Natural Chewing Research Articles

Monitoring Chewing and Eating in Free-Living Using Smart Eyeglasses.

We propose to 3-D-print personal fitted regular-look smart eyeglasses frames equipped with bilateral electromyography recording to monitor temporalis muscles' activity for automatic dietary monitoring. Personal fitting supported electrode-skin contacts are at temple ear bend and temple end positions. We evaluated the smart monitoring eyeglasses during in-lab and free-living studies of food chewing and eating event detection with ten participants. The in-lab study was designed to explore three natural food hardness levels and determine parameters of an energy-based chewing cycle detection. Our free-living study investigated whether chewing monitoring and eating event detection using smart eyeglasses is feasible in free-living. An eating event detection algorithm was developed to determine intake activities based on the estimated chewing rate. Results showed an average food hardness classification accuracy of 94% and chewing cycle detection precision and recall above 90% for the in-lab study and above 77% for the free-living study covering 122hours of recordings. Eating detection revealed the 44 eating events with an average accuracy above 95%. We conclude that smart eyeglasses are suitable for monitoring chewing and eating events in free-living and even could provide further insights into the wearer's natural chewing patterns.

The Effects of Both Chewing Rate and Chewing Duration on Temporal Flavor Perception

Previous research showed that the number of chews has been shown to influence flavor perception in crispy potato chips. This study aimed to further determine how the number of chews modulates the temporal dynamics of flavor perception (i.e., flavor development) in potato chips. The number of chews was manipulated not only by changing chewing rate (40, 80, and 120 chews/min) for a fixed swallowing time (at 25 s after the onset of the first bite; experiment 1), but also by changing the time to swallow (10, 20, and 30 s after the onset of the first bite) for a constant chewing rate (80 chews/min; experiment 2). In experiment 1, the time-intensity (TI) analysis showed that the maximum flavor intensity (Imax) and the area under the curve (AUC) were significantly higher for the medium (80 chews/min) and fast (120 chews/min) chewing rates than for the slow (40 chews/min) chewing rate in both plain and spicy flavored chips. In experiment 2, the temporal flavor perception was altered by the interaction between the chewing duration before swallowing and the flavor type of the potato chips. More specifically, in the natural chewing rate, while the Imax and AUC of spicy flavored chips were the greatest when the bolus was swallowed after the natural chewing-duration (for 20 s), the AUC of plain flavored chips was significantly greater in the longer chewing-duration (for 30 s) than the natural chewing-duration. This study supports and extends the notion that the number of chews, and corresponding parameters such as chewing rate and duration, affect temporal flavor perception in the plain and spicy flavored potato chips. Our findings show that flavor intensity of plain and spicy potato chips can be reduced when people chew the chips slowly and/or swallow quickly.

Evaluation of electromyogram activity and masticatory efficiency in edentulous individuals whose maxillomandibular horizontal relationship records were obtained with three different methods

This study was performed to investigate the electromyographic (EMG) activity of the masseter muscle and the anterior temporalis muscle, as well as the masticatory efficiency after insertion of the dentures in edentulous individuals whose maxillomandibular horizontal relationship records were obtained with three different methods. Ten edentulous individuals were enrolled in this study. Three types of complete dentures for these 10 edentulous patients were made according to their different maxillomandibular horizontal relationship records. The maxillomandibular horizontal relationship of complete dentures was recorded by three methods. In the first method (A), the maxillomandibular horizontal relationship was determined at the gothic arch tracing apex. In the second method (B), the relationship was 1mm anterior to the tracing apex with the gothic arch. In the last method (C), the horizontal jaw relation was recorded by natural chewing. The muscular activities of the three complete dentures were examined by EMG. The masticatory efficiency was evaluated based on the absorbance. The differences among the dentures were statistically analyzed with SPSS 17.0. The muscular activities of dentures B and C were much higher than that of denture A during clenching in the center occlusion and during chewing (P<0.05). The highest asymmetry index was found indenture C, which was significantly higher than those of dentures A and B (P<0.05). A statistically significant increase in the absorbance was observed between dentures B and C (P<0.05); otherwise, no statistically significant differences were observed (P>0.05) between B and C. Given the limitations of this experimental design, in edentulous individuals the maxillomandibular horizontal relationship recorded at 1mm anterior to the tracing apex with the gothic arch can improve the function of masticatory muscles and strengthen masticatory performance.

Electrical Stimulation of the Human Cerebral Cortex by Extracranial Muscle Activity: Effect Quantification With Intracranial EEG and FEM Simulations.

ObjectiveElectric fields (EF) of approx. 0.2 V/m have been shown to be sufficiently strong to both modulate neuronal activity in the cerebral cortex and have measurable effects on cognitive performance. We hypothesized that the EF caused by the electrical activity of extracranial muscles during natural chewing may reach similar strength in the cerebral cortex and hence might act as an endogenous modality of brain stimulation. Here, we present first steps toward validating this hypothesis.MethodsUsing a realistic volume conductor head model of an epilepsy patient having undergone intracranial electrode placement and utilizing simultaneous intracranial and extracranial electrical recordings during chewing, we derive predictions about the chewing-related cortical EF strength to be expected in healthy individuals.ResultsWe find that in the region of the temporal poles, the expected EF strength may reach amplitudes in the order of 0.1–1 V/m.ConclusionThe cortical EF caused by natural chewing could be large enough to modulate ongoing neural activity in the cerebral cortex and influence cognitive performance.SignificanceThe present study lends first support for the assumption that extracranial muscle activity might represent an endogenous source of electrical brain stimulation. This offers a new potential explanation for the puzzling effects of gum chewing on cognition, which have been repeatedly reported in the literature.

Peripheral and central control of swallowing initiation in healthy humans

We investigated (1) how peripheral inputs might assist central inputs in the control of voluntary evoked swallowing, (2) inter-individual variation in involuntary and voluntary swallowing initiation, and (3) whether natural chewing behavior affects the initiation of involuntary swallowing in healthy humans. Eleven participants completed a repetitive saliva swallowing test (RSST), chewing test (CHEW), and rest period (REST). In RSST, participants repetitively swallowed as quickly as possible. In CHEW, subjects chewed gum freely. We delivered pharyngeal electrical stimulation (PEStim) to the laryngopharynx and compared the number of swallows that occurred with and without PEStim. PEStim significantly increased the number of voluntary evoked swallows in RSST, as well as the number of swallows in CHEW and REST trials, although this facilitatory effect was larger in REST trials. We found a positive correlation between the number of swallows at RSST without PEStim and that at REST with PEStim within individuals. Additionally, we found a significant positive correlation between the number of swallows at RSST with PEStim and the sum of that at RSST without PEStim and at REST with PES. Based on the current results, we suggest that (1) peripheral inputs within a certain range appear to facilitate the central inputs that control voluntary swallowing, (2) inter-individual variations in swallowing initiation may arise from differences in the excitability of the common neural network in the lower brainstem, and (3) during chewing, food reduction in the oral cavity is prioritized, such that the neural network associated with chewing may regulate swallowing initiation.

Modulation of the masticatory path at the mandibular first molar throughout the masticatory sequence of a hard gummy jelly in normal occlusion.

In this study, the authors investigated the modulation of the masticatory path at the mandibular first molar during natural chewing of a hard gummy jelly in adults with normal occlusion. The unilateral mastication sequence was divided into three stages, and the masticatory path of the mandibular first molar on the working side was analyzed at 2.0, 3.0, 4.0, and 5.0 mm vertical slice levels below the intercuspation in the frontal and sagittal views. In the frontal view, the closing and opening angles and cycle width of the final stage at 3.0, 4.0, and 5.0 mm slice levels were smaller and narrower than those of the initial stage, although those at the 2.0 mm slice level were little changed. Masticatory paths of the mandibular first molar at slice levels greater than 3.0 mm were evidently modulated to adapt to the changing properties of the food, and those at the 2.0 mm slice level remained stable throughout the masticatory sequence.

Motor behavior during the first chewing cycle in subjects with fixed tooth- or implant-supported prostheses.

Appropriate sensory information from periodontal mechanoreceptors (PMRs) is important for optimizing the positioning of food and adjustment of force vectors during precision biting. This study was designed to describe motor behavior during the first cycle of a natural chewing task and to evaluate the role of such sensory input in this behavior. While 10 subjects with natural dentition, 11 with bimaxillary fixed tooth-supported prostheses (TSP) and 10 with bimaxillary fixed implant-supported prostheses (ISP) (mean age 69 [range 61-83]) chewed a total of five hazelnuts, their vertical and lateral jaw movements were recorded. Data obtained during the first chewing cycle of each hazelnut were analyzed. The amplitude of vertical and lateral mandibular movement and duration of jaw opening did not differ between the groups, indicating similar behavior during this part of the chewing cycle. However, only 30% of the subjects in the natural dentate group, but 82% of those in the TSP and 70% in the ISP group exhibited slippage of the hazelnut during jaw closure in at least one of five trials. The TSP and ISP groups also exhibited more irregular and narrower patterns of motion (total lateral/vertical movement = 0.15 and 0.19, respectively, compared to 0.27 for the natural group). Subjects with fixed tooth- or implant-supported prostheses in both jaws show altered behavior, including inadequate control of the hazelnut, during the first chewing cycle. We propose that these differences are due to impairment or absence of sensory signaling from PMRs in these individuals.

The Application of Temporal Dominance of Sensations (TDS) for Oral Processing Studies: An Initial Investigation

AbstractSensory trajectories of foods can be described using the temporal dominance of sensations method (TDS). This study aims to investigate the influence of TDS on oral processing variables and understand the optimum number of subjects required for oral processing studies. The work was carried out with a solid model food system (biscuits). Formulation differences in the model biscuits influenced texture perception but did not affect oral processing parameters apart from chewing frequency. Completing the TDS task influenced both mastication duration and the number of chews, although the different natural chewing behaviors observed between products were not affected. Training of subjects resulted in quicker attribute selection and greater dominance rates being observed even though the resulting TDS curves were similar. Analysis using a correlation technique suggests that 15–20 untrained subjects may be required to generate useful TDS curves for oral processing research assessing food properties.Practical ApplicationsThe dynamic and simple nature of temporal dominance of sensations (TDS) has given the technique great potential for use while simultaneously measuring oral processing parameters such as jaw movement, muscle activity and food bolus assessment. This study shows the differences in basic oral processing behavior between subjects who are, and are not, using the TDS technique. It shows that TDS can influence oral processing, but it has also potential for use with oral processing research. The research shows that slightly greater number of subjects than those commonly used in oral processing trials may be needed to generate a TDS curve effectively.

Temporal profile and amplitude of human masseter muscle activity is adapted to food properties during individual chewing cycles

Jaw actions adapt to the changing properties of food that occur during a masticatory sequence. In the present study, we investigated how the time-varying activation profile of the masseter muscle changes during natural chewing in humans and how food hardness affects the profile. We recorded surface electromyography (EMG) of the masseter muscle together with the movement of the lower jaw in 14 healthy young adults (mean age 22) when chewing gelatin-based model food of two different hardness. The muscle activity and the jaw kinematics were analysed for different phases of the chewing cycles. The increase in the excitatory drive of the masseter muscle was biphasic during the jaw-closing phase showing early and late components. The transition between these components occurred approximately at the time of tooth-food contact. During the masticatory sequence, when the food was particularised, the size of the early component as well as the peak amplitude of the EMG significantly decreased along with a reduction in the duration of the jaw-closing phase. Except for amplitude scaling, food hardness did not appreciably affect the muscle's activation profile. In conclusion, when chewing food during natural conditions, masseter muscle activation adapted throughout the masticatory sequence, principally during the jaw-closing phase and influenced both early and late muscle activation components. Furthermore, the adaptation of jaw actions to food hardness was affected by amplitude scaling of the magnitude of the muscle activity throughout the masticatory sequence.

Endplate Potential Oscillation of Jaw Closing Muscles in Natural Chewing

Surface electromyograms (EMGs) in natural gum chewing were recorded in a monopolar manner from paired anterior temporalis and masseter muscles of four subjects. Electrodes were placed on the temple of the former muscle, and on the inferior portion of the latter muscle. The endplate potential (EPP) component was extracted from raw EMGs of the muscles using a digital filter: the frequency of the high-cut digital filter for eliminating action potentials was set to 12.5 Hz or 45 Hz. The EPP component of the EMG burst of each stroke in the natural chewing showed two phases, early negative slow wave and following oscillation, which was same as observed in the clenching task. From FFT analysis, the frequencies of the ipsilateral EPP oscillations were around 30 Hz for both the temporalis and masseter muscles, which was also the same for the clenching task. It is concluded that the contraction of the jaw closing muscles is regulated in an oscillating manner of the EPP even in natural chewing behaviors. This oscillation phenomenon of the EPP gives a useful hint about the mechanism of muscular movements including chewing.

Phasic bursts of the antagonistic jaw muscles during REM sleep mimic a coordinated motor pattern during mastication

Sleep-related movement disorders are characterized by the specific phenotypes of muscle activities and movements during sleep. However, the state-specific characteristics of muscle bursts and movement during sleep are poorly understood. In this study, jaw-closing and -opening muscle electromyographic (EMG) activities and jaw movements were quantified to characterize phenotypes of motor patterns during sleep in freely moving and head-restrained guinea pigs. During non-rapid eye movement (NREM) sleep, both muscles were irregularly activated in terms of duration, activity, and intervals. During rapid eye movement (REM) sleep, clusters of phasic bursts occurred in the two muscles. Compared with NREM sleep, burst duration, activity, and intervals were less variable during REM sleep for both muscles. Although burst activity was lower during the two sleep states than during chewing, burst duration and intervals during REM sleep were distributed within a similar range to those during chewing. A trigger-averaged analysis of muscle bursts revealed that the temporal association between the bursts of the jaw-closing and -opening muscles during REM sleep was analogous to the temporal association during natural chewing. The burst characteristics of the two muscles reflected irregular patterns of jaw movements during NREM sleep and repetitive alternating bilateral movements during REM sleep. The distinct patterns of jaw muscle bursts and movements reflect state-specific regulations of the jaw motor system during sleep states. Phasic activations in the antagonistic jaw muscles during REM sleep are regulated, at least in part, by the neural networks involving masticatory pattern generation, demonstrating that waking jaw motor patterns are replayed during sleep periods.

Cortical area inducing chewing-like rhythmical jaw movements and its connections with thalamic nuclei in guinea pigs

Repetitive electrical stimulation to the cortical masticatory areas (CMA) evokes rhythmical jaw movements (RJM), whose patterns vary depending on the stimulation site, in various species. In guinea pigs, although alternating bilateral jaw movements are usually seen during natural chewing, it is still unclear which cortical areas are responsible for chewing-like RJM. To address this issue, we first defined the cortical areas inducing chewing-like RJM by intracortical microstimulation. Stimulation of the most lateral area of the CMA, the granular cortex, induced chewing-like RJM, but from the region medial to this area, simple vertical RJM were induced. Subsequently, to reveal the properties of these two areas in the CMA, the connections between the CMA and the dorsal thalamus were examined by neuronal tract-tracing techniques. The area inducing chewing-like RJM possessed strong reciprocal connections, mainly with the medial part of the ventral posteromedial nucleus, which is the sensory-relay thalamus. On the other hand, the simple vertical RJM-inducing area had reciprocal connections with the motor thalamus. The present study suggests that the CMA inducing chewing-like RJM is different from the CMA inducing simple vertical RJM, and plays a role in cortically induced chewing-like RJM under the influence of the sensory thalamus in guinea pigs.

Using a Motion‐Capture System to Record Dynamic Articulation for Application in CAD/CAM Software

One of the current limitations of computer software programs for the virtual articulation of the opposing teeth is the static nature of the intercuspal position. Currently, software programs cannot identify eccentric occlusal contacts during masticatory cyclic movements of the mandible. Chewing trajectories with six degrees of freedom (DOF) were recorded and imposed on a computer model of one subject's maxillary and mandibular teeth. The computer model was generated from a set of high-resolution micro-CT images. To obtain natural chewing trajectories with six DOF, an optoelectronic motion-capturing system (VICON MX) was used. For this purpose, a special mandibular motion-tracking appliance was developed for this subject. Mandibular movements while chewing elastic and plastic food samples were recorded and reproduced with the computer model. Examples of mandibular movements at intraoral points are presented for elastic and plastic food samples. The potential of such a kinematic computer model to analyze the dynamic nature of an occlusion was demonstrated by investigating the interaction of the second molars and the direction of the biting force during a chewing cycle. The article described a methodology that measured mandibular movements during mastication for one subject. This produced kinematic input to 3D computer modeling for the production of a virtual dynamic articulation that is suitable for incorporation into dental CAD/CAM software.

Automatically Generating Subject-specific Functional Tooth Surfaces Using Virtual Mastication

High-accuracy geometrical models of a subject's mandibular and maxillary teeth are combined with recordings of natural chewing trajectories of the same subject to obtain a subject-specific virtual model of mastication-the virtual masticator. The virtual masticator and a shape-optimization algorithm, which is based on removing collisions occurring between a generic maxillary tooth/teeth and the mandibular antagonists during mastication, is used to automatically reconstruct functional tooth surfaces. The process was tested using a chewing trajectory stemming from recordings made of an individual while eating elastic-type foods, a generic maxillary tooth, and the mandibular second molar of that individual. Comparing the obtained results with the actual tooth, the errors within the occlusal and functional regions of the the right second maxillary molar range between -90 and 200 mum and these errors do not change any more after three chewing cycles. These results indicate that a small number of chewing cycles is sufficient to remove occlusal interferences in the virtual tooth model. Such automatically reconstructed tooth surfaces can provide guidance during the design stage of dental fixed restorations manufactured using computer-aided design and manufacturing (CAD/CAM) systems and provide additional information for the design of dental implants or bridges.

The production and marketing of sustainable forest products: chewing gum in Mexico

Natural chewing gum (chicle) represents just 3.5 per cent of the total chewing-gum market, which is dominated by synthetic chewing gum made from hydrocarbons. However, recent interest in sustainable livelihood strategies has opened up opportunities for enlarging chicle commercialisation for what is still a small, niche market. The production of chicle can serve to strengthen forest conservation and provide regular employment to those dependent on forest products, as part of a range of sustainable forest activities. However, the production and marketing of natural chewing gum have faced several serious problems: producers in Mexico have been organised in ways that enabled them to be exploited by both intermediaries and state institutions, and the processes of certification for organics and fair trade are unwieldy and expensive. This article suggests a number of ways of addressing these problems.

The Role of the Mexican State in the Development of Chicle Extraction in Yucatán, and the Continuing Importance of Coyotaje

Most commentaries on the development of chicle (natural chewing gum) in the Yucatán Peninsula have emphasised the connections that were maintained between the chicle entrepreneurs and the companies, like William Wrigley's, which bought the raw gum for processing. The Mexican state is usually depicted as seeking to protect vulnerable forest workers from exploitation by foreign entrepreneurs and the vicissitudes of the free market. Our research, which uses archive material from Mexico City and Chetumal, interviews with former chicleros and entrepreneurs, as well as field research in Quintana Roo, suggests a slightly different interpretation. The Mexican state, far from contributing to the demise of personalistic relations (coyotaje) actually used these forms of mediation to manage and control the producers. The vulnerability of the chicleros to the full effect of market forces, their lack of physical and financial security, as well as corruption among some of the leaders of the cooperative movement, have all contributed to the continuance of coyotaje, often tacitly supported by state institutions. The article goes on to show that the need to meet demanding product and environmental standards, to achieve ‘certification’ as producers of a natural forest product, have compounded the problems of chicle producers today.

Effect of an auditory cue on chewing cycle kinematics

This study analysed the systematic and random effects of a rhythmic auditory cue on chewing cycle kinematics. The chin movements of 25 subjects (19-35 years of age) with normal class I occlusion were recorded at 100Hz (Optotrak) Northern Digital) during two natural gum chewing (2.5 g) sequences to determine the chewing rate of each subject. Another sequence was recorded with the subjects chewing at their natural rate following an audible cue. Multilevel modeling procedures were used to evaluate differences between natural chewing with and without an audible cue. Differences were found between experimental conditions for excursions, velocities and cycle shape. When chewing with the audible cue velocities were slower and there was less excursion of the chin marker, with the exception of initial lateral movements toward the balancing side. No differences in between-subject variability were found when chewing with or without an audible cue. Within-subject variability was 44% smaller for total cycle duration and 53% smaller for total 3D excursion when chewing with the auditory cue. Chewing at one's normal rate while following an auditory cue produces more consistency in chewing cycle kinematics. This method may be applicable, with some limitations, to reduce within-subject variability in chewing cycle kinematics.

Time series analysis of jaw muscle contraction and tissue deformation during mastication in miniature pigs.

Masticatory muscle contraction causes both jaw movement and tissue deformation during function. Natural chewing data from 25 adult miniature pigs were studied by means of time series analysis. The data set included simultaneous recordings of electromyography (EMG) from bilateral masseter (MA), zygomaticomandibularis (ZM) and lateral pterygoid muscles, bone surface strains from the left squamosal bone (SQ), condylar neck (CD) and mandibular corpus (MD), and linear deformation of the capsule of the jaw joint measured bilaterally using differential variable reluctance transducers. Pairwise comparisons were examined by calculating the cross-correlation functions. Jaw-adductor muscle activity of MA and ZM was found to be highly cross-correlated with CD and SQ strains and weakly with MD strain. No muscle's activity was strongly linked to capsular deformation of the jaw joint, nor were bone strains and capsular deformation tightly linked. Homologous muscle pairs showed the greatest synchronization of signals, but the signals themselves were not significantly more correlated than those of non-homologous muscle pairs. These results suggested that bone strains and capsular deformation are driven by different mechanical regimes. Muscle contraction and ensuing reaction forces are probably responsible for bone strains, whereas capsular deformation is more likely a product of movement.

Green Consumers and Natural Chewing Gum

Green Consumers and Natural Chewing Gum

Effects of the inferior alveolar nerve stimulation on tongue muscle activity during mastication in freely behaving rabbits

Genioglossus (Gg) reflexes elicited by electrical stimulation of the inferior alveolar nerve were examined in naturally chewing rabbits. To eliminate possible contaminations of the digastric (Dig) activity in the Gg responses, the Dig nerve was denervated bilaterally. Masticatory and tongue muscles were well coordinated during chewing after the denervation; i.e., there were no significant differences in the phase durations between before and after denervation. The Gg reflex measured was divided into three categories depending on the chewing phase (i.e., jaw-opening, OP; fast-closing, FC; and slow-closing, SC) in which the stimulus was delivered. The reflex amplitude was phasically modulated for the phases, in that the amplitude in the OP phase was larger than that in any other phase ( P<0.05). On the other hand, the amplitude in the FC and SC phases was not significantly different to each other and from the control value obtained when the animal was awake and resting. The pattern of the modulation in the reflex amplitude was different from the previous report as to the Dig reflex in that OP<FC∼SC<control was obtained. The results suggest that the modulatory mode in the Gg and Dig reflexes may be different in the pattern of the modulation under the natural chewing behavior and the Gg reflex is independent of the masticatory muscles in the nature. The reflex could be more sensitive to control the tongue movements collecting food bolus in the OP phase during chewing than in the jaw-closing phase.