknown.

Methods

In this study, 6-week-old, male, juvenile Sprague–Dawley (SD) rats were randomized into the control (C) and tooth loss (TL) groups. In the TL group, all right maxillary molars of SD rats were extracted, while in the C group, no teeth were extracted. After 3 months, the learning and memory behavior were examined by Morris Water Maze (MWM), and the protein expression and mechanic signaling pathways were analyzed by real-time polymerase chain reaction, and cresyl violet staining.

Results

Two days after the operation, the body weight of both groups recovered and gradually returned to the level before operation. Three months after tooth extraction, the completion time of the C group in the MWM was significantly shorter than the TL group. The mRNA expression of BDNF, TrkB, AKT1, and NR2B in the C group were significantly higher than in the TL group. The pyramidal neurons in the TL group was fewer than in the C group.

Conclusion

Tooth loss in the juvenile SD rats will reduce the number of pyramidal neurons in the hippocampus, inhibit the expression of BDNF, TrkB, AKT1, and NR2B, and eventually lead to cognitive dysfunction.

The Effect of a Masticatory Muscle Training Program on Chewing Efficiency and Bite Force in People with Dementia

Until now, no study has investigated the effects of masticatory muscle training on chewing function in people with dementia. This study aimed to investigate whether physiotherapeutic exercises for the masticatory muscles have an influence on chewing efficiency and bite force in people with dementia. In a clinical trial with stratified randomization subjects were assigned to three groups based on the Mini Mental State Examination (MMSE: group 1—28–30, group 2—25–27, group 3—18–24). Each group was divided into an experimental (ExpG, intervention) and control group (ConG, no intervention). As intervention a Masticatory Muscle Training (MaMuT) (part 1: three physiotherapeutic treatments and daily home exercises, part 2: daily home exercises only) was carried out. Chewing efficiency and bite force were recorded. The MaMuT influenced the masticatory performance regardless of the cognitive state. Bite force increased in ExpG 1 and 2. Without further training, however, the effect disappeared. Chewing efficiency increased in all ExpG. After completion of the training, the ExpG 2 and 3 showed a decrease to initial values. Subjects of ExpG 1 showed a training effect at the final examination, but a tendency toward the initial values was observed. ExpG 3 seemed to benefit most from the physiotherapeutic exercises in terms of improving chewing efficiency by the end of the intervention phase. ExpG 1 showed the greatest gain in bite force. The MaMuT program is a potential method of improving masticatory performance in people with cognitive impairment or dementia when used on a daily basis.

The OrBiD (Oral Health, Bite Force and Dementia) Pilot Study: A Study Protocol for New Approaches to Masticatory Muscle Training and Efficient Recruitment for Longitudinal Studies in People with Dementia

Research with people with dementia is a great challenge in terms of recruitment, study participation and adherence to interventions resulting in less research activity and higher financial, organizational and personnel efforts. As dementia progresses, there is a deterioration in general and oral health and chewing function. Oral treatment options often focus on healthy patients. Interventions for people with dementia are needed. The aims of the paper were to describe the study protocol of the OrBiD (Oral Health, Bite Force and Dementia) pilot study as well as the description of two new methodological approaches. These are (A) an efficient recruitment process of people with dementia, simultaneous double study participation and (B) a novel approach to train the masticatory muscles by using physiotherapy. A novel methodology for the recruitment process (A) and, in particular, for the assignment of subjects to the experimental and control groups was developed and successfully tested. Additionally, a physiotherapy program (B) to train strength and coordination of the masticatory muscles was newly developed with the challenge to ensure that this training could also be carried out with people with cognitive impairments and dementia, if necessary, in cooperation with their relatives or caregivers. This was also successfully implemented. Recommendations for a feasibility assessment of a study involving people with dementia were made considering the organizational effort, the required personnel, structural and financial resources, the required number of subjects and the type of study design. When planning crossed studies, it must be ensured that the content, the interventions or their possible results of the study arms do not influence each other. The overall aim of this paper is to demonstrate the sustainable and efficient feasibility of studies with people with dementia.

A prospective association between tooth status and cognitive performance among older adults in Europe

OBJECTIVES

This study set out to examine both the longitudinal association between tooth status and cognitive performance among older adults in Europe, and the mediating effects of loneliness and quality of life on this association.

METHODS

We conducted a prospective analysis using data from 38,614 participants aged 50 or older, taken from the Survey of Health, Ageing and Retirement in Europe (SHARE) of 2013 (baseline) and 2015 (follow up). Bootstrapping with resampling strategies was used for testing a multiple mediator model.

RESULTS

The average age of participants was 66.9 (SD = 9.4). About 23% of the participants had full sets of their own teeth and 38.2% had missing teeth fully replaced by dental implants or dentures. Participants who had partially replaced teeth (B = 0.038, p < 0.001), and with fully replaced teeth (B = 0.041, p < 0.001), or had all their teeth in place (B = 0.055, p < 0.001), had better cognitive performance compared to those who did not replace their missing teeth. It was also found that quality of life and loneliness partially mediated these relationships - Having all teeth in place or replacing all or partially missing teeth was found to affect cognitive performance also via improved quality of life and through lower loneliness.

CONCLUSION

In later life, poor tooth status can be directly associated with cognitive decline and indirectly linked to cognitive performance, in light of decreasing quality of life and increasing loneliness. Clinicians should be aware of both the impact of poor tooth status on cognitive status and the implications for the wellbeing of older adults.

Nitinol Type Alloys General Characteristics and Applications in Endodontics

A very extensive literature review presents the possibilities and needs of using, in endodontics, the alloys commonly known as nitinol. Nitinol, as the most modern group of engineering materials used to develop root canals, is equilibrium nickel and titanium alloys in terms of the elements’ atomic concentration, or very similar. The main audience of this paper is engineers, tool designers and manufacturers, PhD students, and students of materials and manufacturing engineering but this article can also certainly be used by dentists. The paper aims to present a full material science characterization of the structure and properties of nitinol alloys and to discuss all structural phenomena that determine the performance properties of these alloys, including those applied to manufacture the endodontic tools. The paper presents the selection of these alloys’ chemical composition and processing conditions and their importance in the endodontic treatment of teeth. The results of laboratory studies on the analysis of changes during the sterilization of endodontic instruments made of nitinol alloys are also included. The summary of all the literature analyses is an SWOT analysis of strengths, weaknesses, opportunities, and threats, and is a forecast of the development strategy of this material in a specific application such as endodontics.

Gastrointestinal Changes and Alzheimer's Disease

BACKGROUND

There is a well-described mechanism of communication between the brain and gastrointestinal system in which both organs influence the function of the other. This bi-directional communication suggests that disease in either organ may affect function in the other.

OBJECTIVE

To assess whether the evidence supports gastrointestinal system inflammatory or degenerative pathophysiology as a characteristic of Alzheimer's disease (AD).

METHODS

A review of both rodent and human studies implicating gastrointestinal changes in AD was performed.

RESULTS

Numerous studies indicate that AD changes are not unique to the brain but also occur at various levels of the gastrointestinal tract involving both immune and neuronal changes. In addition, it appears that numerous conditions and diseases affecting regions of the tract may communicate to the brain to influence disease.

CONCLUSION

Gastrointestinal changes represent an overlooked aspect of AD, representing a more system influence of this disease.

What Are the Chances of Resilon to Dominate the Market Filling Materials for Endodontics?

This paper is a literature review with additional virtual analyses of the authors’ own experimental research results. Knowledge from various areas was synergistically combined, appropriately for concurrent engineering, presenting several possible methodological approaches used in research, optimizing the selection of engineering materials and the conditions of their application with particular application in endodontics. Particular attention was paid to the theoretical aspects of filling material strengths, weaknesses, opportunities, and threats SWOT analysis. Attention was paid to the original concepts of Sustainable Dentistry Development in conjunction with Dentistry 4.0, which includes endodontics as an important element. The dentists’ actions, among others, in conservative dentistry, along with endodontics, requires close cooperation with engineers and the enginering sciences. Methods of root canal preparation were described, together with selected tools, including those made of nitinol. Principles concerning the process of cleaning and shaping the pulp complex are presented. The importance of obturation methods, including the Thermo-Hydraulic-Condensation THC technique, and the selection of filling materials with the necessary sealants for the success of endodontic treatment are discussed. The experimental studies were carried out in vitro on human teeth removed for medical reasons, except for caries, for which two groups of 16 teeth were separated. After the root canal was prepared, it was filled with studs and pellets of a filling material based on polyester materials, which has gained the common trade name of resilon or, less frequently, RealSeal (SybronEndo) with an epiphany sealant. The teeth for the first group were obturated by cold lateral condensation. In the second case the obturation was performed using the Thermo-Hydraulic-Condensation technique using System B and Obtura III. The experimental leakage testing was done using a scanning electron microscope SEM and a light stereoscopic microscope LSM, as typical research tools used in materialography. The research results, in a confrontation with the data taken from the literature studies, do not indicate the domination of resilon in endodontics.

Comparison of the effect of conventional and implant-retained overdentures on brain activity and cognition in a geriatric population - A Functional MRI study

PURPOSE

This study aims to evaluate the effect of rehabilitation with complete dentures versus implant-retained overdenture on activity in various parts of the brain cognition in a geriatric edentulous population via Functional MRI (fMRI) studies and the Mini-Mental State Examination (MMSE).

METHODS

Ten completely edentulous patients were rehabilitated with both complete dentures and two-implant retained overdentures for three months each. fMRI studies were performed for each modality during chewing and recall tasks at three time periods: T0: Completely Edentulous(CE) T1: after three months of wearing Conventional Complete Dentures(CD) and T2: after three months of wearing Implant-retained Overdentures (IOD). The Z scores obtained from the fMRI at these phases of examination were tabulated and correlated with MMSE scores obtained at the corresponding time periods.

RESULTS

Z scores obtained during the memory recall tasks at T2 were the greatest (Prefrontal Cortex (p=0.059) and Hippocampus (p=0.036). The MMSE scores obtained were significantly higher for the IODs when compared to the CDs and Baseline values (p < 0.05)Conclusion: IODs may potentially result in superior sensory feedback in edentulous patients and lead to improved cognitive performance when compared to conventional complete dentures.

Tooth loss, dental prostheses use and cognitive performance in older Brazilian adults: The SABE cohort study

AIM

To investigate the within- and between-person longitudinal effects of tooth loss and the use of dentures, clinically assessed by dentists, on cognitive decline in a representative sample of community-dwelling older Brazilian adults.

METHODS

Data came from 1265, 1112 and 1021 individuals aged ≥60 years who participated in the second (2006), third (2010) and fourth (2015) waves, respectively, of the Health, Well-being and Aging study (SABE). Cognitive performance was evaluated with the abbreviated version of the Mini-Mental State Examination (MMSE). The number of natural teeth was classified according to three categories: none, 1-19 and ≥20 teeth. The presence of removable full or partial dentures in each dental arch (yes/no) was recorded. Hybrid regression models, adjusted for sociodemographic, behavior and health-related covariates, were used to estimate the between- and within-person effects of the longitudinal association between cognitive performance and oral health.

RESULTS

Participants with 1-19 and no teeth had, respectively, 1.15 (95% CI 0.65-1.66) and 1.54 (95% CI 0.99-2.09) units lower MMSE score than those with ≥20 teeth. Denture wearers had 1.54 (95% CI 1.13-1.95) units greater MMSE score than non-denture wearers, and those who started wearing dentures during the follow up had 0.83 (95% CI 0.21-1.45) units greater MMSE score after the transition.

CONCLUSION

Our main findings showed that the use of dental prostheses might be a protective factor for cognitive decline. Geriatr Gerontol Int 2021; 21: 1093-1098.

The relationship between periodontal disease and cognitive impairment in older adults of Korea

AIMS

A potential association between the periodontal disease and cognitive impairment has been suggested, but the results are not yet conclusive. This study investigated the association between the two diseases.

METHODS AND RESULTS

This study included 140 individuals (M: 48, F: 92, average age: 77.2). For assessing cognitive ability, MMSE-KC was used. The BGI index categorizes the periodontal disease based on important clinical parameters. In model 1 using the BGI index and the number of residual teeth as independent variables, the cognitive function status was significantly lower in the DL/MB group (β = -0.294), DL/LB group (β = -0.237). In Model 2 including systemic disease was the DL/MB group (β = -0.316) and in Model 3 which also added demographic characteristics, the DL/MB group (β = -0.229) was identified as a related factor (p < .05).

CONCLUSION

It can be concluded that periodontal disease is strongly associated with cognitive ability.

Resident and Institutional-Level Factors, Frailty, and Nursing Homes Residents

BACKGROUND

Frailty is a major cause of adverse health outcomes such as hospitalization, falls, disability, and morbidity among older adults; the elucidation of factors affecting frailty trends over time may facilitate the development of effective interventions.

OBJECTIVES

This study aimed to examine the trend of frailty over time (at baseline, with 6-month and 12-month follow-ups) among Chinese nursing home residents and identify associated resident- and institutional-level factors.

METHODS

This longitudinal study included 353 residents who were admitted into 27 nursing homes in Jinan, China. Frailty was defined based on the seven self-reported components of the FRAIL-NH scale, which was designed for nursing home residents. Information was gathered using scales that assessed resident-level (sociodemographic characteristics and physical, psychological, and social factors) and institutional-level characteristics (hospital affiliation, fitness sites, green space, occupancy percentage, staff-resident ratio, staff turnover rate). These data were subjected to a multilevel linear analysis.

RESULTS

Frailty was identified in 49.7% of residents at baseline and exhibited a progressively worsening trend over 1 year. Among institutional-level characteristics, the provision of fitness sites in nursing homes was a protective factor for frailty. Among resident-level characteristics, undernutrition was a significant independent risk factor and played a key role in increasing frailty over time. Other risk factors for frailty included younger age, poorer self-rated health, lower physical function, chewing difficulty, loneliness, anxiety, and being less active in leisure activities.

DISCUSSION

Frailty was highly prevalent among Chinese nursing home residents and gradually increased over time. The results of this study could be used to inform the development of interventions targeted at modifiable risk factors and shape public health policies aimed at promoting healthy aging and delaying frailty and its adverse outcomes.

Factors affecting subjective and objective masticatory function in older adults: Importance of an integrated approach

OBJECTIVES

This study aimed to subjectively and objectively assess masticatory function and identify related factors in older adults.

METHODS

From July 2017 to September 2018, we enrolled 115 healthy participants aged between 65 and 86 years. They underwent oral examination, and their stimulated salivary secretion rate and masseter muscle tone and biomechanical properties were assessed. Masticatory performance with two-colored chewing wax was objectively evaluated using the mixing ability index (MAI). Key food intake ability (KFIA) was subjectively assessed using a questionnaire.

RESULTS

The MAI score was significantly associated with the number of remaining teeth (r = 0.524, p < 0.001) and the tone (r = -0.222, p = 0.017), elasticity (r = -0.242, p = 0.009), and dynamic stiffness (r = -0.265, p = 0.004) of the masseter muscles. In contrast, the KFIA score was only significantly associated with the number of remaining teeth (r = 0.450, p < 0.001). A weak association between the MAI and KFIA scores was observed (r = 0.304, p = 0.001).

CONCLUSIONS

A combination of objective and subjective methods should be used to accurately assess masticatory function in older adults. In addition to physical factors such as the number of remaining teeth, properties of the masticatory muscles should be evaluated to improve the masticatory function of older adults.

CLINICAL SIGNIFICANCE

In addition to dental problems, various maxillofacial and oral factors must be considered when establishing management strategies for the improvement of masticatory function in older adults.

Is Gutta-Percha Still the “Gold Standard” among Filling Materials in Endodontic Treatment?

The paper is an extensive monographic review of the literature, and also uses the results of the authors’ own experimental research illustrating the noticed developmental tendencies of the filling material based on gutta-percha. The whole body of literature proves the correctness of the research thesis that this material is the best currently that can be used in endodontics. Caries is one of the most common global infectious diseases. Since the dawn of humankind, the consequence of the disease has been the loss of dentition over time through dental extractions. Both tooth caries and tooth loss cause numerous complications and systemic diseases, which have a serious impact on insurance systems and on the well-being, quality, and length of human life. Endodontic treatment, which has been developing since 1836, is an alternative to tooth extraction. Based on an extensive literature review, the methodology of qualifying patients for endodontic treatment was analyzed. The importance of selecting filling material and techniques for the development and obturation of the root canal during endodontic treatment was described. Particular attention was paid to the materials science aspects and the sequence of phase transformations and precipitation processes, as well as the need to ensure the stoichiometric chemical composition of Ni–Ti alloys, and the vacuum metallurgical processes and material processing technologies for the effects of shape memory and superelasticity, which determine the suitability of tools made of this alloy for endodontic purposes. The phenomena accompanying the sterilization of such tools, limiting the relatively small number of times of their use, play an important role. The methods of root canal preparation and obturation methods through cold side condensation and thermoplastic methods, including the most modern of them, the thermo-hydraulic condensation (THC) technique, were analyzed. An important element of the research hypothesis was to prove the assumption that to optimize the technology of development and obturation of root canals, tests of filling effectiveness are identified by the density and size of the gaps between the root canal wall, and the filling methods used and devices appropriate for material research, using mainly microscopy such as light stereoscopic (LSM) and scanning electron (SEM). The most beneficial preparations were obtained by making a longitudinal breakthrough of 48 natural human teeth, extracted for medical reasons, different from caries, with compliance with all ethical principles in this field. The teeth were prepared using various methods and filled with multiple obturation techniques, using a virtual selection of experimental variants. The breakthroughs were made in liquid nitrogen after a one-sided incision with a narrow gap created by a diamond disc using a materialographic cutter. The best effectiveness of the root canal filling was ensured by the technology of preparing the root canals with K3 rotary nitinol tools and filling the teeth with the THC thermoplastic method using the System B and Obtura III devices with studs and pellets of filling material based on gutta-percha after covering the root canal walls with a thin layer of AH Plus sealant. In this way, the research thesis was confirmed.

Chewing function and related parameters as a function of the degree of dementia: Is there a link between the brain and the mouth?

Background

To date, no study has investigated the association between chewing function and related parameters as a function of the degree of dementia using a finer subdivision of the values of the Mini‐Mental State Examination (MMSE).

Objective

This study aimed to investigate the differences in chewing function and related parameters as a function of the degree of dementia.

Methods

An analysis of cross‐sectional data obtained from the OrBiD (Oral Health, Bite Force, and Dementia) pilot study was performed. The participants were stratified into five groups based on the outcomes of the MMSE (no dementia, MMSE 28–30; mild cognitive impairment, MMSE 25–27; mild dementia, MMSE 18–24; moderate dementia, MMSE 10–17; severe dementia, MMSE <10). The chewing efficiency, maximum occlusal force and related parameters (number of supporting zones, number of teeth, Eichner index, tooth/denture status, denture quality, and dental treatment needs) were recorded.

Results

The MMSE groups showed significantly different chewing efficiencies (p = .003, Jonckheere‐Terpstra test) and maximum occlusal forces (p = .003, Jonckheere‐Terpstra test), but the number of supporting zones (p = .055, chi‐square test) and the number of natural teeth (p = .126, chi‐square test) were not different. The Eichner index, tooth/denture status, denture quality and dental treatment need showed no significant associations with the degree of dementia.

Conclusion

An improvement in the usability of the measurement methods for assessing chewing function in people with dementia is needed. Research involving people with dementia is necessary because the nutritional situation often deteriorates rapidly within a multifactorial system, which includes chewing ability and oral health.

Cognitive changes and neural correlates after oral rehabilitation procedures in older adults: a protocol for an interventional study

BACKGROUND

Epidemiological studies show an association between masticatory function and cognitive impairment. This has further strengthened the notion that tooth loss and impaired masticatory function may be risk factors for dementia and cognitive decline. Animal experiments have indicated a causal relationship and several possible mechanisms have been discussed. This evidence is, however, lacking in humans. Therefore, in the current interventional study, we aim to investigate the effect of rehabilitation of masticatory function on cognition in older adults.

METHODS

Eighty patients indicated for prosthodontic rehabilitation will be randomly assigned to an experimental or a control group. Participants will conduct neuropsychological assessments, masticatory performance tests, saliva tests, optional magnetic resonance imaging, and answer questionnaires on oral health impact profiles and hospital anxiety and depression scale before, 3 months, and 1 year after oral rehabilitation. The difference between the two groups is that the control group will be tested an additional time, (at an interval of about 3 months) before the onset of the oral rehabilitation procedure. The primary outcome is a change in measures of episodic memory performance.

DISCUSSION

Although tooth loss and masticatory function are widespread in older people, it is still an underexplored modifiable risk factor potentially contributing to the development of cognitive impairment. If rehabilitation of masticatory function shows positive effects on the neurocognitive function, this will have great implications on future health care for patients with impaired masticatory status. The present project may provide a new avenue for the prevention of cognitive decline in older individuals.

TRIAL REGISTRATION

The protocol for the study was retrospectively registered in ClinicalTrials.gov Identifier: NCT04458207, dated 02-07-2020.

Factors Related to Depression Associated with Chewing Problems in the Korean Elderly Population

Unlike younger adults, depression in older adults is sometimes related to chewing problems. This study examined the risk factors related to depression associated with chewing problems in 3747 elderly individuals using the Korean National Health and Nutrition Examination Survey. Approximately 41.2% of the total subjects reported chewing problems. There were significant differences in age, education, marital status, individual income, current smoking status, and aerobic physical activity in relation to chewing problems (p < 0.001 for all). The subjects who experienced chewing problems showed a higher score on the EuroQoL 5 Dimension index (p < 0.001) but a lower health-related quality of life than those with no chewing problems (p < 0.001). The prevalence of depression, which was classified by the patient health questionnaire—9, in subjects with chewing problems was approximately 2 times higher than that in those with no chewing problems (p < 0.001). Subjects with chewing problems were found to have a 1.945-fold higher adjusted risk of depression than those who did not have chewing problems (95% CI = 1.583–2.390, p < 0.001), and subjects with high protein consumption showed a 1.410-fold greater risk of depression (95% CI = 1.144–1.739, p = 0.001) than those with low protein consumption.

Neurodegeneration of Trigeminal Mesencephalic Neurons by the Tooth Loss Triggers the Progression of Alzheimer's Disease in 3×Tg-AD Model Mice

BACKGROUND

The mesencephalic trigeminal nucleus (Vmes) is not only anatomically adjacent to the locus coeruleus (LC) but is also tightly associated with the function of the LC. The LC can be the first area in which Alzheimer's disease (AD) develops, although it is unclear how LC neuronal loss occurs.

OBJECTIVE

We investigated whether neuronal death in the Vmes can be spread to adjacent LC in female triple transgenic (3×Tg)-AD mice, how amyloid-β (Aβ) is involved in LC neuronal loss, and how this neurodegeneration affects cognitive function.

METHODS

The molars of 3×Tg-AD mice were extracted, and the mice were reared for one week to 4 months. Immunohistochemical analysis, and spatial learning/memory assessment using the Barnes maze were carried out.

RESULTS

In 4-month-old 3×Tg-AD mice, aggregated cytotoxic Aβ42 was found in granules in Vmes neurons. Neuronal death in the Vmes occurred after tooth extraction, resulting in the release of cytotoxic Aβ42 and an increase in CD86 immunoreactive microglia. Released Aβ42 damaged the LC, in turn inducing a significant reduction in hippocampal neurons in the CA1 and CA3 regions receiving projections from the LC. Based on spatial learning/memory assessment, after the tooth extraction in the 4-month-old 3×Tg-AD mice, increased latency was observed in 5-month-old 3×Tg-AD mice 1 month after tooth extraction, which is similar increase of latency observed in control 8-month-old 3×Tg-AD mice. Measures of cognitive deficits suggested an earlier shift to dementia-like behavior after tooth extraction.

CONCLUSION

These findings suggest that tooth extraction in the predementia stage can trigger the spread of neurodegeneration from the Vmes, LC, and hippocampus and accelerate the onset of dementia.

Virtual Approach to the Comparative Analysis of Biomaterials Used in Endodontic Treatment

The importance of endodontics is presented within our own concept of Dentistry Sustainable Development (DSD) consisting of three inseparable elements; i.e., Advanced Interventionist Dentistry 4.0 (AID 4.0), Global Dental Prevention (GDP), and the Dentistry Safety System (DSS) as a polemic, with the hypothesis of the need to abandon interventionist dentistry in favour of the domination of dental prevention. In view of the numerous systemic complications of caries that affect 3−5 billion people globally, endodontic treatment effectively counteracts them. Regardless of this, the prevention of oral diseases should be developed very widely, and in many countries dental care should reach the poorest sections of society. The materials and methods of clinical management in endodontic procedures are characterized. The progress in the field of filling materials and techniques for the development and obturation of root canals is presented. The endodontics market is forecast to reach USD 2.1 billion in 2026, with a CAGR of 4.1%. The most widely used and recognized material for filling root canals is gutta-percha, recognized as the “gold standard”. An alternative is a synthetic thermoplastic filler material based on polyester materials, known mainly under the trade name Resilon. There are still sceptical opinions about the need to replace gutta-percha with this synthetic material, and many dentists still believe that this material cannot compete with gutta-percha. The results of studies carried out so far do not allow for the formulation of a substantively and ethically unambiguous view that gutta-percha should be replaced with another material. There is still insufficient clinical evidence to formulate firm opinions in this regard. In essence, materials and technologies used in endodontics do not differ from other groups of materials, which justifies using material engineering methodology for their research. Therefore, a detailed methodological approach is presented to objectify the assessment of endodontic treatment. Theoretical analysis was carried out using the methods of procedural benchmarking and comparative analysis with the use of contextual matrices to virtually optimize the selection of materials, techniques for the development and obturation of root canals, and methods for assessing the effectiveness of filling, which methods are usually used, e.g., in management science, and especially in foresight research as part of knowledge management. The results of these analyses are presented in the form of appropriate context matrices. The full usefulness of the research on the effectiveness and tightness of root canal filling using scanning electron microscopy is indicated. The analysis results are a practical application of the so-called “digital twins” approach concerning the virtual comparative analysis of biomaterials used in endodontic treatment.

Apolipoprotein ɛ4 Allele and Dental Occlusion Deficiency as Risk Factors for Alzheimer's Disease

Compromised dentition has been suggested to pose a significant risk factor for dementia. It was mainly investigated through insufficient tooth number, disregarding contact between opposing teeth (dental occlusion). The ɛ4 allele of apolipoprotein (APOE4) is the primary genetic marker for the late onset of Alzheimer's disease (AD). However, APOE4 and dental occlusion have not yet been investigated as possible associated risk factors for AD. The study was aimed to examine the impact of dental status and different APOE gene variants on AD occurrence. Secondly, sociodemographic variables were investigated as factors potentially associated with AD. The case-control study included two groups: 116 patients with AD (according to the NINDS-ADRDA criteria) and 63 controls (Mini-Mental State Examination scores ≥24). The analysis of APOE gene polymorphism was conducted through PCR reaction. Dental examination included recording of number of teeth, presence of fixed or removable dentures, and number of functional tooth units (FTU). Regression analysis was used to investigate the joint effect of the clinical and genetic variables on AD. Results showed that patients with AD were more often carriers of ɛ3/ɛ4 genotype and ɛ4 allele, had lower number of teeth and FTU, and were less likely to be married, live in home, and had less chronic diseases, compared to the controls. Regression analysis showed that presence of APOE4 allele and the number of total FTU remained associated with AD, even when adjusted for age, sex, and level of education. In conclusion, deficient dental occlusion and presence of APOE4 may independently increase risk for AD.

Increase in masseter muscle activity by newly fabricated complete dentures improved brain function

PURPOSE

To reveal effects of improvement of masseter muscle activity on brain function in elderly people wearing complete dentures.

METHODS

Subjects were 14 edentulous patients with a chief complaint of the inconvenience of their complete dentures. The surface electromyographic (EMG) activity of the masseter muscles was measured. Brain activities were analyzed with functional magnetic resonance imaging (fMRI), employing chewing gum as the task program. Cognitive functions were evaluated with Trail Making Test Part A (TMT-A), Rey Auditory Verbal Learning Test (RAVLT) and Rey-Osterrieth Complex Figure Test (R-OCFT). Those evaluations were performed in which subjects wore their old dentures (OD) or newly fabricated dentures (ND).

RESULTS

We compared ND condition with OD condition. The masseter muscle activity significantly increased in ND condition (p < 0.05, Wilcoxon signed rank test). The brain activity increased significantly in the superior frontal gyrus, precentral gyrus, putamen, inferior parietal lobule, cerebellum, inferior frontal lobe, and middle frontal gyrus under the ND condition than under the OD condition (p < 0.01, uncorrected, cluster size > 10 voxels). Results of TMT-A, RAVLT, and R-OCFT were also significantly improved (p < 0.05, Wilcoxon signed rank test).

CONCLUSIONS

In the edentulous elderly, the brain activity was increased following the improvement of the masseter muscle activity. Consequently, it is possible that the improvement of the masseter muscle activity might influ ence on the attention, verbal skills, and visual memory.

Effects of masticatory exercise on cognitive function in community-dwelling older adults

BACKGROUND:

Mastication improves cognitive function by activating cerebral cortical activity, and it is important to demonstrate the cognitive effects of masticatory training using a variety of different interventions.

OBJECTIVE:

This study aimed to evaluate the effects of masticatory exercise on cognitive function in healthy older adults living in the community.

METHODS:

For six weeks, twelve participants performed a masticatory exercise using a NOSICK exerciser device, and thirteen subjects performed daily life without masticatory exercises. Trail Making Test, Digit Span Test, and Stroop test were used to measure the cognitive function.

RESULTS:

The participants in the experimental group showed significant improvements in TMT-A/B (p= 0.001 and 0.004), DST-forward (p= 0.001), and ST-word (p= 0.001). The effect sizes after the intervention were calculated as (1.2 and 0.8) for TMT-A/B, (0.8 and 0.2) for Digit Span Test forward/backward, and (0.6 and 0.2) for Stroop test color/word.

CONCLUSIONS:

We suggest that the masticatory exercises improve cognitive function in healthy older adults. Therefore, masticatory exercises can be used as a therapeutic exercise during cognitive rehabilitation.

Chewing Discomfort According to Dental Prosthesis Type in 12,802 Adults: A Cross-Sectional Study

This study examined the prevalence of self-perceived chewing discomfort depending on the type of dental prosthesis used in South Korean adults. The subjects were 12,802 people over 20 years of age who participated in a health interview and dental examination. Chewing discomfort was examined using a self-assessed report with a structured questionnaire. Using multivariable logistic regression analysis, adjusted odds ratios were evaluated along with their 95% confidence intervals (α = 0.05). After adjusting for covariates, including age, gender, smoking, drinking, hypertension, diabetes, body mass index, education, income, and toothbrushing frequency, the odds ratios (95% confidence intervals) for chewing discomfort in groups without a dental prosthesis, with fixed dental prostheses, with removable partial dentures, and with removable complete dentures were 1 (reference), 1.363 (1.213-1.532), 2.275 (1.879-2.753), and 2.483 (1.929-3.197), respectively. The association between the prevalence of chewing discomfort and the type of dental prosthesis used was statistically significant even after adjusting for various confounders (p < 0.0001). The type of dental prosthesis was related to chewing discomfort among South Korean adults.

The Concept of Sustainable Development of Modern Dentistry

This paper concerns the assessment of the current state of dentistry in the world and the prospects of its sustainable development. A traditional Chinese censer was adopted as the pattern, with a strong and stable support on three legs. The dominant diseases of the oral cavity are caries and periodontal diseases, with the inevitable consequence of toothlessness. From the caries 3.5–5 billion people suffer. Moreover, each of these diseases has a wide influence on the development of systemic complications. The territorial range of these diseases and their significant differentiation in severity in different countries and their impact on disability-adjusted life years index are presented (DALY). Edentulousness has a significant impact on the oral health-related quality of life (OHRQoL). The etiology of these diseases is presented, as well as the preventive and therapeutic strategies undertaken as a result of modifying the Deming circle through the fives’ rules idea. The state of development of Dentistry 4.0 is an element of the current stage of the industrial revolution Industry 4.0 and the great achievements of modern dental engineering. Dental treatment examples from the authors’ own clinical practice are given. The systemic safety of a huge number of dentists in the world is discussed, in place of the passive strategy of using more and more advanced personal protective equipment (PPE), introducing our own strategy for the active prevention of the spread of pathogenic microorganisms, including SARS-CoV-2. The ethical aspects of dentists’ activity towards their own patients and the ethical obligations of the dentist community towards society are discussed in detail. This paper is a polemic arguing against the view presented by a group of eminent specialists in the middle of last year in The Lancet. It is impossible to disagree with these views when it comes to waiting for egalitarianism in dental care, increasing the scope of prevention and eliminating discrimination in this area on the basis of scarcity and poverty. The views on the discrimination of dentistry in relation to other branches of medicine are far more debatable. Therefore, relevant world statistics for other branches of medicine are presented. The authors of this paper do not agree with the thesis that interventional dental treatment can be replaced with properly implemented prophylaxis. The final remarks, therefore, present a discussion of the prospects for the development of dentistry based on three pillars, analogous to the traditional Chinese censer obtaining a stable balance thanks to its three legs. The Dentistry Sustainable Development (DSD) > 2020 model, consisting of Global Dental Prevention (GDP), Advanced Interventionist Dentistry 4.0 (AID 4.0), and Dentistry Safety System (DSS), is presented.

Food consumption frequency of Korean adults based on whether or not having chewing difficulty using 2013-2016 KNHANES by sex-stratified comparative analysis

BACKGROUND/OBJECTIVES

This study examined the associations between food consumption frequency of Korean adults and self-perceived chewing difficulty, using the food frequency questionnaire (FFQ, 112 items) from 2013-2016 of the Korea National Health and Nutrition Examination Survey (KNHANES).

SUBJECTS/METHODS

Subjects were divided into not difficult in chewing (NDC) and difficult in chewing (DC) groups, with 24.17% being classified into DC. Males and females consumed 35 and 37 items less frequently than the other sex, respectively. Due to the remarkable sex difference in food consumption, sex-stratified one-sided survey regression analysis was performed after adjusted for the effect of age, household income, and self-rated health status.

RESULTS

Thirty-four items of FFQ were significantly less consumed by the DC group. Females exclusively consumed less beverages and alcohol while males showed the same for fruits and milk·dairy products. Consumption frequency of 8 items such as steamed potatoes·grilled potatoes, stir fried beef, other kimchi·fresh vegetable kimchi, orange, sour pork·pork cutlet, tteokbokki and green tea were significant only in males. In contrast, 17 items including cooked rice with other grains and legumes, boiled egg·steamed egg, Korean cabbage kimchi, banana, and tofu stew·soft tofu stew were significant only for females. Finally, items that showed significance for both were 9 items including loaf bread, ready-to-eat cereal, steamed sweet potatoes·grilled sweet potatoes, stir-fried lotus roots·stir-fried burdock, green laver salad·brown seaweed salads, apples, tomato·cherry tomatoes, squid (raw, dried shredded, boiled, stir-fried), and curd type yogurt.

CONCLUSIONS

Findings in this study suggest chewing difficulty may be an important nutritional issue that has to be dealt with for healthful food consumption, with distinct interest of sex.

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

INTRODUCTION

Ageing leads to physiological cognitive decline that it is worsened in people with neurodegenerative diseases such as Alzheimer's disease. Despite the ongoing search for a solution to this cognitive decline, no effective remedies have been established. It has been determined that modifiable external factors, such as oral health and occlusal function, prevent cognitive decline.

OBJECTIVE

To analyse the primary interactions between occlusal function and cognitive functions.

MAIN FINDINGS

Masticatory function is related to cognitive functions. In particular, current evidence, from both animal and human studies, suggests that the activation of masticatory muscles and proper mastication, with natural teeth or dental prosthesis, induces the release of several mediators and the activation of specific brain areas. Together, they result in higher neuronal activity, neurotrophic support, blood flow and the prevention of amyloid-beta plaque formation. Thus, all the components of the masticatory system must work together in order to preserve cognitive function.

CONCLUSIONS

Available evidence suggests that oral and cognitive health are more interconnected than previously thought. Therefore, maintenance and adequate restoration of the whole masticatory system are important for the prevention of cognitive decline. In summary, oral and chewing health lead to healthy cognitive ageing.

Development and validation of a chewing function questionnaire for Chinese older adults

OBJECTIVES

To develop and validate a questionnaire for assessing chewing function of Chinese older adults.

METHODS

The chewing function questionnaire was validated on older adults recruited from a dental hospital, an elderly home and three community centers in Hong Kong. The participants were asked to indicate their ability to chew on each of the 20 selected food items and to self-rate their overall chewing ability. Chewing function was objectively assessed by asking the participant to chew a color-changeable gum for 90 s. The color of the chewed gum was assessed using a colorimeter. Participant's maximum bite force was also measured by an electronic detector.

RESULTS

A total of 211 elders participated in this study. Ten out of the 20 food items were selected to create the final unidimensional chewing function questionnaire (CFQ). The overall Cronbach's alpha value for the CFQ was 0.912. The weighted kappa value of each food item ranged from 0.6 to 1. In general, participants with larger color change of the chewed gum had significantly higher median rank of the CFQ total score and of the score of each food item (p < 0.01). The CFQ total score was correlated with the color change of the chewed gum as measured by colorimeter (p < 0.001), the maximum bite force (p < 0.001) and self-rated chewing ability (p < 0.001).

CONCLUSION

The new unidimensional chewing function questionnaire is a valid and reliable questionnaire for assessing self-rated chewing ability of Chinese older adults.

CLINICAL SIGNIFICANCE

The newly developed self-reported questionnaire can be used to assess the chewing function of Chinese older adults and dentists can use the information obtained to discuss with their patients regarding the need for oral function rehabilitation, such as the treatment need for fixed or removable dental prosthesis.