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At least 1,531 records · Page 85Linked to original sources
PubMed1998

Satiation and masticatory function modulated by brain histamine in rats.

Both the ventromedial hypothalamus (VMH) and the mesencephalic trigeminal sensory nucleus (Me5) are densely innervated by histaminergic neurons. The depletion of neuronal histamine (HA) from the Me5 by the bilateral microinfusion of 448 nmol/rat alpha-fluoromethylhistidine (FMH), a specific suicide inhibitor of histidine decarboxylase, reduced the eating speed and prolonged meal duration, while leaving the meal size unaffected. HA depletion from the VMH increased the size of the meal and prolonged its duration, but not the eating speed. When the HA turnover rate was measured at 15 min after the scheduled feeding following fasting for less than 24 hr, the rate increased in the region including the Me5, but not in the hypothalamus. The turnover rate reached higher levels at 60 min in both regions. Gastric intubation of an isocaloric liquid diet or an equivolume of water with the liquid diet abolished the increase in HA turnover both in the Me5 region and the hypothalamus. The present findings indicate that brain HA thus modulates satiation through both the VMH and masticatory function as well as due to the action of the Me5. The HA function activated by mastication began earlier in the Me5 and later in the hypothalamus due to a signal originating from the oral proprioceptors and initiated by chewing.

Animals↗
PubMed1992

[Masticatory training with chewing gum on young children].

Mastication is a developmental function. It matures through learning experiences. The biting force is one of the components of masticatory function. The biting force increases with age. During the developmental stage, it is believed feasible to enhance the maturation of the masticatory function by increasing the biting force. The previous results of masticatory training for adults and school children had revealed 20% to 30% increase of the biting force. In this study, masticatory training with specially fabricated chewing gum for young (preschool) children was performed. The subjects were 5 males and 5 females from 3 years old to 5 years old. These children were instructed to bite on the chewing gum for 5 minutes, 2 times a day, for 3 months. The results show that there was a 94% average increase of biting force after 3 months of training. It was also noted that the rate of the increase of the biting force was remarkable during the first month of training.

Age Factors↗
PubMed1993

[Clinical study of masticatory movements in complete denture wearers--paths of masticatory movements and occlusal contacts].

Bilateral balanced occlusion is believed to be one of the ideal types of occlusion for a complete denture since the occlusal contacts on the non-working side are concerned with the stability of the complete denture during mastication. In this study, the role of the occlusal contacts on the non-chewing side was investigated. The paths of masticatory movements were measured by sirognasograph and the occlusal contacts on the non-chewing side were measured by the 6-channel telemetry system. The results were follows; 1. The frequency of normal chewing pattern was observed to be higher in chewing on the habitual chewing side than in chewing on the non-habitual chewing side. 2. The average value in lateral deviations at the maximum opening point and maximum lateral closing point was larger in chewing on the habitual chewing side than in chewing on the non-habitual chewing side. 3. Excursive closures were found in 36.0-71.1% among the total closures when chewing on the habitual chewing side and 4.9-20.9% on the non-habitual chewing side. 4. The majorities of the excursive closures consisted of glidings from the lateral position to the centric position. 5. The width of the gliding in lateral excursion on the occlusal surface of the lower first molar was mostly 0.2-1.2mm.

Aged↗
PubMed1994

[Short-latency responses of jaw-movements to loading and unloading in complete denture wearers].

The reaction of the masseter muscles was studied by giving various loads to the mandible. Five dentulous volunteers and five edentulous patients participated in this study. They were asked to bite two bars in which the upper was immovable and the lower was connected with the torquemotor and to maintain the mandibular position although their mandibles were given the load changes. The load changes corresponded to the food consistency and were performed by the torquemotor rapidly. When the load force increased rapidly, the full-rectified electromyographic activity of the masseter muscle was facilitated 7.5-9.4 ms in the dentulous and 9.3-11.7 ms in the edentulous. Similarly, when the load force decrease rapidly, it was depressed to 11.1-12.9 ms and 10.6-16.4 ms, respectively. The number of synapses in the neuronal mechanism of loading and unloading reflexes showed no difference between the edentulous and the dentulous. Therefore, it is clear that the periodontal mechano-receptor does not cause the loading and unloading reflexes. As a result, the author suggests that the main receptor for the rapid masticatory movement should be the jaw-closer muscle spindle, which implicates that the complete denture wearers can masticate various kinds of foods smoothly.

Adult↗
PubMed1999

[Functional mobility measurement of removable partial dentures using newly-developed analyzing system in six degrees of freedom--effect of cusp inclination of molar artificial teeth on denture displacement in function].

A measuring system to record three-dimensional displacement of removable partial dentures (RPDs) in six degrees of freedom has been developed. The system employed three pairs of photodiode and LED that were set up in a triangle. This system was capable of recording the in vivo RPD displacement with a recording sensitivity of 0.1 mm. In vivo displacement of upper RPDs with unilateral distal extension saddle was investigated using this measuring system to determine the effect of artificial cusp inclination of molar teeth on denture mobility. Two groups of different artificial dentition were switched to be attached to each of three experimental RPDs. The artificial teeth with cusp inclinations were calibrated to contact with opposing natural dentition during lateral grinding of the mandible, while the other artificial teeth were prepared to disclude with the mandibular teeth (flat-cusp group). Displacement range and average position of a reference point at the first molar of the RPDs during mastication were measured and analyzed as a function of the cusp inclination and the test food. As a result, the average displacement of the RPDs toward the edentulous ridge was smaller in the cusp group than that in the flat-cusp group, while the range of horizontal displacement in the buccal-palatal direction was greater in the former group than the latter. The denture wearers demonstrated typical grinding strokes at the end of the closing phase of the mandiblar movements when they chewed a peanut, which was attributed to a wide range of horizontal displacement of the dentures.

Denture, Partial, Removable↗
PubMed1999

[Influence of interocclusal distance of mandibular unilateral distal extension removable partial denture on masticatory function].

The purpose of this study was to elucidate the influence on masticatory function when the mandibular unilateral distal extension removable partial denture changed the interocclusal distance. The experiments, crushability, the sense of mastication, and the masticatory strokes until swallowing, were conducted, on four subjects, using the denture with the apparatus that enabled to change the interocclusal distance. The results were as follows: The particle size distribution showed that the ratio of small particle (diameter 2.5-4.5 mm) decreased, while that of large particle (more than 5.0 mm) increased, on three of four subjects, and the value of crushability diminished. A reduction of the value of crushability when the interocclusal distance was extended more than 800 microns was found. As for the other subject, no change was recognized on the particle size distribution under experimental condition, and the value of crushability showed no significant change.

Dental Occlusion↗
PubMed2001

[A clinical and physiological evaluation of the unilateral occlusal deficit and its RPD treatment--a four-year follow-up study].

The aim of this study was to evaluate the longitudinal clinical and physiological changes in masticatory function for unilateral shortened arch, partially edentate patients by treatment with removable partial denture prostheses from the denture insertion over approximately four years of observation. The present follow-up study was conducted using objective findings and standpoints of unilateral occlusal deficit case, especially the clinical and physiological relation between musculature activity and changes of load center location periodically. The changes in masticatory functions by the muscle activity observed in EMG, and the occlusal loads and distributions throughout the arc, were surveyed by the modified Prescale system. The findings were statistically analyzed by using a sophisticated computer system that was developed by our research institute. The results were as follows: i) The functional musculature of unilateral shortened arc patients was clearly activated by using the unilateral RPD, and the improvements continued for four years after initial denture insertion. ii) The activation of masticatory muscle by denture-wearing over time, was in edentate side masseter, although the amplification of anterior temporal muscle was distinct in mandibular cases. iii) The muscle activity during rhythmical motion, such as tapping with denture-wearing, increased about two times than that of two and three years from the starting edentate value similarly to the clenching values within the measured period. iv) The masticatory efficacy of unilateral free end saddle prosthodontics was estimated using the changes in I-EMG values during peanut mastication. These findings suggested that the use of RPD accomplished an arc form and improved masticatory function for agglomeration of foods and masticatory efficiency over time.

Adult↗
PubMed1998

Chewing performance and occlusal contact area with the shortened dental arch.

The aim of this study was to investigate the effect of the loss of posterior teeth on the effectiveness of mastication. To evaluate this, chewing performance and occlusal contact area were investigated in 10 edentate subjects having implants stabilising a mandibular overdenture. A copy of the original lower denture was made for each subject, with removable teeth, which could be separated to convert a complete dental arch to a shortened dental arch, an extremely shortened dental arch, or a broken dental arch. Both post canine occlusal contact area and chewing performance demonstrated significant differences between the different arches. It was concluded that chewing performance is reduced by removing posterior teeth from implant stabilised mandibular complete dentures.

Bicuspid↗
PubMed1976

[2 cases with unusual lid-jaw co-movements].

General review of the literature makes it apparent that there exist various combinations of associated movements between cranial nerves. Most of them involve four of nerves, the oculomotor, the abducens, the facial, and the motor potion of the trigeminal nerve. We report two patients in whom left upper eyelids produced peculior up and down movements in accompany with mastication. The one was a 9-year-old female who had shown left eye-lid retraction since 3 months; the other, a 4-year-old male, had produced the synkinesis one year since. Either children showed contraction of left palpebral levators associated with volitional mouth opening, deviation of the mandible toward the right, and sucking. Their pupils were normal and their upper eye-lids showed no ptosis on the affected side. The EEG showed high voltage rhythmic slow waves in parieto-occipital areas bilaterally. Head injuries or hereditary defects not being recorded in their histories, their synkinesis is assumed to be congenital in orgin. Abnormal neural connections have been presumed to be affected in the course of the development between the trigeminal and the oculomotor nuclei within the midbrain. In triggering the synkinesis, however, stretched muscle-spindles of the masseter muscle most play an important role. After all, synchronizing lid-jaw co-movements as observed in our two children represent an unusual pattern of the Marcus Gunn phenomenon.

Child↗
PubMed1999

Membrane stretch and salivary glands - facts and theories.

Cell shape in salivary glands is affected by mechanical forces. In the acini and ducts cell shape is modified by the contractions of the myoepithelial cells in both the secretory and ductal portions of the glands. At the organ level shape changes are due to muscle contraction during mastication, food intake and speech. All these factors may cause some degree of stretching of salivary cell membranes. Recent studies suggest that physical forces influence signal transduction, gene expression, secretory function, cell differentiation and proliferation. Here we overview membrane stretch-activated cellular events. Evidence from a variety of tissues suggests that mechanical forces may alter the properties of acinar cells leading to cytoskeletal reorganisation, changes in ion fluxes, modulation of secretory activity and subsequent release of transmitters such as ATP. Transmitters released from acinar cells may modulate the secretory activity of salivary tissue, and interact with classical regulatory pathways.

Adenosine Triphosphate↗
PubMed1975

[Prosthetic problems after excisional surgery].

The authors present a few cases maxillary and facial reconstruction with restoration of the esthetic appearance, mastication and phonation, using the obturator muscles and prostheses made up of acrylic resin and silicone elastomers.

Acrylic Resins↗
PubMed1975

Analysis of human mandibular movement.

The parametric electrical outputs of the six-transducer mandibulograph were used to analyze three-dimensional pathways, displacement profiles, and velocity profiles of selected mandibular areas during jaw movement. This was accomplished by means of digital computer implementation of derived mathematical equations of motion. Five jaw movements were studied: chewing, open-close, right lateral, left lateral and protrusive. The results demonstrate the analytical and diagnostic value of this method and provice new clarification and insight into the nature of mandibular movements. The following observations summarize the principal findings derived from the analysis of jaw movement patterns of a normal patient. The chewing jaw movement exhibited a smoothly coordinated sequence of events. Lateral jaw motion appeared to be prominent during the masticatory phase and throughout the movement cycle. Mastication was abruptly terminated by a vertical desscent of the mandible through the freeway space, until the condyles began their forward movement producing a rotation in the sagittal plane. T occlusal area continued its downward descent along a nearly vertical pathway producing a compressed figure eight pattern in the frontal plane. The open-close jaw movement exhibited minor periods of hesitancy. Jaw movement was initiated with a forward and downward movement of the condyle occurring at the same time as a downward and backward movement of the occlusal area. This motion produced a rotation in the sagittal plane about a moving axis which was not coincident with the intercondylar axis. The general form of the command open-close jaw movement was that of noncoincident curved pathways in the sagittal plane with little lateral displacement. Closing jaw movement occurred with the condyle in a protruded position...

Adult↗
PubMed1975

[The development of strength in the masticatory muscles and its sensory control].

By means of inductive dynamometers the absolute force of mastication as well as factors influencing that force are studied. In addition to the mechanical effects resulting from the lower jaw's acting as lever arm, the pulp, especially its coronal portion, showed a dominating influence on the extent of the developed adduction force.

Dental Pulp↗
PubMed1976

[Orthodontics and speech therapy].

The author recalls the suction and deglutition are indeed primary functions; mastication and spoken speech are rooted in them. One must also take time, forth dimension, into consideration. The postural state represents the starting point of the movement; one pronounces phonemes just as one holds one's tongue or swallows. Having so described the preparation of the first phase of the first sequence of the swallowing act, the author points out that the unfolding of the process then depends upon neurophysiological laws. Deglutition and phonetic articulation are making use of the same osteo-neuro-muscular effectors. The author is showing the close link there is between dysmorphosis and neuro-muscular dysfunction. In the second part the fact is emphasized that morphological modifications and changes in neuro-muscular behavior go hand in hand and complement each other. Hence the need for a closer collaboration between orthodontists and orthophonists, which may be very useful. The presentation of five case histories of children being in double treatment, e.g. with both the use of an appliance and neuro-muscular reeducation, upholds the argument.

Child↗
PubMed1999

Understanding wear in dentistry.

Tooth wear is an increasing problem in dentistry. Traditionally, it has been divided into three categories: abrasion, attrition, and erosion. However, most clinical cases of tooth wear involve more than one of these processes. It is often easier to make a diagnosis by looking for the signs of the fundamental wear processes rather than trying to categorize the individual case. Wear can be caused by direct surface-to-surface wear, an intervening slurry, or a corrosive environment. Wear occurs during mastication, but also at other times, often at night. Although it may be possible to institute a preventive regimen, this will not always help the patient if his or her prime concern is esthetics. The same processes that cause tooth wear will cause wear to restorative materials. To diagnose and prevent wear, its processes must be understood.

Adult↗
PubMed1976

[Foundations of the neurophysiology of the masticatory organ].

The most important research findings in the field of neuro-physiology of the masticatory system are described, e.g. the clinico-neurological aspects of the swallowing reflex, cortical and subcortical control systems interfering with mastication and especially the two masticatory reflexes taking place at the level of the brain stem, the jaw-opening reflex and the jaw-jerk reflex. A short neuro-anatomic and electrophysiological description of the nucl. tractus mesencephalici, the nucl. supratrigeminalis and the dental pressosensors completes this survey. It concludes with a discussion of possible pathological reflex circles in the pathogenesis of myorthropathies.

Deglutition↗
PubMed1999

Generation of rhythmical ingestive activities of the trigeminal, facial, and hypoglossal motoneurons in in vitro CNS preparations isolated from rats and mice.

The central pattern generator (CPG) for masticatory movements has been located in the medial bulbar reticular formation, by using cortically induced rhythmical jaw and tongue movements as a model. To analyze how stationary input from the cortex is transformed into rhythmical output in the neuronal population comprising the CPG, rhythmical neural activities representing rhythmical food ingestive movements were experimentally induced in vitro. Bath-application of N-methyl-D-aspartate (NMDA) induced rhythmical activities in the trigeminal (V), facial (VII) and hypoglossal (XII) nerves of in vitro brainstem-spinal cord preparations isolated from newborn rats and mice. This paper will review evidence for the notion that (1) the rhythmical XII nerve activity represents rhythmical sucking movements; (2) the population of neurons critically involved in the rhythm generation of the XII nerve is localized in the ventromedial medulla oblongata on both sides, and can induce rhythmical XII nerve activity on the same side independently of each other; (3) the rhythmical activities in the V, VII, and XII motoneurons are induced by separate CPGs, which are located segmentally at the respective level of the V motor, VII, and XII nuclei. In addition, rhythmical masticatory-like EMG activity of jaw muscles can be induced by repetitive stimulation of the pyramidal tract in the in vitro brainstem isolated from adult mice together with the oral-facial structures. We propose that the in vitro brainstem preparation is a useful tool for longitudinal analysis of postnatal development of the central pattern generation of food ingestive movements, including conversion from sucking to mastication.

Age Factors↗
PubMedDate not supplied

Masticatory function in patients with juvenile rheumatoid arthritis.

PURPOSE: Children with Juvenile Rheumatoid Arthritis (JRA) rarely report temporomandibular joint (TMJ) pain, which may be due to pain avoidance mechanisms resulting in compromised masticatory function. This study examined the relationship between self-report measures of pain and dysfunction and measures of chewing performance in 44 JRA children and 34 normal controls. METHODS: The children were divided into three groups: Group 1, JRA children with temporomandibular joint disorder (TMD); Group 2, JRA children without TMD; Group 3, normal control children without TMD. Both visual and analog scales of jaw pain, ability to chew, and quality of life were administered before and after chewing tasks. Children chewed standardized portions of an artificial food for 20 cycles and expectorated the particles into a cup. This process was repeated five times. Median particle size and a broadness of particle distribution index were measured. Also, the number of chewing cycles prior to the child's first swallow for a cube of carrot was recorded. RESULTS: The broadness of particle distribution index was greater for Group 1 (P < 0.001) and Group 2 (P < 0.03) than for Group 3 with no difference in number of chews for carrot mastication among groups. Group 1 reported more pain and dysfunction before the chewing tasks than Groups 2 or 3 (P < 0.05). Interestingly, only Group 3 reported increased pain and decreased ability to chew after chewing tasks (P < 0.02). CONCLUSION: Children with JRA compromise their masticatory function as a pain avoidance mechanism. Such findings may have profound implications with regard to the nutritional status for these children.

Adolescent↗