Choosing new ways to chew

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Masticatory biomechanics in the rabbit : a multi-body dynamics analysis

Acknowledgement We thank Sue Taft (University of Hull) for the µCT-scanning of the rabbit specimen used in this study. We also thank Raphaël Cornette, Jacques Bonnin, Laurent Dufresne, and l'Amicale des Chasseurs Trappistes (ACT) for providing permission and helping us capture the rabbits used for the in vivo bite force measurements at la Réserve Naturelle Nationale de St Quentin en Yvelines, France.Peer reviewedPublisher PD

MANDIBULAR SHAPE IN MYOSTATIN-DEFICIENT MICE: A GEOMETRIC MORPHOMETRIC ANALYSIS

The relationship between muscle function and mandibular morphology is unclear. Manipulating the size or function of muscle and then observing the effect on adjacent bone is one way to explore this relationship. The premise is that muscles under function create stress and strain on bone, thereby altering bone morphology. Myostatin knockout (MKO) mice are hypermuscular and may be used as an animal model to study this muscle-bone association. Previous studies comparing MKO mice have used conventional cephalometric analyses to compare their skeletal morphology to wild-type controls. The objective of our study is to provide a phenotypic description of the mandible in MKO mice compared to wild-type CD-1 control mice by quantifying their shape variation at 28 days of age utilizing a geometric morphometric approach. The hypothesis proposes that epigenetic muscle-bone interactions during development cause mandibular shape changes in MKO mice compared to the wild-type controls by 28 days of age. The present sample included nine wild-type and eight MKO mice 28 days old. Eleven mandibular landmarks were recorded on each cephalogram. The landmarks were aligned using Procrustes superimposition method and new coordinates were created to perform a canonical variates analysis (CVA). Results found a significant difference in the mean mandibular shape between the MKO and wild-type groups (Procrustes statistic: 0.047; p = 0.014). The inferior border of the mandible of the myostatin-deficient mice showed increased curvature and decreased ramal height when compared to the wild-type mice. The curved mandible phenotype here may be analogous to the ‘rocker’ mandible reported to be prominent in the Polynesian population. These findings suggest that changing muscular forces altered mandibular morphology most dramatically in regions associated with masticatory muscle attachments

Association between masticatory ability and oral functions

Mastication is the process of breaking ingested food with the teeth and mixing it with saliva to form a mass that is easy to swallow. However, few studies have reported on oral functions, such as occlusal force, tongue pressure, and mastication. The purpose of this study was to evaluate the association between masticatory function and oral functions, such as occlusal force and tongue pressure. In this study, there were 113 patients (41 men and 72 women; mean age, 68.4 ± 11.3 years) who visited dentists at the Hiroshima University Hospital, Hiroshima, Japan between April 2015 and November 2018. Masticatory function of the patients was evaluated using a masticatory ability test system. In addition, occlusal force was measured using a pressure-sensitive film and the maximum tongue pressure was measured with a tongue pressure measuring device according to a conventional method. The relationship of masticatory ability with occlusal force and tongue pressure was examined using multivariate analysis while considering patients? age, gender, and the number of remaining teeth. Masticatory ability was significantly related to occlusal force, maximum tongue pressure, age, body mass index, the number of remaining teeth, and occlusal contact area (p< 0.05). Multiple regression analysis identified that masticatory ability was significantly associated (p< 0.05) with occlusal force and maximum tongue pressure. Masticatory ability was significantly associated with occlusal force and maximum tongue pressure, indicating that the large muscle mass in the oral cavity is indispensable for improving masticatory function

Orofacial muscles activity in children with swallowing dysfunction and removable functional appliances

Swallowing dysfunction is a frequent disorder among children and refers to an altered tongue posture and abnormal tongue movement during swallowing. Removable functional appliance is one of the treatments applied by dentistry to correct this disorder. The aim of this study was to evaluate any differences on orofacial muscles activity in children with swallowing dysfunction with and without removable functional appliances. 68 children were eligible for the study and divided into the orthodontic group (OG) and the no-orthodontic group (NO-OG). Both groups performed a dental occlusion-class evaluation, a swallowing function test and a myoscan analysis in order to measure perioral forces (i.e. tongue extension force, lip pressure, masseter contraction force). Our results showed a significant difference (P=0.02) between OG and NO-OG for the tongue extension force, whereas no significant differences (P&gt;0.05) were found for the other parameters. Our findings suggest that children with swallowing dysfunction and removable functional appliance show orofacial muscles activity within the range of reference values (except for the lip pressure). However, we hypothesize that orthodontic treatment can achieve more effective results with integration of myofunctional therapy

New image analysis of large food particles can discriminate experimentally suppressed mastication

Objective parameters that could provide a basis for food texture selection for elderly or dysphagic patients have not been established. We, therefore, aimed to develop a precise method of measuring large particles (>2 mm in diameter) in a bolus and an analytical method to provide a scientific rationale for food selection under masticatory dysfunction conditions. We developed a new illumination system to evaluate the ability of twenty female participants (mean age, 23·4 ± 4·3 years) to masticate carrots, peanuts and beef with full, half and one quarter of the number of masticatory strokes. We also evaluated mastication under suppressed force, regulated by 20% electromyographic of the masseter muscle. The intercept and inclination of the regression line for the distribution of large particles were adopted as coefficients for the discrimination of masticatory efficiency. Single set of coefficient thresholds of 0·10 for the intercept and 1·62 for the inclination showed excellent discrimination of masticatory conditions for all three test foods with high specificity and sensitivity. These results suggested that our method of analysing the distribution of particles >2 mm in diameter might provide the basis for the appropriate selection of food texture for masticatory dysfunction patients from the standpoint of comminution

Consensus on the terminologies and methodologies for masticatory assessment

A large number of methodological procedures and experimental conditions are reported to describe the masticatory process. However, similar terms are sometimes employed to describe different methodologies. Standardisation of terms is essential to allow comparisons among different studies. This article was aimed to provide a consensus concerning the terms, definitions and technical methods generally reported when evaluating masticatory function objectively and subjectively. The consensus is based on the results from discussions and consultations among world-leading researchers in the related research areas. Advantages, limitations and relevance of each method are also discussed. The present consensus provides a revised framework of standardised terms to improve the consistent use of masticatory terminology and facilitate further investigations on masticatory function analysis. In addition, this article also outlines various methods used to evaluate the masticatory process and their advantages and disadvantages in order to help researchers to design their experiments

Relationship of Nutritional Status with Oral Health Status in Visual Impairment

To analyze the relationship of nutritional status with oral health status among visual impairment. The subjects were 146 elderly people (70 males and 76 females) aged 20-72 years (mean 48.8&plusmn;6.2 years), Phitsanulok, Thailand. Mini Nutritional Assessment (MNA) questionnaires were administered. Oral examinations investigated the number of present teeth, DMFT and Functional Tooth Units (FTUs). According to the MNA score, 44.5% of subjects were categorized as normal nutrition, 47.3% as questionable, and 8.2 % as malnutrition. The mean numbers of present teeth and FTUs were 17.8&plusmn;6.9 and 6.9&plusmn;3.2, respectively. Subjects with malnutrition had lower numbers of present teeth (10.7&plusmn;1.4) and FTUs (4.3&plusmn;1.7) than those with normal nutrition (20.2&plusmn;0.7 and 12.3&plusmn;0.5) (p&le;0.05). Nutritional status of visual impaired Thai was associated with mean numbers of present teeth and FTUs. Keeping many natural teeth or having appropriate numbers of FTUs by replacing missing teeth with dentures would prevention malnutrition

Brown adipose tissue in the buccal fat pad during infancy.

BackgroundThe buccal fat pad (BFP) is an encapsulated mass of adipose tissue thought to enhance the sucking capabilities of the masticatory muscles during infancy. To date, no conclusive evidence has been provided as to the composition of the BFP in early postnatal life.ObjectiveThe purpose of this study was to examine whether the BFP of neonates and infants is primarily composed of white adipose tissue (WAT) or brown adipose tissue (BAT).Materials and methodsThe percentage of fat in the BFP in 32 full-term infants (16 boys and 16 girls), aged one day to 10.6 months, was measured using magnetic resonance imaging (MRI) determinations of fat fraction.ResultsBFP fat fraction increased with age (r = 0.67; P&lt;.0001) and neonates had significantly lower values when compared to older infants; 72.6 ± 9.6 vs. 91.8 ± 2.4, P&lt;.0001. Multiple regression analysis indicated that the age-dependent relationship persisted after accounting for gender, gestational age, and weight percentile (P = .001). Two subjects (aged one and six days) depicted a change in the MRI characteristics of the BFP from primarily BAT to WAT at follow-up examinations two to six weeks later, respectively. Histological post-mortem studies of a 3 day and 1.1 month old revealed predominantly BAT and WAT in the BFP, respectively.ConclusionThe BFP is primarily composed of BAT during the first weeks of life, but of WAT thereafter. Studies are needed to investigate the contributions of BAT in the BFP to infant feeding and how it is altered by postnatal nutrition

Functional evolution of the feeding system in rodents

The masticatory musculature of rodents has evolved to enable both gnawing at the incisors and chewing at the molars. In particular, the masseter muscle is highly specialised, having extended anteriorly to originate from the rostrum. All living rodents have achieved this masseteric expansion in one of three ways, known as the sciuromorph, hystricomorph and myomorph conditions. Here, we used finite element analysis (FEA) to investigate the biomechanical implications of these three morphologies, in a squirrel, guinea pig and rat. In particular, we wished to determine whether each of the three morphologies is better adapted for either gnawing or chewing. Results show that squirrels are more efficient at muscle-bite force transmission during incisor gnawing than guinea pigs, and that guinea pigs are more efficient at molar chewing than squirrels. This matches the known diet of nuts and seeds that squirrels gnaw, and of grasses that guinea pigs grind down with their molars. Surprisingly, results also indicate that rats are more efficient as well as more versatile feeders than both the squirrel and guinea pig. There seems to be no compromise in biting efficiency to accommodate the wider range of foodstuffs and the more general feeding behaviour adopted by rats. Our results show that the morphology of the skull and masticatory muscles have allowed squirrels to specialise as gnawers and guinea pigs as chewers, but that rats are high-performance generalists, which helps explain their overwhelming success as a group