Chewing Rate Research Articles

Ten-year analysis of oral cancer focusing on young people in northern Thailand.

The objective of the present study was to assess the current situation of oral squamous cell carcinoma (OSCC) in northern Thailand, with an emphasis on patients <40 years of age. Medical records of patients histologically diagnosed with OSCC were collected from the Cancer Registry of Maharaj Nakorn Chiang Mai Hospital, Thailand between 2001 and 2010. The clinico-demographic data of patients aged <40 years (young group) and those aged ≥40 years (old group) were compared. A total of 874 patients were included in this study, of which 4.1% were <40 years of age. The tongue was the most common cancer site in both age groups. Most patients in both age groups were diagnosed with oral cancer at stage IV. Tobacco smoking (62.3%) and alcohol consumption (52.3%) were the most common risk factors in both age groups. However, the rates of betel quid chewing (17.5%) had decreased from those found in our study in the previous decade (50.2%); these rates were not found in the young group. The 5-year survival rate was 27.4% for the old group and 56.2% for the young group. OSCC remains a serious oral health problem in northern Thailand, and it has not been resolved among young adults.

Prevalence and Associated Factors of Khat Chewing among Atse Fasil Campus Student in University of Gondar, North West Ethiopia

Introduction: Khat is a shrub or tree its leaves have been chewed for centuries in the Eastern part of Africa and the Arabian Peninsula. Globally, khat chewing habit is being a hot issue of discussion and spreading at an alarming rate in the young generation, especially in higher institutions; where there are intensive academic activities are more intended. Similarly in Ethiopia it is consumed by some population groups commonly youths. It has a reported negative economic and health impact on the individuals engaging in the habit of khat chewing. There were no studies conducted to investigate the prevalence and associated factors of khat chewing in our study area. Objective: This study was conducted to assess the prevalence and associated factors of khat chewing among students of the Atse Fasil campus at the University of Gondar, North West Ethiopia. Methods: Institution based cross-sectional study was conducted from April 29 to May 03, 2013, in Aste Fasil campus, University of Gondar. A total of 310 students were selected using a stratified random sampling technique in which only 302 answer the question making the response rate of 97.4%. The data was entered and analyzed using SPSS version 20 software. Odds ratio and chi-square were used to test the association between different variables and also frequency, proportion and summary statistic was used to describe the study population. The analysis was taken a confidence interval of 95% and association with a P-value of &lt; 0.05. Results: The study revealed 9.6% lifetime prevalence rate of khat chewing. The current prevalence of khat chewing was found to be 6.95%. There were 6.72% female khat chewers and 11.7% male khat chewers. A large proportion (58.6%) lifetime chewers were started khat chewing after joining the university. Tigre ethnic group was significantly associated factor (AOR=0.041, 95%CI (0.002-0.718) with the outcome variable. Conclusion: The prevalence of khat chewing seems to decrease among university students. According to the study, Tigre ethnic group were at low risk of chewing khat than another ethnic group. The majority of the students were started chewing after joining the university. Increasing control measures and awareness about the health and social problems associated with khat chewing need to be implemented. Recreational alternatives for young people have to be found. &#x0D;

The role of betel-quid chewing in smoking cessation among workers in Taiwan.

BackgroundCurrent smokers exhibit a higher rate of betel-quid chewing than non-smokers. However, little is known regarding the extent to which betel-quid chewing may affect attempts to quit smoking and smoking cessation. The aim of the present study is to examine the association between betel-quid chewing and patterns of quitting smoking. Specifically, we explore whether betel-quid chewing is associated with (1) current smokers who have never attempted to quit versus those who have attempted to quit and have failed, those who are in the process of quitting, and successful cessation smokers, and (2) current smokers who have attempted to quit and have failed versus those who have successfully quit smoking.MethodsA telephone survey of 7,215 workers was conducted and obtained an 88.6% response rate. In the survey, the respondents’ smoking and betel-quid chewing statuses were recorded and a list of covariates was assessed.ResultsAfter controlling for the effect of the covariates, betel-quid chewing was found to be more highly associated with current smokers who have never attempted to quit, compared to current smokers who are in the process of quitting (OR = 12.72; 95% CI = 1.05–154.26), successful cessation smokers (OR = 3.62; 95% CI = 2.32–5.65), and smokers who have attempted to quit and have failed (OR = 1.37; 95% CI = 1.06–1.77), respectively. In addition, betel-quid chewing is more highly associated with a failure to quit smoking than with successfully quitting smoking (OR = 3.46; 95% CI = 2.17–5.51).ConclusionThe findings support four plausible reasons why betel-quid chewing may dissuade smokers from quitting. These reasons highlight additional avenues for potentially reducing the smoking population in workplaces, such as considering work contexts and social norms, and product sales in smoking-cessation campaigns.

Relationships between masticatory rhythmicity, body mass and cephalometrically-determined aesthetic and functional variables during development in humans

ObjectiveWe studied the relationship between chewing rhythmicity, craniomandibular morphology, and age in humans. DesignSixty subjects (10M:10F/group×three age groups, viz., 4–8, 10–14, and 17–21 years) participated. Subjects chewed gum for 2min while jaw movements in the frontal plane were videorecorded. Mean and variation in mean chewing cycle duration (TC) were quantified using maximum opening to maximum opening as cycle boundaries. Five “aesthetic” cephalometric variables (e.g., ANB) and seven “functional” variables (e.g., jaw length) were quantified from subjects’ lateral cephalographs. Simple linear regression models and several multivariate analyses were used in comparisons. ResultsMean TC increased and variation in TC decreased significantly with age. Body mass correlated with age, height, TC, all seven “functional” variables and only two “aesthetic” variables. Mean TC was correlated significantly with jaw length, distance from condylion to first molar point, distance from gonion to zygomatic arch, and distance from hyoid to menton. ConclusionsTC appeared to adapt with age. Although TC scaled most significantly with age, it is more likely that TC is mechanistically linked to jaw length or size. The decrease in TC variation with age suggests improved efficiency. TC did not scale with “aesthetic” variables, suggesting that these do not impact chewing rate; however, clinical procedures that impact jaw length may. The negative allometric scaling of TC with “functional” variables may reflect the pedomorphic jaw and face of humans. Further human studies will provide insights into the nature of scaling and adaptation of rhythmic chewing during development.

Socioeconomic status, personal habits, and prevalence of Helicobacter pylori infection in the inhabitants of Lanyu

Lanyu Island is a closed environment inhabited by the Yami people, Taiwan's smallest and most primitive tribe. This study assessed the prevalence and risk factors of Helicobacter pylori infection among Lanyu Island residents. A cross-sectional study was conducted among the inhabitants of Lanyu Island, using the (13)C urea breath test to determine the prevalence of H. pylori. All study participants completed a form requesting demographic data and anthropometric measurements and a questionnaire evaluating socioeconomic characteristics and personal habits. Multiple logistic regression analyses were used to identify independent factors of H. pylori infections, and a two-sided p<0.05 was considered significant. Among 796 participants, the mean age was 45±13.2 years, with a range of 12-89 years. The overall prevalence of H. pylori infection was 72.1%, and there was no significant difference between genders. The H. pylori-infected group contained higher proportions of Yami people, married individuals, as well as higher rates of alcohol consumption and betel chewing, but lower family incomes and education levels. Multiple logistic models found that Yamiethnicity [odds ratio (OR)=2.567, 95% confidence interval (CI): 1.344-4.905], alcoholconsumption (OR=1.641, 95% CI: 1.151-2.341), and marital status (OR=1.779, 95% CI: 1.043-3.032] were associated with H. pylori infection. This cross-sectional study identified a high prevalence of H. pylori infection on Lanyu Island. When investigating H. pylori infection status in a closed environment, such as Lanyu Island, it is important to consider all factors relating to the host population, including environment and lifestyle.

Trophic niche flexibility in Glossophaga soricina: how a nectar seeker sneaks an insect snack

Summary Omnivory enables animals to fill more than one trophic niche, providing access to a wider variety of food resources with potentially higher nutrient value, particularly when resources become scarce. Animals can achieve omnivory using different strategies, for example opportunistic foraging, or switching between multiple trophic niches. The Neotropical bat Glossophaga soricina (Pallas, 1766) is a common and widespread species known for nectar feeding, but it also eats fruit and insects. Approaching stationary objects (flowers and fruits) or moving objects (insects) poses different sensory tasks and should require different echolocation behaviours. Here we tested the contrasting hypothesis that G. soricina can approach both stationary and moving objects using the same echolocation behaviour, thus feeding at different trophic levels by a single sensory mechanism. Using DNA barcoding, we demonstrate that G. soricina eats beetles (Coleoptera), flies (Diptera) and noctuid moths with bat‐detecting ears. Laboratory observations show that G. soricina actively hunts for prey so insect consumption does not appear to be opportunistic. After capture, individuals consumed prey while perched and manipulated them with jaw, thumb, wrist and wing movements, but food handling was longer and chewing rate slower than in obligate insectivores. In contrast to most insectivorous bats, the echolocation calls of G. soricina are of high frequency and low intensity, and G. soricina did not produce feeding buzzes when approaching insects. An acoustic model of detection distances shows that its low‐intensity calls fail to trigger the auditory neurons of eared moths, allowing G. soricina to overcome auditory prey defences. Individuals achieved niche flexibility using a unique but generalist behavioural approach rather than employing two different specialist methods. Our findings provide a novel insight into the functional mechanisms of insect capture in G. soricina and highlight the importance of considering niche flexibility in classifying trophic links in ecological communities.

Effect of chewing speed on energy expenditure in healthy subjects

Objective. The aim of the study was to investigate the effect of rate of chewing on energy expenditure in human subjects. Materials and methods. Fourteen healthy subjects (aged 18–24 years) within the normal range of BMI participated in a cross-over experiment consisting of two 6-min sessions of gum chewing, slow (∼60 cycles/min) and fast (∼120 cycles/min) chewing. The resting energy expenditure (REE) and during gum chewing was measured using a ventilated hood connected to a gas analyzer system. The normality of data was explored using the Shapiro-Wilk test. The energy expenditure rate during chewing and the energy expenditure per chewing cycle were compared between the two chewing speeds using Wilcoxon signed ranks tests. Results. The energy expenditure per chewing cycle during slow chewing (median 1.4, range 5.2 cal; mean 2.1±1.6 cal) was significantly higher than that during fast chewing (median 0.9, range 2.2 cal; mean 1.0±0.7 cal) (p < 0.005). However, the energy expenditure rate was not significantly different between the two chewing speeds (p > 0.05). Conclusions. The results of this study suggest that chewing at a slower speed could increase the energy expenditure per cycle and might affect the total daily energy expenditure.

Offspring sex, current and previous reproduction affect feeding behaviour in wild eastern grey kangaroos

In mammals, lactation is the most energetically demanding component of female reproduction. Theory predicts an increase in food intake by lactating females, but very few studies have used contraceptives to experimentally test the influence of reproduction on foraging behaviour of wild mammals. From 2009 to 2011, we observed 182 individually marked female eastern grey kangaroos, Macropus giganteus, in two populations, including 29 that received an experimental contraceptive treatment. We sought to determine whether lactating females increase their foraging rate compared to contracepted and naturally nonlactating females. The proportion of time spent foraging during 10 min focal samples did not vary according to reproductive status in one population. In the other, lactating females spent 4% less time feeding than nonlactating females. Day and midday activity and bite and chewing rates were higher in lactating than in nonlactating females. Bite rate increased with the size of the pouch young and was higher for mothers of sons than for mothers of daughters. Bite rate was also affected by reproductive effort in the previous year, being higher for females that had weaned a young. Foraging behaviour was independent of body mass and group size, but bite rate appeared to decrease with female age. In one population, we found strong effects of date and year on foraging behaviour. Our study is a rare experimental manipulation of reproduction in free-ranging large mammals. We found that foraging behaviours were affected by both previous and current reproductive effort and varied with individual characteristics and environmental conditions.

An investigation of dentinal fluid flow in dental pulp during food mastication: simulation of fluid–structure interaction

This study uses fluid-structure interaction (FSI) simulation to investigate the relationship between the dentinal fluid flow in the dental pulp of a tooth and the elastic modulus of masticated food particles and to investigate the effects of chewing rate on fluid flow in the dental pulp. Three-dimensional simulation models of a premolar tooth (enamel, dentine, pulp, periodontal ligament, cortical bone, and cancellous bone) and food particle were created. Food particles with elastic modulus of 2,000 and 10,000 MPa were used, respectively. The external displacement loading (5 μm) was gradually directed to the food particle surface for 1 and 0.1 s, respectively, to simulate the chewing of food particles. The displacement and stress on tooth structure and fluid flow in the dental pulp were selected as evaluation indices. The results show that masticating food with a high elastic modulus results in high stress and deformation in the tooth structure, causing faster dentinal fluid flow in the pulp in comparison with that obtained with soft food. In addition, fast chewing of hard food particles can induce faster fluid flow in the pulp, which may result in dental pain. FSI analysis is shown to be a useful tool for investigating dental biomechanics during food mastication. FSI simulation can be used to predict intrapulpal fluid flow in dental pulp; this information may provide the clinician with important concept in dental biomechanics during food mastication.

Sex-Age Related Rumination Behavior of Père David’s Deer under Constraints of Feeding Habitat and Rainfall

Extensive studies have been conducted on the rumination behavior of domestic herbivores. However, studies on wild animals are limited, particularly wild animals with specific ruminating parameters. In this study, Père David’s deer, a previously extirpated species, was observed to analyze the effects of sex-age, feeding habitat, and rainfall on rumination behavior in the Dafeng Nature Reserve, China. Rumination behavior was investigated based on four parameters: proportion of bedding time spent chewing, bolus processing time (s/bolus), chewing frequency (chews/bolus), and chewing rate (chews/s). Results showed that all three factors affect rumination behavior. The extent of their effects varied based on the four rumination parameters. Chewing rate and frequency decreased based on sex–age levels, i.e., from fawns to juvenile female, juvenile male, adult female, stag, and harem holder. Therefore, body size played a major role in shaping rumination behavior. Deer found in grasslands could chew faster compared with deer found in woodlands. This result might be caused by the effects of dietary composition and sunlight intensity. A deer spends a longer time ruminating while bedding during rainy days compared with rainless days to maximize energy and nutrition intake and compensate for the loss of feeding time during rainy days. Therefore, rumination behavior is plastic and is shaped by intrinsic and extrinsic factors.

Relationship Between Chewing Rate and Masticatory Performance

The influence of mandibular movement timing on food breakdown remains unclear. The authors, therefore, sought to relate chewing rate with masticatory performance. Chewing rate, defined as the number of masticatory cycles habitually achieved per minute, was measured in 55 healthy dentulous subjects (age, 22.2±5.0 years). Subjects were grouped according to obtained values (cycles/minute): slower: <70; middle: 70-90; and faster: >90. Masticatory performance was determined through the sieve method, and the estimated comminuted median particle size (X50). Data was analyzed using the one-way ANOVA and chi-square tests (α=.05). Subjects with slower chewing rates showed higher (p<.05) masticatory performance (X50 = 3.05±0.77 mm). X50 was associated with chewing rate when subjects were categorized as better or poorer performers (chi-square=11.25, p<.005). Thus, chewing rate was related to masticatory performance, with smaller food particles being achieved with a slower chewing rate.

Areca nut chewing and risk of atrial fibrillation in Taiwanese men: a nationwide ecological study.

Background: Areca nut chewing is associated with the risk of obesity, metabolic syndrome, hypertension, and cardiovascular mortality. Although a few case reports or case series have suggested the link between areca nut chewing and cardiac arrhythmias, information about the relationship between areca nut chewing and atrial fibrillation (AF) is lacking. Thus, a nationwide ecological study was conducted to investigate this.Methods: Two national datasets, the nationwide population-based 2005 Taiwan National Health Insurance Research dataset (NHIRD) and the 2005 National Health Interview Survey (NHIS), were used for analyses. The clinical characteristics, inhabited area and medical histories for 375,360 eligible males were retrieved from the 2005 NHIRD. Health related behaviors including areca nut chewing, cigarette smoking, infrequent vegetable eating, and exercise habit were collected from the 2005 NHIS. The prevalence of AF and the areca nut chewing rate were evaluated by multivariate analysis.Results: Of the 375,360 males (mean age, 44 years old), 1,326 (0.35%) were diagnosed with AF. The higher areca nut chewing rate, the higher prevalence rate of AF in Taiwan (Spearman correlation coefficient r = 0.558, p = 0.007). After adjusting for other covariates, the current areca nut chewing rate was found to be independently associated with the prevalence of AF. The adjusted odd ratio for areca nut chewing was 1.02 (95% CI = 1.00-1.04) in risk of AF prevalence.Conclusions: Areca nut chewing is independently associated with the prevalence of AF in Taiwanese men. However, further exploration of the underlying mechanisms is necessary.

Relationship between Body Fat and Masticatory Function

The aim of this cross-sectional study was to investigate the relationship between body fat and masticatory function. One hundred dentate and partially edentulous participants (33 male; mean age, 39.7 ± 16.6 years) were selected. Body fat was established through body mass index (BMI). Masticatory function was evaluated by quantifying occlusal pairs and determining masticatory efficiency and swallowing threshold with the sieving method. During the swallowing threshold test, chewing rate was registered. Masticatory ability was also evaluated with a 5-point Likert scale questionnaire. Data were analyzed with Spearman and chi-square tests, as well as binary logistic regression analysis for the presence of increased BMI (α= 0.05). Age (rho = 0.517), occlusal pairs (chi-square = 26.353), masticatory efficiency (chi-square = 30.935), masticatory ability (chi-square = 25.132; p < 0.001), and swallowing threshold (chi-square = 8.730; p < 0.005) were related to BMI. Age (odds ratio, OR = 1.048, 95% CI = 1.008 to 1.089) and lower masticatory efficiency (OR = 4.792, 95% CI = 1.419 to 16.183) were predictive of increased body fat (p < 0.05). Gender (chi-square = 0.402, p= 0.526) and chewing rate (rho =-0.158, p= 0.117) were not related to BMI. These results suggest that people with lower masticatory efficiency may be at risk for increased body fat.

Oral processing characteristics of solid savoury meal components, and relationship with food composition, sensory attributes and expected satiation

Background: The modern food supply is often dominated by a large variety of energy dense, softly textured foods that can be eaten quickly. Previous studies suggest that particular oral processing characteristics such as large bite size and lack of chewing activity contribute to the low satiating efficiency of these foods. To better design meals that promote greater feelings of satiation, we need an accurate picture of the oral processing characteristics of a range of solid food items that could be used to replace softer textures during a normal hot meal. Aim: The primary aim of this study was to establish an accurate picture of the oral processing characteristics of a set of solid savoury meal components. The secondary aim was to determine the associations between oral processing characteristics, food composition, sensory properties, and expected satiation. Methods: In a within subjects design, 15 subjects consumed 50g of 35 different savoury food items over 5 sessions. The 35 foods represented various staples, vegetables and protein rich foods such a meat and fish. Subjects were video-recorded during consumption and measures included observed number of bites, number of chews, number of swallows and derived measures such as chewing rate, eating rate, bite size, and oral exposure time. Subjects rated expected satiation for a standard 200g portion of each food using a 100mm and the sensory differences between foods were quantified using descriptive analysis with a trained sensory panel. Statistical analysis focussed on the oral processing characteristics and associations between nutritional, sensory and expected satiation parameters of each food. Results: Average number of chews for 50g of food varied from 27 for mashed potatoes to 488 for tortilla chips. Oral exposure time was highly correlated with the total number of chews, and varied from 27s for canned tomatoes to 350s for tortilla chips. Chewing rate was relatively constant with an overall average chewing rate of approximately 1chew/s. Differences in oral processing were not correlated with any macronutrients specifically. Expected satiation was positively related to protein and the sensory attributes chewiness and saltiness. Foods that consumed in smaller bites, were chewed more and for longer and expected to impart a higher satiation. Discussion: This study shows a large and reliable variation in oral exposure time, number of required chews before swallowing and expected satiation across a wide variety of foods. We conclude that bite size and oral-sensory exposure time could contribute to higher satiation within a meal for equal calories.

The impact of chewing gum resistance on immediate free recall

Although the facilitative effects of chewing gum on free recall have proved contentious (e.g., Tucha, Mecklinger, Maier, Hammerl, & Lange, 2004; Wilkinson, Scholey, & Wesnes, 2002), there are strong physiological grounds, for example, increased cerebral activity and blood flow following the act of mastication, to suppose facilitation. The present study manipulated resistance to mastication, that is, chewing four pellets versus one pellet of gum, with the assumption that increased resistance will accentuate cerebral activity and blood flow. Additionally, chewing rate was recorded for all participants. In a within-participants design, participants performed a series of immediate free recall tasks while chewing gum at learning (one or four pellets) and recall (one or four pellets). Increased chewing resistance was not associated with increased memory performance, despite consistent chewing rates for both the one and four pellet conditions at both learning and recall. However, a pattern of recall consistent with context-dependent memory was observed. Here, participants who chewed the equivalent number of gum pellets at both learning and recall experienced significantly superior word recall compared to those conditions where the number of gum pellets differed.

Self-reports of eating quickly are related to a decreased number of chews until first swallow, total number of chews, and total duration of chewing in young people

ObjectiveThe validity of a self-questionnaire about eating quickly remains unclear. If a significant relationship between subjective and objective methods to evaluate eating quickly can be confirmed, then the subjective method can be widely and reliably used in many fields. This study investigated relationships between subjective and objective methods to evaluate eating quickly and also numerically characterized the kinesis of eating quickly in young people. DesignOne hundred and thirteen students (44 males and 69 females; mean age 22.8±2.0 years) were selected. All subjects completed written questionnaires, and number of chews until first swallow, total duration of chewing, number of chews, chewing rate and bite size were measured using test products (a Japanese cracker and rice ball). ResultsBoth male and female subjects who reported eating quickly showed a significantly lower number of chews until first swallow (Japanese cracker), a lower number of chews overall (rice ball), and a shorter total duration of chewing (rice ball) than other subjects. There was no difference in chewing rate between subjects who ate quickly or not. ConclusionsThese findings suggest that using test products, self-reports of eating quickly are related to a decreased number of chews until first swallow, total number of chews, and total duration of chewing, but not chewing rate, and that a self-reported questionnaire to evaluate eating rate is valid in young people.

Behavioral, Ecological, and Evolutionary Aspects of Meat-Eating by Sumatran Orangutans (Pongo abelii)

Meat-eating is an important aspect of human evolution, but how meat became a substantial component of the human diet is still poorly understood. Meat-eating in our closest relatives, the great apes, may provide insight into the emergence of this trait, but most existing data are for chimpanzees. We report 3 rare cases of meat-eating of slow lorises, Nycticebus coucang, by 1 Sumatran orangutan mother–infant dyad in Ketambe, Indonesia, to examine how orangutans find slow lorises and share meat. We combine these 3 cases with 2 previous ones to test the hypothesis that slow loris captures by orangutans are seasonal and dependent on fruit availability. We also provide the first (to our knowledge) quantitative data and high-definition video recordings of meat chewing rates by great apes, which we use to estimate the minimum time necessary for a female Australopithecus africanus to reach its daily energy requirements when feeding partially on raw meat. Captures seemed to be opportunistic but orangutans may have used olfactory cues to detect the prey. The mother often rejected meat sharing requests and only the infant initiated meat sharing. Slow loris captures occurred only during low ripe fruit availability, suggesting that meat may represent a filler fallback food for orangutans. Orangutans ate meat more than twice as slowly as chimpanzees (Pan troglodytes), suggesting that group living may function as a meat intake accelerator in hominoids. Using orangutan data as a model, time spent chewing per day would not require an excessive amount of time for our social ancestors (australopithecines and hominids), as long as meat represented no more than a quarter of their diet.Electronic supplementary materialThe online version of this article (doi:10.1007/s10764-011-9574-z) contains supplementary material, which is available to authorized users.

Botulinum toxin in masticatory muscles: Short- and long-term effects on muscle, bone, and craniofacial function in adult rabbits

Paralysis of the masticatory muscles using botulinum toxin (BTX) is a common treatment for cosmetic reduction of the masseters as well as for conditions involving muscle spasm and pain. The effects of this treatment on mastication have not been evaluated, and claims that the treatment unloads the jaw joint and mandible have not been validated. If BTX treatment does decrease mandibular loading, osteopenia might ensue as an adverse result. Rabbits received a single dose of BTX or saline into one randomly chosen masseter muscle and were followed for 4 or 12weeks. Masticatory muscle activity was assessed weekly, and incisor bite force elicited by stimulation of each masseter was measured periodically. At the endpoint, strain gages were installed on the neck of the mandibular condyle and on the molar area of the mandible for in vivo bone strain recording during mastication and muscle stimulation. After termination, muscles were weighed and mandibular segments were scanned with micro CT. BTX paralysis of one masseter did not alter chewing side or rate, in part because of compensation by the medial pterygoid muscle. Masseter-induced bite force was dramatically decreased. Analysis of bone strain data suggested that at 4weeks, the mandibular condyle of the BTX-injected side was underloaded, as were both sides of the molar area. Bone quantity and quality were severely decreased specifically at these underloaded locations, especially the injection-side condylar head. At 12weeks, most functional parameters were near their pre-injection levels, but the injected masseter still exhibited atrophy and percent bone area was still low in the condylar head. In conclusion, although the performance of mastication was only minimally harmed by BTX paralysis of the masseter, the resulting underloading was sufficient to cause notable and persistent bone loss, particularly at the temporomandibular joint.

The influence of auditory and visual information on the neuromuscular control of chewing crispy food

The influence of auditory and/or visual information on the neuromuscular control of chewing a crispy food was investigated. Participants chewed biscuits of three different levels of crispness under four experimental conditions: no masking, auditory masking, visual masking, and auditory plus visual masking. The order of the four masking condition blocks was randomized. The sound of chewing was masked by loud sounds on a headphone, and visual masking of the food was achieved by closing the eyes. Mechanical tests were performed on the biscuits to determine their characteristics, yield force, and sound production. Skull vibration, jaw-muscle activity, and jaw movement were measured while the subjects chewed and swallowed the food. Auditory and/or visual masking did not have a significant effect on skull vibration, muscle activity, and number of chewing cycles until swallowing. However, auditory and/or visual masking significantly increased the chewing cycle duration, but only for the participants who started the experiments with auditory and/or visual masking. The other participants were not influenced by masking. The memory of the unmodified stimuli helped these subjects to maintain their habitual chewing rate in later trials.

Effect of forage quality on intake, chewing activity, faecal particle size distribution, and digestibility of neutral detergent fibre in sheep, goats, and llamas

This study investigated the effect of forage quality on intake, eating and ruminating activities, faecal particle size distribution, and neutral detergent fibre (NDF) digestibility in three ruminating species. The experimental design included ad libitum feeding of three ruminating species with two types of forage for two periods in a crossover design. The species included six adult, non-pregnant female Danish Landrace goats, Shropshire sheep, and Lama glama llamas with body weights of 45±5, 75±6, and 135±20kg (mean±SD), respectively. Forage included chopped artificially dried grass hay (GH) and grass seed straw (GSS). The contents of NDF in dry matter (DM) and of in situ indigestible NDF (%NDF) were 58 and 15% for GH and 81 and 28% for GSS, respectively. Total faeces were collected for five days. The faecal samples were washed in nylon bags and freeze dried before being sorted into six sieving fractions with pore sizes in the 2.4–0.1mm range and a bottom bowl. The dimension of each particle in sub-samples from each fraction was measured using image analysis. The DM intake per metabolic body weight (BW) was higher in sheep and llamas fed GH than in those animals fed GSS (P<0.05). Sheep and goats had a higher NDF intake per kg BW than did llamas when fed GSS (P<0.001). The mean and effective times spent eating per kg of DM intake, ruminating, and in total chewing per kg of DM and NDF intakes were higher when GSS was fed (P<0.05). The total daily and effective time spent chewing was higher in sheep than in goats (P<0.05). The mean daily and effective times spent chewing per kg of DM and NDF intakes were higher in goats than in sheep (P<0.05). The ratio between the basic chewing rate during eating and ruminating was lower in llamas than in goats or sheep (P<0.001) and was affected by forage type, species, and their interactions (P<0.05). The proportions of small (<0.2mm) and large particles (LP) (>1mm) were significantly reduced by feeding GSS. Feeding GH rather than GSS resulted in lower most frequent particle size, length, and width values (P<0.001) and a lower median particle size (P<0.05). NDF digestibility was highest when GH was fed (P<0.05). In conclusion, feeding low-digestible forage leads to a higher mean chewing time per kg of DM and NDF intakes and longer ruminating periods and cycles than when feeding medium-digestible forage. Feeding more digestible forage caused thinner and longer faeces particles than did feeding low-digestibility forage. The overall particle size, length, and width characteristics values in faeces did not differ between sheep, goats, and llamas, which indicates the same mechanism of selective retention of LP in the forestomach system. Across animal species and forage type, the mean particle size in faeces was negatively correlated with NDF digestibility.