Influence of age on adaptability of human mastication

Short-term follow-up of masticatory adaptation after rehabilitation with an immediately loaded implant-supported prosthesis: a pilot assessment

Background

When teeth are extracted, sensory function is decreased by a loss of periodontal ligament receptions. When replacing teeth by oral implants, one hopes to restore the sensory feedback pathway as such to allow for physiological implant integration and optimized oral function with implant-supported prostheses. What remains to be investigated is how to adapt to different oral rehabilitations.

The purpose of this pilot study was to assess four aspects of masticatory adaptation after rehabilitation with an immediately loaded implant-supported prosthesis and to observe how each aspect will recover respectively.

Methods

Eight participants with complete dentures were enrolled. They received an implant-supported acrylic resin provisional bridge, 1 day after implant surgery. Masticatory adaptation was examined by assessing occlusal contact, approximate maximum bite force, masticatory efficiency of gum-like specimens, and food hardness perception.

Results

Occlusal contact and approximate maximum bite force were significantly increased 3 months after implant rehabilitation, with the bite force gradually building up to a 72% increase compared to baseline. Masticatory efficiency increased by 46% immediately after surgery, stabilizing at around 40% 3 months after implant rehabilitation. Hardness perception also improved, with a reduction of the error rate by 16% over time.

Conclusions

This assessment demonstrated masticatory adaptation immediately after implant rehabilitation with improvements noted up to 3 months after surgery and rehabilitation. It was also observed that, despite gradually improved bite force in all patients, masticatory efficiency and food hardness perception did not necessarily follow this tendency. The findings in this pilot may also be used to assess adaptation of oral function after implant rehabilitation by studying the combined outcome of four tests (occlusal contact, maximum bite force, masticatory efficiency, and food hardness perception).

Electromyographic activity of masticatory muscles in elderly women - a pilot study

Objectives

To evaluate the effect of age and chosen factors related to aging such as dentition, muscle strength, and nutrition on masticatory muscles electromyographic activity during chewing in healthy elderly women.

Background

With longer lifespan there is a need for maintaining optimal quality of life and health in older age. Skeletal muscle strength deteriorates in older age. This deterioration is also observed within masticatory muscles.

Methods

A total of 30 women, aged 68–92 years, were included in the study: 10 individuals had natural functional dentition, 10 were missing posterior teeth in the upper and lower jaw reconstructed with removable partial dentures, and 10 were edontoulous, using complete removable dentures. Surface electromyography was performed to evaluate masticatory muscles activity. Afterwards, measurement of masseter thickness with ultrasound imaging was performed, body mass index and body cell mass index were calculated, and isometric handgrip strength was measured.

Results

Isometric maximal voluntary contraction decreased in active masseters with increasing age and in active and passive temporalis muscles with increasing age and increasing body mass index. In active masseter, mean electromyographic activity during the sequence (time from the start of chewing till the end when the test food became ready to swallow) decreased with increasing age and during the cycle (single bite time) decreased with increasing age and increasing body mass index. In active and passive temporalis muscles, mean electromyographic activity during the sequence and the cycle decreased with increasing age, increasing body mass index, and loss of natural dentition. Individuals with natural dentition had significantly higher mean muscle activity during sequence and cycle in active temporalis muscles than those wearing full dentures and higher maximal activity during cycle in individuals with active and passive temporalis muscles than in complete denture wearers.

Conclusion

Decrease in electromyographic activity of masticatory muscles in elderly women is related to age, deterioration of dental status, and body mass index.

In vitro assessment of retention and resistance failure loads of two preparation designs for maxillary anterior teeth

STATEMENT OF PROBLEM

Parallel labiolingual walls and the preservation of the cingulum in anterior tooth preparations have been advocated. However, their contribution to retention and resistance form has not been evaluated.

PURPOSE

The purpose of this in vitro study was to evaluate the retention and resistance failure loads of 2 preparation designs for maxillary anterior teeth.

MATERIAL AND METHODS

Forty metal restorations were fabricated and paired with 40 cobalt-chromium prepared tooth analogs. Twenty of the specimens had parallel buccolingual walls at the cervical part (group PBLW; the control group), whereas the remaining 20 had converging buccolingual walls (group CBLW; the experimental group). The restorations were cemented to the tooth analogs with a resin-modified glass ionomer luting agent. Ten specimens from each group were subjected to tensile loading with a universal testing machine; the rest were subjected to compression loading until failure. Descriptive statistics and the independent t test (α=.05) were used to determine the effect of failure loads in the tested groups.

RESULTS

The independent t test revealed statistically significant differences between the tested groups in tensile loading (P<.001) and in compressive loading (P<.001). The PBLW group presented a higher tensile failure load than the CBLW. On the contrary, the PBLW group presented a smaller compression failure load than the CBLW.

CONCLUSIONS

Parallelism of the buccolingual axial walls in anterior maxillary teeth increased the retention form but decreased the resistance form.

Effects of age and non-oropharyngeal proprioceptive and exteroceptive sensation on the magnitude of anticipatory mouth opening during eating

To best prevent and treat eating/swallowing problems, it is essential to understand how components of oral physiology contribute to the preservation and/or degradation of eating/swallowing in healthy ageing. Anticipatory, pre-swallow motor movements may be critical to safe and efficient eating/swallowing, particularly for older adults. However, the nature of these responses is relatively unknown. This study compared the magnitude of anticipatory mouth opening during eating in healthy older (aged 70-85) and younger (aged 18-30) adults under four eating conditions: typical self-feeding, typical assisted feeding (being fed by a research assistant resulting in proprioceptive loss), sensory loss self-feeding (wearing blindfold/headphones resulting in exteroceptive loss) and sensory loss assisted feeding (proprioceptive and exteroceptive loss). Older adults opened their mouths wider than younger adults in anticipation of food intake under both typical and most non-oropharyngeal sensory loss conditions. Further, the loss of proprioceptive and exteroceptive cues resulted in decreased anticipatory mouth opening for all participants. Greater mouth opening in older adults may be a protective compensation, contributing to the preservation of function associated with healthy ageing. Our finding that the loss of non-oropharyngeal sensory cues resulted in decreased anticipatory mouth opening highlights how important proprioception, vision, and hearing are in pre-swallow behaviour. Age- and disease-related changes in vision, hearing, and the ability to self-feed may reduce the effectiveness of these pre-swallow strategies.

EMG Activity of Masseter Muscles in the Elderly According to Rheological Properties of Solid Food

Objective

To assess the impact of aging on masticatory muscle function according to changes in hardness of solid food.

Methods

Each of fifteen healthy elderly and young people were selected. Subjects were asked to consume cooked rice, which was processed using the guidelines of the Universal Design Foods concept for elderly people (Japan Care Food Conference 2012). The properties of each cooked rice were categorized as grade 1, 2, 3 and 4 (5×10³, 2×10⁴, 5×10⁴, and 5×10⁵ N/m²) respectively. Surface electromyography (sEMG) was used to measure masseter activity from food ingestion to swallowing of test foods. The raw data was normalized by the ratio of sEMG activity to maximal voluntary contraction and compared among subjects. The data was divided according to each sequence of mastication and then calculated within the parameters of EMG activities.

Results

Intraoral tongue pressure was significantly higher in the young than in the elderly (p<0.05). Maximal value of average amplitude of the sequence in whole mastication showed significant positive correlation with hardness of food in both young and elderly groups (p<0.05). In a comparisons between groups, the maximal value of average amplitude of the sequence in whole mastication and peak amplitude in whole mastication showed that mastication in the elderly requires a higher percentage of maximal muscle activity than in the young, even with soft foods (p<0.05).

Conclusion

sEMG data of the masseter can provide valuable information to aid in the selection of foods according to hardness for the elderly. The results also support the necessity of specialized food preparation or products for the elderly.

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.

The Effects of Age and Preoral Sensorimotor Cues on Anticipatory Mouth Movement During Swallowing

PURPOSE

The aim of this study was to investigate the effects of preoral sensorimotor cues on anticipatory swallowing/eating-related mouth movements in older and younger adults. It was hypothesized that these cues are essential to timing anticipatory oral motor patterns, and these movements are delayed in older as compared with younger adults.

METHOD

Using a 2 × 2 repeated-measures design, eating-related lip, jaw, and hand movements were recorded from 24 healthy older (ages 70-85 years) and 24 healthy younger (ages 18-30 years) adults under 4 conditions: typical self-feeding, typical assisted feeding (proprioceptive loss), sensory-loss self-feeding (auditory and visual loss/degradation), and sensory-loss assisted feeding (loss/degradation of all cues).

RESULTS

All participants demonstrated anticipatory mouth opening. The absence of proprioception delayed lip-lowering onset, and sensory loss more negatively affected offset. Given at least 1 preoral sensorimotor cue, older adults initiated movement earlier than younger adults.

CONCLUSIONS

Preoral sensorimotor information influences anticipatory swallowing/eating-related mouth movements, highlighting the importance of these cues. Earlier movement in older adults may be a compensation, facilitating safe swallowing given other age-related declines. Further research is needed to determine if the negative impact of cue removal may be further exacerbated in a nonhealthy system (e.g., presence of dysphagia or disease), potentially increasing swallowing- and eating-related risks.

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.

A influência da função mastigatória na deglutição orofaríngea em idosos saudáveis

Objetivo Verificar se as características da mastigação influenciam os achados da deglutição orofaríngea em idosos. Métodos Foram analisados os dados de 47 idosos saudáveis - 29 mulheres e 18 homens - avaliados por meio da aplicação do protocolo clínico da mastigação e exame clínico funcional da deglutição orofaríngea. A avaliação da mastigação foi registrada em vídeo, tendo sido analisado o tipo mastigatório, a formação do bolo alimentar e o tempo mastigatório. Durante a avaliação clínica da deglutição foi verificado o desempenho dos pacientes quando testados alimentos de diferentes consistências, sendo que, após a realização da avaliação clínica, os indivíduos foram classificados quanto ao grau de disfunção da deglutição orofaríngea. Os dados foram analisados de modo descritivo e utilizando-se testes estatísticos de comparação e correlação. Resultados A média do tempo mastigatório foi de 32,45 segundos. A maioria dos indivíduos apresentou tipo mastigatório bilateral (62%), formação do bolo alimentar adequada (75%) e cerca de metade (47%), quadro de disfagia orofaríngea de grau moderado. De acordo com a análise estatística, não houve correlação entre o grau da disfunção da deglutição e o tipo mastigatório e a formação do bolo alimentar, porém, houve correlação positiva moderada entre o grau da disfunção da deglutição e o tempo de mastigação. Conclusão Para os idosos deste estudo, o tempo mastigatório influenciou o grau de disfunção da deglutição, não tendo sido encontrada relação para o tipo mastigatório e formação do bolo alimentar quanto aos achados da deglutição orofaríngea.

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.

Chewing ability in an urban and rural population over 40 years in Shandong Province, China

Objectives

This study aimed to assess chewing ability related to dental status.

Material and methods

One thousand four hundred sixty-two Chinese subjects over 40 years, dentate in both jaws, were categorized in a hierarchical functional classification system with and without tooth replacements. Chewing ability was analyzed using multivariable logistic regression including five dental conditions (≥10 teeth in each jaw’; ‘complete anterior regions’; “sufficient premolar regions’ (≥3 posterior occluding pairs (POPs)); ‘sufficient molar regions’ (bilaterally ≥1 POP); and tooth replacement), adjusted for six background variables. Likelihood ratios for chewing problems were assessed at each level of the hierarchical classification system based on these dental conditions.

Results

Seventy-eight to 91 % of subjects reported no or minor chewing problems. The conditions ‘≥10 teeth in each jaw’, and ‘complete anterior regions’ were not associated, whereas ‘sufficient’ premolar regions’ and ‘sufficient molar regions’ were associated with chewing problems (Ors, 0.33–0.58). If classified hierarchically, the condition ‘≥10 teeth in each jaw’ was relevant for chewing problems (likelihood ratios 3.3–3.7). ‘Sufficient premolar region’ and ‘sufficient molar region’ were relevant to reduce the likelihood ratios for having chewing problems (both approximately with a factor 2), both for soft and for hard foods. Subjects with artificial teeth added had similar chance for chewing problems compared to counterparts with natural teeth only. However, if comparing replaced teeth with natural teeth, subjects with tooth replacement showed higher chance for chewing problems.

Conclusions

Chewing ability was strongly associated with dental conditions.

Clinical relevance

The presence of at least 10 teeth in each jaw had highest impact on chewing ability.

Comparison between Trans-Cranial Electromagnetic Stimulation and Low-Level Laser on Modulation of Trigeminal Neuralgia

[Purpose] To determine which of the transcranial electromagnetic stimulation or low level laser therapy is more effective in the treatment of trigeminal neuralgia of multiple sclerosis patients. [Methods] Thirty multiple sclerosis patients of both sexes participated in this study. The age of the subjects ranged from 40 to 60 years and their mean age was (56.4-6.6). Participants were randomly selected from Dental and Neurology Outpatient Clinics at King Khalid Hospital, Najran University, Saudi Arabia. Patients were randomly divided into two equal groups of 15. The Laser group received a low level laser therapy, 830 nm wavelength, 10 Hz and 15 min duration, while the Electromagnetic group received repetitive transcranial electromagnetic stimulation at a frequency of 10 Hz, intensity of 50 mA and duration of 20 minutes. Patients were assessed pre and post treatment for degree of pain using a numerical rating scale, maximal oral mouth opening using a digital calibrated caliper, masseter muscle tension using a tensiometer and a compound action potentials of masseter and temporalis muscles. [Results] There were significant improvements after treatment in both groups, with a significant difference between the Electromagnetic and Laser groups, in favor of the Electromagnetic group. [Conclusion] Repetitive transcranial electromagnetic stimulation at 10 Hz, 50 mA, and 20 minutes duration is more effective than low level laser therapy at reducing trigeminal pain, increasing maximum oral mouth opening, masseter and temporalis muscle tension in multiple sclerosis patients.

Increased masticatory activity and quality of life in elderly persons with dementia--a longitudinal matched cluster randomized single-blind multicenter intervention study

Background

Worldwide, millions of people are suffering from dementia and this number is rising. An index of quality of life (QoL) can describe the impact a disease or treatment has on a person’s wellbeing. QoL comprises many variables, including physical health and function, and mental health and function. QoL is related to masticatory ability and physical activity. Animal studies show that disruption of mastication due to loss of teeth or a soft diet leads to memory loss and learning problems. Since these are common complaints in dementia, it is hypothesized that improvement of masticatory function and normalization of diet consistency can increase QoL in elderly persons suffering from dementia. Therefore, the goal of the present study is to examine whether an increase in masticatory activity, achieved by increased food consistency and enhancement of masticatory function through improved oral health care has a positive effect on QoL, including cognition, mood, activities of daily living (ADL), and circadian rhythm in elderly persons with dementia.

Methods and design

The described study is a prospective longitudinal matched cluster randomized single-blind multicenter study. Participants are elderly persons living in the Netherlands, suffering from dementia and receiving psychogeriatric care. An intervention group will receive improved oral health care and a diet of increased consistency. A control group receives care as usual. Participants will be assessed four times; outcome variables besides QoL are cognition, mood, independence, rest-activity rhythm, blood pressure, and masticatory function.

Discussion

This research protocol investigates the effect of an intervention executed by daily caregivers. The intervention will increase masticatory activity, which is achieved by three different actions, (providing oral health care, increasing food consistency, or a combination of both). There is a certain amount of variety in the nature of the interventions due to local differences in nursing homes. This might be a scientific weakness in the study design; however, a practical implementation of any findings will be subject to the same factors, making this study design clinically relevant.

Trial registration

NTR1561

Influence of edentulism on human orbit and zygomatic arch shape

Edentulism, or tooth loss, seriously alters the appearance of the lower facial skeleton. The aim of this study was to determine if complete maxillary edentulism also impacts the curvature shape of the orbits and zygomatic arches in elderly adults. The study was conducted on 80 crania comprising two cross-sectional populations of elderly African- and European-Americans (60-80 years old). Forty of the crania possessed intact dentition; the remaining 40 exhibited complete edentulism with tooth socket resorption. Three-dimensional semilandmarks representing the curvature of the orbits and zygomatic arches were collected using a hand-held digitizer. Each craniofacial region's semilandmarks were aligned into a common coordinate system via generalized Procrustes superimposition. Regional variation in shape was explored via principal component analysis, multivariate analysis of variance, discriminant function analysis, cross-validation, and vector plots. Shape differences between the edentulous and dentate groups were detected in both the orbits (P = 0.0022) and zygomatic arches (P = 0.0026). Ancestry and sex differences were also identified in both regions. Orbit data correctly classified dentate crania 65% of the time and edentulous crania 72.5% of the time. Zygomatic arch data correctly classified 75% dentate and 60% of edentulous crania. The individual curves constituting each region also exhibited shape alteration with tooth loss, with the exception of the inferior zygomatic curve. Vector plots revealed patterns of superoinferior expansion, and medial and lateral recession depending on the region examined. These results suggest a relationship exists between maxillary edentulism and changes in the surrounding craniofacial structures.

Relationship between masticatory ability and physical performance in community-dwelling edentulous older adults wearing complete dentures

OBJECTIVE

This study aimed to elucidate the association between masticatory ability and physical performance in community-dwelling edentulous older adults wearing complete dentures.

BACKGROUND

Physical performance parameters are significant predictors of decreased activities of daily living. Previous studies have shown the relationships between oral conditions and these parameters. Here, we focused on complete denture wearers.

METHODS

Two hundred and ten edentulous adults aged ≥65 years and wearing complete dentures were enrolled. The following oral conditions were examined: masticatory ability measured by colour-changing chewing gum, number of foods considered chewable, pain when using dentures and denture base fit. Handgrip strength (HG) and one-leg standing time with eyes open (OLST) were used to evaluate muscle strength and static balance. Spearman's rank correlation coefficients were calculated to examine the correlations between oral conditions and physical performance. Forward stepwise linear regression models were applied with each physical performance parameters as the dependent variable and oral conditions as the independent variable.

RESULTS

The women did not show significant correlations between oral conditions and the physical performance. In men, significant and positive correlations were found between the number of chewable foods and HG, and between the colour scores and OLST. The significant correlation between the colour scores and OLST was still noted in the stepwise liner regression analysis after adjusting for demographic, social and medical conditions, and other oral conditions.

CONCLUSION

In Japanese elderly edentulous men wearing complete dentures, masticatory ability evaluated as the mixing ability may be associated with static balance.

Wearing of complete dentures reduces slow fibre and enhances hybrid fibre fraction in masseter muscle

Edentulous conditions and use of complete dentures alter the function of jaw muscles, which is presumably reflected in the myosin heavy chain (MyHC) isoform composition. This study is the first dealing with MyHC isoforms expression in edentulous persons with the aim to clarify to which extent the decreased functional load following teeth loss contributes to the changed muscle phenotype during ageing. We analysed MyHC expression in old masseter muscle at decreased and full functional load by comparing age-matched edentulous and dentate subjects. Edentulous subjects had upper and lower complete dentures. Dentate subjects had at least 24 natural teeth in continuous dental arches with two molars present in each quadrant and normal intermaxillary relationship. The adaptive response to the reduced masticatory load was lower numerical and area proportion of MyHC-1 expressing fibres and higher numerical proportion of hybrid fibres in edentulous compared with dentate subjects with no significant difference in the proportion of MyHC-neo-expressing fibres between both groups. We conclude that the observed differences in the proportion of fibre types between denture wearers and dentate subjects cannot be ascribed to degenerative changes intrinsic to the ageing muscle, but to functional differences in muscle activity and to morphological alterations of stomatognathic system accompanying the complete teeth loss.

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.

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.

Association of masticatory performance with age, gender, number of teeth, occlusal force and salivary flow in Japanese older adults: is ageing a risk factor for masticatory dysfunction?

OBJECTIVE

In general, ageing is a risk factor for sensory and motor deterioration, with the rate of decline varying amongst individuals. Concerning masticatory function, missing teeth along with oral disease seem to accelerate the dysfunction. Here, we aimed to confirm whether masticatory dysfunction by ageing is inevitable. This study investigated the effect of age, gender, number of natural teeth, occlusal force and salivary flow on the masticatory performance in a large sample of elderly adults.

DESIGN

The study sample consisted of 1288 independently living people aged 60-84 years. Masticatory performance was determined by the comminuted particles of test food. Bilateral maximal occlusal force in the intercuspal position was measured with pressure sensitive sheets. Stimulated whole saliva was collected.

RESULTS

Masticatory performance was significantly correlated to age, number of residual teeth, occlusal force and stimulated salivary flow rate by Pearson's correlation test. The multiple linear regression analysis showed that, with other variables controlled, masticatory performance was significantly associated with the number of residual teeth (β=0.456, P<0.001), occlusal force (β=0.244, P<0.001) and stimulated salivary flow rate (β=0.069, P=0.003). Age was not related to masticatory performance (β=-0.007, P=0.753).

CONCLUSIONS

Declines in the number of residual teeth, occlusal force and salivary flow were associated with a reduction of masticatory performance in older adults. If tooth loss is not considered as an attribute of physiological ageing, then ageing by itself may not be a risk factor for masticatory dysfunction.

Regional shape change in adult facial bone curvature with age

Life expectancies have increased dramatically over the last 100 years, affording greater opportunities to study the impact of age on adult craniofacial morphology. This article employs a novel application of established geometric morphometric methods to examine shape differences in adult regional facial bone curvature with age. Three-dimensional semilandmarks representing the curvature of the orbits, zygomatic arches, nasal aperture, and maxillary alveolar process were collected from a cross-sectional cranial sample of mixed sex and ancestry (male and female; African- and European-American), partitioned into three age groups (young adult = 18-39; middle-aged = 40-59 years; and elderly = 60+ years). Each facial region's semilandmarks were aligned into a common coordinate system via generalized Procrustes superimposition. Regional variation in shape was then explored via a battery of multivariate statistical techniques. Age-related shape differences were detected in the orbits, zygomatic arches, and maxillary alveolar process. Interactions between age, sex, and ancestry were also identified. Vector plots revealed patterns of superoinferior compression, lateral expansion, and posterior recession depending on the population/subpopulation, location, and age groups examined. These findings indicate that adult craniofacial curvature shape is not static throughout human life. Instead, age-related spatial modifications occur in various regions of the craniofacial skeleton. Moreover, these regional alterations vary not only through time, but across human populations and the sexes.

Intraspecific scaling of chewing cycle duration in three species of domestic ungulates

In mammals, chewing cycle duration (CCD) increases with various measures of size, scaling with body mass0.13–0.28 and jaw length0.55. Proposed explanations for these scaling relationships include the allometry of body size, basal metabolic rate and tooth size, on the one hand, and pendular mechanics treating the jaw as a gravity-driven pendulum, on the other. Little is known, however, about the relationship between CCD and size within species. Recent research in dogs demonstrates altogether different scaling exponents and weaker correlations. This research suggests that breed-specific growth rates influence the maturation of the neural networks generating chewing rhythm, which may be altered because of changes in jaw mass during early postnatal growth. Here, we explored the intraspecific scaling of CCD within a sample of adult horses ranging from miniatures to draft breeds and an ontogenetic sample of goats and alpacas from infants to adults. In horses, CCD scales with body mass0.19 and jaw length0.57, although in neither case is the correlation significant. In the ontogenetic samples of goats and alpacas, CCD is significantly correlated with body mass, scaling as CCD∝body mass0.37 in both species. In goats, but not alpacas, CCD is also significantly correlated with jaw length, scaling as jaw length1.032. As in dogs, the scaling of CCD in horses may reflect the influence of selective breeding on growth trajectories of different breeds, resulting in reduced body and jaw size differences among infants, when CCD is established, compared with adults. However, the allometric scaling of tooth size in horses of different breeds may be a potential influence on the scaling of CCD. The scaling of CCD with body and jaw size in goats, and to a lesser extent in alpacas, also suggests that the development of peripheral masticatory structures such as the teeth and occlusal relations may play a role in changes in CCD during the earliest stages of postnatal ontogeny.