Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MASTICATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,297 records · Page 72Linked to original sources
PubMed1986

An unusual function for the medial pterygoid muscle in the guinea pig.

This muscle has some physiological properties resembling those of jaw-opening muscles. Biomechanical analysis showed that, because of the anatomical peculiarities of the feeding apparatus in caviid rodents, the action of the muscle changes from closing to opening as the mandibular condyles are protruded in the groove-like mandibular fossa. This unusual changing function may be useful in producing the ventral, medial and anterior power stroke of mastication.

Animals↗
PubMed1991

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.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Estimation of the mechanical lifetime of dental restorations: method and preliminary results.

To assess the clinical performance of restorative materials with respect to mechanical failure, the shape of the restoration, the strength and fatigue properties and the loading history are important. This study deals with the feasibility of a method to estimate the mechanical lifetime of dental restorations. The method takes into account that the mechanical lifetime is a stochastic quantity determined by shape, strength and fatigue properties and by the cyclic nature of the mastication forces. The general outline of the method is described and the necessary experimental data are discussed. Preliminary estimates of the lifetime of a composite and an amalgam restoration are made. The method is found to be feasible and the estimated lifetimes of the restoration are of the same order of magnitude as found clinically.

Bicuspid↗
PubMed1976

A method of measuring pressures against tissues supporting functioning complete dentures.

A metod for measuring pressures exerted by denture bases against the supporting tissues during mastication which yields valid quantitative results was developed. Use of a specially designed diaphragm pressure transducer overcomes the disadvantages of a cantilever-beam arrangement which gave inaccurate results in earlier studies. On going research using this method was described. Several suggestions for additional applications of this method for prosthodontic research were presented.

Dental Stress Analysis↗
PubMed1976

Temporomandibular joint function and its effect on concepts of occlusion.

Many of the premises of dentistry that have evolved empirically have been re-evaluated in the light of newly-developed concepts of TMJ function. Centric relation, although duplicable, may not necessarily be correct. A "functional" centric relation exists when the TMJ radiographs can be correlated with the occlusal findings, in which case, the retruded classical centric relation should be used. When a "dysfunctional" centric relation is present (no correlation between the TMJ radiographs and occlusal findings), the most retruded position should not be used and a therapeutic centric occlusion should be created by the dentist. Subclinical TMJ dysfunction occurs more frequently than commonly thought, because TMJ radiographs are not routinely used. Retruded condylar displacements can be easily overlooked, because the lateral pterygoid muscle has relatively few stretch receptors compared to the elevator muscles of the mandible. Condylar retrusion, therefore, would not necessarily cause lateral pterygoid spasm as might be expected. The exact mechanism of the TMJ suspension system is unknown, although experimental evidence has shown that the condyle can be displaced superiorly with posterior unsupported muscle force. This indicates that the immutability of the condylar path under varying clinical conditions is questionable. Due to the superior displacement characteristics of the TMJ, the condyle does not act as the fulcrum in mandibular kinetics. The fulcrum, therefore, shifts to the teeth and/or bolus, depending on the specific situation. In either instance, whether considering bruxism or mastication, for most patients, an occlusion based on group function is preferable to a canine-protected occlusion to insure TMJ health. Scientifically, no one scheme of occlusion or articulation has been proven to be superior to any other scheme; therefore, the choice is a matter of the personal preference of the dentist.

Cuspid↗
PubMed1976

Tissue pressure under complete maxillary dentures.

This preliminary report has shown the following interesting points: (1) Measurements of tissue pressures beneath dentures are possible using the Sanborn 350 recorder. (2) Stable dentures produce high pressures on the supporting tissues and transmit these pressures from region to region, varying with how the patient uses the dentures. (3) Most often, an opposite large or negative pressure immediately followed the production of positive pressure at the same site beneath the denture. Thus, each movement actually traumatizes the tissue twice. (4) Nonmasticatory pressures produced under dentures are as great as or greater than masticatory pressures. (5) Wave forms for each biting maneuver or sound produced can be charted and are typical for each patient, probably representing denture movement. (6) Swallowing unassociated with eating or drinking produced very high positive and very low negative pressures, giving the greatest ranges of pressures recorded in this experiment. (7) Smoking (recorded in only one patient) also produced a great range of pressures. (8) Sticky foods such as cheddar cheese produced greater negative pressures than the other foods tested. (9) The one patient with natural teeth opposing his denture gave much more uniform and lower pressures than did the patients with complete dentures. (10) This method allows visualization of pressure movement under dentures. The effect of these continually occurring, nonmasticatory, induced pressure changes and pressure waves beneath the dentures may well be of greater significance than that of mastication.

Adult↗
PubMed1979

The measurement of forces transmitted to abutment teeth of removable partial dentures.

Despite the limited number of patients in the study, the following conclusions may be made regarding the magnitude and direction of forces transmitted to abutment teeth of extension-base removable partial dentures. 1. A technique was presented for using strain gauges to determine the magnitude and direction of forces transmitted to abutment teeth of removable partial dentures. 2. There are variations in force magnitude with a patient and between patients from chewing cycle to chewing cycle. 3. The transmitted forces vary when different removable partial denture designs are used. 4. Improving adaptation of the extension bases to the residual ridge is an excellent means for providing maximum support, increasing patient comfort, and decreasing forces to abutment teeth. 5. Extension bases apply mesially directed forces to abutment teeth during mastication. 6. Further research is needed to elucidate the effects of the various philosophies of removable partial denture design.

Alveolar Process↗
PubMed1979

Psychological factors involved in maxillofacial prosthetics.

1. No significant difference existed between the MMPI means of the test group and the MMPI means of the Mayo Clinic patient group. 2. The means of the test group and the Mayo Clinic patient group deviated from the MMPI normative data. 3. No apparent change in personality of the test group was suggested by the MMPI. 4. A much larger percentage of the patients than expected failed to complete the initial MMPI. One patient refused, and four patients had a raw score of "cannot say" responses greater than 120, thus invalidating the test. 5. The changes in the means of the ACL scales of total number checked, autonomy, change, and abasement were significant (p less than .05). 6. The patient became more outgoing and optimistic, as measured by the ACL, during the immediate postoperative period. 7. Speech and mastication were problems for some patients even after prosthodontic rehabilitation. 8. Most of the rehabilitated patients resumed their normal social habits. 9. The patients in the study seemed to respond to the new situation according to their already existing personality structure.

Adolescent↗
PubMed1980

Prosthodontic and speech rehabilitation after partial and complete glossectomy.

A multidisciplinary approach to the rehabilitation of four glossectomy patients has been presented. Points emphasized were the anatomic defects, their effect on the three oral functions of mastication, deglutition, and speech, and the various prosthetic modifications found most effective to restore the impaired oral functions.

Aged↗
PubMed1985

Studies of biologic parameters for denture design. Part III: Effects of occlusal adjustment, base retention, and fit on masseter muscle activity and masticatory performance.

EMG recordings of ipsilateral and contralateral masseter muscles and standardized masticatory performance tests were made in 20 denture wearers before and after modifications were made to their clinically unsatisfactory dentures. The improvement of retention and stability by correction of gross occlusal prematurities and by the use of a denture adhesive or base reline with a soft tissue-conditioning material did not significantly alter the chewing performance or muscle activity during mastication in denture wearers. The results support our previous findings that the influence of denture factors on chewing ability of denture wearers is limited. To avoid variations in EMG activity caused by changes in electrode positions, all tests for a given subject were made at the same sitting. Thus the study design did not provide time to denture wearers for their neuromuscular mechanism to adapt to the modifications prior to testing masticatory function. A replication of this study that permits sufficient adaptation time after each modification is suggested to validate the findings.

Adhesives↗
PubMed1985

The influence of altered working-side occlusal guidance on masticatory muscles and related jaw movement.

The effect of four different occlusal situations (group function, canine guidance, working side occlusal interference, and hyperbalancing occlusal interference) on EMG activity in jaw elevator muscles and related mandibular movement was investigated on 12 subjects. With a computer-based system, EMG and displacement signals were collected simultaneously during specific functional (unilateral chewing) and parafunctional tasks (mandibular gliding movements and various tooth clenching efforts) and analyzed quantitatively. When a naturally acquired group function was temporarily and artificially changed into a dominant canine guidance, a significant general reduction of elevator muscle activity was observed when subjects exerted full isometric tooth-clenching efforts in a lateral mandibular position. The original muscular coordination pattern (relative contraction from muscle to muscle) remained unaltered during this test. With respect to unilateral chewing, no significant alterations in the activity or coordination of the muscles occurred when an artificial canine guidance was introduced. Introduction of a hyperbalancing occlusal contact caused significant alterations in muscle activity and coordination during maximal tooth clenching in a lateral mandibular position. A marked shift of temporal muscle EMG activity toward the side of the interference and unchanged bilateral activity of the two masseter muscles were observed. The results suggest that canine-protected occlusions do not significantly alter muscle activity during mastication but significantly reduce muscle activity during parafunctional clenching. They also suggest that non-working side contacts dramatically alter the distribution of muscle activity during parafunctional clenching, and that this redistribution may affect the nature of reaction forces at the temporomandibular joints.

Adult↗
PubMed1986

Medial pterygoid muscle activity during chewing and clenching.

Specific activity of the human medial pterygoid muscle in relation to jaw movements and occlusion during mastication and clenching tasks is unclear. EMG activity of the medial pterygoid, masseter, anterior, and posterior temporal muscles was recorded simultaneously with three dimensional incisor point movement of the mandible. Data were sampled and analyzed by an on-line computer system. Patterns of medial pterygoid muscle activity were consistent for ipsilateral chewing and demonstrated activity of the muscle on the chewing side that peaked near the onset of intercuspation. The muscle on the contralateral side was active at the onset of intercuspation for subjects with a chopping stroke and inactive for those with a more lateral stroke guided into intercuspation on cuspal inclines. Activity in the early part of the closing phase was associated with a marked jaw movement toward the chewing side. There was generally less activity in protrusive than intercuspal clenching when occlusion was normal but more activity if marked incisal wear was present or multiple tooth contacts could be attained on protrusion. Intercuspal clenching initiated less activity when force was directed posteriorly and more activity when directed anteriorly than vertical intercuspal clenching.

Adolescent↗
PubMed1987

A review of masticatory muscle function.

Current reports of the actions of the major muscles of mastication are reviewed for clenching tasks in centric occlusion and eccentric jaw positions, mandibular opening, and unilateral chewing. The relationship of the mandible to the maxillae in the intercuspal position and, consequently, the relationship of the condyle to the fossa of the temporomandibular joint may be controlled by the clinician. Similarly, the number and site of tooth contacts in the intercuspal position and in eccentric jaw positions may be altered. These alterations all produce alteration of muscle activity during functional and parafunctional acts. Some of these alterations are now predictable. Nevertheless, much more study needs to be done before the outcomes of morphologic changes on the muscular system can be accurately predicted. Even now, however, clinicians must understand the nature of clenching and chewing muscle activity and how it can be altered to a more favorable situation for each individual. This review indicates that: The elevator muscles demonstrate maximum activity when even bilateral occlusal contacts occur during clenching in the intercuspal position. The elevator muscles are activated together in the intercuspal zone of tooth contact during chewing when the occlusal contacts are balanced bilaterally in this intercuspal position. Increasing the number of eccentric tooth contacts increases the muscle activity during both chewing and clenching. The medial pterygoid muscle is variable in its action. This variability appears to be related to the chewing pathway and the type of occlusion. Its action is enhanced during laterally directed chewing actions of the mandible. The inferior head of the lateral pterygoid muscle has a reciprocal role with the medial pterygoid muscle during chewing and contributes to forward and lateral bracing of the condyle of the mandible. Although the superior head of the lateral pterygoid muscle appears to be active during mandibular closing, the significance of this finding is not fully understood.

Electromyography↗
PubMed1988

Frontal chewing patterns of the incisor point and their dependence on resistance of food and type of occlusion.

This study has shown that mastication in normal dentate subjects is associated with a great variety of movement modes. The dependence of chewing patterns on the resistance of food proves that the chewing system is capable of marked variations. A complete assessment of chewing behavior therefore demands the use of both tough and soft foods. Physiologic chewing of tough food is dominated by angulated grinding-type movements, whereas soft consistencies are chewed with drop-shaped or lenticular patterns. In a random sample of patients with good chewing function, approximately 95% of Angle class I and II occlusions were found, which statistically differed neither in chewing pattern distribution nor in movement parameters. As shown in this study, certain occlusal or functional properties cannot be characterized by a single type of chewing pattern but instead by a specific distribution of patterns. As a basis for the evaluation of such investigations, a method for the classification and ordered documentation of observed movement modes is necessary. The scheme used here includes all types of chewing movements that have been presently observed. It permits the recognition of patterns and the quantitative description of their frequencies and variations.

Adolescent↗
PubMed1990

Prosthetic and surgical management of osteogenic sarcoma of the maxilla.

Maxillary surgical defects resulting from resection of oral neoplasms vary in size from small perforations of the hard and soft palate to complete removal of these structures. Osteogenic sarcoma is of unknown etiology and is a rapidly growing tumor that may produce pain, paresthesia, and anesthesia. The recommended treatment of radical resection often results in defects that produce significant orofacial disfigurement. These defects, regardless of size, present significant functional disability, with compromised esthetics, mastication, and deglutition. Restoration with a maxillary obturator prosthesis can reestablish the physical separation between oral and nasal cavities and, in soft palate defects, enable normal palatopharyngeal function. Most patients can be rehabilitated successfully with restoration of speech and swallowing to normal levels and significant improvement in appearance.

Deglutition Disorders↗
PubMed1992

Reproducibility of mandibular motion and muscle activity levels using a commercial computer recording system.

A commercial computer recording system (BioPak) was tested for its accuracy and reproducibility in recording mandibular motion and muscle activity levels (EMG). Accuracy of measurements of mandibular motion was tested using sliding calipers. Accuracy of muscle activity levels was checked with a sine-wave calibration signal of known amplitude and frequency. Reproducibility of motion and of EMG was made using five control subjects each tested on 3 separate days. Computer measurements of motion were found to require correction for nonlinearity at openings beyond 45 mm. Most maximum voluntary excursions were found to be more reproducible than motions during mastication. However, lateral deviation during opening was strongly affected by magnet orientation and varied greatly between trials. Electromyographic recordings were distorted by improper treatment of high-frequency components of the signal and also varied greatly between trials. This study suggests that the BioPak system may indicate changes in some measures of mandibular motion and EMG levels in patients for whom no changes have occurred.

Adult↗
PubMed1992

Masticatory function in patients with extensive fixed cantilever prostheses.

Eleven patients with complete maxillary dentures and 12-unit fixed partial dentures that included the mandibular canines were studied before and during specific intervals after prosthodontic treatment. Established methods for evaluation of oral function were used and the last examination was performed 30 months after treatment. All patients reported that their masticatory function had been substantially improved and there were no symptoms of dysfunction in the masticatory system. Masticatory efficiency improved after the prosthodontic treatment because both the number of cycles before the initial swallow and the total number of strokes including the time for completed mastication diminished after treatment. The occlusal force elevated after the prosthodontic treatment. Although great individual variations were recorded for all occasions and force levels, forces recorded on the extensions of the cantilever were similar to those on the canine regions.

Bite Force↗