Hard Food Research Articles

Fossils and FEA

This article explores the application of finite element analysis (FEA) in studying the evolution of animals, including dinosaurs. Scientists have applied the method to determine how dinosaurs originally looked and functioned, and how they and other animals changed and evolved through the years. FEA is a useful tool to reconstruct the mechanical behavior of the muscle and skeletal system in zoological and paleontological studies because it is non-invasive and reconstructs stress at multiple sites and depths throughout the skeleton. It can be used to study extinct animals by way of their fossilized remains and can deal with complex geometries and load conditions. FEA is now routinely used to interpret skeletal forms for function in both medical and biological applications. The scientists believe that FEA will hopefully allow to see the effect of eating hard foods, such as the belemnites with their bullet-shaped guards. FEA allows a far more intricate, accurate, and precise picture of the bone to be used in studies.

Interleukin-6 Maintains Glucose Homeostasis to Support Strenuous Masseter Muscle Activity in Mice

The cytokine interleukin-6 (IL-6) is released from working skeletal muscles and reportedly plays key roles in their glucose homeostasis. However, it is unclear whether IL-6 plays such roles in the masseter muscle (MM), which is important in normal and pathological chewing behaviors, such as bruxism and/or prolonged clenching. When restrained (R+) in a narrow cylinder blocked at the front end with a thin plastic strip, a mouse gnaws away (G+) the strip to escape. The absolute weight of plastic gnawed away serves as an index of MM activity. Using this model, we examined the roles of IL-6 in MM with the following results. R+G+ increased the expression levels of IL-6 and glucose transporter 4 (Glut4) mRNAs in MM and the serum level of IL-6 protein. IL-6-deficient mice exhibited about 60% less gnawing activity than wild-type mice at 3-4 h after the start of R+G+, slower recovery of glycogen levels (indicating poorer glucose supply) in MM after R+G+, and no significant change in Glut4 mRNA in MM upon R+G+. During an R+G+ test conducted after "training" (repeated R+G+ sessions), wild-type mice exhibited greater gnawing activity than untrained controls, but no increase in IL-6 mRNA in MM. IL-6 mRNA increased in MM when hard food was eaten by mice raised on soft food for 3 weeks from weaning, but not in those raised on (accustomed to) hard food. Thus, IL-6 may maintain glucose homeostasis in MM in support of unusually strenuous activity, but not of accustomed activity levels.

15. Persistent pain following alvogyl treatment of post extraction alveolar osteitis

A 51-year-old man presented with pain on eating hard food for 2 years following extraction of the left mandibular second pre-molar and second molar teeth. The extraction was complicated by alveolar osteitis (dry socket). Initial imaging did not show any bony deficiency but subsequent imaging hinted at a possible bony defect and the underlying mandibular bone was debrided. At the time of debridement material, in retrospect, consistent with Alvogyl was noted. Light microscopy showed low grade chronic inflammation in the soft tissues secondary to refractile vegetable matter like material consistent with Alvogyl. Some of the foreign material was associated with aggregates of multinucleated giant cells and some islands of new bone. The mandibular bone present in the specimen was viable. Alvogyl is a commonly used alveolar dressing with fibres derived from Cibotium species (tree fern). According to the manufacturer (Septodont) this fibrous consistency allows adherence to the alveolus and the product is self-eliminated with assistance from the patient’s tongue movements. A very small number of studies have shown Alvogyl to retard wound healing. There are no published case reports of chronic pain due to the retention of Alvogyl and chronic inflammation.

Abrasive, silica phytoliths and the evolution of thick molar enamel in primates, with implications for the diet of Paranthropus boisei.

BackgroundPrimates—including fossil species of apes and hominins—show variation in their degree of molar enamel thickness, a trait long thought to reflect a diet of hard or tough foods. The early hominins demonstrated molar enamel thickness of moderate to extreme degrees, which suggested to most researchers that they ate hard foods obtained on or near the ground, such as nuts, seeds, tubers, and roots. We propose an alternative hypothesis—that the amount of phytoliths in foods correlates with the evolution of thick molar enamel in primates, although this effect is constrained by a species' degree of folivory.Methodology/Principal FindingsFrom a combination of dietary data and evidence for the levels of phytoliths in plant families in the literature, we calculated the percentage of plant foods rich in phytoliths in the diets of twelve extant primates with wide variation in their molar enamel thickness. Additional dietary data from the literature provided the percentage of each primate's diet made up of plants and of leaves. A statistical analysis of these variables showed that the amount of abrasive silica phytoliths in the diets of our sample primates correlated positively with the thickness of their molar enamel, constrained by the amount of leaves in their diet (R2 = 0.875; p<.0006).Conclusions/SignificanceThe need to resist abrasion from phytoliths appears to be a key selective force behind the evolution of thick molar enamel in primates. The extreme molar enamel thickness of the teeth of the East African hominin Paranthropus boisei, long thought to suggest a diet comprising predominantly hard objects, instead appears to indicate a diet with plants high in abrasive silica phytoliths.

Brief communication: Enamel thickness and durophagy in mangabeys revisited

The documentation of enamel thickness variation across primates is important because enamel thickness has both taxonomic and functional relevance. The Old World monkeys commonly referred to as mangabeys have figured prominently in investigations of feeding ecology and enamel thickness. In this article, we report enamel thickness values for four mangabey taxa (Cercocebus atys, Cercocebus torquatus, Lophocebus aterrimus, and Lophocebus albigena), offer revised interpretation of the significance of thick enamel in papionin evolution, and place our new data in a broader comparative framework. Our data indicate that all mangabeys have thick enamel and that the values obtained for Cercocebus and Lophocebus equal or exceed those published for most extant non-human primates. In addition, new field data combined with a current reading of the dietary literature indicate that hard foods make up a portion of the diet of every mangabey species sampled to date. Clarification on the relationship between diet and enamel thickness among mangabeys is important not only because of recognition that mangabeys are not a natural group but also because of recent arguments that explain thick enamel as an evolved response to the seasonal consumption of hard foods.

The effect of aging and dental status on the frequency of eating out

Although many studies have investigated the effect of impaired dentition on eating habits and social expression, very few studies have evaluated the effect of age and dental status on the frequency of eating out, which was the purpose of the present study. A sample of 161 community-dwelling adults aged between 20 and 94 years of age was interviewed and then clinically examined to record dental and denture status. The bivariate analyses revealed that those who were eating out less often were more likely older, widowed, pensioners, with elementary or less than elementary education, suffering from hypertension, overweight or obese, with bad self-rated health, complaining for xerostomia, with difficulties chewing hard food and with fewer natural teeth. Multiple logistic regression analysis identified as significant predictors for less frequently eating out older age and low educational level. These results suggest that in the particular cultural environment the dental status is not an independent predictor of the frequency of eating out, but other biological and social factors play a more significant role.

Tooth root morphology as an indicator for dietary specialization in carnivores (Mammalia: Carnivora)

The Carnivora occupy a wide range of feeding niches in concordance with the enormous diversity in their skull and dental form. It is well established that differences in crown morphology are linked to variations in the material properties of the foods ingested and masticated. However, how tooth root form is related to dietary specialization is less well known. In the present study, we investigate the relationship between tooth root morphology and dietary specialization in terrestrial carnivores (canids, felids, hyaenids, and ursids). We specifically address the question of how variation in tooth root surface area is related to bite force potentials as one of the crucial masticatory performance parameters in feeding ecology. We applied computed tomography imaging to reconstruct and quantify dental root surface area in 17 extant carnivore species. Moreover, we computed maximal bite force at several tooth positions based on a dry skull model and assessed the relationship of root surface area to skull size, maximal bite force, food properties, and prey size. We found that postcanine tooth root surface areas corrected for skull size serve as a proxy for bite force potentials and, by extension, dietary specialization in carnivores. Irrespective of taxonomic affinity, species that feed on hard food objects have larger tooth roots than those that eat soft or tough foods. Moreover, carnivores that prey on large animals have larger tooth root surface areas. Our results show that tooth root morphology is a useful indicator of bite force production and allows inferences to be made about dietary ecology in both extant and extinct mammals.

MicroCT-scans of fossil micromammal teeth: Re-defining hypsodonty and enamel proportion using true volume

Both hypsodonty and proportion of enamel are important measures for reconstructing diets and environments of fossil mammals. Classically, the first is calculated using crude dimensions and the second using specific cross-sections. With the increased availability of three-dimensional imaging techniques such as (micro)CT scanning, an upgrade towards new indices using actual 3D volumes is highly appropriate. Here we present examples from fossil small mammals to illustrate a straightforward and objective protocol to calculate new volume-based indices. Both hypsodonty and enamel proportion are defined in a consistent way with regard to orientation, and both are robust against damage or loss of dentine. Whereas hypsodonty values in the studied rodents are reduced by more than one third with regard to the older methods, they are lowered by more than a factor two in taxa with a very strong dental relief, such as insectivores. Thus, relative positions of taxa on the continuum between animal and plant consumers change, by using actual dental volume and mean height instead of maximum height. Although enamel proportion and hypsodonty are expected to be positively correlated across rodents in general, the two parameters may easily get decoupled, for instance when thick enamel is needed to break down hard but high-nutrition food items such as seeds or nuts, or when thin enamel blades are needed to cut low-nutrition items, such as grass leaves.

FUNDAMENTAL FRACTURE PROPERTIES ASSOCIATED WITH SENSORY HARDNESS OF BRITTLE SOLID FOODS

ABSTRACTA series of biscuit‐like model foods that vary primarily in hardness, while keeping other sensory attributes less variable, was developed and used to investigate the relationship between fundamental fracture properties and the sensory perception of hardness of brittle solid foods. Fifteen biscuit samples were evaluated by both a trained sensory panel and three instrumental tests (three‐point bending test, single‐edge notched bend test and modified texture profile analysis), and their relationships were determined by simple linear regression analysis. Correlations revealed that the perceived hardness during biting or chewing is fracture related, and it is directly related to the amount of stress required to initiate and propagate a crack in a material (i.e., fracture stress [σ] and critical stress intensity factor [KIC], respectively). The fracturing of these hard and brittle biscuits appeared to be associated with the release of energy as sound, and thus, the perceived hardness and crunchiness were indistinguishable.PRACTICAL APPLICATIONSSensory evaluation is time consuming and expensive, and, therefore, reliable and practical (faster, less expensive and reproducible) instrumental methods are needed to accurately predict sensory texture attributes, at least, in the product development and quality control stages. This study demonstrated that the perceived hardness of biscuits can be tracked by σ and KIC with remarkable precision. These properties may be used as a reliable replacement for a sensory assessment of hardness in brittle solid foods, where applicable.

Chewing abilities of elderly populations in Europe

To describe variations in chewing abilities of elderly populations in different European countries. We used data from the Survey of Health, Ageing, and Retirement in Europe (SHARE Wave 2) and estimated a series of multivariate logistic regression models in order to analyse variations in self-reported ability to bite and chew on hard foods by persons aged 50+ from 14 European countries (P < 0.05). Abilities to bite and chew on hard foods are comparably high in Sweden, Switzerland and the Netherlands but comparably low in Spain, Denmark, France, Greece, Belgium, Italy, Czechia, and Poland. Median levels are observed in Austria, Germany, and Ireland. The best chewing abilities seem to exist amongst elderly populations in Sweden, Switzerland, and the Netherlands but comparably low chewing abilities appear to prevail amongst those in Spain, Denmark, France, Greece, Belgium, Italy, Czechia, and Poland. Future research is encouraged to identify the exact causes and consequences of such disparities in oral health.

New material of the shrew Macroneomys Fejfar, 1966 (Mammalia, Soricomorpha, Soricidae) from the British early Middle Pleistocene, with comments on its palaeobiology and European range

Abstract. A lower incisor and two lower premolars of Macroneomys, from the early Middle Pleistocene archaeological site at Pakefield (Suffolk, UK), add to the relatively small number of finds of this enigmatic shrew known from the Pleistocene of Europe. Molluscs and vertebrates associated with the Pakefield Macroneomys suggest deposition in a large, fast-flowing river, bordered by open herbaceous vegetation and regional deciduous woodland. Macroneomys from Sugworth (near Oxford) and West Runton (Norfolk) is also associated with fluvial environments. This suggests that the species may have had an ecological preference for aquatic habitats. The thick enamel and bulbous morphology of the lower premolars from Pakefield may indicate a specialization for crushing, consistent with a diet of ‘hard’ or abrasive foods that may have included large molluscs and small vertebrates.

Effects of mastication on glucose metabolism in rats, with emphasis on differences in properties of food consumed whilst breeding

ObjectiveIn this study, to elucidate the effects of preferred properties of food that affect the daily masticatory habits on the onset of lifestyle-related disease, we investigated whether groups of rats continuously fed with diet having distinct properties show differences in glucose metabolism. DesignThirty-six male Wistar rats aged 4 weeks were divided into two groups; only the pellet type feed was given to one (solid diet group), and the powdered feed to the other (powder diet group).The oral glucose tolerance test (OGTT) was performed to measure glucose metabolism.For the determination of statistical significance (p<0.05), blood glucose level and areas under the blood glucose response curve (AUC) were analysed using the Mann–Whitney U-test. ResultsThe AUC values were significantly different between the two diet groups when the animals were 45 and 51 weeks of age. The median blood glucose level in 45-week-old rats fed with the powder diet was significantly higher than those in age-matched rats fed with solid diet 45 and 120min after glucose load. Similarly, the median blood glucose level in the 51-week-old rats in the powder diet group was significantly higher than those in the solid diet group at 30, 45, 60, and 120min after glucose load. ConclusionsWe showed that the rats which had been fed with solid diet and therefore had been masticating the feed plentifully enhanced glucose metabolism. This can suggest the possible use of masticatory and dietary intervention, which promotes sufficient mastication of hard food, in the prevention and cure of human lifestyle-related diseases.

The Physiology and Ontogeny of Daily Oral Behaviors

In the masticatory system, activities of muscles are the main source of force. The daily activity of the jaw muscle is a measure of the total daily loading of the tissues involved. This article gives an overview on the recent assessments of the physiology and ontogeny of the daily use of the jaw muscles. Variations in the characteristics of daily activity could be linked to differences in the types of fibers composing the muscles as well as to the properties of the underlying bone, although these relationships are not absolute. Experimental decrease of the hardness of foods eaten by rats and rabbits showed a significant decrease in the number of daily bursts of feeding. These reductions in daily muscular activity were accompanied by higher mineralization of bone and by a transition toward "faster" fiber types in the muscles. It was revealed in rabbits that the characteristics of the daily activities of muscles (total duration of activity, number and lengths of bursts) were not altered during the transition from suckling to chewing and remained largely unaffected during further postnatal development. These results suggest that, despite large anatomical and functional changes, the average daily load on the jaw muscles by the masticatory system appears to be established before chewing develops and remains largely unchanged all the way through development. Whenever the daily muscular activity changes, this seems to have a significant effect on the properties of the tissues involved.

Embarking On A New Course: Environmental Health Coverage

Embarking On A New Course: Environmental Health Coverage

Reduced masticatory function in non-elderly obese Japanese adults

Abnormal eating behaviors such as compulsive overeating, eating fast, chewing less, palatable soft food preferences and avoiding hard food are often observed in obese individuals, and these behaviors may affect their masticatory function, but little information of masticatory function in obese subjects are available at present. The present study investigated masticatory function in non-elderly obese Japanese adults and explored the relationships between obesity and masticatory function. Seventy-five obese subjects (BMI ≥ 25; male: 34, female: 41) and 98 subjects with normal weight (BMI 18.5-25; male: 63, female: 35) aged 25-40 years old were enrolled in the present study. The status of masticatory function was determined using a chewing gum mixing method, a direct method of examining masticatory function, and the numbers of present teeth, untreated decayed teeth, missing teeth, and filled teeth were also examined. Masticatory function was significantly lower in the obese subjects both in male and female, whereas the numbers of present teeth, decayed teeth, missing teeth and filled teeth did not differ significantly between the obese subjects and the controls both in male and female. Multiple regression analysis revealed a significant correlation between obesity and reduced masticatory function after adjustment for gender, age, and numbers of decayed teeth, missing teeth, and filled teeth. Significantly reduced masticatory function was found in male and female non-elderly obese adults based on direct measurement of masticatory function. Multiple regression analysis suggested that obesity might induce reduced masticatory function.

Adaptation to hard-object feeding in sea otters and hominins

The large, bunodont postcanine teeth in living sea otters ( Enhydra lutris) have been likened to those of certain fossil hominins, particularly the ’robust’ australopiths (genus Paranthropus). We examine this evolutionary convergence by conducting fracture experiments on extracted molar teeth of sea otters and modern humans ( Homo sapiens) to determine how load-bearing capacity relates to tooth morphology and enamel material properties. In situ optical microscopy and x-ray imaging during simulated occlusal loading reveal the nature of the fracture patterns. Explicit fracture relations are used to analyze the data and to extrapolate the results from humans to earlier hominins. It is shown that the molar teeth of sea otters have considerably thinner enamel than those of humans, making sea otter molars more susceptible to certain kinds of fractures. At the same time, the base diameter of sea otter first molars is larger, diminishing the fracture susceptibility in a compensatory manner. We also conduct nanoindentation tests to map out elastic modulus and hardness of sea otter and human molars through a section thickness, and microindentation tests to measure toughness. We find that while sea otter enamel is just as stiff elastically as human enamel, it is a little softer and tougher. The role of these material factors in the capacity of dentition to resist fracture and deformation is considered. From such comparisons, we argue that early hominin species like Paranthropus most likely consumed hard food objects with substantially higher biting forces than those exerted by modern humans.

Associations between self-assessed masticatory ability and higher brain function among the elderly

Among the elderly, the quality of higher brain function is a contributing factor in performing activities of daily living. The aim of the study is to elucidate, epidemiologically, associations between mastication and higher brain function. A total of 208 community-dwelling elderly persons, aged 70-74 years, were enrolled. Self-assessed masticatory ability (masticatory ability) was classified into one of three categories: ability to chew all kinds of food, ability to chew only slightly hard food, or ability to chew only soft or pureed food. Brain function was assessed by four neuropsychological tests: Raven's Colored Progressive Matrices (RCPM) test, the Verbal Paired Associates 1 (VerPA) task and the Visual Paired Associates 1 task (from the Wechsler Memory Scale Revised Edition), and the Block Design subtest (from the Wechsler Adult Intelligence Scales-Third Edition). Correlations between masticatory ability and each test were examined using Spearman rank correlation coefficients. Multinominal logistic regression models were conducted with the neuropsychological tests as the dependent variables and masticatory ability as the principal independent variable to adjust for age, gender, educational background, social activity, drinking/smoking habits, chronic medical conditions and dental status. Significant correlations were found between the RCPM test, the VerPA task, the Block Design test and masticatory ability. In multinominal logistic regression models, poor masticatory ability was significantly and independently related to the categories under the mean-s.d. points compared with those of the mean ± s.d. ranges for RCPM test and the VerPA task. Significant associations may exist between mastication and higher brain function among the elderly.

Para-masticatory wear facets and their functional significance in hunter–gatherer maxillary molars

The mastication of tough and hard foods combined with the extensive use of teeth as tools, have been considered possible antemortem causes in determining enamel microfractures of the tooth crown. This phenomenon, known as dental chipping, has been found in different fossil hominins and in several pre-historic and historic human populations who adopted different subsistence strategies. However, little is understood of the mechanism, function and the formation of dental chipping. In this study we analyze the maxillary molar wear areas associated with dental chipping (and named para-facets) of several hunter–gatherer specimens, using the Occlusal Fingerprint Analysis method. We employ three-dimensional digital models of tooth crowns created by surface scanning of dental replicas, to analyze the dip and dip directions of normal occlusal wear areas and para-facets. This allows us to reconstruct the jaw movements responsible for the creation of para-facets, and investigate whether they are produced during normal mastication or not. Vectors of the para-facets do not show any preferred direction and are distributed randomly as visualized by the occlusal compass, displaying significant differences with the major jaw movements in action during the normal chewing cycle. More importantly, no antagonist contacts in the lower teeth are associated with the para-facets of the upper teeth. This excludes the possibility that the para-facets are created during normal mastication. We therefore suggest that this unusual type of tooth wear is mainly due to attritional and abrasive contacts generated through daily task activities for foods processing and/or manufacturing of objects.

Timing of ectocranial suture activity in Gorilla gorilla as related to cranial volume and dental eruption

Research has shown that Pan and Homo have similar ectocranial suture synostosis patterns and a similar suture ontogeny (relative timing of suture fusion during the species ontogeny). This ontogeny includes patency during and after neurocranial expansion with a delayed bony response associated with adaptation to biomechanical forces generated by mastication. Here we investigate these relationships for Gorilla by examining the association among ectocranial suture morphology, cranial volume (as a proxy for neurocranial expansion) and dental development (as a proxy for the length of time that it has been masticating hard foods and exerting such strains on the cranial vault) in a large sample of Gorilla gorilla skulls. Two-hundred and fifty-five Gorilla gorilla skulls were examined for ectocranial suture closure status, cranial volume and dental eruption. Regression models were calculated for cranial volumes by suture activity, and Kendall's tau (a non-parametric measure of association) was calculated for dental eruption status by suture activity. Results suggest that, as reported for Pan and Homo, neurocranial expansion precedes suture synostosis activity. Here, Gorilla was shown to have a strong relationship between dental development and suture activity (synostosis). These data are suggestive of suture fusion extending further into ontogeny than brain expansion, similar to Homo and Pan. This finding allows for the possibility that masticatory forces influence ectocranial suture morphology.

Tooth loss, chewing habits, and food choices among older Nigerians in Plateau State: a preliminary study

To determine the association between tooth loss, chewing habits, and food choices among older Nigerians. A questionnaire was administered by an interviewer to 500 randomly selected Nigerians, aged 50 and above, drawn from households in Plateau State in the North Central part of Nigeria. Intake of fruits/vegetables, and hard food items such as nuts, roast corn and nontender meat, was assessed. The subjects were then examined clinically to chart their dentitions. The sample comprised of approximately equal numbers of men and women from predominantly rural and semi-urban communities. Those participants who had more than 20 teeth selected fruits/vegetables more frequently than those with fewer teeth; in addition, they chewed hard foods more frequently. On the other hand, a larger proportion of people with 20 or fewer teeth indicated that they avoided certain food items because of their teeth/mouth conditions. One-way anova showed that the people who selected fruits/vegetables daily or weekly compared to occasionally or rarely had significantly more teeth on average. Multivariable logistic regression analysis, controlling for age, gender, income, and education showed that the number of remaining teeth was significantly associated with the selection of vegetables/fruits and other hard food items. Tooth loss affects selection of specific foods by older Nigerians in Plateau State and thus, could impact on the nutritional status of these individuals.