Food Crushing Research Articles

The Food-Crushing Reflex and Its Inhibition

Anterior tooth (ANT) contacts induce a short-latency reflex inhibition of the human jaw-closing muscles. The jaw is a rigid class 1 lever for pinpoint targeting muscle force into a single bite point, the pivoting food particle. Seesaw reflex movements around the food particle fulcrum multiply the food-crushing force. Unpredictable jolts of reaction force caused by food crushing are subjected to the rostral ANT and caudally to the two articulate ends of the jaw triangle. The compression/distraction strains of food crushing must be monitored and inhibited by withdrawal reflexes. The mesencephalic ganglion (Vmes), neural myelin sheath, and muscle stretch receptors evolved subsequently to the advent of jaws to improve the velocity of proprioceptive and withdrawal reflexes. In mammalians, the spindles of the taut motor units, stretched by the food fulcrum, send excitatory monosynaptic feedback for the efferent neurons of the respective ipsilateral muscle units via the Vmes. In the Vmes, the spindle-input-mediating afferent neurons are coupled with another source of afferent feedback, which is also excitatory, from the back tooth (BAT) mechanoreceptors. The two sources of excitatory pulses are summated and targeted for the efferent neurons to boost the stretched and taut motor units. Likewise, the afferent feedback from the ANT mechanoreceptors is also coupled in the Vmes with concomitant feedback from spindles. The ANT output, however, is inhibitory to negate the excitatory feedback from the stretched jaw muscle units. The inhibitory feed from the anterior teeth temporarily blocks the excitatory potential of the masticatory motor efferent neurons to protect the anterior teeth and jaw joints from inadvertent strains. The inhibitory inputs from the anterior teeth alternate with the excitatory inputs from the BAT to determine which jaw-closing muscle units are activated or inhibited at any given instant of food crushing. The Vmes exists in all jawed vertebrates, and its evolution was probably motivated by demands for the control of bite force. The monosynaptic unilateral food-crushing excitatory and inhibitory reflexes (UFCRs) override the coexisting bilaterally executed feed for the jaw muscles from the central nervous system. The hypothesis proposed in this study is that the Vmes-mediated UFCRs combine neural inputs from tooth contacts with concomitant feedback from the muscle stretch receptors for the control of the mammalian food-crushing bite force.

Mathematical tools for recovery of the load on the fissure according to the micro-CT results

In the present paper X-ray microtomographic research of a molar tooth was conducted. The study revealed regions with a reduced mineral density in the vicinity of the fissure tip. The basic assumption investigated is that corrosion induced enamel mineral density decrease is enhanced by high tensile stresses generated by mechanical load on the occlusal surface of the tooth during crushing of food. Magnitude and location of tensile stress concentration occurs at the fissure tip and may be determined by solving the problem of the stress-strain state of the tooth crown enamel with a wedge-shaped notch. The study of stresses in the vicinity of fissure tip make it possible to construct the boundaries of enhanced enamel virtual fracture. Comparison of the sizes and locations of areas with a reduced enamel mineral density with the sizes and locations of areas of virtual enamel fracture made it possible to establish their approximate congruence. This circumstance made it possible to recreate by mathematical means the nature and magnitude of the force load on the lateral surface of the fissure. Degree of influence of the main parameters of the fissure on the geometrical characteristics of the virtual fracture, such as its area and diameters, were determined.

Relationship between Food Crushing and Oral Function in Older Adults Requiring Nursing Home Care: A Pilot Study.

We investigated how jelly is crushed and examined the relationship between tongue pressure and tongue food crushing ability among older adults requiring nursing home care. Seventy-two participants were instructed to freely crush the test foods soft jelly (SJ) and hard jelly (HJ). We visually evaluated the crushability of the test food and identified the intraoral tissues (active sites) used to crush the test food. The active sites were consistent for all participants for both SJ and HJ, and they included the maxillary and mandibular teeth in 41 participants, teeth and residual ridges in 15 participants, maxillary and mandibular residual ridges in 10 participants, and tongue and palate in six participants. Two participants failed to crush the SJ; the active sites in both participants were the tongue and palate. No participant using the tongue and palate as active sites could crush the HJ. Furthermore, 64 participants could crush the SJ and 23 could crush the HJ using the tongue and palate. The cutoff value of the tongue pressure for crushability of the HJ was 22.0 kPa. Assessing tongue pressure and intraoral active sites involved in food crushing could help determine an appropriate diet for older adults requiring nursing home care.

An investigation of palaeodietary variability in European Pleistocene canids

Temporal and interspecific dietary variability were investigated in three canid taxa, Canis lupus, Canis mosbachensis and Canis etruscus, across a range of British and mainland European wolf assemblages from the Early Pleistocene to Recent periods. Using established cranio-dental indicators to reveal dietary specialisations towards bone eating, flesh slicing, and non-flesh food crushing, inferences were made concerning the proportions of flesh to non-flesh foods in the diet, and hence the level of carnivory adopted by each taxon. Significant temporal differences were found in the diet and frequency of tooth wear of C. lupus from MIS 3, 5a and 7 in Britain. Relative body size comparisons based on lower carnassial length also revealed variation in body size for the Pleistocene age groups, correlating with differences in diet. Stepwise Discriminant Function Analyses revealed large-bodied MIS 5a C. lupus to be hypercarnivorous and specialised in fast flesh slicing and to some extent bone consumption, whereas relatively smaller-bodied MIS 3 and 7 C. lupus were both less carnivorous and more specialised in crushing non-meat foods. Modern wolves from central Sweden are smaller than those of MIS 5a and hypercarnivorous, although with greater specialisation towards crushing of non-meat foods. Temporal variations in diet were related to changes in prey diversity, competition from other carnivores, openness of the environment, and ultimately climate, and reflect the cranio-dental plasticity of C. lupus. In contrast, no temporal differences in diet were found in age groups of C. mosbachensis and C. etruscus, which may relate to more stable overall conditions in comparison to the later Pleistocene. The cranio-dental characteristics of the smaller-bodied mesocarnivore C. etruscus indicate adaptations to non-meat food crushing, whereas in the similarly small C. mosbachensis, enhanced flesh slicing capabilities and reduced crushing abilities indicate that it was more carnivorous than C. etruscus. C. etruscus and C. mosbachensis were both more specialised than C. lupus.

ПРОГРАММНОЕ ОБЕСПЕЧЕНИЕ «СEREC-BIOGENERIC» — ГАРМОНИЯ С ПРИРОДОЙ, ЭКСПЕРИМЕНТАЛЬНОЕ ОБОСНОВАНИЕ ИНДИВИДУАЛЬНЫХ ОСОБЕННОСТЕЙ КЕРАМИЧЕСКИХ РЕСТАВРАЦИЙ

<p>Cause of infringement of functional balance of chewing system most often is teeth. Violation of natural parameters of tooth can lead to change of its function therefore chewing pressure goes not on a tooth axis. At the wrong arrangement and modeling of hillocks the chewed food can be distributed out of limits of an occlusive field. Plane contacts between teeth antagonists complicate uniform crushing of food, load of a periodontium thus increases, the erasing of teeth.</p>

1A2-B03 糖質を摂取する自己充足可能なロボットのための小型食物粉砕システムの提案(バイオミメティクス・バイオメカトロニクス(2))

1A2-B03 糖質を摂取する自己充足可能なロボットのための小型食物粉砕システムの提案(バイオミメティクス・バイオメカトロニクス(2))

Main occluding area in partially edentulous patients: changes before and after implant treatment

The 'main occluding area', the location where food crushing occurs during the first stroke of mastication, is reported to be an important concept; however, it is currently limited to findings in individuals with normal dentition. The purpose of this study was to assess the changes in the location, area and bite force of the main occluding area before and after implant treatments. We enrolled 50 partially edentulous and 22 normally dentate subjects. To identify the location of the main occluding area, each subject was instructed to freely bite once on a dental stopping using the partially edentulous side or the normally dentate area. The location, occluding contact area and bite force of the main occluding area before and after the implant treatments were analysed. The main occluding area was located at a reproducible location in the partially edentulous and normally dentate subjects. This location was principally the first molar region, and for the partially edentulous patients with missing teeth in the molar regions, it moved from the premolar region to the first molar region after treatment. The occluding contact area and bite force for the main occluding area increased (P < 0·05) after the implant treatment in the partially edentulous patients with missing teeth in the molar regions. These results suggest that the main occluding area can be restored to the first molar region after implant treatment and may be an important factor in the assessment of prosthodontic treatment.

The microstructure of enamel, dentine and cementum in advanced Taeniodonta (Mammalia) with comments on their dietary adaptations

ABSTRACT The cheek teeth of Ectoganus and Stylinodon, the most derived genera of Taeniodonta following recent phylogenies, show various morphological and microstructural characteristics that are unusual for herbivores of their size. Their continuously growing premolars and molars have blunt occlusal surfaces without shearing facets and enamel is restricted to the lingual and buccal sides of the teeth. The anterior and posterior walls of the teeth are covered with a thick layer of cementum to which the periodontal ligament is attached. The enamel band is relatively thin. The schmelzmuster is one-layered and features weakly developed Hunter-Schreger bands that are only recognizable in longitudinal section. In cross-section, the enamel prisms show a ‘keyhole pattern’ with an incomplete prism sheath. There is no interprismatic matrix. The microstructure of the dentine has the regular mammalian pattern and shows no special similarity to that of xenarthrans. Taeniodonts seem to have used their hypsodont cheek teeth almost exclusively for squeezing and some crushing of food and only to a minor degree for grinding. Weakly developed Hunter-Schreger bands indicate only light loading during mastication.

Oral physiology and mastication

Mastication is a sensory-motor activity aimed at the preparation of food for swallowing. It is a complex process involving activities of the facial, the elevator and suprahyoidal muscles, and the tongue. These activities result in patterns of rhythmic mandibular movements, food manipulation and the crushing of food between the teeth. Saliva facilitates mastication, moistens the food particles, makes a bolus, and assists swallowing. The movement of the jaw, and thus the neuromuscular control of chewing, plays an important role in the comminution of the food. Characteristics of the food, e.g. water and fat percentage and hardness, are known to influence the masticatory process. Food hardness is sensed during mastication and affects masticatory force, jaw muscle activity, and mandibular jaw movements. When we chew for instance a crispy food, the jaw decelerates and accelerates as a result of resistance and breakage of food particles. The characteristic breakage behaviour of food is essential for the sensory sensation. This study presents a short review of the influence of oral physiology characteristics and food characteristics on the masticatory process.

Influence of oral characteristics and food products on masticatory function

Mastication is a complex process that involves activities of the facial muscles, the elevator and suprahyoidal muscles, and the tongue. These activities result in patterns of rhythmic mandibular movements, food manipulation, and the crushing of food between the teeth. Saliva facilitates mastication by moistening food particles, making a bolus, and assisting swallowing, whereas food consistency modifies masticatory forces, the mandibular jaw movements, the duration of the mastication cycle, and the number of cycles preceding the first swallow. Jaw elevator EMG activity research shows a clear relation between muscular activity and food properties. The teeth, masticatory muscles, and temporomandibular joints are also important because together they form the mechanism by which the food particles are fragmented. Hard and dry foods require more chewing cycles and a longer time in the mouth until swallowing for sufficient breakdown to take place and for enough saliva to be added to form a coherent bolus safe enough for swallowing. Product characteristics, the amount of saliva, dentition, and bite force affect the chewing performance. This study presents an update and synopsis of the effects of saliva, food, dentition, muscle force, and temporomandibular disorders on the masticatory process.

そしゃく機能からみた選択

The characteristics of full balanced occlusion (FBO) and lingualized occlusion (LO), which are occlusions that make up removable dentures, were investigated from the standpoint of masticatory function, and an attempt was made to clarify criteria for selecting and configuring occlusions to suit individual cases. Since there have been few studies that have quantitatively compared FBO and LO from the aspect of masticatory function, we decided to organize and present the characteristics of both in this paper based on our findings from studies carried out in our department. We found that LO offered a higher ability of food crushing, showed higher masticatory performance in the case of hard foods, displayed faster as well as smoother masticatory movement, and showed chewing patterns that were closer to the chopper type compared with FBO. Moreover, subjective evaluation by subjects indicated that "it was easier to eat and the food tasted better" with the LO compared with the FBO in the case of general foods. Furthermore, a comparison of anatomical form and bladed form of upper lingual cusps in the case of LO showed no difference between the anatomical form and the bladed form in terms of masticatory performance in the case of any of the test foods, but the bladed form offered a higher ability of food crushing, displayed faster and smoother masticatory movement, and showed chewing patterns that were closer to the chopper type. In addition, subjective evaluation by subjects showed that it was easier for them to eat raw carrots and pickled radish, which are hard foods generally thought to be difficult to eat with dentures, with the bladed form compared with the anatomical form.

頬側こう頭間隙量が負担圧分布に及ぼす影響 シミュレータによる検討

Various types of occlusal scheme have been developed for a complete denture. Some investigators recommended lingualized occlusion as the scheme of occlusion for acomplete denture, but how to determine the buccal interocclusal distance in lingualized occlusion isunclear. The purpose of this study was to investigate the influence of the buccal interocclusal distance in lingualized occlusion on the pressure distribution under a complete denture. In this study, eight pressure transducers were placed in the basal surface of a mandibular denture. The pressure distribution under a complete denture and the required force were recorded when crushing three different foods: kamaboko, carrot, and peanuts.The results were as follows:1. The required force for crushing all test foods decreased as the buccal interocclusal distance increased.2. During the food crushing tests the positive pressure values were observed mainly on the working side and the positive pressure values decreased as the buccal interocclusal distance increased.3. The negative pressure values were observed on the non-working side, and the negative pressure values decreased as the buccal interocclusal distance increased.4. The required force for crushing test foods and the pressure applied to supporting tissues greatly decreased when crushing hard foods.

Masticatory muscle responses associated with unloading of biting force during food crushing.

The aim of this study was to evaluate masticatory muscle responses during food crushing. Electromyograms were recorded simultaneously with mandibular movement and the sound of food fracture in eight healthy adult males at the superior and inferior heads of the lateral pterygoid muscles, the anterior belly of the digastric muscle, the temporal muscle, and the masseter muscle. After fracture of the food, silent periods of the elevator muscles and excitatory responses of the depressor muscles were observed. The latency and duration of the silent periods increased significantly with increasing incisal velocity after fracture. The mean latency of the excitatory responses of the depressor muscle was stable. After the application of anaesthetic into the temporomandibular joint capsule, the excitatory response disappeared, whereas the silent period was partly maintained. These findings suggest that the excitatory response of the depressor muscle occurs via a polysynaptic reflex arc, and that several reflex arcs are involved in the development of the silent period during food crushing. An important role for the temporomandibular joint receptors is implied.

そしゃく時の食物動態に関する研究

The object of mastication is to crush food and form a swallowable food bolus. To comprehend masticatory function, it is essential to understand food behavior during mastication. However, there are almost no reports available there of.The purpose of this study was to observe food behavior after food crushing and consider the association between food behavior and chewing patterns.I designed a new method to estimate food behavior. Peanuts, which were chewed, were gathered separately from the buccal side and lingual side after varying numbers of chewing strokes, and then the amount and the degree of crushing of each peanut was measured. As subjects, twenty cases of chewing sides were selected, and food behavior and chewing patterns were measured. The results were as follows:1. As mastication proceeded, the amount of broken peanuts on the buccal side decreased significantly and those on the lingual side increased gradually. In addition, the degree of crushing was higher on the lingual side than on the buccal side.2. Food behavior was influenced by chewing patterns. The amount of peanuts on the lingual side was greater and the degree of crushing was less in case of Type III (compound type) than Types I (grinding type) and II (chopping type).

Contribution of periodontal receptors and food qualities to masseter muscle inhibition in man.

Previous studies of human muscle inhibition during chewing have shown that many factors contribute to the incidence and intensity of this reflex but few studies have been in a physiological context. During the first crushing cycle of brittle foods ipsilateral masseter muscle EMG, mandibular movement and vibration were recorded simultaneously in four healthy dentate subjects. Experiments were repeated before and during anaesthesia of the cheek teeth on the chewing side. The results suggest that vibration seems to be the most important factor in muscle inhibition during food crushing; conversely periodontal sensation, mandibular closing movement and the preload by the muscle at the onset of food fracture play a minor role.

Short electromyographic bursts in the rabbit digastric muscle during the jaw-closing phase

Masseter and digastric muscle activities and jaw movement trajectories were recorded in freely moving rabbits during eating. The patterns in these trajectories and activities were similar to those described in previous studies on restrained animals. Although the duration of masticatory sequences, which started with food intake followed by grinding movements and ended by swallowing, varied, the total number of chewing cycles in a chain of masticatory sequences was consistent (1043 ± 51, mean ± SD; n = 5, for chow pellets) among the animals tested. When animals ate hard foods, extra bursts in the digastric electromyograms occurred frequently in the jaw-closing phase. The digastric activities were rather short (6.1 ± 1.0 ms; n = 100) and the amplitude of these digastric short bursts (DSBs) was much larger (1.69 ± 0.81 mV; n = 100) than in the opening phase (0.56 ± 0.33 mV; n = 100), which actually depressed the jaw. When a soft food (bread) was tested, this activity was not observed. The proportion of occurrences of the DSB in a chewing cycle was high at the slow-closing phase, indicating that the DSBs were due to tooth contacts during food crushing. Of 1035 chewing cycles examined in the five animals, 124 were associated with a DSB and 415 cycles with a masseter inhibitory period (MIP). The proportion of the occurrences of the MIP was significantly larger than that of the DSBs. Of 124 DSBs, 85 (68.5 per cent) coincided with an MIP. Four were not associated with clear MIPs, although there was masseter activity at the time of the DSBs. The other 35 DSBs were out of phase with the masseter bursts, although still in a closing phase. The durations of the MIPs accompanied by a DSB were significantly longer than those not so associated. The DSB may be a reflex response mediated by periodontal mechanoreceptors when the upper and lower teeth come together while chewing hard food. The reflex arc for the DSB may be independent of that for the MIP, and the threshold for the DSB may be higher.

Predicting foodstuff from jaw dynamics during masticatory crushing in man

In previous in vitro experiments using an Instron instrument, each test food was found to have characteristic textural properties. In vivo experiments were now made (1) to determine the degree to which variations in the vertical jaw movements during the crushing phase of mastication can be explained by the inherent properties of the foodstuff being chewed, and (2) to establish the degree to which the foodstuff being chewed can be identified by certain features of the jaw dynamics. Five adults were used for chewing tasks with standardized pieces of beef, carrot or peanut. Each subject made two trials with each foodstuff. The movement of the lower incisal point was monitored; features of movement associated with jaw closing in the first chewing cycle were considered. Five of these features were not suitable to categorize the various test foods. Each of the remaining 4, however, was able to distinguish either one food from the 2 others (2 cases), or one from another (2 cases). Pattern recognition techniques based upon principal component analysis could differentiate jaw closing patterns associated with chewing beef from those involving peanut or carrot. The extent to which peanut could be distinguished from carrot was not as predictable as the categorization of peanut or carrot versus beef. Cross-correlation of in vitro force-time breakage characteristics and the jaw movement data showed that on average 52% of the variation in the vertical jaw movement during crushing of food could be explained by the inherent properties of the food. Because the masticatory apparatus acts as a low-pass filter, the high-frequency components of food breakage characteristics found in vitro were attenuated in vivo. It appears that the inherent filter properties of the masticatory apparatus limit the range of sensory and motor function of the jaw.

Evaluation of masticatory efficiency using TV-measuring analyzer

In order to evaluate masticatory efficiency easily, the method of appreciation of chewing ability was determined applying the particle analyzer by TV measuring system (PLAMSYSTEM). Ten subjects with normal dentition were tested. The test food was two grams weight of peanut. After 10 masticatory strokes, the crushed particles remaining on 10 mesh sieve were measured. The sieve-analysis represented particles as the equivalent of sphere, therefore, in this study, particle size distribution was analyzed by the equivalent of diameter.1. The particle size distribution showed a peak at 2-2.5mm diameter. In a part of large particles, the number of particles exhibited rapid decrease, and the particles above 4mm were few.2. In the particle weight distribution obtained by calculating from the size distribution, the chewing ability were divided into three patterns according to the difference of the distribution in a part of large particles.3. With increase of masticatory strokes, large particles were crushed selectively.4. The ability of food crushing was observed clearly in the particle weight distribution, especially in the part of large particles.

Research into mastication*

An electronic method of recording displacement was used to study mandibular movement during mastication. The technique enables the parameters of muscle activity, the sound of tooth contact, the force developed between opposing teeth, and the displacement of the mandible to be recorded at the same time on a single U/V chart. Previous reports on mandibular movement using cine-photographic techniques were confirmed in relation to mastication, but additional information was obtained in relation to muscle activity in the final closing movements. It appears that tooth contact initiates a latent-silent period in masseter and temporalis which occurs before movement is arrested in the final intercuspal position. It is considered that the kinetic energy of the mandible on closing is reduced by the cessation of activity in these two muscles during the silent period and finally absorbed by the crushing of food during the terminal intercuspal slide to rest. A description of mastication is given and a theory advanced that this may be controlled by a central clock mechanism.

Use of the First Gill Slits for Water Intake in a Shark

ABSTRACT The use of the first gill slits as an alternate or accessory route for the intake of respiratory water in the Port Jackson shark is described. This pattern of ventilation is an effective means of oxygenating the blood, but not as effective as normal respiration using the mouth. The use of the first gill slits for water intake is thought to allow respiration to continue during either the crushing of food or obstruction of the mouth while scavenging for food on the bottom. This therefore provides an interesting parallel with the use of the spiracles in skates and rays.