Hard Food Research Articles

Subjective Evaluation of Denture Adhesives: A Multicenter Randomized Controlled Trial.

Many reports show that denture adhesives improve the retention and stability of dentures. However, few randomized controlled trials have examined the effects of denture adhesives. This 10-center randomized controlled trial with parallel groups involving 200 edentulous patients wearing complete dentures aimed to evaluate the effects of short-term use of cream and powder denture adhesives. Patients were allocated into 2 cream- and powder-type adhesive groups and 1 control group. Intervention groups were treated with the 2 adhesives (1 each), and the control group received saline solution. Adhesive or control was applied to the denture-mucosal surface for 4 d, and data at baseline and after day 4 of intervention (i.e., 8 meals) were obtained. Patient satisfaction was evaluated with a 100-mm visual analog scale. Oral health-related quality of life was measured with the Japanese version of the Oral Health Impact Profile for Edentulous Patients. Perceived chewing ability was evaluated by a questionnaire regarding ease of chewing and swallowing food. Between-group comparisons were performed with Kruskal-Wallis tests with the Mann-Whitney U test adjusted by Bonferroni correction. Within-group comparisons of pre- and postintervention measurements were performed with the Wilcoxon signed-rank test. Intention-to-treat analysis was also performed. Between-group comparisons showed no significant differences for general satisfaction or Oral Health Impact Profile for Edentulous Patients. However, significant differences in satisfaction with various denture functions with cream- and powder-type adhesives were seen in pre- and postintervention comparisons (P < 0.05). Significant differences were also observed for perceived chewing ability of hard foods (P < 0.05). These results suggest that although denture adhesives do not invariably improve denture function, they do affect subjective evaluations and possibly chewing of hard foods. Therefore, the effects of denture adhesive use are insufficient to resolve any fundamental dissatisfaction with dentures ( ClinicalTrials.gov NCT01712802 ). The results of this study suggest that denture adhesives should be applied under certain conditions; however, an appropriate diagnosis is important before application. These practice-based data provide information to establish evidence-based guidelines for applying denture adhesives.

The taste system in fishes and the effects of environmental variables

The adaptability of the taste system in fish has led to a large variety in taste bud morphology, abundance and distribution, as well as in taste physiology characteristics in closely related species with different modes of life and feeding ecology. However, the modifications evoked in the sense of taste, or gustation, particularly during ontogeny when fishes are subject to different environmental variables, remain poorly studied. This review paper focusses on current knowledge to show how plastic and resistant the taste system in fishes is to various external factors, linked to other sensory inputs and shifts in physiological state of individuals. Ambient water temperature is fundamental to many aspects of fish biology and taste preferences are stable to many substances, however, the taste-cell turnover rate strongly depends on water temperature. Taste preferences are stable within water salinity, which gives rise to the possibility that the taste system in anadromous and catadromous fishes will only change minimally after their migration to a new environment. Food-taste selectivity is linked to fish diet and to individual feeding experience as well as the motivation to feed evoked by attractive (water extracts of food) and repellent (alarm pheromone) odours. In contrast, starvation leads to loss of aversion to many deterrent substances, which explains the consumption by starving fishes of new objects, previously refused or just occasionally consumed. Food hardness can significantly modify the final feeding decision to swallow or to reject a grasped and highly palatable food item. Heavy metals, detergents, aromatic hydrocarbons and other water contaminants have the strongest and quickest negative effects on structure and function of taste system in fish and depress taste perception and ability of fishes to respond adequately to taste stimuli after short exposures. Owing to phenotypic plasticity, the taste system can proliferate and partially restore the ability of fishes to respond to food odour after a complete loss of olfaction. In general, the taste system, especially its functionality, is regarded as stable over the life of a fish despite any alteration in their environment and such resistance is vital for maintaining physiological homeostasis.

Using image compression to quantify enamel complexity

In mammals, complexity of enamel prism decussation has long been recognized as a reflection of biomechanical demands placed upon teeth. Crisscrossing prisms or bundles of prisms, known as decussation, have been demonstrated to limit crack propagation through tooth enamel, and help maintain overall functional integrity of a tooth; therefore, prism decussation tends to appear more frequently and with more complexity in animals that must break down hard foods and/or who place other high loads upon their teeth. Hunter‐Schreger bands are alternating bundles of prisms with common orientations that decussate with respect to adjacent bands. The more severe the loading regime of a tooth that a species experiences, the more complex its decussation and Hunter‐Schreger banding patterns tend to be. Species whose diets primarily create abrasive wear on teeth and who are at low risk of cracking have simple enamel whose prisms all run in parallel fashion from dentine to surface, referred to as radial enamel.In order to assess the biomechanics of teeth and microstructural adaptations to loading both within extant and fossil taxa, it would be useful to have a simple quantitative measurement that could assess overall complexity of enamel decussation. However, previous studies of enamel complexity tend to be descriptive and are often so complex in terms of their discussion of prism pathways that such studies are of limited use when comparing large numbers of teeth and/or species.The objective of this study is to solve this problem using modern, commonly available computer algorithms to find a way to quickly and easily quantify enamel complexity from histological images of teeth. Specifically, we use image compression ratio as a proxy variable for identifying tooth complexity. This ratio reflects the compressed size of a standard .jpg image as compared to an original, uncompressed .tif image (in our case generated by a digital microscopy system), and has been used successfully by prior studies to quantify complexity of tooth cusp relief.We here apply the compression ratio method to two‐dimensional photomicrographic images of tooth thin‐sections taken in circularly polarized light (CPL). CPL creates visual contrast in complex teeth by highlighting regions of differing prism orientations with different colors in the final image. We captured 90 images of teeth with varying decussation complexity in CPL, then deleted non‐enamel components of the image (dentine, artifacts, etc.) using digital image processing software. The original .tif images were then compressed to .jpg format, and the compression ratio (.jpg size / .tif size, in bytes) was analyzed statistically in comparison with subjectively assigned “complexity” categories. The compression ratio of radial enamel images was significantly different from images of decussating enamel. Moreover, we found a significant correlation between compression ratio and our complexity categories. These data suggest that image compression ratio is useful for comparing overall complexity of dental enamel in mammals.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Enamel Distribution in 3D: Is Enamel Thickness More Uneven in the Upper Second Molars of Durophagous Hominoids?

Enamel thickness is not uniform across the dental crown of primates. It has been suggested that enamel distribution could be used in taxonomy or for ecological inferences. For instance, the thickness of molar enamel in mammals consuming hard food is expected to be uneven, despite differing reports on extant and extinct apes. Overall estimations of average and relative enamel thickness may mask the details of enamel distribution in complex teeth such as molars. Investigating enamel distribution and its purported relationship with ecology or phylogeny would require more detailed assessments. This paper aims to assess whether apes that consume hard foods on a regular basis, such as Pongo pygmaeus, can be characterized by the evenness or unevenness of enamel thickness. To do so, we combined topographic maps and distribution histograms of enamel thickness with cumulative profiles of its variation, or “pachymetric profiles”. We investigated a sample of 25 unworn hominoid upper second molars scanned by X-ray microtomography, and further compared this to a sample of 32 cercopithecines and colobines. Topographic maps show uniformly thin enamel for Gorilla gorilla and Hylobates sp., unevenly thin enamel for Pan paniscus and Pan troglodytes, and unevenly thick enamel for Pongo pygmaeus. The skewness of enamel distribution does not distinguish between ape species, but does separate apes from OldWorld monkeys. Contrary to previous reports on OldWorld monkeys, the slope of enamel thickness profiles, or pachymetric slope, does not predict the diet of extant apes. However, it does separate the Pan genus, which is characterized by a higher pachymetric slope indicating more uneven enamel distribution compared to other apes. The uneven thickness of enamel distribution observed on topographic maps for P. pygmaeus is not supported by its low pachymetric slope, which instead indicates uniform enamel distribution. This discrepancy in the results obtained for P. pygmaeus can be interpreted as an evolutionary tradeoff between fine-scale versus overall enamel distribution. On the one hand, unevenly thick enamel at a fine scale, combined with strongly decussated enamel as observed in P. pygmaeus, is expected to increase local resistance to crack propagation. On the other hand, uniformly thick enamel at the overall scale would improve the overall resilience of the enamel in coping with challenging food on a daily basis. Although understanding the effects of ecology on enamel distribution in apes requires further investigation, the results presented in this paper confirm the interest of enamel distribution for taxonomy and phylogeny.

Modelling the performance of subterranean rodent mandibles using finite element analysis

Subterranean rodents spend most of their lives underground. As such they have developed efficient ways of excavating soil for burrow formation. Most subterranean rodents dig in one of two ways; chisel‐tooth digging, where enamel covered incisors dig through soil; or scratch digging, where keratin covered claws are used. It is thought that chisel‐tooth digging evolved in order to utilize the resilient enamel covered incisor to dig through harder soils compared to keratin filled claws, which can only dig through softer soils. Chisel‐tooth digging requires a high bite force in concert with a wide gape to achieve optimal removal of soil. A previous study compared the performance of the cranium between chisel‐tooth and scratch digging rodents at different gapes which showed the chisel‐tooth digging rodent cranium maintained higher bite forces at wider gapes. The current study compared the performance of chisel‐tooth and scratch digging mandibles using finite element analysis (FEA). To test this hypothesis, finite element models of the mandible were created and solved at varying gapes. Our results show that at small gapes, the chisel‐tooth and scratch digging mandibles show similar performance parameters. However, as gapes increase the chisel‐tooth digging mandibles outperform the scratch digging mandible. Subterranean rodents have a hard food diet and so it is no surprise that there was little difference in performance at small gapes. However, only chisel‐tooth diggers require a larger gape to excavate hard soils. The results of this study show that the mandibular morphology of chisel‐tooth digging rodents has adapted to meet its functional demands.Support or Funding InformationGill Dilliard Faculty Enrichment Fund ABAC FoundationNatural Environment Research Council, Grant/Award Number: G001952This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Dental microwear texture analysis of Homo sapiens sapiens: Foragers, farmers, and pastoralists.

The current study seeks to determine if a sample of foragers, farmers, and pastoralists are distinguishable based on their dental microwear texture signatures. The study included a sample of 719 individuals from 51 archeological sites (450 farmers, 192 foragers, 77 pastoralists). All were over age 12 and sexes were pooled. Using a Sensofar® white-light confocal profiler we collected dental microwear texture analysis (DMTA) data from a single first or second molar from each individual. We leveled and cleaned data clouds following standard procedures and analyzed the data with Sfrax® and Toothfrax® software. The DMTA variables were complexity and anisotropy. Statistics included ANOVA with partial eta squared and Hedges's g. We also performed a follow-up K-means cluster analysis. We found significant differences between foragers and farmers and pastoralists for complexity and anisotropy, with foragers having greater complexity than either the farmers or the pastoralists. The farmers and pastoralists had greater anisotropy than the foragers. The Old World foragers had significantly higher anisotropy values than New World foragers. Old and New World farmers did not differ. Among the Old World farmers, those dating from the Neolithic through the Late Bronze Age had higher complexity values than those from the Iron Age through the medieval period. The cluster analysis discerned foragers and farmers but also indicated similarity between hard food foragers and hard food farmers. Our findings reaffirm that DMTA is capable of distinguishing human diets. We found that foragers and farmers, in particular, differ in their microwear signatures across the globe. There are some exceptions, but nothing that would be unexpected given the range of human diets and food preparation techniques. This study indicates that in general DMTA is an efficacious means of paleodietary reconstruction in humans.

Risk Factors of Gastric Cancer in High-Risk Region of China: A Population-Based Case-control Study

Background:The reason for the high incidence of gastric cancer (GC) in Xianyou County of China was largely unknown. We aimed to explore the potential sociodemographic risk factors and their associations to GC.Methods:A population-based case-control study was conducted during March 2013 and April 2016 in Xianyou County. All newly diagnosed patients of GC were recruited as cases, while controls were selected by matching for cases’ sex, age (± 3 years) and the place of residence.Results:A total of 523 GC cases and 523 matched healthy controls were included in the final analysis with mean age of 66.27±8.81 years for cases and 66.31±8.83 years for controls, respectively. Participants with low socioeconomic status were observed with higher GC risk compared to those in high socioeconomic status (adjusted OR=2.10, 95% CI: 1.13-3.89). Compared to those regularly drink green tea, patients did not have this dietary habit had nearly 3-fold increased GC risk (adjusted OR=2.91, 95% CI: 1.38-6.13). Other dietary habit, including consumption of hard food, omission of breakfast, consumption of pickled vegetables 30 years ago, overeating were all associated with increased risk of GC. Interaction effect were found. Patients in low socioeconomic status and skipped breakfast had 10-fold higher risk of GC compared to reference group in high socioeconomic status and eat breakfast regularly (OR=10.71, 95% CI: 5.19-22.10). Furthermore, patients in low socioeconomic status and consumed pickled vegetable 30 years ago had 6-fold higher risk of GC compared to those in high socioeconomic status but did not intake pickled vegetables 30 years ago (OR=6.11, 95% CI: 3.87-9.66).Conclusion:High incidence of GC risk in Xianyou County might be partly attributed to various sociodemographic factors. Specific prevention effort could be target on population in low socioeconomic status combined with habit of breakfast omission or intake of pickled vegetables.

Effect of food properties and chewing condition on the electromyographic activity of the posterior tongue.

Retraction of the posterior tongue facilitates bolus formation, food transfer and Stage II transport in chewing and swallowing. Surface electromyography of the neck region (N-EMG) enabled the evaluation of muscle function at the posterior tongue. Although previous studies showed that food hardness increased masticatory muscles EMG activity and volitional chewing altered swallowing, the effect of food properties and chewing condition on N-EMG activity has not yet been elucidated. To investigate the effect of food properties and chewing conditions on N-EMG. Twelve healthy adults (six men and six women, mean age 28.1±2.7) participated in this study. Three test foods were used: a cookie (solid food), crushed cookies adjusted using agar and water (semisolid food) and crushed cookies adjusted using thickening agent and water (soft food). Masseter and submental muscle EMG and N-EMG activity were recorded while chewing the three test foods. Participants were instructed to masticate the three test foods in three chewing conditions: (a) chewing freely, (b) chewing test foods with the same number of chewing cycles as when chewing solid food and (c) chewing with a maximum effort. Total N-EMG activity when chewing solid food was higher than that in the other two test foods regardless of the chewing condition. In soft food and semisolid food, the total N-EMG activity was increased by increasing the number of chewing cycles. The total N-EMG activity was increased while chewing hard food, which indicates the positive effect of chewing hard food on rehabilitation at the posterior tongue.

Electromyographic Connectivity of Masseter Muscle with Different Retentive Attachments for Implant Overdentures in Patients with Atrophied Mandibular Ridges: A Crossover Study.

The aim of this crossover study was to evaluate electromyographic (EMG) connectivity of masseter muscle with different attachments used to retain implant overdentures in patients with atrophied mandibular ridges. Twenty-four edentulous participants with atrophic mandibular ridges received conventional dentures (control). Three months after the adaptation period, two implants were placed in the canine areas of the mandible. After osseointegration, each participant was successively given the following prostheses in a crossover manner: (1) ball-retained overdentures, (2) bar-retained overdentures, and (3) -retained overdentures. The EMG parameters (amplitude, chewing area, chewing rate, duration of chewing cycle, duration of chewing burst, and chewing time) were measured 3 months after wearing the following prostheses: conventional dentures, ball overdentures, bar overdentures, and Locator overdentures. Measurements were made during chewing of hard (carrot) and soft (cake) foods. The highest EMG activity/amplitude, chewing area, duration of chewing cycle, and duration of chewing burst were noted with ball overdentures, followed by bar overdentures and Locator overdentures, and the lowest values were observed with conventional dentures. The highest chewing rate and masticatory time were noted with conventional dentures and the lowest values were observed with ball overdentures. With the exception of chewing area, no significant differences in all tested parameters between bar overdentures and Locator overdentures were observed. Except for duration of chewing cycle, all tested parameters were significantly higher during chewing of hard food than soft food. Within the limitations of this study, two-implant overdentures recorded higher muscle functions compared to conventional dentures regardless of the type of attachment used. For such overdentures, ball attachment may be recommended over bar and Locator attachments, as it was associated with improved muscle activity and function.

Surface Replication, Fidelity and Data Loss in Traditional Dental Microwear and Dental Microwear Texture Analysis

Dental microwear studies often analyze casts rather than original surfaces, although the information loss associated with reproduction is rarely considered. To investigate the sensitivity of high magnification (150x) microwear analysis to common surface replication materials and methods, we compared areal surface texture parameters (ISO 25178-2) and traditional microwear variables (pits and scratches) generated from teeth and casts of rat molars exposed to experimental diets involving hard and soft foods in which abrasive materials had been added. Although the data from the original and replicated surfaces were correlated, many significant differences were found between the resulting data of the casts and original teeth. Both areal surface texture parameters and traditional microwear variables showed diminished ability to discriminate between the eight diet treatments when casts were analyzed. When areal surface texture parameters and traditional microwear variables were combined into a single discriminant function analysis, the cast data and original data produced the most similar results. Microwear researchers tend to favor either texture analysis or traditional microwear methods, better results may be generated by combining them. Although surface textures were not accurately reproduced by the casts, they retained sufficient information to discriminate between microwear of the experimental diets to a degree similar to the original teeth.

The effect of retraining hypofunctional jaw muscles on the transverse skull dimensions of adult rats

Objective: To experimentally investigate the effects of increased masticatory muscle function on the transverse cranial dimensions on adult rats with an earlier reduced masticatory muscle function.Material and method: Sixty young male rats were used. The experimental group received soft diet for a prolonged period, so that the animals developed weak masticatory muscles. A control group received ordinary hard food during the whole experimental period (27 weeks). After 21 weeks when the animals had nearly ceased their body growth the rats in the experimental group were divided into two groups. One group continued with soft diet until the end of the experiment (hypofunctional group). The other group received ordinary hard food to get the possibility to retrain their masticatory muscles (rehabilitation group). At week 21 and at the end of the experimental period (week 27), axial cephalograms were taken. Fourteen landmarks were defined to measure seven transverse distances of the skull.Results: The increase of the anterior zygomatic arch width and interzygomatic width during the experimental period were larger in the rehabilitation group compared to both the normal and the hypofunctional group.Conclusion: Retraining of masticatory muscles in adult rats leads to increase of some transverse cranial dimensions.

Molecular Basis for Periodontal Ligament Adaptation to In Vivo Loading

A soft food diet leads to changes in the periodontal ligament (PDL). These changes, which have been recognized for more than a century, are ascribed to alterations in mechanical loading. While these adaptive responses have been well characterized, the molecular, cellular, and mechanical mechanisms underlying the changes have not. Here, we implicate Wnt signaling in the pathoetiology of PDL responses to underloading. We show that Wnt-responsive cells and their progeny in the PDL space exhibit a burst in proliferation in response to mastication. If an animal is fed a soft diet from the time of weaning, then this burst in Wnt-responsive cell proliferation is quelled; as a consequence, both the PDL and the surrounding alveolar bone undergo atrophy. Returning these animals to a hard food diet restores the Wnt signaling in PDL. These data provide, for the first time, a molecular mechanism underlying the adaptive response of the PDL to loading.

Manifestation of hemispheric laterality in chewing side preference and handedness.

Introduction: Humans manifest a behavioral inclination towards more utility of one side of the body, in relation with the dominant hemisphere of the brain. The current investigation assessed handedness together with chewing preference which have not been evaluated in various food textures before. Methods: Nineteen young and healthy volunteers chewed hard (walnut) and soft (cake) foods, during surface electromyography recording from masseter muscles. The side of the first and all chews in the two food types were determined and compared with the side of the dominant hand. Results: Results indicated the two lateralities in the same side considerably (60%-70%), implying the solidarity in the control of the dominant hemisphere of the brain. The unilaterality was more prominent in the assessment of all chews in hard food, with higher statistical agreement and correlation. Conclusion: Thereupon masticatory preference is found with probable origins in the dominant hemisphere of the brain.

Difference of brain-derived neurotrophic factor expression and pyramid cell count during mastication of food with varying hardness.

Previous studies suggested that mastication activity can affect learning and memory function. However, most were focused on mastication impaired models by providing long-term soft diet. The effects of chewing food with various hardness, especially during the growth period, remain unknown.Objective:To analyze the difference of hippocampus function and morphology, as characterized by pyramidal cell count and BDNF expression in different mastication activities.Materials and Methods:28-day old, post-weaned, male-Wistar rats were randomly divided into three groups (n=7); the first (K0) was fed a standard diet using pellets as the control, the second (K1) was fed soft food and the third (K2) was fed hard food. After eight weeks, the rats were decapitated, their brains were removed and placed on histological plates made to count the pyramid cells and quantify BDNF expression in the hippocampus. Data collected were compared using one-way ANOVA.Results:Results confirmed the pyramid cell count (K0=169.14±27.25; K1=130.14±29.32; K2=128.14±39.02) and BDNF expression (K0=85.27±19.78; K1=49.57±20.90; K2=36.86±28.97) of the K0 group to be significantly higher than that of K1 and K2 groups (p<0.05); no significant difference in the pyramidal cell count and BNDF expression was found between K1 and K2 groups (p>0.05).Conclusion:A standard diet leads to the optimum effect on hippocampus morphology. Food consistency must be appropriately suited to each development stage, in this case, hippocampus development in post-weaned period.

Comparison between Two Different Impression Techniques in Ball and Socket Attachments Supported Complete Implant Overdentures on Electromyographic Activity

Purpose: The purpose of this study was to compare between two different impression techniques in ball and socket attachments supported complete implant overdentures on electromyographic activity. Material and Methods: Ten fully edentulous patients were chosen from the patient clinic of removable prosthodontics department, Patients were divided into 2 groups according to the type of impression technique Group 1: The patients received the denture with the open impression tray technique then a washing period of two weeks elapsed and then switched to the other denture with closed impression tray technique. Group 2: The patients received the denture with the closed impression tray technique then washing period of two weeks elapsed and then switched to the other denture with open tray impression technique. Electromyographic activity measurements were made when the patient in each group wear dentures for one month then a wash out period for two weeks and once more measurements were made when the patient wear the other denture respectively. Masticatory efficiency and electromyographic activity were tested. Results: Patients received dentures made with closed tray impression techniques showed higher masticatory efficiency and lower electromyographic activity than patients received dentures with open tray impression techniques during chewing hard food so significant difference between two techniques were calculated. Conclusions: From the findings of this study; it was concluded that: 1-Masticatory efficiency improved and also the electromyographic activity decreased in patients using closed tray impression technique than that with open tray impression technique during chewing hard food

Исследование напряженного состояния нижней челюсти с имплантатами

Actuality. The absence of teeth leads to functional changes in the maxillofacial system. Rehabilitation of patients is an urgent and still unresolved problem.Objective: to perform a comparative analysis of the tensile state of the mandible with two prosthesis supports on four implants with and without splinting; to investigate the peculiarities of stress distribution in the area of contact of the implant with bone and different angle of implant abutment.Methods. Finite element method and determination of tensile state of the mandible with implants were performed using the ANSYS software package. The Mises equivalent stress distribution in the dental system was used as a criterion for analyzing the results. A number of 3D models of the mandible bone with four implants (with different angles of the abutment axis for lateral (molar) implants) have been developed.Results. With a vertical load of 100 N and a horizontal load of 50 N, which corresponds to the chewing of hard food, maximum stresses occurred in the range from 33.5 to 70.2 MPa depending on load distribution, implant shape and splint presence or absence. In the investigated models with an angle of entry of 45° of the implant into the bone, the maximum stresses did not exceed the maximum permissible values, but at the installation of the splint decreased from 70.2 to 67.8 MPa (when loaded on the lateral implant) and from 33.7 to 33.5 MPa (when loaded on the front implant). When installing a tire for implants with a 0° angle, the tension increased from 66.8 to 68.4 MPa (when loaded on the lateral implant) and decreased from 37.3 to 37.0 MPa (when loaded on the anterior implant).Conclusions. Conducted research testify the significant influence of the implant shape on the stress state of the dental system. The established patterns extend the possibilities of implantation and increase its efficiency by choosing the angle of inclination of the implant abutment.Key words: implant, splint, prosthesis, stress state, mandible.

Early impacts of modified food consistency on oromotor outcomes in mouse models of Down syndrome

Down syndrome (DS) in humans is associated with differences of the central nervous system and oromotor development. DS also increases risks for pediatric feeding challenges, which sometimes involve the use of altered food consistencies. Therefore, experimental food consistency paradigms are of interest to oromotor investigations in mouse models of Down syndrome (DS). The present work reports impacts of an altered food consistency paradigm on the Ts65Dn and Dp(16)1Yey mouse models of DS, and sibling control mice. At weaning, Ts65Dn, Dp(16)1Yey and respective controls were assigned to receive either a hard food or a soft food (eight experimental groups, n = 8–10 per group). Two weeks later, mice were assessed for mastication speeds and then euthanized for muscle analysis. Soft food conditions were associated with significantly smaller weight gain (p = .003), significantly less volitional water intake through licking (p = .0001), and significant reductions in size of anterior digastric myofibers positive for myosin heavy chain isoform (MyHC) 2b (p = .049). Genotype was associated with significant differences in weight gain (p = .004), significant differences in mastication rate (p = .001), significant differences in a measure of anterior digastric muscle size (p = .03), and significant reductions in size of anterior digastric myofibers positive for MyHC 2a (p = .04). In multiple measures, the Ts65Dn model of DS was more affected than other genotype groups. Findings indicate a soft food consistency condition in mice is associated with significant reductions in weight gain and oromotor activity, and may impact digastric muscle. This suggests extended periods of food consistency modifications may have impacts that extend beyond their immediate roles in facilitating deglutition.

Chewing function, general health and the dentition of older Australian men: The Concord Health and Ageing in Men Project.

To describe the associations between chewing function with oral health and certain general health characteristics, in a population of community-dwelling older Australian men. Analysis of data obtained from a cross-sectional analysis of the 4th wave of the Concord Health and Ageing in Men Project cohort of 614 participants, 524 whom were dentate, aged 78years and over. Their chewing capacity was assessed using three main indicators: capacity to chew eleven food items ranging from boiled eggs through to fresh carrots and nuts; discomfort when eating; and interruption of meals. Associations with chewing were tested for dentate vs edentate participants, numbers of teeth present, active dental disease and key general health conditions such as disabilities, comorbidities and cognitive status. Log binomial regression models adjusted for age, country of birth, income, education and marital status. Prevalence ratios and 95% confidence intervals were estimated. Twenty-one per cent of participants could not eat hard foods, while 23.1% reported discomfort when eating, and 8.8% reported interrupted meals when eating. There was a threefold difference in the capacity of dentate men to chew firm meat over that of edentulous men (95% CI, 2.0-4.9); a 2.5 times greater likelihood of edentate men reporting discomfort when eating (95% CI: 1.5-4.3); and 1.9 times greater likelihood of edentate participants reporting having meals interrupted (95% CI: 1.4-2.6). Chewing/eating difficulties were associated with both dental status (number of teeth, active dental caries) and self-rated dental health. Fewer than 20 teeth and the presence of active coronal or root decay were associated with more discomfort when eating. General health conditions associated with chewing function included disability, physical activity, comorbidities, cognitive status and depression. Older men's self-rated oral health and general health perceptions were also associated with aspects of chewing function. Poorer self-reported oral health was associated with inability to eat hard foods (95% CI: 1.3-2.7) and with discomfort when eating (95% CI: 2.6-5.1), while poorer self-reported general health was associated with discomfort when eating (95% CI: 1.2-2.2). Falling rates of edentulism may lead to improved chewing and eating function in older men. Maintaining 20 or more natural teeth, and preventing active coronal and root caries should enhance chewing function and promote self-reported health and oral health. Lower capacity to chew hard foods and a higher reporting of discomfort when eating is associated with co-morbidity in older Australian men.

First Case of Dual Size Asymmetry in an Identical Arthropod Organ: Different Asymmetries of the Combative (Sexual) and Cutting (Non-Sexual) Parts of Mandibles in the Horned Stored-Product Beetle Gnatocerus cornutus (Fabricius, 1798).

Although it is known that separate insect body structures may be asymmetrical within one species, the different functional asymmetries within a single organ as a result of differential selective regimes have not been described. Based on microscopic measurements and SEM photography, we examined the size, shape and asymmetry of the mandibular structures of males and females of the sexually dimorphic broad-horned flour beetle, Gnatocerus cornutus (Tenebrionidae, Coleoptera). It was found that sexual dimorphism only manifests in certain outgrowth parts (horns) of male mandibles, while the remaining cutting parts of the mandibles hold identical morphologies for both sexes. A more interesting finding—since this is the first published case of dual functionally selected asymmetry in an identical arthropod organ—was that the cutting part of the male mandible exhibited directional asymmetry, whereas the outgrowth horn part of the mandible showed a high degree of symmetry. Moreover, there was no relationship between the size and asymmetry of horns. The results indicate different regulatory mechanisms of sexually selected combative horns and the food-functional, more conservative (constrained by hard food and adult long life) cutting parts of mandibles.

Electromyographic Evaluation of Jaw Muscles in Edentulous Patients with Implant-Supported Prosthesis

The purpose of this study was to evaluate the effect of implant-supported oral rehabilitation in the mandible on the electromyographic (EMG) activity during chewing in completely edentulous individuals. Material and methods: Twelve completely edentulous patients were selected for this study, being six females and six males, aged 55 to 65 years old. The patients were divided into three groups according to the treatment protocol; (GI) All the completely edentulous patients had conventional maxillary and mandibular complete denture, (GII) six patients had two mandibular implants supported overdenture at the canine region and (GIII) six patients had one mandibular implant supported over-denture at the symphesial area. All patients were submitted to EMG evaluation of the masseter, and the temporalis muscles, after three months of placement of the conventional prosthesis and after three months of both implant-supported systems by using different textures of foods. The recordings data were analyzed using One Way ANOVA followed by post hoc analysis using LSD test.P< 0.05 was considered statistically significant. Results: the highest EMG activity of the masseter and temporalis muscles was recorded by chewing soft and hard foods in GI, while the reduction of muscular activity after implant supported oral rehabilitation was seen. No significant differences in the analyzed EMG parameters were found between the patients in GII and GIII. Conclusion: mandibular implant-supported prosthesis in edentulous individuals revealed a decrease in EMG amplitude for the masseter and temporalis muscles during chewing, which may indicate adaptation to new conditions of stability provided by support of the complete denture in the mandibular arch