Oral tactile sensitivity and masticatory performance are impaired in stroke patients

Improvement of oral function and its impact on oral food intake in subacute stroke patients: A prospective study with dental intervention

BACKGROUND

The association between oral food intake and oral function during the subacute stage of stroke is not well known.

OBJECTIVE

To investigate (1) oral function changes in subacute stroke patients and (2) association between oral function and oral intake status at several time points.

METHODS

In a prospective study involving 324 stroke patients at a convalescent rehabilitation unit, four oral function parameters (maximum tongue pressure, MTP; lip-tongue motor function, LTMF; maximum occlusal force, MOF and oral health assessment tool, OHAT) were quantitatively measured upon admission (T0), at 1 month (T1) and 2 months (T2). Oral feeding status was assessed using the Functional Oral Intake Scale (FOIS) and divided based on the FOIS score into the dysphagic and regular diet groups. The changes in oral functions at the three time points were tested using generalized estimating equation analysis. The association between FOIS groups and oral functions at T1 and T2 was analysed by means of logistic regression analysis.

RESULTS

All oral function parameters improved significantly over time during the hospital stay (mean differences: 4.9 for MTP, 0.6 for LTMF, 1.1 for MOF and -1.8 for OHAT). The FOIS groups were significantly associated with MTP (p < .05) and OHAT (p < .05) at both T1 and T2.

CONCLUSION

Our findings suggest that oral function significantly improves in patients during subacute stroke rehabilitation and better oral health can be associated with better oral intake. Improved oral function through dental intervention and oral rehabilitation may contribute to gains in oral food intake.

The Feel of Speech: Multisystem and Polymodal Somatosensation in Speech Production

PURPOSE

The oral structures such as the tongue and lips have remarkable somatosensory capacities, but understanding the roles of somatosensation in speech production requires a more comprehensive knowledge of somatosensation in the speech production system in its entirety, including the respiratory, laryngeal, and supralaryngeal subsystems. This review was conducted to summarize the system-wide somatosensory information available for speech production.

METHOD

The search was conducted with PubMed/Medline and Google Scholar for articles published until November 2023. Numerous search terms were used in conducting the review, which covered the topics of psychophysics, basic and clinical behavioral research, neuroanatomy, and neuroscience.

RESULTS AND CONCLUSIONS

The current understanding of speech somatosensation rests primarily on the two pillars of psychophysics and neuroscience. The confluence of polymodal afferent streams supports the development, maintenance, and refinement of speech production. Receptors are both canonical and noncanonical, with the latter occurring especially in the muscles innervated by the facial nerve. Somatosensory representation in the cortex is disproportionately large and provides for sensory interactions. Speech somatosensory function is robust over the lifespan, with possible declines in advanced aging. The understanding of somatosensation in speech disorders is largely disconnected from research and theory on speech production. A speech somatoscape is proposed as the generalized, system-wide sensation of speech production, with implications for speech development, speech motor control, and speech disorders.

Chewing Function with Efficiency Tests in Subjects Wearing Clear Aligners

This study assessed the masticatory function of participants wearing clear aligners in order to determine whether these devices can be worn even when eating and therefore worn to extend treatment time and boost treatment effectiveness. An intercontrol test was conducted on 20 patients who received Invisalign® treatment. Each participant was instructed to chew two pieces of Hue-Check Gum® chewing gum (one pink and the other blue) in 5, 10, and 20 cycles both with and without aligners. After being removed from the oral cavity, the gum was dried and pressed using a 1 × 50 × 50 mm model that was 3D printed with a transparent layer in between. After being scanned on both sides with a flatbed scanner at 600 dpi, the samples were saved as jpg files and subjected to an optoelectronic examination using ViewGum software. To validate the procedure, a control group from a different institution (University of Bern) was used. A statistical analysis of the data was carried out. The Shapiro-Wilk test was used to confirm the normality of the samples. A one-way ANOVA test, a homogeneity of variance test, and a t-test did not reveal statistically significant differences between the two control groups, thus validating the methodology employed. In summary, clear aligners do not radically change the masticatory function while they are worn. As a result, clinicians can exploit the aligners for chewing to obtain a better fit of the plastic material to the dental surface and to attachments. Treatment times for patients could also be shorter.

Methodological approaches to assess tactile sensitivity in the food context-A scoping review

In contrast to taste sensitivity, the assessment of texture or tactile sensitivity has received relatively little attention in the food context. Texture plays an important role in food preferences and food intake, and individual differences make it important to understand physiological drivers of perception as tactile sensitivity. The multi-dimensional and dynamic aspects of texture perception suggest there is not one single method that can explain individual differences. This scoping review aims to systematically map methods assessing tactile sensitivity, in the context of food, highlighting differences in approach and implementation. Eligibility criteria included papers describing methods to assess individual differences in tactile sensitivity, that involved human participants and the context was relevant to food behavior. Sources are peer-reviewed publications of original research in English. In mapping the methods, we assessed how they relate to food texture parameters (mechanical, geometrical, and surface) and the dynamics of breaking down (touch with hand, first bite/sip, oral processing, residual or after-swallowing sensations). We also review other parameters associated (oral processing, preference, diet and food intake behavior). The literature in this relatively young area is still very fragmented and it is difficult to have a clear picture regarding best practices or recommendations for the measurement of tactile sensitivity in the food context. Future studies should aim to methodological harmonization for application in the food behavior area, with a design of experiment combining different aspects of tactile sensitivity to food, focusing on the thresholds and perceived intensity of textural parameters as well as affective and behavioral responses, and covering the whole spectrum of tactile texture perception (mechanical, geometrics, and surface), including the dynamics of perception.

Feel it or deal with it: Oral perception and aspiration risk in early stroke

BACKGROUND

Sensation and perception impairments are significant problems faced by individuals with early-stage stroke. Sensory inputs needed in swallowing guide the perceptual process with the involvement of cognitive functions. In the absence of sensory input, bolus perception may be altered, and swallowing safety may be compromised.

OBJECTIVES

This study aims to evaluate the oral perception of volume change and the aspiration risk of individuals with stroke and determine the relationship between oral perception and aspiration risk.

METHODS

Total participants were 35. The Gugging Swallowing Screening Test (GUSS) was used to determine individuals' risk of aspiration and divide them into groups 'aspiration risk' and 'non-aspiration risk'. The Oral Perception of Liquid Volume Changes Test (OPLVCT) was used to determine the level of oral perception.

RESULTS

The groups were statistically similar in terms of age and other descriptives. When the OPLVC test was examined, the scores of the aspiration risk group were significantly lower (p < .001). In addition, a moderate negative correlation was found between aspiration risk and the OPLVC scores (r: -0.502; p < .001).

CONCLUSION

In this study, a relationship was found between aspiration risk and oral perception. It also revealed that individuals with stroke who are at risk of aspiration have low oral perception abilities. Based on these results, it was concluded that these individuals cannot reliably determine the maximum volume of liquid to be consumed without assistance. We suggest that evaluations and training of oral perception should be added to the rehabilitation of individuals with stroke.

Clinical Characteristics and Rehabilitation Strategies for the Stomatognathic System Disturbances in Patients with Stroke: A Systematic Review

Background: Understanding the stomatognathic system disturbances is key to diagnosing them early and implementing rehabilitation approaches to promote functional recovery. The objective of this study was to systematically review all published data that examined the assessment and rehabilitation strategies for the stomatognathic system disturbances in patients with stroke. Methods: Five databases (i.e., PubMed/MEDLINE, Scopus, Science Direct, Web of Science, and PEDro), were screened for manuscripts that included the assessment and rehabilitation strategies for stomatognathic system disturbances. The methodological quality was evaluated using the Mixed Methods Appraisal Tool. Results: Sixteen articles were included in this systematic review. The most frequently reported symptoms in patients with stroke included stiffness and thickness of the masseter muscle on the affected side and suprahyoid muscles; facial muscles' asymmetry and weakness; temporomandibular disorders; and a reduced maximum lip force, tongue pressure, and saliva flow rate. The rehabilitation strategies more frequently reported included exercises directed to the jaw, temporomandibular joint, tongue, and neck. The mean score for methodological quality was 85%. Conclusion: The stomatognathic system disturbances are frequently reported among patients with stroke, leading to dysfunction in masticatory performance or swallowing. More studies on interventions for stomatognathic system disturbances are required before conclusions may be drawn. Key Practitioner Message: This systematic review has clinical implications for rehabilitation practices, given that the results may help to develop early assessment and rehabilitation strategies for stomatognathic disturbances in patients with stroke.

Masticatory function of stroke patients: A systematic review with meta-analysis

PURPOSE

The present systematic review and meta-analysis aimed to summarise the current information on the masticatory function of stroke patients.

METHODS

Four electronic databases (Medline, Embase, CINAHL and Web of Science) were searched for relevant observational studies and clinical trials (up to Jun 2021) on the masticatory function of stroke patients. Two reviewers independently performed study selection and quality assessments (using JBI Critical Appraisal Checklist). Meta-analysis was conducted for the comparison of bite force and masticatory performance using standardised mean difference (SMD). Of the 3837 records identified, nine studies, corresponding to 11 papers and 302 participants, were included in the analysis.

RESULTS

The maximum bite force of stroke patients was significantly lower than that of the healthy individuals (SMD -0.52, 95% CI: -0.95 to -0.08, P = .02). There was no significant difference between the ipsi-lesional and the contra-lesional sides of the same stroke patient (SMD 0.13, 95% CI: -0.14 to 0.39, P = .34). Stroke patients had lower masticatory performance than healthy people (SMD -0.97, 95% CI: 0.57 to 1.37, P < .00001), and the contra-lesional side was worse than the ipsi-lesional side. Electromyographic analysis indicated that muscle activation of stroke patients was poorer than the healthy individuals, and stroke patients seem to exhibit dysfunction in the recruiting and firing of motor units.

CONCLUSIONS

Stroke patients have lower maximum bite force and masticatory performance than healthy people, with masticatory performance being the most affected.

Associations of general health conditions with masticatory performance and maximum bite force in older adults: A systematic review of cross-sectional studies

OBJECTIVES

To give an overview of the current evidence on the associations of general health conditions with masticatory performance and maximum bite force in older adults.

DATA/SOURCES

Three electronic databases (Medline via PubMed, Embase via Ovid and CINAHL Plus via EBSCOhost) were searched up to September 2021 for cross-sectional studies on general health conditions and masticatory performance or maximum bite force in older adults. Methodological quality of the included studies was independently evaluated based on Joanna Briggs Institute critical appraisal checklist for analytical cross-sectional studies. Data on the associations between general health conditions and masticatory performance or maximum bite force were extracted.

STUDY SELECTION

Of the 5133 records identified, 39 studies (43 articles) were included in this review. Significant negative associations were found between masticatory performance and stroke, sarcopenia, amyotrophic lateral sclerosis, chronic obstructive pulmonary disease, dyspepsia, dysphagia, anorexia, and carotid atherosclerosis. Significant negative association was found between maximum bite force and sarcopenia. There were equivocal results on the association between masticatory performance and diabetes mellitus, and between maximum bite force and stroke, and amyotrophic lateral sclerosis. There was no significant association between masticatory performance and metabolic syndrome, and between maximum bite force and progress of Parkinson's disease. Most studies revealed positive associations of physical function with masticatory performance and maximum bite force.

CONCLUSIONS

Negative associations between masticatory function of older adults and presence of several systemic diseases have been reported in a number of studies while there are positive associations between masticatory function and some physical function indicators.

CLINICAL SIGNIFICANCE

This study provides valuable information on the association of masticatory function with general health, which draws clinicians' attention to the masticatory function of older adults who suffer from certain systemic diseases or physical dysfunction, and to the need to improve their masticatory ability to achieve healthy aging.

Age-related changes in oral sensitivity, taste and smell

Oropharyngeal sensitivity plays a vital role in the initiation of the swallowing reflex and is thought to decline as part of the aging-process. Taste and smell functions appear to decline with age as well. The aim of our study was to generate data of oral sensitivity in healthy participants for future studies and to analyse age-related changes and their interdependence by measuring oral sensitivity, taste, and smell function. The experiment involved 30 participants younger than and 30 participants older than 60. Sensitivity threshold as a surrogate of oral sensitivity was measured at the anterior faucial pillar by electrical stimulation using commercially available pudendal electrode mounted on a gloved finger. Smell and taste were evaluated using commercially available test kits. Mean sensitivity was lower in young participants compared to older participants (1.9 ± 0.59 mA vs. 2.42 ± 1.03 mA; p = 0.021). Young participants also performed better in smell (Score 11.13 ± 0.86 vs 9.3 ± 1.93; p < 0.001) and taste examinations (Score 11.83 ± 1.86 vs 8.53 ± 3.18; p < 0.001). ANCOVA revealed a statistical association between sensitivity and smell (p = 0.08) that was moderated by age (p = 0.044). Electrical threshold testing at the anterior faucial pillar is a simple, safe, and accurate diagnostic measure of oral sensitivity. We detected a decline of oral sensitivity, taste, and smell in older adults.Trial registration: Clinicaltrials.gov, NCT03240965. Registered 7th August 2017- https://clinicaltrials.gov/ct2/show/NCT03240965 .

Sociomedical and oral factors affecting masticatory performance in an older population

OBJECTIVES

To assess the sociomedical and oral factors affecting masticatory performance in a community-dwelling older population.

MATERIALS AND METHODS

Community-dwelling persons over 60 years were investigated using medical and dental oral interviews, oral and denture examination (natural teeth, tooth mobility, number of occluding tooth pairs, and removable dentures' prevalence and quality), and evaluation of masticatory performance using a mixing ability test.

RESULTS

A total of 130 participants with a mean age of 73.9±8.5 years were recorded. Fifty-eight (44.6%) used various types of removable prostheses. Twenty were edentulous and used a pair of complete dentures. Univariate analyses revealed statistically significant associations (p≤0.05) between masticatory performance and aging, marital status, subjective chewing ability, use of removable dentures, use of various combinations of complete dentures, pain caused by maxillary denture, number of teeth, tooth mobility, posterior chewing pairs, all chewing contacts natural or prosthetic, retention of mandibular partial dentures, and dentures' occlusion. The multivariable quantile regression analysis revealed that fewer natural teeth (95% CI: -0.02-0.01, p<0.001), being edentulous and using a pair of complete dentures (95% CI: 0.09-0.35, p=0.001), and larger percentage of severely mobile teeth (95% CI: 0.07-0.82, p=0.020) were associated with lower masticatory performance.

CONCLUSIONS

Poor masticatory performance in older adults was associated with fewer teeth, being edentulous and using a pair of complete dentures, and increased prevalence of severe tooth mobility.

CLINICAL RELEVANCE

Retaining the natural dentition and preventing and treating periodontal disease are important measures to maintain masticatory performance in older adults.

Oral diadochokinesis and associated oro-facial function in young and old German mother-tongue speakers: A cross-sectional study

Objectives

The aims of this study were to compare oral diadochokinesis and to test associations with oro‐facial functional parameters in healthy young and old German speakers.

Background

Oral diadochokinesis is a key component in the concept of oro‐facial hypofunction and relates to tongue and lip motor function but may depend on the linguistic background.

Materials and methods

Healthy German speakers with a minimum of 20 teeth were recruited to form a young (<60 years) and an older group (≥60 years). Oral diadochokinesis was assessed as the number of repetitions/s for the monosyllables /pa/, /ta/ and /ka/ to evaluate movement capacity of the lip, the anterior region of the tongue and the posterior region of the tongue, respectively. Maximum voluntary lip force, maximum voluntary bite force, masticatory performance, maximum voluntary tongue pressure, xerostomia and swallowing function were assessed with validated instruments. Results are presented as median (IQR).

Results

Sixty participants formed the younger group (n = 35, 30.0 years [24.0‐49.0]) and the older group (n = 25, 64.0 years [62.0‐72.0]). Counts/s of /ta/ were different between age groups (younger group: 6.0 vs older group: 5.4) but not for syllables /pa/ (younger group: 6.0 vs older group: 5.8) and /ka/ (younger group: 5.6 vs older group: 5.0). The oral diadochokinesis with /pa/ was overall associated with maximum voluntary lip force; oral diadochokinesis performed with /ta/ was associated with tongue pressure, and oral diadochokinesis with /ka/ with swallowing function. Masticatory performance was not associated with oral diadochokinesis but with maximum voluntary bite force, xerostomia and with maximum voluntary tongue pressure.

Conclusions

The published thresholds for oral diadochokinesis should be reconsidered in non‐Japanese mother‐tongue speakers. However, they still play an important role in the overall concept of oro‐facial functional assessment.

Bite Force, Thickness, and Thermographic Patterns of Masticatory Muscles Post-Hemorrhagic Stroke

OBJECTIVE

Stroke is a neurological deficit of cerebrovascular origin, considered a 21st-century epidemic that causes functional changes in the human body. This study aimed to evaluate the stomatognathic system of patients after hemorrhagic stroke through the bite force, thickness, and skin temperature in the region of the masseter and temporalis muscles.

MATERIAL AND METHODS

Twenty-four subjects were divided into groups: post-hemorrhagic stroke; with right side of the affected body (n = 12) and without the neurological disorder (n = 12). Maximum molar bite force was verified using a digital dynamometer. Muscle thickness was measured using ultrasound images obtained at rest and during maximal voluntary contraction of the masseter and temporalis muscles. Thermographic camera was used to record the thermographic patterns of the masseter and temporalis muscles. Data were subjected to Student's t-test (P < .05).

RESULTS

The maximum molar bite force showed significant differences in the right (P = .04) and left (P = .03) sides, with a reduction in force in the post-hemorrhagic stroke group on the affected and unaffected sides. There was a significant difference (P < .05) in the thickness of the left temporal muscle at mandibular rest (P = .01) between groups. The post-hemorrhagic stroke group clinically presented greater muscle thickness in almost 100% of the muscles evaluated in both clinical conditions. There were no significant differences in skin temperature in the masseter and temporal muscles between the groups.

CONCLUSIONS

Our results suggest functional changes in the stomatognathic system of subjects after a hemorrhagic stroke, especially concerning molar bite force and masticatory muscle thickness in the temporal muscle (unaffected side).

Facilitation of oral sensitivity by electrical stimulation of the faucial pillars

Dysphagia is common in neurological disease. However, our understanding of swallowing and its central nervous control is limited. Sensory information plays a vital role in the initiation of the swallowing reflex and is often reduced in stroke patients. We hypothesized that the sensitivity threshold of the anterior faucial pillar could be facilitated by either electrical stimulation (ES) or taste and smell information. The sensitivity threshold was measured by ES in the anterior faucial pillar region. The measurement was repeated 5 min after baseline. Thirty minutes after baseline, the participants underwent a test for taste and smell. Immediately after the test, the ES was repeated. Thirty healthy volunteers with a mean age of 27 ± 5.1 participated in the trial. Mean sensitivity threshold at baseline was 1.9 ± 0.59 mA. The values 5 min after baseline (1.74 ± 0.56 mA, p = 0.027) and 30 min after baseline (1.67 ± 0.58 mA, p = 0.011) were significantly lower compared to the baseline, but there was no difference between the latter (p = 0.321). After 5 min, a potentially facilitating effect was found on oral sensitivity by ES of the faucial pillar area. Thirty minutes later, this effect was still present.

Trial registration Clinicaltrials.gov, NCT03240965. Registered 7th August 2017—https://clinicaltrials.gov/ct2/show/NCT03240965.

Consensus on the terminologies and methodologies for masticatory assessment

A large number of methodological procedures and experimental conditions are reported to describe the masticatory process. However, similar terms are sometimes employed to describe different methodologies. Standardisation of terms is essential to allow comparisons among different studies. This article was aimed to provide a consensus concerning the terms, definitions and technical methods generally reported when evaluating masticatory function objectively and subjectively. The consensus is based on the results from discussions and consultations among world‐leading researchers in the related research areas. Advantages, limitations and relevance of each method are also discussed. The present consensus provides a revised framework of standardised terms to improve the consistent use of masticatory terminology and facilitate further investigations on masticatory function analysis. In addition, this article also outlines various methods used to evaluate the masticatory process and their advantages and disadvantages in order to help researchers to design their experiments.

Quantification of the Masseter Muscle Hardness of Stroke Patients Using the MyotonPRO Apparatus: Intra- and Inter-Rater Reliability and Its Correlation with Masticatory Performance

BACKGROUND Chewing dysfunction is one of the most common serious complications after a stroke. It may be influenced by the hardness of the masseter muscle and masticatory performance; however, the association between these 2 factors is not explicit. Thus, it is meaningful to explore the functional status of the masseter muscle among stroke patients. The main objectives of this study were to examine the intra- and inter-rater reliability of the MyotonPRO apparatus in measuring masseter muscle hardness in stroke patients and to investigate the correlation between the bilateral masseter muscle hardness and masticatory performance in these patients. MATERIAL AND METHODS A total of 20 stroke patients participated in our study. The hardness of the masseter muscle was measured by 2 physiotherapists using the MyotonPRO apparatus. Overall, each patient masticated 2 pieces of red-blue bicolor chewing gum for 20 chewing cycles each. The chewing pieces were analyzed using ViewGum software for masticatory performance. RESULTS The intra- and inter-rater reliability of the MyotonPRO apparatus for measuring bilateral masseter hardness of stroke patients was excellent. The correlation analysis showed that the hardness index of the masseter muscle on the affected side was moderately correlated with the masticatory performance of the same side. CONCLUSIONS The MyotonPRO device can be used for measuring the masseter muscle hardness of stroke patients, with excellent reliability. This study established the construct validity between the stiffness of the masseter muscle and masticatory performance.

Single versus two-implant mandibular overdentures using early-loaded titanium-zirconium implants with hydrophilic surface and ball attachments: 1-year randomized clinical trial

OBJECTIVE

This randomized clinical trial aimed to compare the outcomes of the mandibular overdenture retained by one (1-IOD) or two (2-IOD) implants.

MATERIALS AND METHODS

Participants received new complete dentures, were assessed at baseline and randomly assigned to groups. Early loaded single midline implant (1-IOD) or two implants in the canine regions bilaterally (2-IOD). Ball attachments were used for overdenture retention. Post-treatment outcomes (6- and 12-month follow-ups) included patient satisfaction, oral health-related quality of life measures, and chewing function. Data analysis included within- and between-group comparisons, and Generalized Estimating Equations. Both superiority and non-inferiority hypotheses were tested.

RESULTS

Forty-seven participants were included (1-IOD = 23; 2-IOD = 24). Significant improvements in OHIP-Edent were observed after insertion of new dentures and at the 1-year follow-up compared with baseline. No differences were found between the 1- and 2-IOD groups for the OHIP-Edent and QoLFAST scores. Patient satisfaction with the mandibular denture improved significantly from baseline to the 6-month follow-up and remained unaltered until 1 year, with no differences between groups. The magnitudes of treatment effect sizes were moderate to large for patient-reported outcomes. Progressive improvement in chewing function occurred in both groups. Non-inferiority testing based on a 15% non-inferiority margin showed inconclusive results for patient-reported outcomes, whilst chewing function in the 1-IOD group was concluded to be not inferior to the 2-IOD group.

CONCLUSIONS

Results support the use of both 1- and 2-IOD. The 1-IOD was also an acceptable alternative to the 2-IOD as a secondary option for the treatment of the edentulous mandible.

Delayed Swallowing Reflex is Overlooked in Swallowing Screening Among Acute Stroke Patients

BACKGROUND AND PURPOSE

Dysphagia in the acute phase of stroke contributes significantly to poor outcomes and is associated with the development of aspiration pneumonia and malnutrition. Therefore, an accurate evaluation of swallowing is necessary before initiating oral food intake. The modified water swallow test (MWST) and the repetitive saliva swallow test (RSST) are commonly used as bedside screening methods for swallowing dysfunction, but it is unclear whether other factors contribute to dysphagia and consequent aspiration. The purpose of this study was to identify characteristics that might be overlooked in screening tests.

METHODS

Participants were prospectively selected from patients hospitalized for stroke at the Suiseikai Kajikawa Hospital between August 1, 2016 and June 30, 2018. Inclusion criteria were conscious and stable medical condition, and patients who were diagnosed with dementia were excluded. A videofluoroscopic (VF) swallowing study was carried out on all patients who met the inclusion/exclusion criteria and who passed both the MWST and the RSST.

RESULTS

Aspiration was observed in 16 of 172 patients (9.3%) when swallowing 3 ml of water. These aspirated patients showed significantly delayed swallowing reflex on VF.

CONCLUSIONS

Swallowing evaluation using a combination of the MWST and the RSST is reasonably effective. However, patients who show a delayed swallowing reflex might be overlooked by this screening procedure.

Reliability and comparability of methods for assessing oral function: Chewing, tongue pressure and lip force

BACKGROUND

Quantitative clinical assessment tests for oral function have become popular in patient assessment; however, their comparability remains unclear.

OBJECTIVE

To assess the reliability and comparability of pairs of different instruments for measuring maximum tongue pressure (MTP), chewing function (CF) and maximum lip force (MLF), and to analyse the influence of subjects' characteristics on the applied instruments.

METHODS

Each pair of instruments, as well as a single device measuring the maximum voluntary bite force (MBF), was assessed across 26 healthy volunteers. The respective pairs of devices were compared using Bland-Altman plots and linear regression analysis. Furthermore, the influence of age, occlusal support zones, number of functional occlusal units, MBF, MTP and MLF were investigated as predictors on CF using a generalised estimating equation model.

RESULTS

Neither the two assessments of CF, nor of MLF were correlated to each other, but there was a significant correlation between the assessments of MTP. Hue-Check Gum was able to demonstrate a significantly higher CF in younger compared to older individuals (P = .004) and individuals with high numbers compared to low numbers of occlusal units (P < .001). Those differences could not be demonstrated with the Vivident chewing gum.

CONCLUSION

The absolute values of MTP assessed by the two applied devices cannot directly be compared, although normalised values may be directly comparable. Moreover, our observations suggest that the Hue-Check Gum was able to discriminate the effects of age and the number of occlusal units on CF. Our observations suggest that the two gums cannot be used interchangeably.

Wireless Sensing of Lower Lip and Thumb-Index Finger 'Ramp-and-Hold' Isometric Force Dynamics in a Small Cohort of Unilateral MCA Stroke: Discussion of Preliminary Findings

Automated wireless sensing of force dynamics during a visuomotor control task was used to rapidly assess residual motor function during finger pinch (right and left hand) and lower lip compression in a cohort of seven adult males with chronic, unilateral middle cerebral artery (MCA) stroke with infarct confirmed by anatomic magnetic resonance imaging (MRI). A matched cohort of 25 neurotypical adult males served as controls. Dependent variables were extracted from digitized records of ‘ramp-and-hold’ isometric contractions to target levels (0.25, 0.5, 1, and 2 Newtons) presented in a randomized block design; and included force reaction time, peak force, and dF/dt_max associated with force recruitment, and end-point accuracy and variability metrics during the contraction hold-phase (mean, SD, criterion percentage ‘on-target’). Maximum voluntary contraction force (MVCF) was also assessed to establish the force operating range. Results based on linear mixed modeling (LMM, adjusted for age and handedness) revealed significant patterns of dissolution in fine force regulation among MCA stroke participants, especially for the contralesional thumb-index finger followed by the ipsilesional digits, and the lower lip. For example, the contralesional thumb-index finger manifest increased reaction time, and greater overshoot in peak force during recruitment compared to controls. Impaired force regulation among MCA stroke participants during the contraction hold-phase was associated with significant increases in force SD, and dramatic reduction in the ability to regulate force output within prescribed target force window (±5% of target). Impaired force regulation during contraction hold-phase was greatest in the contralesional hand muscle group, followed by significant dissolution in ipsilateral digits, with smaller effects found for lower lip. These changes in fine force dynamics were accompanied by large reductions in the MVCF with the LMM marginal means for contralesional and ipsilesional pinch forces at just 34.77% (15.93 N vs. 45.82 N) and 66.45% (27.23 N vs. 40.98 N) of control performance, respectively. Biomechanical measures of fine force and MVCF performance in adult stroke survivors provide valuable information on the profile of residual motor function which can help inform clinical treatment strategies and quantitatively monitor the efficacy of rehabilitation or neuroprotection strategies.

Optimizing a determination of chewing efficiency using a solid test food

A test using a solid food is relevant to measure chewing ability (CA) as (a) it includes an integrated functioning of all oral structures involved, (b) an impairment of chewing a solid food causes inevitably diet restrictions, and (c) chewing efficiency (CE) can easily be defined. CE is the number of chewing cycles, N(1/2-Xo), needed to attain a particular chewing outcome (a median particle size, X ₅₀ , which is half the initial particle size Xo) whereas chewing performance (CP) is a state of chewing outcome (X ₅₀ ) at an arbitrary number of chewing cycles. The use of CE is preferable for CA because inter-subject ratios are constant regardless of the initial conditions of the test food. Furthermore, the inter-subject variation is two times larger for CE values than for CP ones, yielding a better inter-subject differentiation of CA. However, a determination of CP needs only one N-value, and that of CE at least two N-values for enabling an interpolation of N(1/2-Xo). Using samples of only two half-cubes (9.6 x 9.6 x 4.8 mm; limiting test load) of Optosil (an artificial test food), and detailed previous information on log(X ₅₀ )-log(N) relationships (Liu et al., Archives of Oral Biology, 2018, 91, 63-77) as a "gold standard," a short procedure has been developed for a priori choosing two appropriate N-numbers, and the subsequent determination of a subject's CE. This procedure has been developed using results from 20 young adults (23.7 years, SD 1.1) and was validated in 10 middle-aged and older adults (52.3 years, SD 10.1), where impairments in the dentition were reflected in the CE-values. Our short procedure to determine CE will improve studies on relationships between CA and food preference, or between CA and dental factors and/or physiological factors. The first type of relationship may be of interest for food industry whereas the second type may be of interest for population studies in rapidly aging societies and for clinical studies in dentistry. Results can be compared between subjects and studies without bias by using CE rather than CP as a measure of CA.

Reduced tongue force and functional swallowing changes in a rat model of post stroke dysphagia

PURPOSE

Dysphagia is a common problem after stroke that is often associated with tongue weakness. However, the physiological mechanisms of post-stroke tongue muscle weakness and optimal treatments have not been established. To advance understanding of physiological mechanisms of post stroke dysphagia, we sought to validate the unilateral transient middle cerebral artery occlusion (MCAO) rat model of ischemic stroke as a translational model of post stroke dysphagia. Our goal was to establish clinically relevant measures and chronicity of functional deficits; criteria that increase the likelihood that findings will translate to the clinic. We hypothesized that MCAO would cause tongue weakness and functional swallowing changes.

METHODS

Maximum voluntary tongue forces and videofluoroscopic swallowing studies were collected in 8-week old male Sprague-Dawley rats prior to receiving either a left MCAO (N = 10) or sham (N = 10) surgery. Tongue forces and VFSS were reassessed at 1 and 8 weeks post-surgery.

RESULTS

Maximum voluntary tongue force, bolus area, and bolus speed were significantly reduced in the MCAO group at the 1 and 8-week timepoints.

CONCLUSION

Clinically relevant changes to swallowing and tongue force support the use of the MCAO rat model as a translational model of post stroke dysphagia. This model will allow for future studies to improve our understanding of the physiology contributing to these functional changes as well as the impact of therapeutic interventions on physiological targets and function.

Effects of Neuromuscular Electrical Stimulation for Masseter Muscle on Oral Dysfunction After Stroke

Objective

To determine positive effect of neuromuscular electrical stimulation (NMES) in conventional dysphagia therapy on masseter muscle oral dysfunction of patients after subacute stroke.

Methods

Among subacute stroke patients who were diagnosed as oropharyngeal dysphagia by videofluoroscopy swallowing study (VFSS), those with oral dysfunction were enrolled. They were randomly assigned to a study group or a control group. The study group received NMES on masseter muscle and suprahyoid muscle simultaneously, while the control group received NMES only on suprahyoid muscle. NMES therapy session as applied 30 minutes each time, two times per day for a total of 20 sessions. Both groups received conventional dysphagia therapy for 2 weeks. All enrolled patients were evaluated by VFSS after 2 weeks. Oropharyngeal swallowing function was evaluated by Penetration-Aspiration Scale, Functional Dysphagia Scale (FDS), and American Speech-Language-Hearing Association National Outcome Measurement System swallowing scale based on results of VFSS.

Results

Patients were randomly assigned to the study group (n=20) or the control group (n=20). There were no significant differences in baseline characteristics or initial values between the two groups. After 2 weeks of NMES, both groups showed improvement in scores of total FDS and pharyngeal phase FDS. Additionally, the study group showed improvement in oral phase FDS. Changes in all measurements were similar between the two groups.

Conclusion

In this preliminary study, NMES for masseter muscle has a therapeutic effect on oral dysfunction of patients after subacute stroke.

Masticatory ability improves after maxillary implant overdenture treatment: A randomized controlled trial with 1-year follow-up

BACKGROUND

The effect of maxillary implant overdentures on masticatory ability in edentulous patients with complaints regarding their conventional maxillary dentures is unknown.

PURPOSE

To assess the change in objective masticatory ability (mixing ability index, MAI), patient reported masticatory ability (questionnaire), and patient satisfaction (GSS) after maxillary implant overdenture treatment with either solitary attachments or bars.

MATERIALS AND METHODS

Two groups randomly received four-implant maxillary overdentures on either solitary attachments (group I, n = 25) or bars (group II, n = 25). The MAI, questionnaire, and GSS were scored before (T0) and 12 months (T12) after treatment.

RESULTS

After treatment, both groups had significantly better MAI outcomes, better questionnaire scores and better GSS. Post-treatment questionnaire scores and GSS were significantly better for group II. Before treatment a strong, positive correlation between the MAI and the questionnaire was found for all participants who had had full conventional dentures combined (group I, n = 17; group II, n = 3).

CONCLUSION

Mixing ability was the same for all the participants treated with maxillary implant overdentures on either solitary attachments or bars. Patient reported masticatory ability and satisfaction was better for participants treated with maxillary implant overdentures on bars. There was a correlation between MAI and patient reported masticatory ability in participants with full conventional dentures.

Characterization of oral tactile sensitivity and masticatory performance across adulthood

Texture perception is one of the most important factors in food acceptance, yet population-wide differences in texture sensations are not well understood. The variation in texture perception across populations is thought to depend on oral tactile sensitivity and masticatory performance. To address this hypothesis, we aimed to measure tactile acuity with a battery of tests and quantitate the relationship to masticatory performance. The study was performed on 98 participants, in three age groups (20-25, 35-45, or over 62). Two main measures of oral sensitivity were performed: to assess bite force, subjects were asked to discriminate between foam samples of varying hardness. Second, to assess lingual sensitivity the subjects were asked to identify 3D printed shapes using their tongue, as well as identify confectionary letters. Additionally, masticatory performance was measured through assessing each participants ability to mix two-colored chewing gum. In general, we found that sensitivity and masticatory performance in the younger age groups was superior to that of older adults. We also found a positive linear trend between bite force sensitivity and masticatory performance with younger participants, a trend not found in older participants. We found no significant relationship between age groups for bite force sensitivity and masticatory performance, suggesting that age-related declines in bite force sensitivity are not a significant cause of altered masticatory performance. This study represents a valuable first step in showing that bite force sensitivity does not depend on age, and the minimal influence of factors such as oral sensitivity on masticatory performance. PRACTICAL APPLICATIONS: In a society that is rapidly aging, it is important to understand the subtle changes in physiology and eating behavior that are associated with aging. This study used a variety of tests oral sensitivity to better understand which aspects of oral physiology are integral for effective chewing. The information gained helps shed light on to the factors that create an effective chewing cycle. Besides moving knowledge forward, this study may help in designing food and rehabilitation programs for those with trouble chewing and swallowing, increasing their overall quality of life.

Validation of a purpose-built chewing gum and smartphone application to evaluate chewing efficiency

OBJECTIVES

To validate a purpose-built two-coloured chewing gum (Hue-Check Gum^® ), and to test the accuracy of a custom-built smartphone application for a colour-mixing ability test to assess chewing function.

METHODS

Fully dentate participants (28D-group) and edentulous participants with implant overdentures (IOD-group) were recruited. They chewed a Hue-Check Gum^® for 5, 10, 20, 30 and 50 chewing cycles, respectively. Maximum voluntary bite force (MBF) was assessed with a digital gauge. The specimens were analysed according to their colour mixture (variance of hue, VOH) with a validated software (VOH_scan) and a newly developed smartphone application (VOH_app).

RESULTS

Participants segregated by dental state were significantly different regarding the number of occluding pairs of teeth, age and MBF. VOH_scan showed a negative logarithmic association with the number of chewing cycles, and VOH could be predicted from chewing cycles, MBF and gender. The clearest discrimination between the IOD and the 28D groups was observed for n = 20 chewing cycles; at this point, VOH was distinguishably different with a P-value < 0.0001. The VOH_app was a very good predictor for VOH_scan with 0.80 < pseudo-R²  < 0.83, depending on light exposure and measuring distance. There was, however, a systematic error in the accuracy of the app for inadequately chewed specimens.

CONCLUSIONS

The use of the two-coloured chewing gum would provide a fast, simple and inexpensive method for the assessment of masticatory performance, which could be used in geriatric wards or in private practices without the requirement of specialised equipment or trained staff.