Age-related changes in brain regional activity during chewing: a functional magnetic resonance imaging study

The potential positive effect of periodontal treatment on brain function activity using functional magnetic resonance imaging analysis

Background/purpose

There are reports on the relationship between periodontal treatment and the whole body. The purpose of the present study was to investigate the effect of periodontal initial treatment on brain function activity by improving periodontal tissue and the occlusal status of subjects with periodontitis.

Materials and methods

The subjects were 13 patients with periodontitis. Following the patient's informed written consent, the periodontal initial treatment provided to the patient included tooth brushing instruction, scaling and root planning, however, occlusal adjustment was not performed at this stage. Periodontal examination, occlusal force examination and fMRI results were also evaluated at the initial and the reevaluation examinations.

Results

After the periodontal initial treatment had been performed, periodontal tissue had significantly improved. In addition, cerebral blood flow in the insula and primary motor cortex was also improved, as confirmed by fMRI.

Conclusion

This result suggests that the periodontal ligament has recovered and the periodontal ligament neuron have been further subjected to clenching in the insula.

Association Between Subjective Masticatory Function and Mild Cognitive Impairment in Older Adults

AIM

This study aimed to examine the effect of subjective masticatory function on the occurrence of mild cognitive impairment (MCI) by analysing the Korean Longitudinal Study of Ageing (KLoSA) data.

METHODS

The study participants were 2954 KLoSA participants aged 60 years or older in the first wave (2006) who had normal cognitive function. The subjective masticatory function was determined using a survey item, and the responses were grouped into 3 categories, ie, good, moderate, and poor. The occurrence of MCI in the 3 groups was followed up until 2020. Cognitive function was assessed based on the Korean Mini-Mental State Examination score. Age, sex, education level, residence, health insurance type, smoking status, drinking status, and the number of chronic diseases were considered as potential confounders. To examine the occurrence of MCI according to subjective masticatory function, Cox proportional hazard regression analysis was performed.

RESULTS

Cox proportional hazard regression models adjusted for confounders yielded the following results: in men, the risk of MCI was higher in those whose subjective masticatory function was moderate and poor, as compared to those with good subjective masticatory function (adjusted hazard ratio [aHR], 1.33; 95% confidence interval [CI], 1.12-1.58; aHR, 1.23; 95% CI, 1.04-1.46). In contrast, in women, subjective masticatory function did not significantly influence the occurrence of MCI (aHR, 1.05; 95% CI, 0.89-1.24; aHR, 1.08; 95% CI, 0.92-1.28).

CONCLUSIONS

This study suggests that poor masticatory function may be a risk factor for MCI in older men.

Exploring the eating experience of a pneumatically-driven edible robot: Perception, taste, and texture

This study investigated the effects of animated food consumption on human psychology. We developed a movable, edible robot and evaluated the participants' impressions induced by the visualization of its movements and eating of the robot. Although several types of edible robots have been developed, to the best of our knowledge, the psychological effects associated with the eating of a robot have not been investigated. We developed a pneumatically driven edible robot using gelatin and sugar. We examined its perceived appearance and the participants' impressions when it was eaten. In the robot-eating experiment, we evaluated two conditions: one in which the robot was moved and one in which it was stationary. Our results showed that participants perceived the moving robot differently from the stationary robot, leading to varied perceptions, when consuming it. Additionally, we observed a difference in perceived texture when the robot was bitten and chewed under the two conditions. These findings provide valuable insights into the practical applications of edible robots in various contexts, such as the medical field and culinary entertainment.

The influence of parenteral nutrition on the condition of the oral cavity: literature review

Oral health plays a pivotal role in the overall well-being of patients. This article delves into the intricate interplay between oral health and systemic health outcomes in various patient populations, including those undergoing parenteral nutrition in childhood, individuals with impaired swallowing function, and those reliant on long-term enteral or parenteral nutrition. Through a comprehensive review of existing literature, the multifaceted role of oral health maintenance in optimizing nutritional therapy outcomes and enhancing overall quality of life is explored. Alternative forms of nutrition have a profound impact on Oral microbiota, which in turn is reflected in general health and wellbeing. Despite its significance, the importance of systematic oral health assessments and nurse involvement in providing holistic care to patients with complex medical needs has been underestimated. By elucidating critical connections between oral health and systemic health outcomes, this article aims to underscore the significance of oral health in comprehensive patient care and stimulate further research to advance our understanding of this crucial aspect of healthcare management.

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.

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.

Neuroimaging meta-analysis of brain mechanisms of the association between orofacial pain and mastication

BACKGROUND

Temporomandibular disorders (TMD) are characterized by pain and impaired masticatory functions. The Integrated Pain Adaptation Model (IPAM) predicts that alterations in motor activity may be associated with increased pain in some individuals. The IPAM highlights the diversity of patients' responses to orofacial pain and suggests that such diversity is related to the sensorimotor network of the brain. It remains unclear whether the pattern of brain activation reflects the diversity of patients' responses underlying the association between mastication and orofacial pain.

OBJECTIVE

This meta-analysis aims to compare the spatial pattern of brain activation, as the primary outcome of neuroimaging studies, between studies of mastication (i.e. Study 1: mastication of healthy adults) and studies of orofacial pain (i.e. Study 2: muscle pain in healthy adults and Study 3: noxious stimulation of the masticatory system in TMD patients).

METHODS

Neuroimaging meta-analyses were conducted for two groups of studies: (a) mastication of healthy adults (Study 1, 10 studies) and (b) orofacial pain (7 studies), including muscle pain in healthy adults (Study 2) and noxious stimulation of the masticatory system in TMD patients (Study 3). Consistent loci of brain activation were synthesized using Activation Likelihood Estimation (ALE) with an initial cluster-forming threshold (p < .05) and a threshold of cluster size (p < .05, familywise error-corrected).

RESULTS

The orofacial pain studies have shown consistent activation in pain-related regions, including the anterior cingulate cortex and the anterior insula (AIns). A conjunctional analysis of mastication and orofacial pain studies showed joint activation at the left AIns, the left primary motor cortex and the right primary somatosensory cortex.

CONCLUSION

The meta-analytical evidence suggests that the AIns, as a key region in pain, interoception and salience processing, contributes to the pain-mastication association. These findings reveal an additional neural mechanism of the diversity of patients' responses underlying the association between mastication and orofacial pain.

Effect of New Complete Dentures and Simple Dietary Advice on Cognitive Screening Test among Edentulous Older Adults: A Randomized Controlled Trial

Mild cognitive impairment (MCI), including memory loss, has been attracting attention in Japan. This study assessed the effect of new complete dentures provision alone and with dietary intervention on cognitive functions assessed using the Japanese version of the Montreal Cognitive Assessment (MoCA-J). A randomized controlled trial was conducted with 70 older adults who required new complete dentures. The participants had new complete dentures fabricated and were randomly classified into the intervention or control group. The intervention group received simple dietary advice, and the control group only received denture care advice. Cognitive function was assessed using the MoCA-J before and at 3 and 6 months after treatment. The between-group comparison and within-group comparison were analyzed. No significant differences were reported for comparisons between the intervention and control groups. A significant increase was revealed in the within-group comparisons for the total scores between the 3- and 6-month assessments (p = 0.002) and between the baseline and 6-month assessments (p = 0.012) in the intervention group. In the control group, a significant increase in the total scores was not revealed between any of evaluation period. Complete denture replacement combined with simple dietary intervention may help improve MoCA-J scores in edentulous older adults.

Prevalence of pre-operative undiagnosed cognitive impairment and its association with handgrip strength, oral hygiene, and nutritional status in older elective surgical patients in Japan

PURPOSE

Preoperative cognitive impairment is a significant factor influencing post-operative delirium. We have been performing routine pre-operative comprehensive assessments, including evaluation of cognitive function, handgrip strength, oral hygiene, and nutritional status, in patients aged ≥ 65 years since April 2021. This study aimed to examine the completion rate of pre-operative comprehensive assessment and assess the prevalence of pre-operative undiagnosed cognitive impairment.

METHODS

In this prospective observational study including patients aged ≥ 65 years scheduled for elective surgery with general or regional anesthesia, cognitive impairment was defined as a Mini-Cog score ≤ 2, and its associations with handgrip strength, oral hygiene, and nutritional status were evaluated. Oral hygiene and nutritional status were assessed using an oral frailty self-checklist and the Mini Nutritional Assessment-Short Form, respectively. The incidence of pre-operative undiagnosed cognitive impairment was estimated, and its associated factors were explored with multiple logistic regression.

RESULTS

Among 331 eligible patients, the completion rate was 97.7% (305/312). The mean age was 74.8 years, and 13.1% (40/305) (95% confidence interval [CI], 9.7-17.3%) of the patients had pre-operative undiagnosed cognitive impairment. Multiple logistic regression revealed that handgrip strength (odds ratio [OR] = 0.94, 95%CI = 0.89-0.99) and oral frailty self-checklist score (OR = 1.19, 95%CI = 1.02-1.40) were associated with pre-operative undiagnosed cognitive impairment, while the Mini Nutritional Assessment-Short Form score was not significantly associated (OR = 0.97, 95%CI = 0.82-1.14).

CONCLUSIONS

Preoperative comprehensive assessment was feasible. The prevalence of pre-operative undiagnosed cognitive impairment was 13%, and poor handgrip strength and worse oral hygiene were significantly associated factors.

Association between occlusal support and cognitive impairment in older Chinese adults: a community-based study

Introduction

The loss of occlusal support due to tooth loss is associated with systemic diseases. However, there was little about the association between occlusal support and cognitive impairment. The cross-sectional study aimed to investigate their association.

Methods

Cognitive function was assessed and diagnosed in 1,225 community-dwelling adults aged 60 years or older in Jing'an District, Shanghai. Participants were diagnosed with mild cognitive impairment (MCI) by Peterson's criteria, or dementia, according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. We determined the number of functional occlusal supporting areas according to Eichner classifications. We used multivariate logistic regression models to analyze the relationship between occlusal support and cognitive impairment and mediation effect models to analyze the mediation effect of age.

Results

Six hundred sixty participants were diagnosed with cognitive impairment, averaging 79.92 years old. After adjusting age, sex, education level, cigarette smoking, alcohol drinking, cardiovascular disease, and diabetes, individuals with poor occlusal support had an OR of 3.674 (95%CI 1.141-11.829) for cognitive impairment compared to those with good occlusal support. Age mediated 66.53% of the association between the number of functional occlusal supporting areas and cognitive impairment.

Discussion

In this study, cognitive impairment was significantly associated with the number of missing teeth, functional occlusal areas, and Eichner classifications with older community residents. Occlusal support should be a significant concern for people with cognitive impairment.

Oral environment and cerebral blood flow in patients with neurodegenerative dementia: comparison of Alzheimer type dementia and dementia with Lewy bodies

BACKGROUND

The number of patients with dementia is increasing worldwide. Modifying risk factors may significantly reduce the prevalence and cost of dementia. The number of remaining teeth, occlusal force, denture use, and periodontal disease status are associated with the risk of developing dementia. The oral environment may be a risk factor for dementia. This study aimed to investigate the association between the oral environment and cerebral blood flow in patients with mild cognitive impairment and dementia (either Alzheimer type dementia (ATD) or dementia with Lewy bodies (DLB)). We aimed to identify differences in the oral environment according to the underlying neurodegenerative disease.

METHODS

The participants were 25 patients with ATD and 25 patients with DLB who visited the Department of Dementia and Geriatric Medicine, Kanagawa Dental University Hospital. Patients were diagnosed with ATD and DLB by well-trained specialists certified by the Japanese Dementia Society and categorised as Level 3 or 4 by the Functional Assessment Staging of Alzheimer Disease scale. The correlation between oral environment (number of teeth, periodontal tissue, and oral function) and cerebral blood flow in each brain area calculated by single photon emission computed tomography was examined.

RESULTS

The DLB group showed a significant correlation between masticatory performance and cerebral blood flow in some areas, while no such correlation was observed in the ATD group. Significant correlations were found between periodontal pocket depth and bleeding on probing and cerebral blood flow in some areas in both groups, although the correlation was considerable in the ATD group.

CONCLUSIONS

The results of this study suggest that the association between changes in the oral environment and cerebral blood flow may differ among patients with ATD and DLB, depending on the underlying causative disease.

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.

Association of Tooth Loss with Alzheimer's Disease Tau Pathologies Assessed by Positron Emission Tomography

BACKGROUND

Deterioration of the oral environment is one of the risk factors for dementia. A previous study of an Alzheimer's disease (AD) model mouse suggests that tooth loss induces denervation of the mesencephalic trigeminal nucleus and neuroinflammation, possibly leading to accelerated tau dissemination from the nearby locus coeruleus (LC).

OBJECTIVE

To elucidate the relevance of oral conditions and amyloid-β (Aβ) and tau pathologies in human participants.

METHODS

We examined the number of remaining teeth and the biofilm-gingival interface index in 24 AD-spectrum patients and 19 age-matched healthy controls (HCs). They also underwent positron emission tomography (PET) imaging of Aβ and tau with specific radiotracers, 11C-PiB and 18F-PM-PBB3, respectively. All AD-spectrum patients were Aβ-positive, and all HCs were Aβ-negative. We analyzed the correlation between the oral parameters and radiotracer retention.

RESULTS

No differences were found in oral conditions between the AD and HC groups. 11C-PiB retentions did not correlate with the oral indices in either group. In AD-spectrum patients, brain-wide, voxel-based image analysis highlighted several regions, including the LC and associated brainstem substructures, as areas where 18F-PM-PBB3 retentions negatively correlated with the remaining teeth and revealed the correlation of tau deposits in the LC (r = -0.479, p = 0.018) primarily with the hippocampal and neighboring areas. The tau deposition in none of the brain regions was associated with the periodontal status.

CONCLUSIONS

Our findings with previous preclinical evidence imply that tooth loss may enhance AD tau pathogenesis, promoting tau spreading from LC to the hippocampal formation.

Molar loss further exacerbates 2-VO-induced cognitive impairment associated with the activation of p38MAPK/NFκB pathway

Background

Vascular dementia is characterized by reduced cognitive function due to chronic cerebral hypoperfusion and has become a significant public health challenge as the global population ages. Recent studies suggested that molar loss, a common problem among the elderly, may trigger the development of cognitive decline. Our previous study found that the molar loss affected cognitive dysfunction, and the astrocytes in the hippocampus of chronic cerebral ischemia rats were affected, but the underlying mechanism is unclear.

Methods

In this study, we established the animal model of molar loss with 2-VO rats and the Morris water maze was used to test the cognitive ability of rats in each group. The damage to neurons was observed via Nissl staining, and neuronal apoptosis was analyzed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay in the hippocampus of the rats. Quantitative Real-Time PCR and immunohistochemistry and histology (IHC) were used to detect the expression of p38MAPK, NFκB, caspase 3, and iNOS in the hippocampus. The astrocytes were detected by IHC and Immunofluorescence analysis for GFAP. After 2-VO MO surgery, rats were administered DMSO or p38MAPK inhibitor (SB203580) by intrathecal injection.

Results

The Morris water maze test showed that the molar loss aggravated spatial memory learning ability with chronic cerebral ischemia decreased in the rats. The neuronal damage and more apoptotic cells were observed in the hippocampus of 2-VO rats. After the molar loss, the mRNA and protein expression of iNOS, p38MAPK, NFκB, and caspase 3 were further upregulated in 2-VO rats. Molar loss upregulated GFAP expression, and the p38MAPK-positive cells were labeled with the astrocyte marker GFAP. SB203580 reduced cognitive impairment and apoptosis of hippocampal neurons in 2-VO rats following the molar loss.

Conclusion

Molar loss can aggravate cognitive impairment in 2-VO rats to a certain extent. The mechanism of molar loss exacerbating the cognitive decline in 2-VO rats may be associated with the activation of the p38MAPK-NFκB-caspase 3 signaling pathway, which induces neuronal apoptosis.

Is bruxism associated with changes in neural pathways? A systematic review and meta-analysis of clinical studies using neurophysiological techniques

This study aimed to systematically review the literature to identify clinical studies assessing neuroplasticity changes induced by or associated with bruxism or a tooth-clenching task using neurophysiological techniques. Searches were performed in five electronic databases (PubMed, EMBASE, Scopus, Web of Science, and Google Scholar) in April 2020. This review included clinical studies using neurophysiological techniques to assess neuroplasticity changes in healthy participants before and after a tooth-clenching task or comparing bruxers and non-bruxers. The quality assessment was performed with the Joanna Briggs Institute tool and Grading of Recommendations Assessment, Development, and Evaluation. Meta-analyses were conducted with studies reporting similar comparisons regarding masseter motor evoked potential amplitude and signal change outcomes. Of 151 articles identified in the searches, nine were included, and five proceeded to meta-analysis. Included studies presented moderate to very low methodological quality. From these included studies, eight evaluated bruxers and non-bruxers, of which five of them observed brain activity differences between groups, and three found no differences. Even so, all studies have suggested distinct difference in the central excitability between bruxers and non-bruxers, the meta-analysis revealed no statistically significant differences (P > 0.05). It appears that bruxism seems, indeed, to be associated with distinct differences in the neural pathways related to the control of the jaw-closing muscles, but that considerable variability in terms of classification of bruxism and assessment of neuroplasticity hamper a definite conclusion. Future research projects should take these concerns into consideration in order to further the understanding of bruxism physiology and pathophysiology.

How the motor system copes with aging: a quantitative meta-analysis of the effect of aging on motor function control

Motor cognitive functions and their neurophysiology evolve and degrade along the lifespan in a dramatic fashion. Current models of how the brain adapts to aging remain inspired primarily by studies on memory or language processes. Yet, aging is strongly associated with reduced motor independence and the associated degraded interaction with the environment: accordingly, any neurocognitive model of aging not considering the motor system is, ipso facto, incomplete. Here we present a meta-analysis of forty functional brain-imaging studies to address aging effects on motor control. Our results indicate that motor control is associated with aging-related changes in brain activity, involving not only motoric brain regions but also posterior areas such as the occipito-temporal cortex. Notably, some of these differences depend on the specific nature of the motor task and the level of performance achieved by the participants. These findings support neurocognitive models of aging that make fewer anatomical assumptions while also considering tasks-dependent and performance-dependent manifestations. Besides the theoretical implications, the present data also provide additional information for the motor rehabilitation domain, indicating that motor control is a more complex phenomenon than previously understood, to which separate cognitive operations can contribute and decrease in different ways with aging.

Many aspects of neuronal control degrade with ageing, including motor control. Using a meta-analysis of functional MRI images, it is made apparent that the ageing brain relies more on visual strategies than sensory stimuli to maintain motor function.

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.

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.

The Association between Age-Related Changes in Oral Neuromechanics and Alzheimer's Disease

The global population of 80 years and older is predicted to reach 437 million by 2050. As overall brain structure and function progressively degrades, older and younger adults show differences in sensorimotor performance and brain activity in the sensorimotor regions. Oral sensorimotor functions are an important area of focus in natural aging and Alzheimer’s Disease (AD) because oral health issues are commonly found in both elderly and AD populations. While human behavioral studies on changes in oral sensorimotor functions abound, very little is known about their neuronal correlates in normal and pathological aging.

Influential Factors of Masticatory Performance in Older Adults: A Cross-Sectional Study

While appropriate nutrient intake is important for older adults, various oral problems cause decreased masticatory function. This cross-sectional study aimed to identify the factors associated with decreased masticatory performance in older adults. Oral examinations were performed on 80 participants (mean age: 75.10 ± 5.64 years) to determine the number of functional tooth units (FTUs). Symptoms of periodontal and temporomandibular diseases were evaluated via a questionnaire. The tone, elasticity, and dynamic stiffness of the masseter muscle were measured using the Myoton^® PRO device. The mixing ability test was used to assess the masticatory performance, and the mixing ability index (MAI) was calculated. The analysis of covariance test was performed to adjust for confounding factors, and multiple logistic regression analysis was performed to identify the risk factors affecting MAI. A lower MAI was significantly associated with higher tone (p = 0.006) and lower elasticity (p = 0.013). The number of FTUs (adjusted odds ratio (OR) = 0.724, p = 0.029), tone (adjusted OR = 1.215, p = 0.016), and elasticity (adjusted OR = 4.789, p = 0.038) were independently associated with the MAI. Muscle function training and prosthetic treatments may help increase masticatory performance in older adults, which would improve overall health.

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.

Evolution of the speech-ready brain: The voice/jaw connection in the human motor cortex

A prominent model of the origins of speech, known as the "frame/content" theory, posits that oscillatory lowering and raising of the jaw provided an evolutionary scaffold for the development of syllable structure in speech. Because such oscillations are nonvocal in most nonhuman primates, the evolution of speech required the addition of vocalization onto this scaffold in order to turn such jaw oscillations into vocalized syllables. In the present functional MRI study, we demonstrate overlapping somatotopic representations between the larynx and the jaw muscles in the human primary motor cortex. This proximity between the larynx and jaw in the brain might support the coupling between vocalization and jaw oscillations to generate syllable structure. This model suggests that humans inherited voluntary control of jaw oscillations from ancestral species, but added voluntary control of vocalization onto this via the evolution of a new brain area that came to be situated near the jaw region in the human motor cortex.

The effect of masticatory behaviour on generalized attention in heathy volunteers

AIM

As our society ages, the number of people living with dementia also steadily increases. Some work has focused on masticatory behaviour as a form of daily health care that could help prevent cognitive impairment and dementia. However, it is not yet clear how masticatory behaviour influences various cognitive functions. Therefore, the purpose of this study was to examine the effect of masticatory behaviour on the decline of generalized attention, an important cognitive function.

METHODS

Participants were 35 healthy, dentulous individuals without stomatognathic abnormalities (24 men, 11 women; mean age: 56.8 ± 4.8 years). All participants completed three interventions: mastication, foot-stepping, and none (control). Pre- and post-intervention measures of generalized attention were measured by using neuropsychological tests to examine general attention; the results were then compared. Simultaneously, during the generalized attention task, the functional activity of the prefrontal cortex was observed on functional near-infrared spectroscopy.

RESULTS

Response time of generalized attention improved in both the masticatory and foot-stepping interventions. There was a transient increase in oxyhaemoglobin activity in the right and left prefrontal cortices in the masticatory intervention.

CONCLUSIONS

Masticatory behaviour may be involved in a partial improvement of generalized attention and may induce prefrontal cortex activity in middle-aged and older adults.

The relation of poor mastication with cognition and dementia risk: a population-based longitudinal study

We investigated the effect of poor masticatory ability on cognitive trajectories and dementia risk in older adults. 544 cognitively intact adults aged ≥50 were followed for up to 22 years. Cognitive domains (verbal, spatial/fluid, memory, and perceptual speed) were assessed at baseline and follow-ups. Dementia was ascertained according to standard criteria. Masticatory ability was assessed using the Eichner Index and categorized according to the number of posterior occlusal zones: A (all four), B (3-1), and C (none).

At baseline, 147 (27.0%) participants were in Eichner category A, 169 (31.1%) in B and 228 (41.9%) in C. After the age of 65, participants in Eichner category B and C showed an accelerated decline in spatial/fluid abilities (β: -0.16, 95% CI: -0.30 to -0.03) and (β: -0.15, 95% CI: -0.28 to -0.02), respectively. Over the follow-up, 52 incident dementia cases were identified. Eichner categories B or C were not associated with an increased risk of dementia, compared to category A (Hazard Ratio [HR]: 0.83, 95% CI: 0.39 to 1.76 and HR: 0.63, 95% CI: 0.30 to 1.29, respectively).

Poor masticatory ability is associated with an accelerated cognitive decline in fluid/spatial abilities, however it was not related to a higher risk of dementia.

An fMRI Study of the Brain Network Involved in Teeth Tapping in Elderly Adults

Cortical activity during jaw movement has been analyzed using various non-invasive brain imaging methods, but the contribution of orofacial sensory input to voluntary jaw movements remains unclear. In this study, we used functional magnetic resonance imaging (fMRI) to observe brain activities during a simple teeth tapping task in adult dentulous (AD), older dentulous (OD), and older edentulous subjects who wore dentures (OEd) or did not wear dentures (OE) to analyze their functional network connections. (1) To assess the effect of age on natural activation patterns during teeth tapping, a comparison of groups with natural dentition—AD and OD—was undertaken. A general linear model analysis indicated that the major activated site in the AD group was the primary sensory cortex (SI) and motor cortex (MI) (p < 0.05, family wise error corrected). In the OD group, teeth tapping induced brain activity at various foci (p < 0.05, family wise error corrected), including the SI, MI, insula cortex, supplementary motor cortex (SMC)/premotor cortex (PMA), cerebellum, thalamus, and basal ganglia in each group. (2) Group comparisons between the OD and OEd subjects showed decreased activity in the SI, MI, Brodmann’s area 6 (BA6), thalamus (ventral posteromedial nucleus, VPM), basal ganglia, and insular cortex (p ¡ 0.005, uncorrected). This suggested that the decreased S1/M1 activity in the OEd group was related to missing teeth, which led to reduced periodontal afferents. (3) A conjunction analysis in the OD and OEd/OE groups revealed that commonly activated areas were the MI, SI, cerebellum, BA6, thalamus (VPM), and basal ganglia (putamen; p < 0.05, FWE corrected). These areas have been associated with voluntary movements. (4) Psychophysiological interaction analysis (OEd vs OE) showed that subcortical and cortical structures, such as the MI, SI, DLPFC, SMC/PMA, insula cortex, basal ganglia, and cerebellum, likely function as hubs and form an integrated network that participates in the control of teeth tapping. These results suggest that oral sensory inputs are involved in the control of teeth tapping through feedforward control of intended movements, as well as feedback control of ongoing movements.

Loss of Functional Dentition is Associated with Cognitive Impairment

BACKGROUND

Although tooth loss is known to increase the risk of cognitive impairment and dementia, few studies have investigated the association between functional teeth including rehabilitated lost teeth and cognitive functionObjective:We investigated the associations of the numbers of functional teeth and functional occlusal units with cognitive impairment and cognitive function in late life.

METHODS

The current study was conducted as a part of the Korean Longitudinal Study on Cognitive Aging and Dementia (KLOSCAD), a community-based elderly cohort study. We analyzed 411 participants who have agreed with the additional dental exam. Geriatric psychiatrists and neuropsychologists administered the Consortium to Establish a Registry for Alzheimer's disease Assessment Packet Clinical and Neuropsychological Assessment Battery to all participants, and dentists examined their dental status.

RESULTS

Higher number of functional teeth (OR = 0.955, 95% CI = 0.914-0.997, p = 0.037) and higher number of functional occlusal units (OR = 0.900, 95% CI = 0.813-0.996, p = 0.042) were associated with lower odds of cognitive impairment. When we analyzed these relationships separated by the location of teeth, only the numbers of functional teeth (OR = 0.566, 95% CI = 0.373-0.857, p = 0.007) and functional occlusal units (OR = 0.399, 95% CI = 0.213-0.748, p = 0.004) in the premolar area were associated with lower odds of cognitive impairment.

CONCLUSION

Loss of functional teeth and functional occlusal units (especially in the premolar region) were associated with increased cognitive impairment.

Functional Adaptation of Oromotor Functions and Aging: A Focused Review of the Evidence From Brain Neuroimaging Research

“Practice makes perfect” is a principle widely applied when one is acquiring a new sensorimotor skill to cope with challenges from a new environment. In terms of oral healthcare, the traditional view holds that restoring decayed structures is one of the primary aims of treatment. This assumes that the patient’s oromotor functions would be recovered back to normal levels after the restoration. However, in older patients, such a structural–functional coupling after dental treatment shows a great degree of individual variations. For example, after prosthodontic treatment, some patients would adapt themselves quickly to the new dentures, while others would not. In this Focused Review, I argue that the functional aspects of adaptation—which would be predominantly associated with the brain mechanisms of cognitive processing and motor learning—play a critical role in the individual differences in the adaptive behaviors of oromotor functions. This thesis is critical to geriatric oral healthcare since the variation in the capacity of cognitive processing and motor learning is critically associated with aging. In this review, (a) the association between aging and the brain-stomatognathic axis will be introduced; (b) the brain mechanisms underlying the association between aging, compensatory behavior, and motor learning will be briefly summarized; (c) the neuroimaging evidence that suggests the role of cognitive processing and motor learning in oromotor functions will be summarized, and critically, the brain mechanisms underlying mastication and swallowing in older people will be discussed; and (d) based on the current knowledge, an experimental framework for investigating the association between aging and the functional adaptation of oromotor functions will be proposed. Finally, I will comment on the practical implications of this framework and postulate questions open for future research.

Effect of Mastication Muscle Activity on Prefrontal Cortex NIRS Measurement: A Pilot Study

Changes in NIRS signals are related to changes in local cerebral blood flow or oxy-Hb concentration. On the other hand, recent studies have revealed the effect of chewing gum on cognitive performance, stress control etc. which accompanied brain activity in the prefrontal cortex (PFC). However, these relationships are still controversial. To evaluate the chewing effect on PFC, NIRS seems to be a suitable method of imaging such results. When measuring NIRS on PFC, blood volume in superficial tissues (scalp, skin, muscle) might have some affect. The aim of the present study was to clarify the effect of the anterior temporal muscle on NIRS signals during gum chewing. Eight healthy volunteers participated. Two-channel NIRS (HOT-1000, NeU, Japan), which can distinguish total-Hb concentrations in deep tissue and superficial tissue layers, was used. In addition to a conventional optode separation distance of 3.0 cm, Hot 1000 has a short distance of 1.0 cm (NEAR channel) to measure NIRS signals that originate exclusively from surface tissues. NIRS probes were placed at Fp1 and Fp2 in the normal probe setting. The headset was displaced to the left in order to allow the left probe to be placed over the left anterior temporal muscle. In the normal setting, the superficial signal curve shows no notable change; however, the neural (calculated and defined in HOT-1000) and deep curves show an increase during the gum chewing task. At the deviated setting, all three signals show marked changes during the task. Total-Hb concentration in the deviated probe setting is significantly large (p < 0.05) than that of in the normal probe setting. When using gum chewing as a task, it would be better to consider a probe position carefully so that the influence of muscle activity on NIRS signal can be distinguished.

Omega-3 PUFA metabolism and brain modifications during aging

In Canada, 5.5 million (16% of Canadians) adults are >65 years old and projections suggest this number will be approximately 20% of Canadians by 2024. A major concern regarding old age is a decline in health, especially if this entails a loss of self-sufficiency and independence caused by a decline in cognition. The brain contains 60% of fat and is one of the most concentrated organs in long chain omega-3 fatty acids such as docosahexaenoic acid (DHA). During aging, there are physiological modifications in the metabolism of lipids that could also have consequences on brain structure and levels of DHA. This review will hence discuss the physiological modifications in the metabolism of lipids during aging with a focus on long chain omega-3 and omega-6 fatty acids and also outline the structural and functional modifications of the brain during aging including brain lipid modifications and its relation to higher levels of DHA and cognition. Therefore, in this review, we outline the importance of collecting more data on the biology of aging since it might highly improve our understanding about what are «normal» modifications occurring during aging and what can become pathological.

Reciprocal cortical activation patterns during incisal and molar biting correlated with bite force levels: an fMRI study

In humans, the incisors and molars have distinct functions during mastication, analogous to the two main types of handgrip, the precision and power grips. In the present study, we investigated cortical activation and masticatory muscle activity during incisal and molar biting via simultaneous functional magnetic resonance imaging and electromyogram (EMG) recordings. We conducted recordings in 15 healthy adult participants while they performed incisal and molar biting tasks at three step-wise force levels using two custom-made splints. Regarding the results of the ROI analysis, we found a significantly stronger positive linear correlation between the blood oxygenation level dependent signal and EMG activity during molar biting than incisal biting, which was particularly prominent in the primary sensorimotor cortex and the cerebellum. We also found a significantly stronger negative linear correlation during incisal biting than molar biting, which was particularly prominent in the rostral cingulate motor area, superior frontal gyrus, and caudate nucleus. These findings indicate that molar biting enables powerful chewing: brain activity in several brain areas related to motor function was increased with increasing bite force levels, while incisal biting enables fine motor control: brain activity in several brain areas related to motor control was increased with reduced bite force levels.

Mind your teeth-The relationship between mastication and cognition

This article explores the multifactorial relationship between mastication and cognition, with a focus on dementia. Older persons, especially those with dementia, are at great risk of suffering from oral health problems such as orofacial pain and loss of natural teeth. A possible explanation could be that the cognitive and motor impairments resulting from dementia cause a decrease in self‐care and as such, a worsening of oral health. An alternative explanation is that cognition and oral health influence each other. Animal studies show that a decrease in masticatory activity, for example, due to a soft diet or loss of teeth, causes memory loss and neuronal degeneration. The relationship between mastication and cognition has also been researched in human studies, but a cause‐effect relationship has not been proven. It is likely that multiple factors play a role in this relationship, such as self‐care, nutrition, stress and pain.

Occlusal force predicts global motion coherence threshold in adolescent boys

Background

Beneficial effects of mastication on cognitive abilities in the elderly have been shown in human studies. However, little is currently known about the effect of masticatory stimulation on cognitive and perceptual ability in younger populations. The purpose of the present study is to investigate the influences of masticatory stimulation on perceptual ability in adolescent boys.

Methods

The present study examined the relationship between occlusal force (i.e., masticatory stimulation) and visual perception ability in adolescent boys. Visual perception ability was quantified by measuring global motion coherence threshold using psychophysical method. As an index of masticatory stimulation, occlusal force was measured by pressure sensitive film. We also measured participants’ athletic ability, e.g. aerobic capacity and grip strength, as potential confounding factor.

Results

The multiple regression analysis revealed a significant negative correlation between global motion coherence threshold and occlusal force, which persisted after controlling for confounding factors such as age and aerobic capacity.

Conclusions

This finding indicates that masticatory stimulation enhances visual perception in adolescent boys, indicating the possibility that beneficial effects of masticatory stimulation are observed not only in the elderly but in developing population consistently with the findings of the previous animal studies.

Mastication as a tool to prevent cognitive dysfunctions

Mastication as we all know has always been related to its primary function of digestion, but little do we know that it produces an enhancing effect on general health, especially the cognitive performance related aspects of memory. Recent studies have shown its association with activation of various brain regions, however little is known about its effects on neuronal activity in these specified regions. According to the enormous evidences collected so far, mastication has proved to be effective in conducting huge amount of sensory information to the brain, and maintaining learning and memory functions of hippocampus. Therefore it is essential that we maintain normal occlusion and preserve the masticatory function as long as possible to prevent the attenuation of hippocampus, caused by occlusal disharmony and reduced mastication. We provide an overview on how mastication activates various cortical areas of the brain and how an increase in the cerebral blood oxygen level of hippocampus and prefrontal cortex (PFC) accentuates the learning and memory process. We also justify why maintaining and establishing a normal occlusion is important from neurological point of view.

Oral health for an ageing population: the importance of a natural dentition in older adults

Despite progress in dentistry, tooth loss in old age is still a reality, even more so in long-term-care residents. However, recent trends indicate that natural teeth are lost later in life. Functional decline and age-related pathologies have to be considered in oral health care for this vulnerable population. Retaining and restoring teeth and oral function in elders is important. Tooth loss significantly impairs masticatory performance, which cannot be fully restored by prosthodontic means. Hence an unconscious change in food intake occurs, often involving malnutrition and withdrawal from common meals. Poor oral appearance and bad breath may further impede social activities. Although a chewing activity may be beneficial for cognitive function, natural teeth can present a considerable risk for fragile elders, in whom aspiration of biofilm can lead to pneumonia and death. The presence of natural teeth is also correlated with higher life expectancy, but socio-economic confounding factors have to be considered. When evaluating oral health in the elderly population, standards and priorities for reporting oral health outcome measures have to be defined. Anatomical indicators such as the number of natural teeth or the presence of prostheses might be one option for reporting. However, functional indicators such as masticatory performance and patient-centred outcome measures may be more relevant. In conclusion, there is an overwhelming body of evidence that maintaining a healthy natural dentition in old age is beneficial from a structural, functional and psycho-social point of view.

Dental deafferentation and brain damage: A review and a hypothesis

In the last few decades, neurobiological and human brain imaging research have greatly advanced our understanding of brain mechanisms that support perception and memory, as well as their function in daily activities. Knowledge of the neurobiological mechanisms behind the deafferentation of stomatognathic systems has also expanded greatly in recent decades. In particular, current studies reveal that the peripheral deafferentations of stomatognathic systems may be projected globally into the central nervous system (CNS) and become an associated critical factor in triggering and aggravating neurodegenerative diseases. This review explores basic neurobiological mechanisms associated with the deafferentation of stomatognathic systems. Further included is a discussion on tooth loss and other dental deafferentation (DD) mechanisms, with a focus on dental and masticatory apparatuses associated with brain functions and which may underlie the changes observed in the aging brain. A new hypothesis is presented where DD and changes in the functionality of teeth and the masticatory apparatus may cause brain damage as a result of altered cerebral circulation and dysfunctional homeostasis. Furthermore, multiple recurrent reorganizations of the brain may be a triggering or contributing risk factor in the onset and progression of neurodegenerative conditions such as Alzheimer's disease (AD). A growing understanding of the association between DD and brain aging may lead to solutions in treating and preventing cognitive decline and neurodegenerative diseases.

Does reduced mastication influence cognitive and systemic health during aging?

There is a growing body of literature which suggests that oral health and mastication can influence cognitive and systemic health during aging. However, it is currently unclear whether oral health, masticatory efficiency, cognitive health and systemic health merely deteriorate independently with age, or whether mechanisms exist linking mastication to cognitive and systemic health directly. The aim of this paper is to review the extent to which reduced mastication influences cognitive and systemic health during aging because this knowledge may underpin future interventions that improve quality of life. Current evidence suggests that a deterioration in mastication and oral health during aging can have: 1) direct effects on systemic health through mechanisms such as the migration of the oral microbiota into the systemic environment, and 2) indirect effects on systemic health through changes nutrient intake. A loss of teeth and reduction in masticatory efficiency during aging can have: 1) direct effects on cognitive performance and potentially impact cognitive health through mechanisms such as enhanced adult hippocampal neurogenesis, and 2) indirect effects on cognitive health through changes in nutrient intake. It is concluded that oral health and masticatory efficiency are modifiable factors which influence the risk poor cognitive and systemic health during aging, although it is currently premature to propose chewing-based interventions to slow the rate of cognitive decline and improve cognitive health during aging. Future research should include large-scale longitudinal studies which control for the types of confounding factors which concurrently influence the association between mastication and cognitive and systemic health.

Revisiting the link between cognitive decline and masticatory dysfunction

Age-related decline in cognitive functions and dementia are major challenges in geriatric healthcare. Accumulating evidence from clinical, epidemiological and animal research suggests that tooth loss may be a risk factor for the decline of cognitive functions. This issue highlights the role of the brain-stomatognathic axis in geriatric medicine. Whether input from the stomatognathic apparatus can affect the brain remains an open debate. By revisiting the evidence published in the past five years, we argue that the hypothesis regarding the association between cognitive decline and masticatory dysfunction should be carefully interpreted. Most of the available clinical and epidemiological studies present only cross-sectional data. With respect to the prospective studies, important confounding factors, such as nutritional and physical conditions, were not fully controlled for. Animal research has revealed that hippocampal deficits may play key roles in the observed cognitive decline. However, experimental intervention and outcome assessments may not capture the condition of human subjects. Brain neuroimaging research may be suitable for bridging the gap between clinical and animal research, potentially contributing to (a) the clarification of the brain network associated with mastication, (b) the identification of brain imaging markers for exploring the mechanisms underlying long-term changes in masticatory functions, and (c) the elucidation of interactions between mastication and other cognitive-affective processing systems. Three potential models of the brain-stomatognathic axis and relevant hypotheses are summarized, focusing on the sensory feedback mechanisms, the compensation of motor control, and cerebellar deficits. Finally, we highlight four critical aspects of study and experimental design that should be considered in future research: (a) the refinement of the considered behavioral assessments, (b) the inclusion of baseline changes in mental and physical conditions,

Occlusal loading during biting from an experimental and simulation point of view

OBJECTIVES

Occlusal loading during clenching and biting is achieved by the action of the masticatory system, and forms the basis for the evaluation of the functional performance of prosthodontic and maxillofacial components. This review provides an overview of (i) current bite force measurement techniques and their limitations and (ii) the use of computational modelling to predict bite force. A brief simulation study highlighting the challenges of current computational dental models is also presented.

METHODS

Appropriate studies were used to highlight the development and current bite force measurement methodologies and state-of-the-art simulation for computing bite forces using biomechanical models.

RESULTS

While a number of strategies have been developed to measure occlusal forces in three-dimensions, the use of strain-gauges, piezo-electric sensors and pressure sheets remain the most widespread. In addition to experimental-based measurement techniques, bite force may be also estimated using computational models of the masticatory system. Simulations of different bite force models clearly show that the use of three-dimensional force measurements enriches the evaluation of masticatory functional performance.

SIGNIFICANCE

Hence, combining computational modelling with three-dimensional force measurement techniques can significantly improve the evaluation of masticatory system and the functional performance of prosthodontic components.

Brain activation patterns during unilateral premolar occlusion

OBJECTIVE

To observe the characteristics of brain activation during unilateral premolar occlusion.

METHODS

Functional magnetic resonance imaging was collected from 10 healthy volunteers during occlusion of the left first premolar (L1), left second premolar (L2), and right first premolar (R1). The brain activation patterns were analyzed, and the primary sensorimotor cortex, supplementary motor area, insula, thalamus, and prefrontal cortex were chosen as regions of interest.

RESULTS

Single premolar occlusion activated the precentral gyrus, postcentral gyrus, cerebellum, thalamus, frontal lobe, hippocampus, cingulate gyrus, and parietal lobe. The brain areas showing activation during single premolar occlusion were similar to those activated by chewing. The activation pattern of L1 was more similar to that of L2 than R1. No significant left and right hemisphere differences in signal intensity were detected within the regions of interest.

CONCLUSION

Brain activation patterns from two ipsilateral premolars were more similar than the pattern from a contralateral premolar.