Human Chewing Research Articles

Bolus size and unilateral chewing cycle kinematics

The purpose of this study was to determine how bolus size alters the human chewing cycle. This prospective within-subject design evaluated chewing cycles of 38 young adults between 20 and 38 years of age (21 males and 17 females). An optoelectric jaw tracking system was used to record movements of the chin during unilateral (right sided) chewing of four randomly ordered bolus sizes (1, 2, 4 and 8 g) of gum. Using each subject’s 10 most representative cycles, multilevel statistical procedures were used to evaluate jaw kinematics. The results showed that bolus size has no consistent effect on opening, closing or total cycle duration. Cycle excursions increased significantly with increasing bolus size. With increasing bolus sizes, chewing cycle excursions along the three axes increased 52–115%. The greatest differences between bolus sizes occurred when the jaw was changing direction (i.e. passing from opening to closing and from working to balancing sides). However, the increases were proportionate and the shape of the chewing cycle was maintained. In order to maintain cycle duration while increasing excursive ranges, jaw velocities increased significantly, with the greatest differences occurring at approximately 70% of opening and 30% of closing. We conclude that humans adapt to larger bolus sizes by increasing chewing cycle perimeter and by increasing cycle speed, while maintaining cycle shape and duration.

Quantification of human chewing-cycle kinematics

This study introduces new methods of quantifying and evaluating the human chewing cycle. These methods were validated on a sample of 26 young adults (11 women and 15 men) between 20–35 years of age. Movements of the mandibular central incisors were recorded (100 Hz) using an optoelectric computer system while the participants chewed gum. A subsample of 10 cycles was automatically selected, based on multiple objective criteria to ensure representative cycles for each individual. Once representative cycles had been identified, multilevel statistical models were used to evaluate and describe the sample’s kinematic patterns. The multilevel procedures allow for missing observations, they do not assume equal intervals, and variation can be partitioned hierarchically. Two-level models showed significantly shorter cycle duration for males (835 msec) than females (973 msec). Inferior–superior (IS) cycle range was 2.6 mm larger and maximum IS velocity was 19.6 mm/sec faster in males than females. There were no significant differences in medial–lateral (ML) and anteroposterior (AP) excursive ranges or velocities. With the exception of cycle duration and ML ranges of motion, random variation was three to five times larger between individuals than between cycles. The three-level models showed that eighth-order polynomials were necessary to describe IS, AP, and ML chewing movements of the entire cycle. The models identified highly significant sex differences in cycle kinematics (excursions, velocities, accelerations, etc.) for each aspect of movement (AP, IS, and ML). It is concluded that this approach provides several important advantages over existing methods, including (a) its objectivity, (b) a more complete description of kinematic patterns, (c) a hierarchical description of variation, and (d) its ability to test hypotheses statistically.

Temporal dynamics of human masticatory sequences

GERSTNER, G. E. AND T. CIANFARANI. Temporal dynamics of human masticatory sequences. PHYSIOL BEHAV 64(4) 457–461, 1998. Many motor behaviors produced by humans and other mammals are temporally segmented. That is, sequences of rhythmic or repetitive behavior occur as a series of brief, 2- to 4-s bouts separated from each other by pauses or posture adjustments. Little is known about the physiological mechanisms underlying temporal segmentation, although several hypotheses have been advanced. Experimental and modeling studies are currently underway to gain insight into this phenomenon. One of the problems hampering advancement is the lack of relatively simple behavior models that can be studied in both humans and other mammals. We have recently reported that temporal segmentation occurs in guinea pig chewing sequences. Thus, it seems logical to explore whether temporal segmentation occurs in human chewing sequences as well. Toward this end, the current study evaluated the temporal dynamics of chewing sequences in humans. Thirteen subjects were videotaped on campus eating areas during lunch-time. Inter-occlude intervals, i.e., time between maximum jaw closures, were calculated using a custom computer program, which also recorded whether the interval represented a chew or a pause in chewing. Chewing rate, pause durations, and chewing burst durations, i.e., duration of continuous chewing uninterrupted by pauses, were calculated. Median chewing burst duration for the sample was 2.91 s. This corroborates other studies’ findings of 3-s temporal segmentation in repetitive movements. We conclude that automatic chewing sequences contain temporal segmentation. Future work is required to gain insight into whether the physiological mechanisms of this time-based phenomenon are similar among different species.

Development and validation of a high-performance liquid chromatography method for the determination of cold relief ingredients in chewing gum

An isocratic high-performance liquid chromatography (HPLC) method for the simultaneous determination of the active compounds paracetamol, pseudoephedrine and chlorpheniramine in chewing gum samples has been developed and validated. The method required a simple liquid–liquid extraction using n-hexane and a mixture of water–acetonitrile prior to HPLC analysis. The chromatographic separation was achieved with an aqueous solution containing hexylamine (pH 3)–acetonitrile as the mobile phase, a Spherisorb C18 column and UV detection at 220 nm. As an application, the proposed method has been used to evaluate the release into saliva of these compounds from samples under a controlled human chewing process.

A Computer Simulation of the Influence of Selection and Breakage of Food on the Chewing Efficiency of Human Mastication

The reduction of food particle sizes during mastication is considered to be the composite result of a selection and breakage process. The chance of a food particle being selected between the teeth was assumed to increase as a power function of the particle's size, whereas the breakage of food particles was described by a cumulative distribution function. The selection and breakage functions were combined with matrix algebra, resulting in a matrix model. By use of this model, particle-size distributions could be calculated after various numbers of chewing cycles. From these distributions, the decrease of the median particle size was determined as a function of the number of chewing cycles. The calculations were performed for various sets of physiologically relevant selection and breakage variables. The number of chewing cycles, N1/2, needed for the initial particle size to be halved was taken as an indication of chewing efficiency. This number varied approximately inversely with both the selection coefficient and the breakage variable. The initial particle size appeared to have the largest influence on N1/2. The theoretical results from the simulation study were also compared with data obtained from experiments on human chewing efficiency.

A NUMERICAL MODEL TO PREDICT THE FORCE OUTPUT OF THE JAW MUSCULATURE

Numerical optimization has been incorporated into a step by step scientific investigation of the mechanical control of a biological system. The system is the human chewing apparatus and the aim is to produce a theoretical model which can use three-dimensional Newtonian mechanics to predict muscle forces based on an individual's occlusion, craniofacial geometry and muscle angulations. However, mechanical principles alone are not sufficient to yield a unique prediction because the force system is innately indeterminate. This indeterminacy may be related to the number of different muscles which can pull on the mandible, and to the bilateral nature of the articulations which can slide as well as rotate. Therefore, it is necessary to model the selection of muscles by the central nervous system using optimizing principles and a numerical algorithm. The predictions from the model can be tested using electromyographic recordings from the masticatory muscles and a scientific learning process is thereby established.

Analysis of repeated-measure multicycle unilateral mastication in children

This study examined systematic and random errors associated with repeated-measure, multiple-cycle unilateral mastication in children during single recording sessions with the Replicator system. Twenty-six recording sessions with 17 children (10 boys, 7 girls) were examined. Nine of these children had a functional-shift unilateral crossbite malocclusion and were recorded before and after crossbite correction. Repeated recordings (trials) of mandibular movement during each session were made of right-side chewing of similar-sized pieces of cheese. The following variables were computed for each chewing cycle (stroke): time closed, maximum closure velocity, maximum opening velocity, chewing rate, vertical opening, and lateral deviation. From the multiple cycles of each trial, two pattern descriptors--the average and standard deviation--were determined for each variable. In addition, the mean and variance of these pattern descriptors were determined from the multiple trials of each recording session and were the dependent variables in a stepwise multiple regression analysis, with treatment status, sex, age, dentition stage, crossbite presence, and right side status the independent variables. The results disclosed bias in repeated measures of human chewing in response to adaptation to the recording session; this was evident in the average response but not in the variability of the measures. Sex and functional status of the subjects were associated with the mean and variance of measures describing the chewing pattern.

Non-linear amplification of electromyographic signals with particular application to human chewing

A method is described for logarithmically-amplifying electromyographic signals so that the most commonly-occurring events within them are enhanced selectively before digital conversion. There is a need to resolve low and intermediate levels of activity during chewing, while preserving the occasional high-level responses. Besides achieving a higher resolution in subsequent digital sampling, this signal-processing technique increased the representation of low and intermediate activities in polygraphic displays. It further ensured that signals were presented to the A/D converter within the code width of the instrument.

ヒトのそしゃく運動経路の分析 正常有歯がく者および総義歯装着者について

Human chewing movement has been considered to be a cyclic movement with a regular rhythm for each individual. Chewing path, however, has been proved to be changed according to‘sensory input’from various peripheral nervous system (PNS). Analysis of paths of human chewing movements have been known to be useful to find clinical disorder of PNS and to diagnose the mandibular function and evaluate the prosthodontic appliances. Analysis of chewing paths for normal dentition adults and favorable full denture wearers have been performed to find and compare the basic data for the functional evaluation.From results of this study, the chewing paths of full denture wearers with good retentive and balancing denture were found to be similar to those of normal dentition adults except delay of the cycle time according to extension of the closing phase and tendency to reduce maximum lateral movement.

N-nitrosamines in snuff and chewing tobacco on the Swedish market in 1983.

Snuff and chewing tobacco on the Swedish market in 1983 were analysed for tobacco-specific and volatile N-nitrosamines using gas chromatography--thermal energy analysis. All 36 samples of snuff analysed were found to contain detectable levels of N'-nitrosonornicotine, N'-nitrosoanatabine, N'-nitrosoanabasine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. Total tobacco-specific N-nitrosamine levels between 2.5 and 51 mg/kg wet weight were found, the mean level being 8.8 mg/kg. Detectable levels of at least two of the four tobacco-specific N-nitrosamines were found in all 18 samples of chewing tobacco analysed. The total concentration of tobacco-specific N-nitrosamines found in chewing tobacco was between 0.1 and 7.8 mg/kg, the mean level being 2.1 mg/kg. The levels of volatile N-nitrosamines found in the 54 samples of snuff and chewing tobacco were very much lower--most of the samples contained less than 10 micrograms/kg and the highest concentration found was 550 micrograms/kg. Since snuff and chewing tobacco contain relatively high levels of carcinogenic N-nitrosamines and there is evidence of an association between the use of these tobacco products and human cancer, snuff and chewing tobacco users should be warned about the possible cancer risk involved in their habit. In addition, efforts should be made to reduce the levels of N-nitrosamines in snuff and chewing tobacco and the formation of these substances in the body from precursors originating from these tobacco products.

Food crushing sounds: An analytic approach

Previously reported work (Drake, 1963, 1965a and b) has shown that mastication sounds contain information related to the Theological properties of the food chewed. The complete relationships, however, have not yet been determined. In the present work, which is an attempt at starting to elucidate the remaining problems, a basic thought is to supplement human chewing with a mechanical crushing. The former is more natural and, of course, the the real thing to study. The latter, however, lends itself to more reproducible experiments, and is therefore to be considered as a valuable research tool.

A telemetry system for measuring chewing behavior in humans

A system is described for detecting and recording human chewing behavior. A small transmitter mounted in the side frame of eyeglasses was used to detect muscle movement associated with chewing. The transmitter signal was received and converted to a direct-current voltage which varied at a rate proportional to the S's chewing movement. Exploratory data are presented which suggest that individuals chew at about the same rate per second, but vary in the total number of chews emitted to consume the same amount of foodstuff.

Mechanical Simulation of Human Chewing Motions

To study the cause of dental attrition frequently found among primitive peoples, a cam-actuated, motor-driven device that could simulate human chewing motions was built. Casts of the dentition could be mounted in this machine and worn down by moderate pressures during chewing action.

Experimental studies in human tooth wear. II.

AbstractStudies of human tooth wear have been carried on for the past two years using a machine designed to approximate human chewing motions. During this time wear patterns that resemble those frequently found on the teeth of various American Indian skulls have been produced on casts of the definition. Noticeably among these patterns produced are examples of wear on the front end of the dental arches that result in an edge to edge bite. This type of wear was produced by wearing down casts of a modern dentition with a “normal” overbite.The forces applied to the casts mounted on the machine are variable over a wide range and numerous force combinations are possible. By noting these forces and the resulting vectors, the motions necessary to produce different wear patterns can be determined. This has especially aided in understanding the ways in which the oblique molar wear is produced.