Relationship between oral sensitivity and masticatory performance

Factors related to subjective evaluation of difficulty in chewing among community-dwelling older adults

AIM

Awareness of difficulty chewing may limit the diversity of food intake in older adults. However, few studies have clarified which factors are related to subjective difficulty in chewing. The aim was to identify factors related to subjective difficulty in chewing in 70- and 80-year-old Japanese older adults.

METHODS

A total of 1680 participants (792 men, 888 women) were surveyed. Difficulty in chewing was assessed with questionnaires regarding food intake, such as rice, apples, beef, and hard rice crackers. The participants were classified into two groups, the "with difficulty" group (participants who answered "cannot eat," "can eat with difficulty," and "can eat if small") and the "without difficulty" group (participants who answered "can eat without problems"), according to their answers to questionnaires for each food. A logistic regression analysis with subjective difficulty in chewing as the dependent variable was performed for each food.

RESULTS

Subjective difficulty in chewing was associated with age, occlusal force, and depression for rice; age, number of remaining teeth, occlusal force, and depression for apples; number of remaining teeth, occlusal force, and depression for beef; and number of remaining teeth and occlusal force for hard rice crackers.

CONCLUSIONS

Age, number of remaining teeth, and occlusal force, as well as depression, might be related to subjective evaluation of difficulty chewing in community-dwelling Japanese older adults. Geriatr Gerontol Int 2024; 24: 327-333.

Biomechanical and Cortical Control of Tongue Movements During Chewing and Swallowing

Tongue function is vital for chewing and swallowing and lingual dysfunction is often associated with dysphagia. Better treatment of dysphagia depends on a better understanding of hyolingual morphology, biomechanics, and neural control in humans and animal models. Recent research has revealed significant variation among animal models in morphology of the hyoid chain and suprahyoid muscles which may be associated with variation in swallowing mechanisms. The recent deployment of XROMM (X-ray Reconstruction of Moving Morphology) to quantify 3D hyolingual kinematics has revealed new details on flexion and roll of the tongue during chewing in animal models, movements similar to those used by humans. XROMM-based studies of swallowing in macaques have falsified traditional hypotheses of mechanisms of tongue base retraction during swallowing, and literature review suggests that other animal models may employ a diversity of mechanisms of tongue base retraction. There is variation among animal models in distribution of hyolingual proprioceptors but how that might be related to lingual mechanics is unknown. In macaque monkeys, tongue kinematics-shape and movement-are strongly encoded in neural activity in orofacial primary motor cortex, giving optimism for development of brain-machine interfaces for assisting recovery of lingual function after stroke. However, more research on hyolingual biomechanics and control is needed for technologies interfacing the nervous system with the hyolingual apparatus to become a reality.

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.

Auditory and Somatosensory Development for Speech in Later Childhood

PURPOSE

This study collected measures of auditory-perceptual and oral somatosensory acuity in typically developing children and adolescents aged 9-15 years. We aimed to establish reference data that can be used as a point of comparison for individuals with residual speech sound disorder (RSSD), especially for RSSD affecting American English rhotics. We examined concurrent validity between tasks and hypothesized that performance on at least some tasks would show a significant association with age, reflecting ongoing refinement of sensory function in later childhood. We also tested for an inverse relationship between performance on auditory and somatosensory tasks, which would support the hypothesis of a trade-off between sensory domains.

METHOD

Ninety-eight children completed three auditory-perceptual tasks (identification and discrimination of stimuli from a "rake"-"wake" continuum and category goodness judgment for naturally produced words containing rhotics) and three oral somatosensory tasks (bite block with auditory masking, oral stereognosis, and articulatory awareness, which involved explicit judgments of relative tongue position for different speech sounds). Pairwise associations were examined between tasks within each domain and between task performance and age. Composite measures of auditory-perceptual and somatosensory functions were used to investigate the possibility of a sensory trade-off.

RESULTS

Statistically significant associations were observed between the identification and discrimination tasks and the bite block and articulatory awareness tasks. In addition, significant associations with age were found for the category goodness and bite block tasks. There was no statistically significant evidence of a trade-off between auditory-perceptual and somatosensory domains.

CONCLUSIONS

This study provided a multidimensional characterization of speech-related sensory function in older children/adolescents. Complete materials to administer all experimental tasks have been shared, along with measures of central tendency and dispersion for scores in two subgroups of age. Ultimately, we hope to apply this information to make customized treatment recommendations for children with RSSD based on sensory profiles.

Association between masticatory performance and oral conditions in adults: A systematic review and meta-analysis

OBJECTIVES

To give an overview of the evidence on the associations between oral condition factors and masticatory performance of adults, and to evaluate the direction and level of the associations.

DATA/SOURCES

Medline (PubMed), Embase (Ovid) and CINAHL Plus (EBSCOhost) were searched up to May 2022 for cross-sectional studies on oral conditions and masticatory performance in adults. Methodological quality of the included studies was independently evaluated based on the Joanna Briggs Institute critical appraisal checklist for analytical cross-sectional studies. Data on the associations between oral condition factors and masticatory performance were extracted. Meta-analysis was conducted on correlation coefficients.

STUDY SELECTION

Of the 8,035 records identified, 97 articles (88 studies) were included in the qualitative synthesis, and 18 studies were included in the meta-analyses. Among the oral condition factors that had associations with masticatory performance, the number of natural/remaining teeth or functional tooth pairs was reported by the largest number of studies, followed by perioral muscle status, dental prosthetic status, oral moisture status and periodontal status. Results of the meta-analyses showed that the positive association with the number of natural/remaining teeth was the strongest (pooled correlation coefficient: 0.51, 95%CI: 0.48 to 0.54), followed by the number of functional tooth pairs, maximum tongue force/pressure, while the association with the oral moisture status was the weakest.

CONCLUSIONS

Number of natural/remaining teeth and functional tooth pairs, perioral muscle status, oral moisture status, dental prosthetic status and periodontal status are the main oral condition factors influencing masticatory performance. Based on the limited evidence available, among these factors, the number of natural/remaining teeth has the strongest positive association, with a very low quality of evidence.

CLINICAL SIGNIFICANCE

This study provides valuable information on the oral condition factors associated with masticatory performance, which would be important for policymakers and clinical practitioners when deciding on the strategies for improving the masticatory performance of adults. This review highlights the need for standardization of measures and classifications of masticatory performance and oral conditions.

REGISTRATION

PROSPERO (registration number: CRD42021256824).

A review on children's oral texture perception and preferences in foods

Texture properties of foods are particular drivers for food acceptance and rejection in children. The texture preferences follow the developmental progression of the child and these changes modulate the present and future food habits. This paper reviews the development and factors influencing texture preferences in children and the methods in food texture research with children. The child's acceptance of more complex food textures is age-dependent. The progression is indorsed by the development of oral processing skills at an early age and bolstered by repeated exposures to foods with varying textures. Children generally reject foods containing pieces or bits (i.e., geometrical textural properties); however, the impact of mechanical textural properties on food acceptance is less clear. Child characteristics such as food neophobia, picky eating, and tactile over-responsivity, negatively affect the acceptance of more diverse food textures. Depending on the child's age, the prevailing methods of characterizing food texture preferences in children include observational techniques and self-reported questionnaires. Despite knowledge of children's development of masticatory skills, learning, and cognitive abilities, the relationships of these changes to food texture acceptance and the recommended test methodology for evaluating product texture acceptance in this period of life are still limited.

Effect of side switch frequency on masticatory performance and rhythm in adults with natural dentition: A randomized crossover trial

BACKGROUND

The relationships between the frequency of masticatory side switches (MSS) and other aspects of masticatory function are not clear.

OBJECTIVES

In this study, we determined the effect of MSS frequency on masticatory performance and rhythm in dentate adults and explored the between-subject relationships among side switch frequency, masticatory rhythm, and laterality.

METHODS

In this crossover study, subjects performed six masticatory patterns of five trials each, chewing bagged silicone for 20 cycles. The six patterns were freestyle, unilateral right, unilateral left, and switching sides one, three, and five times. Masticatory performance and rhythm were determined for each style by median particle size (MPS) and chewing cycle duration, respectively. In the freestyle mastication pattern, masticatory laterality was assessed by the unilateral chewing index and the frequency of MSS was assessed by the MSS Index. Data were analyzed using Friedman's test and repeated-measures analysis of variance.

RESULTS

We included 29 participants (15 women; median age, 23 years). No significant between-subjects differences in the MPS were detected obtained by switching one, three, or five times per trial. Chewing cycle duration increased with the MSS number per trial. During freestyle mastication, the MSS Index was inversely correlated with the unilateral chewing index (Rho -0.569; 95%CI -0.25 to -0.78; P=0.001; Spearman test), but not with the MPS or chewing cycle duration.

CONCLUSION

Differences in MSS frequency do not affect masticatory performance, but they do alter the masticatory rhythm. Individuals with a higher MSS frequency also have a more symmetrical chewing pattern.

Deterioration of periodontal status affects declines in masticatory performance: The Suita study

AIM

We aimed to clarify the association between deterioration of periodontal status and masticatory performance in a longitudinal follow-up study of a general urban population.

MATERIALS AND METHODS

This study investigated 663 participants in the Suita study with no changes in the number of functional teeth or occlusal support areas during a 5-year follow-up period. Participants were classified into three groups according to changes in periodontal status during the survey period: a recovered group; a stable group; and a deteriorated group. Rate of masticatory performance change was calculated by subtracting the value at baseline from the value at follow-up and dividing the resulting value by the baseline value.

RESULTS

Median rates of masticatory performance change were -11.7% in the recovered group, -19.2% in the stable group, and -30.8% in the deteriorated group, and these values were significantly different (p < .001). Multiple regression analysis revealed periodontal status group (recovered group: reference; stable group: p = .029; deteriorated group: p = .006) as an independent variable was significantly associated with the rate of masticatory performance change.

CONCLUSION

The present results suggest that deterioration of periodontal status increases the risk of age-related declines in masticatory performance.

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.

A prediction model of masticatory performance change in 50- to 70-year-old Japanese: The Suita study

OBJECTIVES

Declines in masticatory performance might be a risk factor for worsening nutritional intake and result in general frailty. The present study constructed and investigated a method to predict the extent to which objective masticatory performance declines with age in cases with poor oral health status.

METHODS

Participants comprised 1201 participants in the Suita study with dental checkup at both baseline and follow-up (500 men and 701 women; age at baseline, 65.6 ± 7.8 years; mean follow-up, 5.1 ± 1.1 years). First, multiple linear regression analysis was performed with masticatory performance at follow-up as the dependent variable and sex as well as baseline age, number of functional teeth, maximum bite force, occlusal support, periodontal status, salivary flow rate, and masticatory performance as independent variables. Scores were assigned to each factor based on the standardized partial regression coefficient obtained from multiple linear regression analysis. Participants were divided into quintile groups (Q1-Q5) based on total scores for factors, and rates of masticatory performance change for each group were calculated and compared.

RESULTS

Mean rates of masticatory performance change in groups Q1-Q5 from the model to predict declining masticatory performance were: Q1, -9.7%; Q2, -12.7%; Q3, -18.0%; Q4, -19.9%; and Q5, -29.8%.Thus there was a trend for masticatory performance to decrease with decreasing score.

CONCLUSIONS

The model developed in this study quantitatively predicted declines in masticatory performance after approximately 5 years.

CLINICAL SIGNIFICANCE

We developed a model for predicting the extent to which masticatory performance will change over the next 5 years. This model may offer a useful tool when taking measures to prevent declines in masticatory performance with aging.

Which variables should be controlled when measuring the granulometry of a chewed bolus? A systematic review

The distribution of food particles in a chewed bolus characterizes the food destruction after food oral processing (FOP). Previous reviews report that it could be affected by a lot of parameters as the number of chewing strokes, the dental status, but the conditions for producing reproducible data allowing inter-studies comparison have not been clearly described yet. This systematic review aims to identify the variables that can affect bolus granulometry determination, and to calculate their relative weights in the median particle size (D₅₀ ) variations. The systematic review focuses on granulometry expressed as D50 of the most used foods (peanuts, carrots, and almonds) and materials (Optosil and Optocal). Based on 58 studies, 5 variables among 60 being extracted could explain the D₅₀ variations. Conceptual differences between the conditions for FOP should be considered. After Chewing-test, the bolus is collected after a predefined number of strokes and its granulometry characterizes the effects of the dental and muscular apparatus on food destruction, while after Mastication-test the bolus is collected at the swallowing threshold, and its granulometry reflects the outcome of the abilities of the subject to adapt his/her mastication behavior to food texture. Experimental conditions related either to physical sieving or image analysis used to analyze the collected boluses impact the D₅₀ values. Finally, when type of test, sieving conditions, type of food or material, number of chewing strokes, and the oral status of the subjects are controlled, mean D₅₀ values are reproducible and could be used for inter-studies comparisons. PRACTICAL APPLICATIONS: This review provides tables that could be useful to control mean D₅₀ variations in further research.

Relationship between oral stereognostic ability and dietary intake in older Japanese adults with complete dentures

PURPOSE

Oral stereognostic ability (OSA) is a useful indicator of oral perception to recognize food characteristics during mastication. Previous studies have shown associations between dietary intake and oral health status, such as taste perception. However, the effect of oral sensory ability on dietary intake is unclear. The purpose of this study was to investigate the association between oral sensory ability and dietary intake in older Japanese complete denture wearers.

METHODS

This cross-sectional study included 164 participants aged 69-71 or 79-81years old, wearing both maxillary and mandibular complete dentures. OSA test was used to evaluate oral tactile perception. Diet during the preceding month was assessed using a self-administered diet history questionnaire. Multivariable linear regression analysis was conducted to assess the association between OSA score and food and nutrient intake after adjusting for age, sex, socioeconomic factors, and occlusal force.

RESULTS

The bivariate analysis showed that OSA score was significantly and positively correlated with intake of green and yellow vegetables and negatively correlated with intake of cereals among examined foods. OSA score was also positively correlated with intake of vitamins A, B₂, and C and α-tocopherol (as a substitute for vitamin E) among examined nutrients. After adjusting for age, sex, socioeconomic factors, and occlusal force, OSA score remained significantly associated with intake of green and yellow vegetables and α-tocopherol.

CONCLUSIONS

OSA was significantly associated with intake of green and yellow vegetables in older complete denture wearers.

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.

Factors Influencing the Changes in Masticatory Performance: The Suita Study

Introduction:

Although previous studies have identified various factors related to masticatory performance, which factors affect longitudinal changes in masticatory performance have not been clarified.

Objectives:

We aimed to clarify factors involved in changes to masticatory performance and construct models from factors related to masticatory performance in a longitudinal study of a general urban population in Japan.

Methods:

A total of 1,005 Japanese subjects (411 men, 594 women; mean age at baseline, 65.7 ± 7.7 years; mean follow-up period, 5.0 ± 0.9 years) were included in the Suita study. These subjects participated in dental checkups both at baseline (June 2008–December 2011) and at follow-up (June 2013–January 2017). The number of functional teeth and occlusal support areas was recorded and the latter assessed using the Eichner index. Subjects’ periodontal status was evaluated based on the Community Periodontal Index. Masticatory performance was determined using test gummy jelly. Factors affecting masticatory performance at follow-up and the degree of their effect were investigated by multiple linear regression analysis.

Results:

In multiple linear regression analysis with masticatory performance at follow-up as the dependent variable, baseline age, masticatory performance, number of functional teeth, and maximum bite force were significant independent variables. The results of multiple linear regression analyses by occlusal support at baseline identified only maximum bite force at baseline in subjects who were Eichner A and baseline age, masticatory performance, and number of functional teeth in subjects who were Eichner B as significant independent variables concerning masticatory performance at follow-up.

Conclusion:

Our study showed a relationship between longitudinal changes in masticatory performance and age, number of functional teeth, and maximum bite force and furthermore showed that the effects of these factors vary according to the residual number of occlusal support areas.

Knowledge Transfer Statement:

Patients and clinicians should recognize the importance of objective and quantitative assessment for chewing efficiency and understand that various factors are related to longitudinal changes in masticatory performance. The results of this study can provide basic data for preventing or improving the decline in masticatory performance for elderly people with varying numbers of occlusal support areas.

Impact of cognitive function on oral perception in independently living older people

OBJECTIVES

Oral tactile perception is important for better mastication, appetite, and enjoyment of food. However, previous investigations have not utilized comprehensible variables thought to have negative effect on oral perception, including aging, denture wearing, and cognitive function. The aim of this study was to elucidate the impact of cognitive function on oral perception in independently living older individuals.

MATERIALS AND METHODS

The study sample was comprised of 987 participants (466 males, 521 females; age 69-71 years). Oral examinations, assessments of cognitive function in preclinical level by Montreal Cognitive Assessment (MoCA)-J, and determination of oral stereognostic ability as an indicator of oral perception were performed. Related variables were selected by univariate analyses; then, multivariate logistic regression model analysis was conducted.

RESULTS

Univariate analyses revealed that number of teeth, removable dentures usage, and cognitive function respectively had a significant relationship with stereognostic score. Next, the subjects were classified into good and poor perception groups (lowest 17.4%) according to oral stereognostic ability. Logistic regression analysis revealed that lower cognitive function was significantly associated with poor oral perception (OR = 0.934, p = 0.017) after controlling for other variables.

CONCLUSIONS

Cognitive decline even in preclinical stage was associated with reduced oral perception after controlling for gender, tooth number and denture use in independent living older people.

CLINICAL RELEVANCE

This study suggested that preclinical level of change in cognitive function affected oral perception. Dental practitioners and caregivers may need to pay attention to reduced oral perception among older people even if they do not have trouble in daily life.

Perceived Intensity and Discrimination Ability for Lingual Electrotactile Stimulation Depends on Location and Orientation of Electrodes

Malfunctioning sensory systems can severely impact quality of life and repair is not always possible. One solution, called sensory substitution, is to use another sensory system to bring lost information to the brain. This approach often involves the use of bioengineered devices that electrically stimulate somatosensory fibers. Interestingly, the tongue is an ideal location for electrotactile stimulation due to its dense innervation, moisture, and protected environment. Success with transmitting visual and vestibular information through the tongue indicates promise for future applications. However, sensitivity and discrimination ability varies between individuals and across the tongue surface complicating efforts to produce reliable and consistent sensations. The goals of the present study were to investigate these differences more precisely to better understand the mechanosensory innervation of the tongue so that future electrotactile devices can be designed more effectively. Specifically, we tested whether stimulation of certain regions of the tongue consistently result in better perception, whether the spacing of stimulating electrodes affects perceived intensity, and whether the orientation of electrodes affects perceived intensity and discrimination. To test these hypotheses, we built a custom tongue stimulation device, recruited 25 participants, and collected perceived intensity and discrimination data. We then subjected the data to thorough statistical analyses. Consistent with previous studies, we found that stimulation of the anterior medial tongue region was perceived as more intense than stimulation of lateral and posterior regions. This region also had the best discrimination ability for electrodes. Dividing the stimulated tongue area into 16 distinct regions allowed us to compare perception ability between anterior and posterior regions, medial and lateral regions, and the left and right sides of the tongue. Stimulation of the most anterior and medial tongue resulted in the highest perceived intensity and the best discrimination ability. Most individuals were able to perceive and discriminate electrotactile stimulation better on one side of the tongue, and orientation of stimulating electrodes affected perception. In conclusion, the present studies reveal new information about the somatosensory innervation of the tongue and will assist the design of future electrotactile tongue stimulation devices that will help provide sensory information to people with damaged sensory systems.

Oral tactile sensitivity and masticatory performance are impaired in stroke patients

Oro-facial impairment following stroke frequently involves reduced chewing performance, that is oral phase dysphagia. The aim was to investigate the sensitivity of oral tissues following stroke and its potential impact on masticatory function. Therefore, hospitalised post-stroke patients were recruited and compared to healthy controls. Outcome measures comprised masticatory performance employing a colour-mixing ability, that is a bolus-kneading test, maximum lip- and bite force and the one-point and two-point tactile thresholds. Food hoarding and prevalence of dry mouth were evaluated with ordinal scales. Twenty-seven stroke patients (age 64·3 ± 14·1 years) and 27 healthy controls (age 60·8 ± 14·3 years, P = 0·254) participated in this study. The groups had similar numbers of occluding units. Stroke patients reported more frequently dry mouth sensations and food hoarding. The intra-oral tactile sensitivity on the contra-lesional side was significantly lower in stroke patients compared to controls (0·0001 < P < 0·0002), and significant intra-group side differences were found only in the stroke group (0·0001 < P < 0·0010). For the lip, both sides were less sensitive in the stroke group compared with controls. The experiments confirmed lower masticatory performance and lip force in the stroke group, but the bite force was similar compared to healthy controls. Oral sensitivity was correlated with masticatory performance when a global correlation model was applied. A stroke may affect the sensitivity of the intra-oral tissues contra-lesionally, thus potentially affecting chewing function. Rehabilitation should therefore not only focus on motor impairment, but equally stimulate the sensitivity of the oral tissues, employing dry ice application or similar specific treatments.

Does shape discrimination by the mouth activate the parietal and occipital lobes? - near-infrared spectroscopy study

A cross-modal association between somatosensory tactile sensation and parietal and occipital activities during Braille reading was initially discovered in tests with blind subjects, with sighted and blindfolded healthy subjects used as controls. However, the neural background of oral stereognosis remains unclear. In the present study, we investigated whether the parietal and occipital cortices are activated during shape discrimination by the mouth using functional near-infrared spectroscopy (fNIRS). Following presentation of the test piece shape, a sham discrimination trial without the test pieces induced posterior parietal lobe (BA7), extrastriate cortex (BA18, BA19), and striate cortex (BA17) activation as compared with the rest session, while shape discrimination of the test pieces markedly activated those areas as compared with the rest session. Furthermore, shape discrimination of the test pieces specifically activated the posterior parietal cortex (precuneus/BA7), extrastriate cortex (BA18, 19), and striate cortex (BA17), as compared with sham sessions without a test piece. We concluded that oral tactile sensation is recognized through tactile/visual cross-modal substrates in the parietal and occipital cortices during shape discrimination by the mouth.

Lingual tactile acuity and food texture preferences among children and their mothers

Despite anecdotal reports of children being more sensitive to texture than adults, and of texture being one of the main drivers of food aversions, there is a paucity of scientific knowledge on the influence of texture perception on food choice in children. The primary goals of this study were to assess the use of a modified letter-identification task to study lingual tactile acuity, one aspect of oral sensitivity, in children and to examine age-related differences in sensitivity. The secondary goal was to explore whether lingual tactile acuity and age relate to various measures of food choice and preference. To this end, children 7-10 years old (31 girls, 21 boys) and their mothers were tested using identical procedures. To assess lingual tactile acuity, children and mothers were asked to use the tips of their tongues to identify raised alphabetical letters of varying size (2.5-8.0 mm) on Teflon strips. To relate lingual tactile acuity to food texture preferences, a forced-choice questionnaire assessed preferences for foods similar in flavor but different in texture (e.g., smooth versus crunchy peanut butter). Children were able to complete the lingual acuity task as well as their mothers and took less time to assess each letter stimulus (p < 0.001); however, there were no age-related differences in lingual acuity (p = 0.14). Age, but not lingual acuity, related to food texture preferences: mothers preferred harder foods (p < 0.001) and those containing more particles (p < 0.04) than did children, although children's preferences became more adult-like with increasing age. The availability of a rapid, child-friendly method for assessing oral sensitivity opens up new possibilities of examining differences in oral tactile perceptions across the life span. That food preferences changed with age and were not related to oral sensitivity underscores the fact that factors such as experience, culture and family food practices have a significant impact on children's food texture preferences.

Oral sensation and function: a comparison of patients with innervated radial forearm free flap reconstruction to healthy matched controls

BACKGROUND

Limited evidence exists for the use of innervated radial forearm free flap (RFFF) reconstruction of hemiglossectomy defects. This study reports on sensation, mastication, and speech outcomes for patients with innervated RFFF reconstruction of the anterior two-thirds of the tongue.

METHODS

Sensation, mastication, and speech intelligibility were assessed in 8 patients and age- and sex-matched controls.

RESULTS

Sensation of intact tongue tissue after reconstruction of the hemitongue did not differ from controls. Although some sensory ability was restored to patients' reconstructed tongue, differences existed between the patient group and controls. However, whole mouth sensations resulted in similar sensory ability as controls. Whereas patients demonstrated adequate masticatory and speech ability, differences existed between patients and controls.

CONCLUSION

Although some sensory ability is preserved in patients who have had tongue reconstruction with an innervated RFFF, functional outcomes such as masticatory ability and speech intelligibility may be affected in some patients.

Oral motor function and masticatory performance in the community-dwelling elderly

This study was performed to ascertain the relationships between oral motor functions, such as those of the tongue and lips, and age in the community-dwelling elderly, as well as to investigate the effects of these factors on masticatory performance. The subjects were 268 healthy elderly Japanese living in Kyoto. They were divided into four age groups and further classified into the following two groups by the presence or absence of posterior occlusal support: Eichner A or B1-B3 (group A), and Eichner B4 or C (group B). They were wearing removable or fixed dentures if they had missing teeth. Oral function evaluation items included (1) masticatory performance and (2) oral motor skills. Significant differences were noted among the age groups in tongue pressure within group A (P < 0.01) and group B (P < 0.05), and in the number of repetitions of the syllables /ta/ and /ka/ in group B (/ta/: P < 0.05, /ka/; P < 0.01). The number of natural teeth (beta = 0.463, P < 0.001) in group A and tongue pressure (beta = 0.436, P < 0.001) in group B were the only predictors of masticatory performance when the data were analyzed by multiple regression analysis. The tongue may compensate for the missing teeth in masticatory performance of those elderly who have lost their natural teeth. The results of this study highlight the importance of tongue function in masticatory performance.

Oral Perception of Bolus in Healthy Young Women

This study was designed to characterize oral perception of both weight and volume of boluses. A total of 80 healthy young female subjects was recruited and divided into bolus weight ( n = 40) and bolus volume ( n = 40) conditions. Tap water (25°C) was the experimental material, and seven reference stimulus amounts ranging from 10 to 40 (grams and mL) were prepared. The reference stimuli, including a modulus of 20 (grams and mL), were delivered to the subjects in randomized order. The estimated magnitudes (Ψ) conformed to both the Fechner's and Stevens' psychophysical laws by the following equations: (1) ΨW = 314.3 log (S+1) −300.2 where S is stimulus intensity or weight, and ΨV = 249.7 log (S+1) −222.3 (volume) on logarithmic (log)-linear scales, and (2) ΨW = 1.908 S1.297 and ΨV = 4.097 S1.032 on log-log scales, respectively. The results indicate that oral perception of bolus weight and bolus volume conforms to the representative psychophysical laws.

Comparison of oral stereognosis in relation to age and the use of complete dentures

The purpose of this study was to examine the age-related difference in oral sensory function by testing oral stereognostic ability (OSA) and to determine the effect of wearing complete dentures on OSA. Subjects were 20 dentate and 30 edentulous elderly patients free from oral symptoms and pathologies, and 30 younger dentate students as controls. The OSA tests were conducted with test pieces of 12 shaped forms. The duration time for recognition was noted and the answers were recorded using a three-point scale. anova and paired t-tests were used to examine significant differences. P-values <0.05 were considered to be statistically significant. The OSA score in older dentate participants and complete denture wearers was significantly higher than in younger dentate subjects. However, no significant difference was found in the OSA score between older dentate participants and complete denture wearers. When older edentulous subjects removed the maxillary and mandible complete dentures, the OSA score was significantly lower and the response time significantly longer than with dentures. Within the limitations of this study, an age-related difference in oral sensory function, as measured by OSA tests, was found. However, oral sensory function was not significantly different between fully dentate persons and complete denture wearers in the elderly.

Effect of aging on bolus kinematics during the pharyngeal phase of swallowing

Swallowing difficulty is a common complaint in the elderly and, although there are data for the biomechanics of liquid swallows, little is known about solid bolus motion, or kinematics, in the elderly. The aims of this study were as follows: 1) to characterize and compare solid and liquid bolus kinematics in the elderly and compare the findings with those in young subjects and 2) to correlate bolus kinematics and dynamics. Concurrent manometric-fluoroscopic techniques were used to study eight young and eight elderly subjects. The subjects performed four swallows each of 0.2-cm-diameter solid barium pellets and 5 ml of liquid barium during sagittal fluoroscopy and six-channel pharyngoesophageal manometry. Images were digitized for analysis of kinematic properties such as velocity and acceleration. Dynamic pressures were recorded and coordinated with kinematic events. Image analysis showed that velocity varied as the pellet passed through the hypopharynx, pharynx, and upper esophageal sphincter. In young subjects, pellet kinematics were characterized by two zones of pellet acceleration: one over the tongue base and another as the pellet passed through the upper esophageal sphincter. Although the elderly showed a similar zone of acceleration over the base of the tongue, the second zone of pellet acceleration was not seen. Decreasing pressure gradients immediately distal to the position of the solid pellet and liquid bolus characterized dynamics for all subjects. This decreasing pressure gradient was significantly larger in elderly than in young subjects. Bolus kinematics and dynamics were significantly altered among elderly compared with young subjects. Among these differences were the absence of hypopharyngeal bolus acceleration and a significant increase in the trans-sphincteric pressure gradient in the elderly.

Relating particles and texture perception

Practically all foods contain particles. It has been suggested that the presence of particles in food may affect the perception of sensory attributes. In the present study we investigated the effect of size and type (hardness and shape) of particles added to a CMC based vanilla custard dessert. The two types of particles included in the study were silica dioxide and polystyrene spheres, varying in size from 2 to 230 microm. Eighteen trained adults participated in the study. They rated the sensation of 17 sensory flavour and texture attributes on a 100-point visual analogue scale (VAS). The results indicate that the addition of particles increased the sensation of roughness attributes and decreased the ratings of a number of presumably favorable texture attributes (smoothness, creamy, fatty and slippery) significantly. These effects increased with increasing particle size up to 80 microm. Roughness ratings deceased for larger particles sizes. Surprisingly, even particles of 2 microm had significant effects: they increased perceived rough lip-tooth feel, and decreased slippery lip-tooth feel and smoothness of the product. The affected attributes had previously been related to lubricative properties of foods. Particles added to semi-solid foods with relatively low levels of fat seem to counteract the lubricating effects of the fat resulting in increased oral friction. In a separate study on size perception the silica dioxide particles were used. By sampling the stimuli between the tongue and palate, subjects rated the size of the particles on a 100-point scale in comparison to anchor stimuli containing no particles and particles of 250 microm. The perceived particle size significantly increased for larger particles. Furthermore, perceived particle size was negatively correlated with roughness ratings. Thus, subjects who were sensitive and perceived the particles as being relatively large reported the same stimuli to have less rough after-feel. In conclusion, particles added to a product induce large effects on texture sensations, and texture sensation is related to individual size perception.