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At least 1,621 records · Page 90Linked to original sources
PubMed1980

[Physiological movements of the teeth].

Studies of 17 test subjects with inductive path recorders in paraocclusal splints showed that 1. With extreme changes in the position of the mandible without antagonist contact and during empty mastication, lingual and distal (anterior to mesial) as well as cranial/caudal movements of the teeth (up to 60 micrometers) are within physiologic limits. 2. With friction (grinding), definitive pathologic alterations develop in the periodontium when this functions is exercised for a longer period of time as bruxism. 3. Guidance of the canine teeth alone protects the lateral teeth from unphysiologic movements.

Bruxism↗
PubMed1981

[Prandial stimulation of reticular movements in sheep: cephalic phase and oral reflex (author's transl)].

Acceleration of reticular contractions when chewing feed (oral reflex of the reticulum, ORR) has been well documented for many years. The aim of the present investigation was to study the evolution of this reflex throughout the meal period. A possible triggering effect of drinking water was also investigated. Reticular contractions and chewing movements were simultaneously recorded from four sheep by means of permanent reticular wire electrodes and foam rubber balloons fastened below the lower jaw. Records were drawn before and during presentation of feed, then during the meal which followed. Similar records were drawn while sheep were drinking during intervals between feeding periods. In every case, intensity of mastication decreases from beginning up to the end of the feeding period. This decrease is paralleled by a slope of reticular frequency, which is very high at the beginning of the meal. The significant correlation between the two phenomena suggests that the decrease of the ORR results from a lesser stimulation of oral mechanoreceptors. Reticular movements are obviously accelerated during isolated drinking periods. Existence of a true cephalic phase of prandial reticular stimulation is evidenced by a moderate acceleration on the sole presentation of feed.

Animals↗
PubMed1995

Generation of masticatory rhythm in the brainstem.

Mastication is a typical rhythmical behavior in mammals. Like respiration, it is now generally accepted that the motor command for the basic pattern of rhythmical oral-facial movements is generated by a neuronal population in the brainstem (central pattern generator, CPG). The central pattern generation of rhythmical masticatory movements can be divided into three processes: (1) generation of the masticatory rhythm, (2) generation of a pattern of activities of the jaw, tongue and facial muscles, and (3) coordination of the activities of these muscles. There are several lines of evidence that the masticatory CPG is functionally subdivided into two neuronal groups: one for generation of the masticatory rhythm, giving the timing signal for rhythmical alternation of jaw closing and jaw opening (central rhythm generator, CRG), and the other for generation of the spatiotemporal pattern of activities of the jaw, tongue and facial muscles. This review will deal, first of all, with the localization of the CRG for rhythmical masticatory jaw movements, sources for its activation, and the premotor neurons mediating its output to the trigeminal motoneurons. Next, we will discuss the neurochemical basis for rhythmical trigeminal motoneurons activity as well as central masticatory rhythm generation. Finally, our recent attempt at induction of neural activities reflecting sucking movements (fictive sucking) in an in vitro preparation is presented.

Animals↗
PubMedDate not supplied

Three-dimensional movements of a maxillary complete denture: the development of a measuring system and preliminary measurement.

To measure the movements of a maxillary denture in vivo it is necessary to analyze the three-dimensional displacements induced. A measuring system consisting of four main units (a magnetic sensor, three optical fiber sensors, a sensor-setting jig, and a recorder) was developed. Using this system, the movements of a maxillary denture were continuously measured during tapping and during the mastication of a peanut.

Aged↗
PubMed1994

Age-related changes to the surface ultrastructure of the rabbit temporomandibular disc.

The ultrastructural characteristics of the temporomandibular disc were investigated by transmission electron microscopy in rabbits, aged from 7 d to 6 y. The disc is interposed between the head of the mandibular condyle below, and the squamous temporal bone above, within the temporomandibular joint. A single layer of flattened mesenchymal cells covered the articular surface of the disc during early postnatal development. Gradual disappearance of this cell layer was succeeded by the development of an articular surface lamina. The first appearance of the lamina coincided with the transition from suckling to adult masticatory function. With advancing age, the lamina increased in thickness from 0.3 to 1.0 micron in adulthood, and was well demarcated from the subsurface tissue. The lamina was a continuous, smooth, electron-dense layer, that reacted biochemically as proteoglycan complex. The surface lamina may be responsible for the low frictional properties associated with articular movement and load, and the selective passage of molecules bidirectionally across the cartilage-fluid interface. Variations in lamina thickness occurred topographically across the disc and were attributed to site concentration of shearing stress. Beneath the articular surface lamina were cells surrounded by collagenous intercellular stroma. Chondrocytic, fibrocytic and fibrochondrocytic cellular phenotypes were present. Subsurface cellular debris accumulated within the rabbit disc from the commencement of mastication. Mature adult disc contained expanses of debris, attributed to cell death in situ. Foci of mineral precipitates were found within ageing discal tissue.

Aging↗
PubMedDate not supplied

Oral stereognostic ability and masticatory performance in denture wearers.

This study examined the relationship between masticatory performance and oral stereognostic ability in 71 dentate individuals and 64 denture wearers. Stereognosis was evaluated in denture wearers with and without dentures in place. No significant differences (P > .05) were noted between the stereognostic scores of either group, with both groups correctly identifying approximately 68% of the items. This suggests that the receptors in the periodontal ligament are of minimal importance in the oral detection of shape and that the loss of teeth and placement of dentures does not diminish the perception of shape differences. Correlations between masticatory performance and stereognostic measures ranged in magnitude from 0.01 to 0.12 (P > .05). Further studies employing smaller test forms may be needed to assess the role of stereognosis on food manipulation during mastication.

Aged↗
PubMedDate not supplied

Ten-year longitudinal study of masticatory function in edentulous patients treated with fixed complete dentures on osseointegrated implants.

Twenty-three edentulous patients who had been treated with a mandibular fixed complete denture retained by osseointegrated implants were followed over a 10-year period. Nine of these patients had received a maxillary fixed implant-supported complete denture prosthesis after the initial placement of the mandibular restoration, while the remainder still used a conventional maxillary complete denture. The maximal occlusal force or mastication efficiency index of those having fixed implant-supported prostheses in both arches did not differ markedly from those having only a mandibular restoration. However, at the 3-year examination, lower values were recorded for the self-rated masticatory ability, while higher values were given after 10 years. It was concluded that placement of a mandibular fixed implant-supported prosthesis in dissatisfied complete denture wearers led to a dramatic improvement of masticatory function that was quite acceptable for many patients. However, some patients subsequently demanded a maxillary fixed prosthesis to feel satisfactorily rehabilitated.

Bite Force↗
PubMedDate not supplied

Age-related change of masticatory function in complete denture wearers: evaluation by a sieving method with peanuts and a food intake questionnaire method.

Age-related changes in masticatory function were investigated in complete denture wearers. The sieving method using peanuts as a test food was compared with the result obtained using a food questionnaire for evaluation of masticatory function. In relationship to aging, both the masticatory performance and the chewing score decreased significantly (the masticatory performance: r = .60, P < .01; the mastication score: r = -.46, P < .05). It is suggested that the masticatory function in complete denture wearers decreases in relationship to aging. The food intake questionnaire is useful for evaluating masticatory function in complete denture wearers.

Age Factors↗
PubMedDate not supplied

Hypoglossal responses elicited by periodontal afferent activation in the rat.

Mechanical stimulation of the ipsilateral incisor tooth in the rat evoked reflex discharges in the hypoglossal nerve branch innervating the intrinsic and extrinsic tongue muscles. Stimulation elicited biphasic potentials in the whole XIIth nerve and influenced the unitary firing rate in 54 out of 80 fibers tested. The fiber responses were characterized by excitation or inhibition in frequency discharge or sequences of excitation-inhibition or inhibition-excitation. The results observed suggest that the periodontal-hypoglossal reflexes play a role in the control of tongue position during mastication.

Afferent Pathways↗
PubMed1994

Scanning electron microscopy of the wild boar and pig lingual papillae.

Lingual papillae of wild boar and pig were studied by means of scanning electron microscopy (SEM). Vallate papillae appear with the typical circumvallate morphology. Their papillary bodies show conical or fungiform-like and spicule-like pseudopapillae in both animals. Taste pores were seen in the papillary grooves. Microplicae or pits are visible at high magnification. In pig and wild boar similar foliate papillae were observed. Pig has less but wider leaves than wild boar. Taste pores on papillary walls were viewed. At high magnification microplicae were seen. Morphologically, fungiform papillae correspond with their denomination. Taste pores open onto the upper surface and they are easily identifiable by SEM. The rostral and lateral regions contain the major number of fungiform papillae. The lateral papillae of wild boar and pig show a high number of pores per papilla. These regions must be considered important in taste sensitivity. Lateral papillae in both animals could provide a source of taste buds for study. In both animals the fungiform papillary epithelium showed a pitted appearance as a consequence of keratinization by food environmental stress. The filiform papillae can be both simple and compound (with body and hairs). Large conical papillae are located caudally and curved in the same direction. Filiform and conical papillae have a function in food mastication, handling and deglutition.

Animals↗
PubMed1994

Application of bioactive ceramics for functional surgery in masticatory organs.

Transplanted and replanted autogenous teeth or implanted artificial roots become easily ankylotic. However, if adequate functional loads are applied to them continuously postop with proper fixation, ankylosis can be prevented. The author found this fact through studies on autogenous tooth replantation 20 years ago. Therefore, not only can tooth transplantation, replantation, and artificial root implantation be done successfully with adequate functional loads, but surgical orthodontics as well as plastic operation of jaw deformity can also benefit in the same way. This therapeutic method is called functional surgery. The ankylotic process can be more effectively prevented by applying bioceramic granules. Using these methods, (a) 30 vital teeth in 23 patients were transplanted or replanted. Follow-up duration was 6 to 96 months. (b) Artificial roots made of compact sintered hydroxyapatite (apatite) were implanted under the new concept of functional surgery. In all, 57 artificial roots in 19 patients were implanted and observed for over 5 years. (c) Masticatory skeletal deformities of the viscerocranium were treated with the new concept of functional surgery applying sintered apatite. For this purpose, artificial bone implantation or simple gnathoplasty, tooth transplantation, and artificial root implantation was carried out in 15 patients, after which mastication training was applied with concomitant corrections of function inclination, i.e., oral-perioral habits. In these clinical experiments, excellent favorable results were obtained. The following conclusion was obtained: Introducing the new concept of functional surgery using bioceramics, not only tooth transplantation, as well as artificial root therapeutics, but deformity of the jaw can be steadily treated.

Adult↗
PubMed1994

[Trends in geriatric dentistry and the future--from the point of view of masticatory function].

In recent years the number of aged persons in developed countries has been steadily increasing. Tooth loss is a typical age-associated stomatognathic change, and edentulism rates in Japan have been reported to be 30%. Dentures are made to restore oral functions after the natural teeth have been lost. However, there are also many stomatognathic changes associated with aging as well as oral manifestations of systemic diseases which can make the wearing dentures difficult in elderly persons. Some of the more significant changes occur in the structure of the mucosa, the function of the oral musculature, the temporomandibular joint, the taste perception, salivary function and the nervous system. Studies on the variety of physical and psychological dynamics associated with the aging process are necessary to provide the latest treatment modalities for the aged. The mastication and dentition status in elderly persons are suggested to be closely related with many kinds of physiological functions. On the other hand, stomatognathic functions are suggested to be influenced by the health of the entire body. They are supposed to have an interdependent relationship. The maintenance and care of occlusion are essential to guarantee the quality of life for the elderly. In future, the relationship between masticatory function and physical activities, such as physical exercise, blood flow, respiration, endocrine function, reproduction etc. require further investigation.

Aged↗
PubMed1994

Muscle spindle and periodontal trigeminal afferents modulate the hypoglossal motoneuronal activity.

Hypoglossal responses to electrical or natural activation of the afferent fibers of the masseteric nerve and to periodontal mechanoreceptors were recorded in rats. Electrical stimulation of the masseteric nerve, at an intensity adequate to excite prevalently the primary spindle afferents, induced various sequences of excitation-inhibition and inhibition-excitation in 55% of the tested hypoglossal motoneurons. Responses were characterized by excitation, inhibition or excitation-inhibition sequences occurring at short and long latencies. Different pattern of responses were evoked in both the protrusive and the retractive motoneurons of the homolateral hypoglossal nucleus. Moreover, jaw lowering and pressure on the incisor tooth induced antagonistic and synergistic effects on the electrical activity of the same hypoglossal motoneurons. The results show for the first time that afferent signals from both muscle spindles and periodontal receptors modulate the activity of the hypoglossal motoneurons aimed at controlling the tongue position in the mouth during mastication.

Action Potentials↗
PubMed1993

Masticatory improvement using osseointegrated implants: analysis of Japanese patients' responses through questionnaires.

Masticatory improvement obtained by the use of osseointegrated implants (Brånemark System) was analyzed through questionnaires collected from 22 Japanese patients. The questionnaires were designed to assess mastication of different Japanese foods. The postoperative score of masticatory function obtained by analysis of the questionnaires was 90.9, as opposed to the preoperative score of 43.9. A multiple regression analysis indicated that the number of placed implants has no significant effect on the improvement of masticatory function, whereas preoperative performance does. Further, the degree of masticatory improvement showed variation according to the condition of the dental arch opposing the implant prostheses. The group having implant prostheses in the opposing arch showed the highest improvement.

Adult↗
PubMed1993

[A study of mandibular movement velocity and acceleration in young adults with normal people].

The velocity and acceleration of mandibular movements including the border movement, habitual movement and functional movement were studied in 25 young adults by using D-SGG measuring instrument. The results showed that the conception of functional velocity and the maximum velocity of mandibular movement were developed. The physiological and clinical significance of the value of mandibular movement acceleration can be explained by Newton's Second law, F = ma. The author pointed out that in order to keep the necessary masticatory efficiency, the masticatory velocity enjoy the priority in matching with the masticatory force in mastication.

Acceleration↗
PubMed1993

[The functional occlusal contact area and masticatory efficiency in complete denture].

The authors developed a new method to measure the occlusal contact area in complete denture by using the IBAS 2000 (Interactive Image Analysis System). The masticatory efficiency and functional occlusal contact area were measured and analysed for 16 cases of complete dentures. The results showed that the relation between occlusal contact area and masticatory efficiency was positive significantly and different region of occlusal contact area had its corresponding masticatory efficiency. It is indicated that a given occlusal contact area is necessary to satisfy the masticatory efficiency required. If the masticatory load is great the width of supporting cusp should be reduced and a definite width of nonsupporting cusp should be preserved for holding the food being masticated.

Aged↗
PubMed1995

Automatic measurement of on/off periods of EMG activity.

A computer-based system was designed and implemented for automatically measuring the periods of EMG burst that show periodic but occasionally irregular and large fluctuations in amplitude during mastication. The reliability of the current measuring system was examined. The EMG data was recorded from the inferior orbicularis oris (OI) muscle and the anterior belly of the digastric (DG) muscle by means of surface electrodes. Applying the current method to the human masticatory and perioral muscle activity during chewing revealed that the absolute differences between human- and computer-determined measurements did not differ significantly. We conclude that the proposed measuring system is effective for automatic measurement of on/off periods of EMG burst.

Algorithms↗
PubMed1996

[Dental rehabilitation using osseointegrated implants: treatment of oro-maxillo-facial cancer. A preliminary study of 7 cases].

Edentulism is often reported after treatment for malignancy of oral cavity. The resulting deformities from loss of teeth and bone create a "social invalid" with difficulties in articulation and mastication. Prosthetic rehabilitation was difficult because of two problems: the risk of osteoradionecrosis development and local anatomic modifications. The introduction of osseointegrated implants improved results of oromandibular reconstruction. A preliminary report of nineteen Branemark implants of seven patients is reported here. Implants have been in place and functioning for a period of one to four years. No major complication occurred and osseointegration permitted good oral rehabilitation. Placement of osseointegrated implants in osteomyocutaneous flaps and in irradiated bone is discussed.

Adult↗