Hard Food Research Articles

The effect of food hardness on chewing movement

The effect of food hardness on chewing movement

Tooth chipping can reveal the diet and bite forces of fossil hominins

Mammalian tooth enamel is often chipped, providing clear evidence for localized contacts with large hard food objects. Here, we apply a simple fracture equation to estimate peak bite forces directly from chip size. Many fossil hominins exhibit antemortem chips on their posterior teeth, indicating their use of high bite forces. The inference that these species must have consumed large hard foods such as seeds is supported by the occurrence of similar chips among known modern-day seed predators such as orangutans and peccaries. The existence of tooth chip signatures also provides a way of identifying the consumption of rarely eaten foods that dental microwear and isotopic analysis are unlikely to detect.

Analysis of reliability of the strength of all-ceramic crown on mandibular first molar

To analyze the reliability of all-ceramic crown on mandibular first molar under randomized biting force, and to explore the failure possibility of all-ceramic crown. Finite element (FE) models of all-ceramic crown on mandibular first molar were established using the Algor FE software. All-ceramic crown was loaded at different occlusal areas and positions with random variables of biting force, and the reliability of all-ceramic crown was analyzed. The occlusal contact positions were located on the fossa, inclined surface and dental cusp. When the occlusal contact area was 0.4 mm(2), The reliability of all-ceramic crown on mandibular first molar were 100% (fossa), 99% (inclined surface), and 97% (cusp) respectively. When the occlusal contact area was 1.5 mm(2), the reliabilities of all-ceramic crown on mandibular first molar were 100% (fossa), 100% (inclined surface), and 99% (cusp) respectively. When the occlusal contact area was increased to 12.6 mm(2), the reliability of all-ceramic crown was 100%. Premature occlusal contact and steep cusp inclination on all-ceramic crown on mandibular first molar will result in stress concentration and the crown will exhibit high failure probabilities. Chewing hard food is another contributing factor to the failure of all-ceramic crowns.

Diet, dietary adaptations and feeding biomechanics in Australopithecus africanus

Australopithecus africanus is an early hominin (i.e., human relative) believed to exhibit stress‐reducing adaptations in its craniofacial skeleton that may be related to the consumption of resistant food items using its premolar teeth. Finite element analyses simulating molar and premolar biting tested the hypothesis that the cranium of A. africanus is structurally more rigid than that of Macaca fascicularis, an Old World monkey that lacks derived australopith facial features. Finite element models of crania of these species were subjected to isometrically scaled loads, permitting a direct comparison of strain magnitudes. Moreover, strain energy in the models was compared after results were scaled to account for differences in bone volume and muscle forces. Results indicate that strains in certain midfacial skeletal regions are higher in M. fascicularis than in A. africanus, and that the A. africanus cranium is, overall, more rigid than that of M. fascicularis during premolar biting. This is consistent with the hypothesis that this hominin may have periodically consumed large, hard food items. However, the strain energy data suggest that the A. africanus cranium is marginally less rigid than that of the macaque during molar biting, raising the possibility that results are being influenced by the allometric scaling of cranial cortical bone thickness. Supported by NSF BCS 0725126.

The Effect of Early Hominin Occlusal Morphology on the Fracturing of Hard Food Items

Tooth profile plays an important role in interpretations of the functional morphology of extinct species. We tested hypotheses that australopith occlusal morphology influences the fracture force required to crack large, hard food items using a combination of physical testing and finite element analysis (FEA). We performed mechanical experiments simulating both molar and premolar biting using metal replicas of four hominin specimens representing species that differ in occlusal relief (Praeanthropus afarensis, Australopithecus africanus, Paranthropus robustus, and P. boisei). The replicas were inserted into an Instron machine and used to fracture hollow acrylic hemispheres with known material properties. These hemispheres simulate a hard and brittle food item but exhibit far less variability in size and strength than actual nuts or seeds, thereby facilitating interpretations of tooth function. Fracture forces and fracture displacements were measured, and analysis of variance revealed significant differences in fracture force and energy between specimens and tooth types. Complementing the physical testing, a nonlinear contact finite element model was developed to simulate each physical test. Experimental and FEA results showed good correspondence in most cases, and FEA identified stress concentrations consistent with mechanical models predicting that radial/median fractures are important factors in the failure of nut and seed shells. The fracture force data revealed functional similarities between relatively unworn Pr. afarensis and P. robustus teeth, and between relatively unworn A. africanus and heavily worn P. boisei teeth. These results are inconsistent with functional hypotheses, and raise the possibility that the tooth morphology of early hominins and other hard object feeders may not represent adaptations for inducing fractures in large, hard food items, but rather for resisting fractures in the tooth crown.

The Structural Rigidity of the Cranium of Australopithecus africanus: Implications for Diet, Dietary Adaptations, and the Allometry of Feeding Biomechanics

Australopithecus africanus is an early hominin (i.e., human relative) believed to exhibit stress-reducing adaptations in its craniofacial skeleton that may be related to the consumption of resistant food items using its premolar teeth. Finite element analyses simulating molar and premolar biting were used to test the hypothesis that the cranium of A. africanus is structurally more rigid than that of Macaca fascicularis, an Old World monkey that lacks derived australopith facial features. Previously generated finite element models of crania of these species were subjected to isometrically scaled loads, permitting a direct comparison of strain magnitudes. Moreover, strain energy (SE) in the models was compared after results were scaled to account for differences in bone volume and muscle forces. Results indicate that strains in certain skeletal regions below the orbits are higher in M. fascicularis than in A. africanus. Moreover, although premolar bites produce von Mises strains in the rostrum that are elevated relative to those produced by molar biting in both species, rostral strains are much higher in the macaque than in the australopith. These data suggest that at least the midface of A. africanus is more rigid than that of M. fascicularis. Comparisons of SE reveal that the A. africanus cranium is, overall, more rigid than that of M. fascicularis during premolar biting. This is consistent with the hypothesis that this hominin may have periodically consumed large, hard food items. However, the SE data suggest that the A. africanus cranium is marginally less rigid than that of the macaque during molar biting. It is hypothesized that the SE results are being influenced by the allometric scaling of cranial cortical bone thickness.

On the Relation of Hardness and Sweetness of the Solid Sweet Foods

On the Relation of Hardness and Sweetness of the Solid Sweet Foods

Do diet and activity restrictions influence recovery after adenoidectomy and partial tonsillectomy?

Objective To determine if restrictions of postoperative diet concerning hard food and hot drinks as well as excessive physical exertion influence recovery during 14 days after T&A surgery. Methods 800 patients aged 3–13 years (median 6) underwent curette adenoidectomy with or without scissors tonsillotomy. 413 adenoidectomies and 387 adenotonsillotomies were performed. Caregivers of the children completed a questionnaire reporting their child's postoperative activity, diet, pain level, peak and duration, episodes of nausea and fever, medication and caregivers’ satisfaction scores. The children were enrolled to food and effort restricted (FER), food non-restricted (FnR), effort non-restricted (EnR), and food and effort non-restricted (FEnR) groups at the end of follow-up. Results Two hemorrhages requiring repeat surgery under general anesthesia in FER group and 42 mild episodes of spontaneously subsiding bleeding from nose or mouth occurred. More than one episodes of hemorrhage were observed in other 8 individuals (total incidence of hemorrhages 9.7%). No hemorrhages were noted in the FEnR and FnR groups. There were 23 (4.4%) participants with episodes of bleeding, among them 21 mild hemorrhages, in the FER group and 21 (12.0%) in the EnR group ( p < 0.001). Peak pain level was lowest in FEnR group ( p < 0.001) and indications for antibiotics most frequent in FnR group ( p < 0.001). Parental satisfaction level was highest in FnR and FEnR groups ( p < 0.001). Conclusions The majority of caregivers reported care of children after T&A surgery according to the instructions. Most frequently disobeyed instructions were those concerning physical exertion. Diet and activity restrictions seem to influence postoperative recovery. Parental satisfaction scores were highest in non-restricted groups.

Changes in rabbit jaw-muscle activity parameters in response to reduced masticatory load

Mechanical food properties influence the neuromuscular activity of jaw-closing muscles during mastication. It is, however, unknown how the activity profiles of the jaw muscles are influenced by long-term alterations in masticatory load. In order to elucidate the effect of reduced masticatory load on the daily habitual activity profiles of three functionally different jaw muscles, the electromyograms of the masseter, temporalis and digastric muscles were recorded telemetrically in 16 male rabbits between seven and 20 weeks of age. Starting at eight weeks of age the experimental animals were fed significantly softer pellets than the control animals. Daily muscle activity was quantified by the relative duration of muscle use (duty time), burst number and burst length in relation to multiple activity levels. The daily duty time and burst number of the masseter muscle were significantly lower in the experimental group than in the control group at 5% and 10% of the maximum activity during the two weeks following the change in food hardness. By contrast, altered food hardness did not significantly influence the activity characteristics of the temporalis and digastric muscles. The findings suggest that a reduction in masticatory load decreases the neuromuscular activity of the jaw-closing muscles that are primarily responsible for force generation during mastication. This decrease is most pronounced in the weeks immediately following the change in food hardness and is limited to the activity levels that reflect muscle contractions during chewing. These findings support the conclusion that the masticatory system manifests few diet-specific long-term changes in the activity profiles of jaw muscles.

Equivalence Randomized Controlled Trial of Bioresorbable Versus Titanium Miniplates in Treatment of Mandibular Fracture: A Pilot Study

The present study was undertaken to test bioresorbable fixation versus titanium for equivalence in terms of clinical union and complications using the American Association of Oral and Maxillofacial Surgeons parameters of care. The study design was a randomized, controlled, equivalence trial. A total of 40 patients were enrolled and allocated to the titanium group and bioresorbable group using a computerized randomization table. All were plated using standard plating principles. In the bioresorbable group, 2 weeks of maxillomandibular fixation was also used. Evaluation of the study endpoint was done at 8 weeks postoperatively. For statistical analysis, the upper limit of the 95% confidence interval was calculated for failure to achieve the primary outcome variable and compared with the maximal clinically acceptable difference between the standard and test modalities in the failure to achieve clinical union (delta). Delta was predetermined as 2%. The other complications were tested for significance using Fisher's exact test. Of the 40 patients, 21 were in the titanium group and 19 were in the bioresorbable group, with 20 men and 1 woman in the titanium group and 18 men and 1 woman in the bioresorbable group. The mean age was 28.7 years in the titanium group and 26.6 years in the bioresorbable group. In the titanium group, the complications noted were nonunion in 0%, malocclusion in 7.7%, continued postoperative swelling in 0%, chronic pain in 2%, infection in 5.2%, an inability to chew hard food after 8 weeks in 7.7%, the need for alternative treatment in 0%, and the need for reoperation in 31%. In the bioresorbable group, the complications were nonunion in 4.17%, malocclusion in 11.1%, swelling in 8.3%, chronic pain in 37.5%, infection in 0%, an inability to chew hard food in 11.1%, the need for alternative treatment in 11.1%, and need for reoperation for plate removal in 0%. The small sample size did not allow any meaningful conclusion to be drawn from the present study in terms of the primary question of achieving union. Both groups matched in outcomes when evaluated only on a clinical basis. The avoidance of repeat surgery for plate removal is a definite advantage of using resorbable plates. However, the results are inconclusive in favor of any particular plating system.

Epigenetic effects on the mouse mandible: common features and discrepancies in remodeling due to muscular dystrophy and response to food consistency

BackgroundIn wild populations phenotypic differentiation of skeletal structures is influenced by many factors including epigenetic interactions and plastic response to environmental influences, possibly blurring the expression of genetic differences. In contrast, laboratory animals provide the opportunity to separate environmental from genetic effects. The mouse mandible is particularly prone to such plastic variations because bone remodeling occurs late in postnatal ontogeny, in interaction with muscular loading. In order to understand the impact of this process on mandible morphology, we investigated how change in the masticatory function affects the mandible shape, and its pattern of variation. Breeding laboratory mice on food of different consistencies mimicked a natural variation in feeding ecology, whereas mice affected by the murine analogue of the Duchenne muscular dystrophy provided a case of pathological modification of the mastication process.ResultsFood consistency as well as dystrophy caused significant shape changes in the mouse mandible. Further differences were observed between laboratory strains and between sexes within strains, muscular dystrophy causing the largest morphological change. The directions of the morphological changes due to food consistency and muscular dystrophy were discrepant, despite the fact that both are related to bone remodeling. In contrast, directions of greatest variance were comparable among most groups, and the direction of the change due to sexual dimorphism was parallel to the direction of main variance.ConclusionsBone remodeling is confirmed as an important factor driving mandible shape differences, evidenced by differences due to both the consistency of the food ingested and muscular dystrophy. However, the resulting shape change will depend on how the masticatory function is affected. Muscular dystrophy caused shape changes distributed all over the mandible, all muscles being affected although possibly to a different degree. In contrast, the chewing function was mostly affected when the mice were fed on hard vs. soft food, whereas grinding likely occurred normally; accordingly, shape change was more localized. The direction of greatest variance, however, was remarkably comparable among groups, although we found a residual variance discarding age, sex, and food differences. This suggests that whatever the context in which bone remodeling occurs, some parts of the mandible such as the angular process are more prone to remodeling during late postnatal growth.

Outcomes of management of early temporomandibular joint disorders: How effective is nonsurgical therapy in the long-term?

AimThe first step in the management of Temporomandibular Disorders (TMD) is usually noninvasive, especially if the disorder is in the early stages. Clinically, pain and clicking are early signs and symptoms of TMD. The management of TMD usually includes “splint therapy” and analgesics. In this study, we report our long-term outcomes in the treatment of patients suffering from early TMD.Materials and Methods:We assessed the records of 138 patients who were referred for management of TMD. Selection was based on pain and/or clicking of the Temporomandibular Joint (TMJ), no pathologic lesions of the TMJ, no anterior disc displacement without reduction (closed lock), no Degenerative Joint Disease, no history of migraine, trauma, osteoarthritis, metabolic disease, or malocclusion (deep bite, cross bite, jaw deformity, etc). The patients were treated with an acrylic maxillary Interocclusal Splint (IOS) cuspid-rise type and were told to refrain from biting, yawning and chewing hard food. The outcome of the treatment, potential etiologic factors (Bruxism), signs and symptoms and patient demographics (such as age, sex, treatment duration, etc.) were assessed. The data were analyzed using the Chi-square test to correlate significance.Results:One hundred thirty-eight patients (26 males and 112 females) with early signs and symptoms of TMD (pain and/or click of the TMJ) were treated from 2001 to 2010; 81% were females and 19% were males. All the 138 patients used the IOS at night only. The patients were followed-up for 1–9 years. Data analysis showed that 64% of the patients were completely relieved of signs and symptoms; 22% were moderately relieved (decreased severity of signs and symptoms) and 14% had no noticeable post-treatment changes in clicking or pain (P = 0.001). Patients with bruxism and those presenting with both pain and clicking showed a better response to IOS treatment (P = 0.046 and P = 0.001, respectively). The results also showed that age, sex, severity of symptoms and duration of the treatment did not influence treatment results in this group of patients with early TMD.Conclusion:In this population, TMD was significantly higher in females. Treatment of early TMD with IOS was effective and moderately effective in long-term in over 80% of the patients during the follow-up period of 1–9 years. Bruxism had a significant etiologic role in TMD; occlusal attrition of the dentition, pain of all the teeth, early morning pain of the masticatory muscles and the TMJ are signs and symptoms to suspect nocturnal bruxism. Use of an IOS is recommended to prevent potential damage to the dentition, periodontium and the TMJ in early TMD.

Nutritional Guidelines for Orthodontic Patients

The orthodontic patients avoid many types of food, particularly fruits, raw vegetables and other hard and tough foods, as they cannot chew these properly, because of pressure sensitivity of the teeth in the initial 3 -5 day period after routine. As a result

The effect of hardness of food on amygdalar histamine release in rats

When animals eat food, the oral cavity receives a variety of sensory information from food. The hardness of food, which elicits somatic sensation, is thought to affect feeding behavior, however, the details of neuronal mechanism are unclear. The histaminergic system is known to be involved in feeding behavior, and our previous studies indicated that gustatory information activates the histaminergic system, and that palatability of tastants influences its activity. From these findings, we hypothesized that the hardness of food may affect the histaminergic system. Thus, in the present study, we examined the effect of the hardness of food on histamine release in the central nucleus of amygdala when rats consumed either of two types of pellets composed of similar ingredients but having different degrees of hardness: hard and soft pellets. Histamine release was significantly increased in the rat fed with hard pellets. By contrast, histamine release was not enhanced in soft pellets-fed rats. There were no significant differences between the hard and soft pellet intakes during the experimental period. When rats acquired a conditioned aversion to soft pellets, histamine release was increased during feeding, in sharp contrast to no change of histamine release pattern seen during unconditioned soft pellet intake. These observations indicate that the amygdalar histaminergic system is modulated by oral somatic sensation from food, and by palatability of food texture.

Built to bite: cranial design and function in the wrinkle‐faced bat

AbstractOne of the major goals of evolutionary biology is to explain phenotypic diversity and understand the limits imposed by those phenotypes. The cranial morphology of the wrinkle‐faced bat Centurio senex (Family Phyllostomidae) is bizarre and enigmatic. Its extremely short and wide skull consistently emerges as an outlier in morphological studies and many researchers have speculated about its function. Here, we investigate the hypothesis that the unique skull morphology of Centurio is associated with the ability to generate high bite forces and/or high bite forces at wide gapes. We accomplish this by comparing bite force data gathered in the field and estimates of gape limitations gathered from museum specimens. We also examine the possibility that Centurio uses unique feeding behaviors that may impose unique loading regimes on the facial skeleton. We found that relative to head size, Centurio generates the strongest bites known for any fruit‐eating phyllostomid bat, but that its ability to generate high bite forces at wide gape angles is likely limited. We also propose that its exceptionally strong bite indicates the ability to consume hard food items when other resources are limited, and that these ‘resource bottlenecks’ may have imposed strong selective pressure on its skull morphology. Behavioral data indicate that Centurio exhibits a unique reliance on unilateral biting (loading) during feeding. Based on data summarizing bite force, estimates of gape ability and feeding behavior, we suggest that Centurio's exceptionally short and wide skull reflects adaptations for high bite forces and repeated unilateral loading of the facial skeleton during feeding.

Stomatognathic adaptive motor syndrome is the correct diagnosis for temporomandibular disorders

Temporomandibular disorder is a generic and inadequate conception to be used as a diagnosis. It fails to express the etiology or the pathophysiology and it is mainly associated with the anatomical site. Moreover, the clinical condition presents a mandibular motor problem and not a joint problem. The hypothesis presents the new diagnosis stomatognathic motor adaptive syndrome, which comprehend a motor response and the adaptive processes it induces. Inadequate occlusal contacts cause the mandible to shift in order to reach an ideal intercuspal position. The condylar displacements are proportional to such movements. Temporomandibular joint (TMJ) receptors respond to the capsular mechanical stress and the information reaches the trigeminal sensory nuclei. The mandibular modified position seems to be relevant information and may interfere with catecholaminergic neurotransmission in basal ganglia. The main motor responses comprise increased jaw muscle tone, decreased velocity of movements and incoordination. The overload of muscle function will produce adaptive responses on many stomatognathic structures. The muscle adaptive responses are hypertonia, pain, fatigue and weakness. Temporomandibular joint presents tissue modification, disc alteration and cracking noise. Periodontium show increased periodontal membrane, bone height loss and gingival recession. Teeth manifest increased wear facets, abfraction and non-accidental fractures. The periodontal and teeth adaptive processes are usually identified as occlusal trauma. The altered stomatognathic functions will show loss of velocity during mastication and speech. Fatigue, weakness in jaw muscle and difficulties to chew hard food are related to hypertonia. Incoordination between stomatognathic muscles groups is found, causing involuntary tongue/cheek biting and lateral jaw movements on speech. Otologic complaints, as aural fullness and tinnitus, are related to the tensor tympani muscle, innervated by the trigeminal nerve.

Fallback foraging as a way of life: Using dietary toughness to compare the fallback signal among capuchins and implications for interpreting morphological variation

The genus Cebus is one of the best extant models for examining the role of fallback foods in primate evolution. Cebus includes the tufted capuchins, which exhibit skeletal features for the exploitation of hard and tough foods. Paradoxically, these seemingly "specialized" taxa belong to the most ubiquitous group of closely related primates in South America, thriving in a range of different habitats. This appears to be a consequence of their ability to exploit obdurate fallback foods. Here we compare the toughness of foods exploited by two tufted capuchin species at two ecologically distinct sites; C. apella in a tropical rainforest, and C. libidinosus in a cerrado forest. We include dietary data for one untufted species (C. olivaceus) to assess the degree of difference between the tufted species. These data, along with information on skeletal morphology, are used to address whether or not a fallback foraging species exhibits a given suite of morphological and behavioral attributes, regardless of habitat. Both tufted species ingest and masticate a number of exceedingly tough plant tissues that appear to be used as fallback resources, however, C. libidinosus has the toughest diet both in terms of median and maximal values. Morphologically, C. libidinosus is intermediate in absolute symphyseal and mandibular measurements, and in measures of postcranial robusticity, but exhibits a higher intermembral index than C. apella. We propose that this incongruence between dietary toughness and skeletal morphology is the consequence of C. libidinosus' use of tools while on the ground for the exploitation of fallback foods.

Indentation as a technique to assess the mechanical properties of fallback foods

A number of living primates feed part-year on seemingly hard food objects as a fallback. We ask here how hardness can be quantified and how this can help understand primate feeding ecology. We report a simple indentation methodology for quantifying hardness, elastic modulus, and toughness in the sense that materials scientists would define them. Suggested categories of fallback foods-nuts, seeds, and root vegetables-were tested, with accuracy checked on standard materials with known properties by the same means. Results were generally consistent, but the moduli of root vegetables were overestimated here. All these properties are important components of what fieldworkers mean by hardness and help understand how food properties influence primate behavior. Hardness sensu stricto determines whether foods leave permanent marks on tooth tissues when they are bitten on. The force at which a food plastically deforms can be estimated from hardness and modulus. When fallback foods are bilayered, consisting of a nutritious core protected by a hard outer coat, it is possible to predict their failure force from the toughness and modulus of the outer coat, and the modulus of the enclosed core. These forces can be high and bite forces may be maximized in fallback food consumption. Expanding the context, the same equation for the failure force for a bilayered solid can be applied to teeth. This analysis predicts that blunt cusps and thick enamel will indeed help to sustain the integrity of teeth against contacts with these foods up to high loads.

Connecting behaviour and performance: the evolution of biting behaviour and bite performance in bats

Variation in behaviour, performance and ecology are traditionally associated with variation in morphology. A neglected part of this ecomorphological paradigm is the interaction between behaviour and performance, the ability to carry out tasks that impact fitness. Here we investigate the relationship between biting behaviour and performance (bite force) among 20 species of ecologically diverse bats. We studied the patterns of evolution of plasticity in biting behaviour and bite force, and reconstructed ancestral states for behaviour and its plasticity. Both behavioural and performance plasticity exhibited accelerating evolution over time, and periods of rapid evolution coincided with major dietary shifts from insect-feeding to plant-feeding. We found a significant, positive correlation between behavioural plasticity and bite force. Bats modulated their performance by changing their biting behaviour to maximize bite force when feeding on hard foods. The ancestor of phyllostomids was likely a generalist characterized by high behavioural plasticity, a condition that also evolved in specialized frugivores and potentially contributed to their diversification.

Kinematic parameters inferred from enamel microstructure: new insights into the diet of Australopithecus anamensis

The dietary adaptations of Australopithecus anamensis are contentious, with suggestions that range from soft fruits to hard, brittle, tough, and abrasive foods. It is unlikely that all propositions are equally valid, however. Here we extend recent finite element (FE) analyses of enamel microstructure ( Shimizu and Macho, 2008) to enquire about the range of loading directions (i.e., kinematics) to which A. anamensis enamel microstructure/molars could safely be subjected. The rationale underlying this study is the observation that hard brittle foods are broken down in crush, while tough foods require shear. The findings are compared with those of Pan and Gorilla. Eighteen detailed FE models of enamel microstructure were created and analysed. The results highlight the uniqueness of A. anamensis dental structure and imply that mastication in this species included a greater shear component than in Pan, as well as a wider range of loading directions; it is similar to that in Gorilla in this respect. These findings are in accord with microwear studies (Grine et al., 2006a). Unlike either of the great apes, however, enamel microstructure of A. anamensis was found to be poorly equipped to withstand loading parallel to the dentino-enamel junction; such loading regimes are associated with mastication of soft fleshy fruits. This, together with broader morphological considerations, raises doubts as to whether A. anamensis was essentially a frugivore that expanded its dietary niche as a result of fluctuations in environmental conditions, e.g., during seasonal food shortages. Instead, it is more parsimonious to conclude that the habitual diet of A. anamensis differed considerably from that of either of the extant African great apes.