Characterization of oral tactile sensitivity and masticatory performance across adulthood

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

BACKGROUND

Oral frailty, characterised by reduced oral function, is associated with systemic health issues in older adults. Although the criteria for diminished oral function often focus on motor and secretory abilities, texture perception also plays a crucial role in health due to its impact on food intake and palatability.

OBJECTIVE

This study aimed to explore the relationship between thickness discrimination ability (TDA) and oral motor and secretory functions in healthy young individuals.

METHODS

Twenty-eight adults were assessed for texture perception using eight concentrations of aqueous xanthan gum solutions to determine TDA scores. Measurements of occlusal force, masticatory performance, tongue pressure, stimulated salivary flow rate and tongue-lip motor function were conducted. Spearman's correlation analysis was used to evaluate the relationship between TDA scores and oral functions. Participants were divided into high-sensitivity and low-sensitivity groups based on their TDA scores to compare oral function test results.

RESULTS

The TDA scores varied among the participants, with higher scores correlating with higher masticatory performance (r = 0.41, p < .05). Masticatory performance in the high-sensitivity group was significantly higher than in the low-sensitivity group (211.9 ± 59.2 mg/dL vs. 157.9 ± 43.0 mg/dL, p = .013), with no significant differences in other oral functions.

CONCLUSION

Masticatory performance was correlated with TDA, suggesting a link between the selection function of mastication and thickness discrimination. These findings highlight the potential relevance of texture perception in oral function and indicate the need for further exploration, particularly in older adults with declining oral health.

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.

Effect of texture preference on food texture perception: Exploring the role of matching food texture and preference

This study aimed to investigate the influence of smooth texture preference on smoothness perception. An online questionnaire (Study 1, n = 464) and a sensory evaluation test (Study 2, n = 65) were administered to Japanese elderly participants (65-74 years), with common Japanese confectionery (Daifuku) as test foods. Through the online questionnaire, four distinct texture preference groups were formed based on the factors of preference for smoothness and firmness of the inner bean paste layer. Analysis of the food preference scale for imbalanced diet (FPSID) revealed that smooth-texture likers were more likely to be picky eaters than firm-texture likers. Furthermore, high (HiSm) and low smoothness preference groups (LoSm) were selected for the food sensory evaluation test to compare perceived textures (smoothness and firmness). Only the HiSm group exhibited a positive association between perceived smoothness and overall texture liking, perceiving smoothness significantly more intense than the LoSm group in situations where overall texture liking was high. This finding indicates that smooth texture preference does not act independently but rather interacts with food texture matching to affect perception. Our findings suggest that when food texture aligns with individuals' preferences, it elicits hedonic emotions and dynamically enhances food texture perception. This preference-involved perceptual process may contribute to the development of more explicit texture preferences.

Texture term usage and hedonic ratings in two age-diverse cohorts of Americans

This study explores the use of food texture terms by adults in the northeastern United States. The purpose of the study was to compare the effect of food texture on food liking and texture term usage among age groups via two complementary online surveys that differed in the specific task given to participants. Survey 1 gathered common food items associated with 25 texture terms using open-ended questions from 345 participants (45% men, 55% women; age range = 20-79 years); it also collected liking scores for foods with these textures. Next, a new group of participants (n = 349, 46% men, 54% women; age range = 20-79 years) completed Survey 2, which asked them to match up to three texture terms to 32 different foods drawn from Survey 1, using a provided list of 35 texture terms. "Tough," "Chalky," and "Rubbery" had a negative impact on food liking scores while "Tender," "Juicy," and "Crispy" were associated with higher mean food liking scores. "Soft," "Crunchy," "Crispy," "Juicy," and "Greasy" were commonly used texture terms regardless of age. Within those aged 50-79 years, "Smooth," "Tender," "Crunchy," "Soft," "Moist," "Crispy," and "Creamy" were used more often while "Chalky," "Rough," "Mealy," "Foamy/Airy," "Gritty" were used less often. Our results identified commonly used texture terms and revealed differential usage in older and younger adults. These data deepen our understanding of the texture of foods in the modern food environment, highlighting how texture perception may vary with age.

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.

Effects of Age Group, Gender, and Consumption Frequency on Texture Perception and Liking of Cooked Rice or Bread

This study aimed to determine whether and how three demographic factors-age group, gender, and consumption frequency-affect texture perception and liking of two staple foods-cooked rice and wheat bread. In total, 346 adults evaluated three cooked rice and four wheat bread samples in terms of three (hardness, stickiness, and chewiness) and four textural attributes (hardness, moistness, chewiness, and softness), respectively, on both 9-point intensity and 5-point Just-About-Right (JAR) scales. Liking of test samples was also rated on 9-point hedonic scales. Age group and gender differed in mean ratings, standard deviations, and JAR responses regarding textural attribute intensity and overall liking of test samples, while the effect of consumption frequency was minimal in this regard. Significant contributors of textural attributes to overall liking of cooked rice and wheat bread differed with age group, gender, and consumption frequency. Effects of age group, gender, and consumption frequency on texture perception and overall liking also varied with test samples. This study provides agricultural and food systems professionals with systematic evidence of how textural attribute perception and liking of foods can change based on demographics and test samples.

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).

Effects of textured food masticatory performance in older people with different dental conditions

BACKGROUND

Physiological deterioration (aging, poor dental status, and reduced tongue pressure) makes chewing difficult. This study aimed to investigate the chewing patterns of older people with or without dentures, evaluate the textural and masticatory properties of texture-modified radish Kimchi, and investigate the correlation between dental status and tongue pressure. Additionally, differences in the subjective-objective concordance of texture-modified Kimchi were investigated using the preference test.

METHODS

This study included 32 Korean women aged between 65 and 85 years. Masticatory behavior was recorded by electromyography, and tongue pressure was measured using the Iowa Oral Performance Instrument. A preference test, with hardness as the relevant textural property, determined the participants' preferences among the test samples (food with a homogeneous structure-radish Kimchi). To assess preference differences, a questionnaire suitable for older people was designed. The preference for cooked radish Kimchi with various blanching times based on overall acceptability and self-reporting of preference was investigated to develop elderly-friendly food. The subjective scores indicated whether the sample (radish Kimchi) was hard or soft based on the chewing ability of the participants. Dental status, muscle activities, and tongue pressure were considered for the food design with optimized texture. The relationship between subject score and mastication properties were examined using multiple regression analysis.

RESULTS

The number of chews and chewing time increased with hardness, significantly activating the masseter and temporalis muscles. The evaluation of masseter muscle activity, particularly for level-6 radish Kimchi, showed that older people with complete dentures chewed less actively than those with natural teeth (p < 0.05). The older people with natural teeth (18.94 ± 10.27 kPa) exhibited higher tongue pressure than those with complete dentures (10.81 ± 62.93 kPa), and the difference was statistically significant (p < 0.01). Older people preferred food with familiar tastes and textures. An association was found between the subjective hardness score and the objective hardness level. The perceived hardness intensity was linked to the chewing ability of the participant. Denture wearers exhibited a lower chewing ability, and at level 6, they perceived greater hardness of food than those with natural teeth.

CONCLUSIONS

Developing food with a modified texture can bridge the gap between physiological and psychological aspects of food texture; texture-modified radish Kimchi, with limited blanching time, may be favorable for older people.

Exploring the association between oral tactile sensitivity measures and phenotypic markers of oral responsiveness

This study investigated the individual variability in oral tactile sensitivity considering touch, by means of Von Frey Hair monofilaments (VFH) and spatial resolution, using the grating orientation test (GOT). The relationships of the two measures with 6-n-propylthiouracil (PROP) responsiveness and fungiform papillae density and size were investigated. One hundred and forty-four subjects (48.6% women, aged 18-30) participated in the study. VFH and GOT thresholds were assessed by three-down/one-up staircase method. Responsiveness to 3.2mM PROP was assessed on the general Labelled Magnitude Scale. Fungiform papillae density (FPD) and size were determined from automated counting. VFH thresholds appeared unsuitable to reveal individual variation in responsiveness to point-pressure on the tongue. The frequency of GOT thresholds approximated a normal distribution and covered the whole range of variation, thus indicating an ability to measure individual variation in oral tactile sensitivity. No significant linear correlations were found between any of the oral tactile sensitivity measures and PROP responsiveness, FPD total and size class. VFH and GOT thresholds were not significantly associated. Agglomerative hierarchical clustering was used to classify participants for their PROP responsiveness, total FPD and GOT threshold. Three clusters were identified, C1 (n=67), Cl2 (n=42) and Cl3 (n=35), differing for PROP responsiveness and FPD only. Results encourage future studies to explore association between GOT and both perception and preference for different food texture. Furthermore, deeper investigation of individual variability in sensitivity to different types of oral tactile stimuli would be helpful to capture differences in tactile sensitivity among the most sensitive individuals.

Current Perspectives on Food Oral Processing

Food oral processing (FOP) is a fast-emerging research area in the food science discipline. Since its first introduction about a decade ago, a large amount of literature has been published in this area, forming new frontiers and leading to new research opportunities. This review aims to summarize FOP research progress from current perspectives. Food texture, food flavor (aroma and taste), bolus swallowing, and eating behavior are covered in this review. The discussion of each topic is organized into three parts: a short background introduction, reflections on current research findings and achievements, and future directions and implications on food design. Physical, physiological, and psychological principles are the main concerns of discussion for each topic. The last part of the review shares views on the research challenges and outlooks of future FOP research. It is hoped that the review not only helps readers comprehend what has been achieved in the past decade but also, more importantly, identify where the knowledge gaps are and in which direction the FOP research will go.

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.

Subjective touch sensitivity leads to behavioral shifts in oral food texture sensitivity and awareness

Neurotypical individuals have subjective sensitivity differences that may overlap with more heavily studied clinical populations. However, it is not known whether these subjective differences in sensory sensitivity are modality specific, or lead to behavioral shifts. In our experiment, we measured the oral touch sensitivity and food texture awareness differences in two neurotypical groups having either a high or low subjective sensitivity in touch modality. To measure oral touch sensitivity, individuals performed discrimination tasks across three types of stimuli (liquid, semisolid, and solid). Next, they performed two sorting exercises for two texture-centric food products: cookies and crackers. The stimuli that required low oral processing (liquid) were discriminated at higher rates by participants with high subjective sensitivity. Additionally, discrimination strategies between several foods in the same product space were different across the groups, and each group used attributes other than food texture as differentiating characteristics. The results show subjective touch sensitivity influences behavior (sensitivity and awareness). However, we show that the relationship between subjective touch sensitivity and behavior generalizes beyond just touch to other sensory modalities.

Improvements and Degradation to Spatial Tactile Acuity Among Blind and Deaf Individuals

Cross-modal reorganization takes place for sensory cortices when there is no more primary input. For instance, the visual cortex in blind individuals which receives no visual input starts responding to auditory and tactile stimuli. Reorganization may improve or degrade processing of other modality inputs, via bottom-up compensational processes and top-down updating. In two experiments, we measured the spatial tactile response in a large sample of early- (N = 49) and late-blind (N = 51) individuals with varying levels of Braille proficiencies, and early-deaf (N = 69) with varying levels of hearing devices against separate hearing and sighted controls. Spatial tactile responses were measured using a standard gradient orientation task on two locations, the finger and tongue. Experiments show limited to no advantage in passive tactile response for blind individuals and degradation for deaf individuals at the finger. However, the use of hearing devices decreased the tactile impairment in early-deaf individuals. Also, no differences in age-related decline in both sensory-impaired groups were shown. Results show less tactile acuity differences between blind and sighted than previously reported, but supports recent reports of tactile impairment among the early-deaf.

Nutritional status and masticatory function of the indigenous compared with non-indigenous people of Nayarit, Mexico

OBJECTIVE

The objective of this study was to compare the nutritional statuses and masticatory function of the non-indigenous and indigenous adult people of the state of Nayarit, Mexico.

DESIGN

Forty-two indigenous (Cora or Huichol ethnic group) and 100 non-indigenous people, all adults with natural dentition, participated in this cross-sectional study. They performed a free-style masticatory test consisting five trials of chewing silicon pieces for 20 cycles. Masticatory performance was determined by sieving the silicon particles, masticatory laterality was determined by calculating the asymmetry index, and the cycle duration was also recorded. Weight and body fat mass were measured using a portable digital weighing machine and height and body circumferences were recorded to calculate the body mass index (BMI), body fat percentage, and the waist-hip ratio. Each aspect of masticatory function and each nutritional variable were compared using T-test, analysis of variance, and Kruskal-Wallis or Mann-Whitney tests, as appropriate.

RESULTS

Body fat percentage, BMI, and waist-hip ratio were higher (P < 0.0005) in the indigenous group compared to the non-indigenous. The indigenous group had a significantly shorter stature than the non-indigenous group. Cora group had a higher BMI and higher percentage of body fat than the Huichol group (P < 0.05). No significant differences were detected between the groups for any aspect of masticatory function.

CONCLUSIONS

Indigenous people from the Nayarit, especially the Cora ethnic group, are more obese, have more total body fat, and more abdominal fat than non-indigenous people. Indigenous people show similar masticatory function.

Chemical, Electrical and Tactile Sensitivity Changes After Middle Ear Surgery

OBJECTIVE/HYPOTHESIS

Taste disturbances are often seen in patients after middle ear surgery due to the stress received by an unprotected chorda tympani. It has also been reported that loss in tactile sensitivity may accompany this issue. The current study was designed to measure electrical, chemical, and tactile sensitives of several senses involved in oral processing, smell, taste and touch, over time.

STUDY DESIGN

Prospective cohort study.

METHODS

For three time points, one before middle ear surgery and two after operation (about 5 and 23 days), sensitivity thresholds were obtained using electrogustometry (electrical taste), taste strips (chemical taste), Sniffin' Sticks (smell) and Von Frey Hairs (point-pressure tactile sensitivity).

RESULTS

The results show a decline in both chemical and electrical taste responses. Additionally, the electrical taste response showed more sensitivity to deviations and no sign of recovery unlike the chemical taste response. Mechanosensory function of the anterior tongue and olfactory function was not strongly affected by middle ear surgery.

CONCLUSION

Taste responses, but not mechanosensory or olfaction function, are altered after middle ear surgery. Due to the effects that taste loss has on quality of life, gustometry is recommended for this group of patients.

LEVELS OF EVIDENCE

4.

Oral Health Awareness among International Dental and Medical Students at Lithuanian University of Health Sciences: a Cross-Sectional Study

Objectives

To evaluate the self-reported oral health awareness, knowledge and attitude among international dental and medical students at the Lithuanian University of Health Sciences (Kaunas, Lithuania).

Material and Methods

A cross-sectional study was conducted among international medical and dental students at the Lithuanian University of Health Sciences in 2016 - 2017. The students were invited to participate in the survey before the beginning of a lecture, and they were informed that participation was voluntary and anonymous. In total, 282 students participated in the study, with a response rate of 92.1%. A self-administered English questionnaire consisting of 25 items with options on a Likert scale (agree, neither agree nor disagree and disagree) about oral health problems and their relation to general health status was used to assess a student’s oral health awareness, attitude and knowledge. The level of significance was set at P < 0.05.

Results

Overall good, fair and poor oral health awareness was reported by 71.3%, 24.1% and 4.6%, respectively, of the international dental and medical students (P < 0.05). The mean score of oral health awareness was 18.2 (standard deviation [SD 3.27]), showing overall good oral health awareness. Moreover, the international dental students reported higher oral health awareness than medical students (19.14 [SD 3.25] vs 17.44 [SD 3.1]) (P < 0.001). Comparing this mean score by gender, no statistically significant difference was found (18.33 [SD 3.39] vs 18.05 [SD 3.16]) (P = 0.371).

Conclusions

Overall oral health awareness among international dental and medical students was high. Meanwhile, international dental students reported higher oral health awareness than international medical students.

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.