The regulation of masticatory function and food bolus formation

Unobtrusive and Wearable Systems for Automatic Dietary Monitoring

The threat of obesity, diabetes, anorexia, and bulimia in our society today has motivated extensive research on dietary monitoring. Standard self-report methods such as 24-h recall and food frequency questionnaires are expensive, burdensome, and unreliable to handle the growing health crisis. Long-term activity monitoring in daily living is a promising approach to provide individuals with quantitative feedback that can encourage healthier habits. Although several studies have attempted automating dietary monitoring using wearable, handheld, smart-object, and environmental systems, it remains an open research problem. This paper aims to provide a comprehensive review of wearable and hand-held approaches from 2004 to 2016. Emphasis is placed on sensor types used, signal analysis and machine learning methods, as well as a benchmark of state-of-the art work in this field. Key issues, challenges, and gaps are highlighted to motivate future work toward development of effective, reliable, and robust dietary monitoring systems.

Heterogeneity of osteoclast activity and bone turnover in different skeletal sites

OBJECTIVE

To compare osteoclasts and bone turnover in the cranial and appendicular skeletons of mice and determine whether estrogen depletion has an impact on these differences.

DESIGN

In vitro osteoclastogenesis (OCG) was performed on osteoclasts precursors derived from calvarial, mandibular and femoral bone marrow. In vitro, mature osteoclasts were stained with TRAP in plastic petri dishes and with DAPI and Phalloidin on glass coverslips to identify mature osteoclasts and compare osteoclast surface area and nuclei number in the different bone sites, respectively. Quantification of osteoclast resorption pit (Rpit) volume and surface area from different bone sites was achieved using dentin slices stained with Picrosirius red and confocal microscopy. In vivo TRAP, static and dynamic histomorphometric analyses were performed on 5-month-old mouse calvarial, long bone and mandibular trabecular bone to compare bone resorption and formation rates, respectively. Mice were ovariectomized (OVX) at 5 months of age and sacrificed at 6 months of age to establish an osteoporosis model for differences in osteoclasts activity and to monitor the changes in bone turnover rates in the three bone sites upon estrogen depletion.

RESULT

s Phalloidin stained calvarial osteoclasts were larger compared to long bone and mandibular osteoclasts. Rpits from osteoclasts derived from mandibular bone were smaller and had lower volume values compared to long bone and calvarial bone Rpits. In vivo analysis showed significant increases in bone formation rates in calvarial trabecular bone compared to long bone and mandibular trabecular bone. Turnover was enhanced upon estrogen depletion in calvarial trabecular bone. Resorption was increased without a corresponding increase in bone formation in the trabecular metaphysis of long bone. Mandibular trabecular bones do not appear to be affected by OVX.

CONCLUSION

The cranial and appendicular skeletons differ from one another in that osteoclasts from calvarial bone have the highest resorptive capacity which is coupled to bone formation both pre and post-OVX. Mandibular bones show the lowest turnover rates and are not affected by OVX.

A Multiphase Flow in the Antroduodenal Portion of the Gastrointestinal Tract: A Mathematical Model

A group of authors has developed a multilevel mathematical model that focuses on functional disorders in a human body associated with various chemical, physical, social, and other factors. At this point, the researchers have come up with structure, basic definitions and concepts of a mathematical model at the "macrolevel" that allow describing processes in a human body as a whole. Currently we are working at the "mesolevel" of organs and systems. Due to complexity of the tasks, this paper deals with only one meso-fragment of a digestive system model. It describes some aspects related to modeling multiphase flow in the antroduodenal portion of the gastrointestinal tract. Biochemical reactions, dissolution of food particles, and motor, secretory, and absorbing functions of the tract are taken into consideration. The paper outlines some results concerning influence of secretory function disorders on food dissolution rate and tract contents acidity. The effect which food density has on inflow of food masses from a stomach to a bowel is analyzed. We assume that the future development of the model will include digestive enzymes and related reactions of lipolysis, proteolysis, and carbohydrates breakdown.

Age-related changes in mastication are not improved by tongue exercise in a rat model

OBJECTIVES/HYPOTHESIS

Aging results in progressive changes in deglutitive functions, which may be due in part to alterations in muscle morphology and physiology. Mastication is a critical component of bolus formation and swallowing, but aging effects on masticatory function have not been well studied.

STUDY DESIGN

The purpose of this study was to 1) quantify the effects of aging on mastication, and 2) determine the effects of tongue exercise on mastication in young adult and old rats. We hypothesized that there would be significant differences in mastication characteristics (number of bites, interval between bites, time to eat) as a function of age, and that tongue exercise would resolve preexercise differences between age groups.

METHODS

We expanded the established model of progressive, 8-week tongue exercise to include a mastication measurement: acoustic recordings of vermicelli pasta biting from 17 old and 17 young adult rats, randomized into exercise and control groups.

RESULTS

We found the following: 1) Mastication characteristics were impacted by age. Specifically in older rats, there was an increase in time to eat and number of bites and intervals between bites decreased, suggesting increased oral motor-processing requirements for bolus formation. 2) tongue exercise did not impact mastication behaviors in young adult or old rats.

CONCLUSION

Tongue exercise may not have been specific enough to result in behavioral changes in mastication or exercise dose may not have been sufficient. Nevertheless, results were noteworthy in expanding the established rat model of aging and have relevant clinical implications for future translation to human populations.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:E29-E34, 2017.

Lithium Disilicate Restorations Fatigue Testing Parameters: A Systematic Review

PURPOSE

To review laboratory studies that investigated fatigue resistance of lithium disilicate (LD) crowns and fixed dental prostheses (FDPs) to elucidate study designs and testing parameters.

METHODS

An electronic search was performed in PubMed, Scopus, and Ovid to identify in vitro studies that investigated fatigue resistance of LD crowns and FDPs. The search included all studies published in English in peer-reviewed journals in the period from 1998 to June 2014. The search followed a specific strategy that included combination of the following keywords: lithium disilicate, e.max, empress, all-ceramic, all ceramic, glass ceramic, fatigue, cyclic loading, dynamic loading, chewing simulator, fracture resistance, thermocycling, laboratory simulation, aging, crown, FDPs, FPDs, fixed partial denture, fixed dental prosthesis, and bridge. Studies were selected if mechanical and thermal loading parameters were clearly identified. Search results with abstracts were transferred into Endnote reference system, and duplicates were deleted. The remaining studies were then reviewed at three levels (title, abstract, full text) to further refine the articles.

RESULTS

The initial search retrieved 1044 eligible studies. After deduplication, 864 records were examined by titles and then abstracts; 826 were excluded, and 38 were assessed by full-text reading. In total, 19 articles met inclusion criteria and were included in this study.

CONCLUSION

The studies reviewed showed a level of heterogeneity, as testing parameters were considered through different setups. The current study demonstrated that various setting of the testing parameters and having a lack of testing standardization has likely led to inconsistency in the reported results. The obvious heterogeneity in the setting of testing variables-especially the magnitude of load and number of cycles applied-made it impractical to run direct comparisons between the reviewed studies. Therefore, specific international standardization of fatigue testing of dental restorations is urgently needed to ensure the delivery of consistent, indicative, and comparable data.

Understanding the gastrointestinal tract of the elderly to develop dietary solutions that prevent malnutrition

Although the prevalence of malnutrition in the old age is increasing worldwide a synthetic understanding of the impact of aging on the intake, digestion, and absorption of nutrients is still lacking. This review article aims at filling the gap in knowledge between the functional decline of the aging gastrointestinal tract (GIT) and the consequences of malnutrition on the health status of elderly. Changes in the aging GIT include the mechanical disintegration of food, gastrointestinal motor function, food transit, chemical food digestion, and functionality of the intestinal wall. These alterations progressively decrease the ability of the GIT to provide the aging organism with adequate levels of nutrients, what contributes to the development of malnutrition. Malnutrition, in turn, increases the risks for the development of a range of pathologies associated with most organ systems, in particular the nervous-, muscoskeletal-, cardiovascular-, immune-, and skin systems. In addition to psychological, economics, and societal factors, dietary solutions preventing malnutrition should thus propose dietary guidelines and food products that integrate knowledge on the functionality of the aging GIT and the nutritional status of the elderly. Achieving this goal will request the identification, validation, and correlative analysis of biomarkers of food intake, nutrient bioavailability, and malnutrition.

Evaluation of silent period on masticatory cycles of different muscles in dentate oral contraceptives users and nonusers

Objective:

The aim of this study was to evaluate the influence of oral contraceptive use on the silent period (SP) of anterior temporal and masseter muscles during the menstrual cycle.

Materials and Methods:

Totally, 28 women on reproductive age were selected including 15 nonusers of any hormone and 13 contraceptive users. All patients were dentate without muscular temporomandibular disorders. Electromyography (SP test) of the anterior temporal and masseter muscles was conducted every week during three consecutive menstrual cycles at 1^st day of menstruation (P₁), 7^th day (P₂), 14^th day (P₃) and 21^st day (P₄).

Results:

The SP values in the anterior temporal and masseter muscles were measured at both sides. The SP values of the right side (13.49 ms) at P₂ were significantly different compared to the left side (12.28 ms). However, there was no significant difference on the interactions among the three factors.

Conclusion:

It can be concluded that the SP values in healthy women in reproductive age may not be influenced by the menstrual cycle with similar results for both muscles.

Effect of mastication on lipid bioaccessibility of almonds in a randomized human study and its implications for digestion kinetics, metabolizable energy, and postprandial lipemia

BACKGROUND

The particle size and structure of masticated almonds have a significant impact on nutrient release (bioaccessibility) and digestion kinetics.

OBJECTIVES

The goals of this study were to quantify the effects of mastication on the bioaccessibility of intracellular lipid of almond tissue and examine microstructural characteristics of masticated almonds.

DESIGN

In a randomized, subject-blind, crossover trial, 17 healthy subjects chewed natural almonds (NAs) or roasted almonds (RAs) in 4 separate mastication sessions. Particle size distributions (PSDs) of the expectorated boluses were measured by using mechanical sieving and laser diffraction (primary outcome). The microstructure of masticated almonds, including the structural integrity of the cell walls (i.e., dietary fiber), was examined with microscopy. Lipid bioaccessibility was predicted by using a theoretical model, based on almond particle size and cell dimensions, and then compared with empirically derived release data.

RESULTS

Intersubject variations (n = 15; 2 subjects withdrew) in PSDs of both NA and RA samples were small (e.g., laser diffraction; CV: 12% and 9%, respectively). Significant differences in PSDs were found between these 2 almond forms (P < 0.05). A small proportion of lipid was released from ruptured cells on fractured surfaces of masticated particles, as predicted by using the mathematical model (8.5% and 11.3% for NAs and RAs, respectively). This low percentage of lipid bioaccessibility is attributable to the high proportion (35-40%) of large particles (>500 μm) in masticated almonds. Microstructural examination of the almonds indicated that most intracellular lipid remained undisturbed in intact cells after mastication. No adverse events were recorded.

CONCLUSIONS

Following mastication, most of the almond cells remained intact with lipid encapsulated by cell walls. Thus, most of the lipid in masticated almonds is not immediately bioaccessible and remains unavailable for early stages of digestion. The lipid encapsulation mechanism provides a convincing explanation for why almonds have a low metabolizable energy content and an attenuated impact on postprandial lipemia.

HV. Autopercepção da capacidade mastigatória em indivíduos idosos

INTRODUÇÃO: A mastigação desempenha importante papel na preparação do alimento e manutenção da atividade muscular necessária para outras funções do sistema estomatognático. No idoso, esta função pode sofrer mudanças decorrentes de alterações estruturais, morfológicas e bioquímicas. OBJETIVO: Estudar a capacidade mastigatória referida pelos idosos, elencando as dificuldades durante a mastigação. MÉTODOS: Trata-se de estudo observacional do tipo transversal com idosos de 60 anos de idade ou mais, em atendimento ambulatorial em hospital universitário. A coleta de dados foi realizada por meio da aplicação de questionário, contendo questões referentes ao processo de alimentação do idoso e sua capacidade mastigatória. Para fins de comparação entre alguns itens do protocolo e a capacidade mastigatória, esta última variável foi dicotomizada em "satisfatória" e "insatisfatória". Para essas análises, foi utilizado o teste Exato de Fisher, considerando o nível de significância de 5%. RESULTADOS: A amostra foi composta por 30 participantes, com idade média de 74,4 anos (+9,1). Verificou-se elevada perda dentária, o que se refletiu na alta frequência de idosos usuários de próteses. Quanto às dificuldades referidas sobre a mastigação, 46,7% estavam impossibilitados de comer algum alimento, 50% sentiam necessidade de ingerir líquidos durante a refeição, e os alimentos que representaram maiores dificuldades para mastigar foram: carne (53,3%), frutas e verduras cruas (46,7%) e cereais (40%). Quanto à autopercepção da capacidade mastigatória, 53,3% referiram como satisfatória e 46,6% como insatisfatória. Observou-se relação estatisticamente significante entre "autopercepção da capacidade mastigatória" e os alimentos referidos pela dificuldade ao mastigar (p≤0,001). CONCLUSÃO: A capacidade mastigatória autorreferida foi satisfatória em sua maioria e os alimentos sólidos mais duros apresentaram maiores dificuldades na mastigação.

Effect of experimental jaw muscle pain on dynamic bite force during mastication

Knowledge about how Temporomandibular Disorder (TMD) pain patients regulate masticatory function is still unclear. To investigate the effect of experimental jaw muscle pain as well as texture and size of food on mastication, twelve healthy participants (30.6±7.5 years old) participated in this study. Experimental pain was induced by an infusion of 0.5 M monosodium glutamate (MSG) with isotonic saline (IS) serving as a control. After the infusions, the Jaw Functional Limitation Scale (JFLS) and Pain Catastrophizing Scale (PCS) were filled out. Electromyographic (EMG) activity in the masseter and temporalis muscles, jaw movements and bite force, which was measured by a customized intra-oral device, were recorded simultaneously during mastication of three different types of food. Pain was scored continuously on a visual analog scale. The results demonstrated a trend towards a decrease in the impulse of the bite force, as well as a significant decrease in EMG activity of the masseter muscle during the first five masticatory cycles, in the MSG session. Also, MSG induced increased JFLS and PCS scores compared with IS. On the other hand, the results suggested that the applied levels of pain may not change habitual masticatory movements. This study has revealed that a clinically relevant level of pain in the masseter muscle has only minor impact on the performance of mastication, probably due to a lack of exacerbation of pain during function. In future studies of jaw muscle function during painful conditions, it is important to include patient-based reports of functional limitation and emotional distress.

Masticatory efficiency in complete denture wearers with reduced dental arches--a randomised cross-over study

One obstacle to placing artificial posterior teeth in manufacturing complete dentures is a reduction of the space between the maxilla and the mandible. Occasionally, second molar placement is not performed, as it does not affect aesthetics, phonetics or comfort. The aim of this study was to compare the masticatory efficiency between patients wearing maxillary and mandibular complete dentures with reduced dental arches (without second molars) (WSM) and with full dental arches (FDA). Twenty subjects were divided into two groups and randomly received new complete dentures. Patients in Group 1 were given dentures WSM, and those in Group 2 were given dentures with FDA. After the post-placement visits, an initial masticatory efficiency test was performed with Optocal, an artificial test food. Fifteen days later, second molars were placed in Group 1 and removed from Group 2, and a new test was performed. Comminuted material was treated and sieved under vibration. The mean and standard deviation of masticatory efficiency with FDA were 10.4 and 8.1, respectively. In the tests WSM, the mean and standard deviation were 8.4 and 3.3, respectively. After removing the second molars in Group 2 and adding them in Group 1, the mean and standard deviation were 15.7 and 14.7 for Group 1 and 12.5 and 10.4 for Group 2, respectively. Within the limitations of this study, placing artificial teeth up to the first molars can be performed when needed without compromising masticatory efficiency.

Mechanical resistance of screwless morse taper and screw-retained implant-abutment connections

OBJECTIVE

The screwless morse taper (SMT) implant-abutment connection is an alternative to conventional external or internal screw-retained (ISR) connections. The aim of this in vitro study was to evaluate mechanical resistance of the SMT connection and to compare it with three different ISR connections.

MATERIALS AND METHODS

Four implant systems were tested in this study: SMT system; Tasarimmed Octo (Istanbul, Turkey), ISR systems; Straumann Bone Level (Basel, Switzerland), Biohorizons Internal (Birmingham, AL, USA), and Dentsply Friadent Xive (Mannheim, Germany). Overall, 64 specimens with stylized single crowns were prepared: 32 for dynamic loading (DL) and 32 for static loading (SL). DL was carried out using a chewing simulator with 120 N at 1.75 Hz for 1.2 × 10(6) cycles, and SL was performed with a universal testing machine at a crosshead speed of 2 mm/min with an angulation of 30°. Cycles until failure from DL and fracture/bending loads at SL were recorded. Statistical analyses were made with Dunn's multiple comparison.

RESULTS

Median cycles until failure in DL were as follows: Octo 86,354 (24,810-153,875), Straumann 1,200,000 (1,156,618-1,200,000), Biohorizons 539,719 (437,224-858,732), Xive 139,411 (139,411-139,411). Median fracture/bending loads in Newton at SL were as follows: Octo 429.6 (404.5-482.7), Straumann 574.6 (544.6-629.9), Biohorizons 548.7 (532.9-567.3), Xive 431.5 (412.5-520.5). There were significant differences between the implant systems under both loading conditions (P ≤ 0.05) revealing that the Octo implant system's SMT connection showed significantly lower cycles to failures and lower fracture/bending loads compared with the ISR connections of the Straumann and Biohorizons implant systems. However, there was no significant difference compared with the Xive implant system.

CONCLUSION

The mechanical resistance of the screwless morse taper implant system is lower than that of the ISR implant systems that might result in more frequent clinical complications.

The effect of rheological properties of foods on bolus characteristics after mastication

OBJECTIVE

To evaluate the effects of physical properties of foods on the changes of viscosity and mass as well as the particle size distribution after mastication.

METHOD

Twenty subjects with no masticatory disorders were recruited. Six grams of four solid foods of different textures (banana, tofu, cooked-rice, cookie) were provided, and the viscosity and mass after 10, 20, and 30 cycles of mastication and just before swallowing were measured. The physical properties of foods, such as hardness, cohesiveness, and adhesiveness, were measured with a texture analyzer. Wet sieving and laser diffraction were used to determine the distribution of food particle size.

RESULTS

When we measured the physical characteristics of foods, the cookie was the hardest food, and the banana exhibited marked adhesiveness. Tofu and cooked-rice exhibited a highly cohesive nature. As the number of mastication cycles increased, the masses of all foods were significantly increased (p<0.05), and the viscosity was significantly decreased in the case of banana, tofu, and cooked-rice (p<0.05). The mass and viscosity of all foods were significantly different between the foods after mastication (p<0.05). Analyzing the distribution of the particle size, that of the bolus was different between foods. However, the curves representing the particle size distribution for each food were superimposable for most subjects.

CONCLUSION

The viscosity and particle size distribution of the bolus were different between solid foods that have different physical properties. Based on this result, the mastication process and food bolus formation were affected by the physical properties of the food.

Myofunctional therapy as an aid to prosthodontic treatment after hemiglossectomy: a clinical report

Although several reports describe the prosthetic management of patients after hemiglossectomy, the techniques are related to the fabrication of the prostheses, no reports on maximizing the functional potential of the remaining tongue musculature and surrounding tissues were identified by the authors. This clinical report describes the use of myofunctional therapy as an aid to the maxillofacial prosthodontic rehabilitation of an edentulous patient who was diagnosed with invasive squamous cell carcinoma of the tongue and underwent hemiglossectomy. Myofunctional therapy was introduced before, during, and after the fabrication of conventional maxillary and mandibular complete dentures. Muscle exercises were devised to improve the posture and muscular tonus of the remaining tongue, and thus help with mastication and adaptation to the mandibular denture. Myofunctional therapy improved the posture and function of the remaining tongue, providing acceptable mastication and increased stability of the mandibular denture.

Relationship between swallowing problems and tooth loss in community-dwelling independent elderly adults: the Fujiwara-kyo study

OBJECTIVES

To investigate the relationship between swallowing problems and the number of remaining teeth in healthy elderly people.

DESIGN

Cross-sectional.

SETTING

Nara, Japan.

PARTICIPANTS

Three thousand six hundred sixty-three male and female volunteers aged 65 and older who were living independently were analyzed.

MEASUREMENTS

Swallowing problems were defined operationally using a questionnaire and the 30-mL water swallow test. Data were collected on the number of remaining teeth, maximum bite force, occlusal status, presence or absence of oral dryness, and medical history.

RESULTS

The prevalence of swallowing problems was 15.1% (n = 554) in this population. A positive correlation was observed between the number of remaining teeth and maximum bite force. The number of remaining teeth was categorized according to tertiles. Multiple logistic regression analysis revealed that the adjusted odds ratios for 0 to 13 or 14 to 24 remaining teeth to 25 to 32 remaining teeth for swallowing problems were 2.04 (95% confidence interval (CI) = 1.60-2.60) and 1.31 (95% CI = 1.02-1.70), respectively. Significant increases in these odds ratios were found in a trend test (P < .001).

CONCLUSION

Tooth loss is associated with swallowing problems. Having fewer teeth inhibits masticatory ability, which disturbs the execution of smooth swallowing. Preventive measures against tooth loss at a younger age may be effective at reducing the risk of laryngeal penetration and aspiration at an older age.

Measurement of dynamic bite force during mastication

Efficient mastication of different types and size of food depends on fast integration of sensory information from mechanoreceptors and central control mechanisms of jaw movements and applied bite force. The neural basis underlying mastication has been studied for decades but little progress in understanding the dynamics of bite force has been made mainly due to technical limitations of bite force recorders. The aims of this study were to develop a new intraoral bite force recorder which would allow the study of natural mastication without an increase in the occlusal vertical dimension and subsequently to analyze the relation between electromyographic (EMG) activity of jaw-closing muscles, jaw movements and bite force during mastication of five different types of food. Customized force recorders based on strain gauge sensors were fitted to the upper and lower molar teeth on the preferred chewing side in fourteen healthy and dentate subjects (21-39 years), and recordings were carried out during voluntary mastication of five different kinds of food. Intraoral force recordings were successively obtained from all subjects. anova showed that impulse of bite force as well as integrated EMG was significantly influenced by food (P<0·05), while time-related parameters were significantly affected by chewing cycles (P<0·001). This study demonstrates that intraoral force recordings are feasible and can provide new information on the dynamics of human mastication with direct implications for oral rehabilitation. We also propose that the control of bite force during mastication is achieved by anticipatory adjustment and encoding of bolus characteristics.

A Sensor System for Automatic Detection of Food Intake Through Non-Invasive Monitoring of Chewing

Objective and automatic sensor systems to monitor ingestive behavior of individuals arise as a potential solution to replace inaccurate method of self-report. This paper presents a simple sensor system and related signal processing and pattern recognition methodologies to detect periods of food intake based on non-invasive monitoring of chewing. A piezoelectric strain gauge sensor was used to capture movement of the lower jaw from 20 volunteers during periods of quiet sitting, talking and food consumption. These signals were segmented into non-overlapping epochs of fixed length and processed to extract a set of 250 time and frequency domain features for each epoch. A forward feature selection procedure was implemented to choose the most relevant features, identifying from 4 to 11 features most critical for food intake detection. Support vector machine classifiers were trained to create food intake detection models. Twenty-fold cross-validation demonstrated per-epoch classification accuracy of 80.98% and a fine time resolution of 30 s. The simplicity of the chewing strain sensor may result in a less intrusive and simpler way to detect food intake. The proposed methodology could lead to the development of a wearable sensor system to assess eating behaviors of individuals.

Time-Frequency Analysis of Chewing Activity in the Natural Environment

The aim of this observational study was to investigate the features of the chewing activity and the variability of the human chewing pace, as assessed in the natural environment. It was hypothesized that the chewing pace is relatively constant within individuals across different days but is variable across individuals. Electromyographic surface activity was recorded unilaterally from the masseter in 21 participants for 3 hours over 3 recording days, in the natural environment, by means of portable recorders. The time-frequency properties of chewing activity were assessed with a previously validated algorithm. Repeated-measurements ANOVA was used for statistical analysis. Chewing activity mainly occurred in the range of 0.94 Hz (5th percentile) and 2.17 Hz (95th percentile). Mean and median chewing frequencies were 1.57 Hz and 1.58 Hz, respectively (95% confidence intervals: 1.45-1.68 Hz). The mean duration of chewing episodes was 13.0 sec, the 5th and 95th percentiles being 2.7 sec and 34.9 sec, respectively. Variability of the mean chewing frequency between individuals was much greater than that within individuals (F = 29.8; p < 0.001). The individual chewing paces were stable across different days (intraclass correlation coefficient = 0.88; 95% confidence intervals = 0.79-0.94). Our findings provide evidence that each individual, in the natural environment, chews with a consistent pace across different days.

Abbreviations: ANOVA, analysis of variance; CPG, central pattern generator; EMG, electromyography; ICC, Intra-class Correlation coefficient; SD, standard deviation.

Description of chewing and food intake over the course of a meal

While the average frequency of chewing and food intake have been reported before, a detailed description of the pattern of chewing and the cumulative intake of food over the course of a meal have not. In order to achieve this goal, video recording of the maxillary-mandibular region of women eating food from a plate was synchronized with video recording of the plate and computer recording of the weight-loss of the plate. Video recording of chewing correlated strongly with chewing identified by magnetic tracking of jaw displacement in a test with chewing gum at three different frequencies, thus ensuring the validity of video recording of chewing. Weight-loss data were corrected by convolution algorithms, validated against human correction, using sliding window filtering to correct errors with video events as reference points. By use of this method, women ate on average 264 g of food over 114 min, they took an average of 51 mouthfuls during the meal and displayed on average 794 chews with 15 chews per chewing sequence. The number of mouthfuls decreased and the duration of the pauses after each mouthful increased in the middle of the meal and these measures were then restored. The ratio between chewing sequences and subsequent pauses remained stable although the weight of each mouthful decreased by the end of the meal, a measure that is hypothesized to be reflected in a decelerated speed of eating. The method allows this hypothesis to be tested and its implication for clinical intervention to be examined.

Effect of dental status on changes in mastication in patients with obesity following bariatric surgery

Background

Patients scheduled for bariatric surgery (BS) are encouraged to chew slowly in order to optimise the digestion process. The influence of dental status on patients' ability to comply with advice on chewing behaviour is poorly documented. This study aims to compare modifications of chewing function before and after BS in three groups of obese patients differing in dental status.

Method and Findings

A cohort of 46 obese women provided three groups: FD group: fully dentate (7–10 functional dental units [FU]); PD group: partially dentate (4–6 FU) without partial dentures; DW group: partial and complete denture wearers. Chewing time (CT), number of chewing cycles (CC), and chewing frequency (CF) were measured before and after surgery during mastication of standardised samples of raw carrot, peanuts, banana, apple and jelly. The median particle-size distribution (D50) of the pre-swallowed bolus was also evaluated for peanut and carrot. Before surgery, the PD and DW groups exhibited greater mean CCs and CTs than the FD group (SNK p<0.05) and produced a bolus with higher granulometry (SNK, p<0.05) than the FD group. After surgery, CT and CC increased for all groups and for all foods, but not statistically significant for jelly. The resulting changes in bolus granulometry observed depended on both food and dental status. The granulometry of carrot bolus remained as fine or as coarse in FD and DW groups respectively as it was before surgery while it was significantly decreased in the PD group (Student's test, p<0.001).

Conclusions

After bariatric surgery, all the obese patients, regardless of dental status modified their chewing kinematics. The effects of this chewing behaviour on bolus granulometry depended on dental status and type of food. Further studies are needed to understand better the impact of dental status on feeding behaviour and nutrition in patients with obesity.

The trigeminal circuits responsible for chewing

Mastication is a vital function that ensures that ingested food is broken down into pieces and prepared for digestion. This review outlines the masticatory behavior in terms of the muscle activation patterns and jaw movements and gives an overview of the organization and function of the trigeminal neuronal circuits that are known to take part in the generation and control of oro-facial motor functions. The basic pattern of rhythmic jaw movements produced during mastication is generated by a Central Pattern Generator (CPG) located in the pons and medulla. Neurons within the CPG have intrinsic properties that produce a rhythmic activity, but the output of these neurons is modified by inputs that descend from the higher centers of the brain, and by feedback from sensory receptors, in order to constantly adapt the movement to the food properties.