Biomedical subjects

T Gay

Publications and source records attributed to T Gay.

At least 19 recordsLinked to original sources

PubMed2000

The effect of denture adhesive on mandibular movement during chewing.

BACKGROUND: The authors conducted a study to determine if reducing mandibular denture movement through the use of a denture adhesive improves chewing function in edentulous patients. METHODS: The authors compared the mean chewing rates of 10 denture wearers who used and did not use a denture adhesive with that of a control group of 10 dentate people. The authors recorded mandibular movements using a multichannel magnetometer tracking system while the subjects chewed standardized pieces of dried apricots and fresh white bread. They made recordings for the test subjects without the use of denture adhesive and at zero, two and four hours after Fixodent denture adhesive cream (Procter & Gamble Co.) was applied to the mandibular denture. RESULTS: The mean chewing rate for the control group was significantly faster than that of the test group at baseline (P < .01). The authors found statistically significant increases in the mean chewing rates for the test group after the denture adhesive was applied at all time points for both foods. None of the after--adhesive-application rates were significantly different from the control group's rate (P > .05). CONCLUSIONS: Use of denture adhesive increased the mean chewing rate in test subjects immediately after and at two and four hours after denture adhesive was applied to a rate that approximated that observed in control subjects (P > .05). CLINICAL IMPLICATIONS: These findings show that using a denture adhesive promotes a faster and more natural rate of chewing.

Adhesives↗

PubMed1995

Retention and stability of the maxillary denture during function.

The objectives of this study were to provide a quantitative account of the extent to which the maxillary complete denture moves during function (chewing, swallowing, and speech production) and to determine whether differences in movement occur as a function of denture fit. A total of 24 patients were studied, 12 with poorly fitting dentures and 12 with well-fitting dentures. Denture movements were measured with a Myotronics kinesiograph that tracked the movements of a small magnet attached to the inferior surface of the denture. Results indicated that denture movement was greatest for the two chewing activities; varied extensively from individual to individual; and that there were no statistically significant overall movement effects as a function of fit. It was concluded that all maxillary dentures are subject to movements in all directions, but that the degree of movement is related more to the individual denture wearer than it is to the fit of the denture.

Aged↗

PubMed1994

Characteristics of muscle fatigue in patients with myofascial pain-dysfunction syndrome.

The purpose of this study was to compare the properties of muscle fatigue in the masseter and temporalis muscles of normal individuals and those with myofascial pain-dysfunction syndrome (MPD). The MPD muscle is presumed to have different characteristics of fatigue than its healthy counterpart; these characteristics can be quantitated using standard electromyogram (EMG) signal-processing techniques. A total of 18 patients diagnosed as having MPD comprised the experimental group and 15 adults with no history or present symptoms of temporomandibular joint pain and dysfunction served as controls. Surface EMG recordings were made for both the masseter and anterior temporalis muscles while the subject held an incisal bite force level of 10 N for as long as possible. The EMG data were transferred to a microcomputer where the power-density spectrum of the signals were calculated for 2-s samples at 10-s intervals. The mean power frequency (MPF) and power (root mean square, r.m.s.) of the signals were calculated from the power-density spectra. Results showed: (1) the endurance times were significantly shorter for the MPD patients; (2) the masseter was not active in three of 17 MPD patients; (3) decreases in MPF over time were significantly greater for the MPD patients than normal subjects; (4) increases in r.m.s. power were significantly greater over time for the MPD patients; (5) bandwidths of the power-density spectra were similar for the two groups. The implication of these results is the MPD muscle is not in a state of constant fatigue, as is currently believed, but rather demonstrates accelerated fatigue.

Adolescent↗

PubMed1994

Estimating human incisal bite forces from the electromyogram/bite-force function.

This study used the electromyogram (EMG)/force-function curve as a means of estimating functional bite forces. Surface EMG recordings were made for the masseter and anterior temporalis muscles bilaterally in ten adults while incisal bite forces were measured using a force transducer embedded in custom-made hydroplastic bite blocks. Measurements were made for mouth openings of 15 and 30 mm. Each subject was first instructed to develop a maximum level of bite force, and then to develop bite-force levels that corresponded to decreasing percentages of his or her maximum, from 90 to 10%, in 10% decrements. After the force measurements had been made, each subject was instructed to incise various food substances. The power-density spectrum and r.m.s. power level were calculated for each sample. Maximum bite-force levels varied considerably among the 10 subjects, ranging from a minimum of 2.5 kg to a maximum of 40 kg. For the subjects as a whole, estimated bite forces for the different types of food ranged from 3.0 to 5.5 kg. This range was independent of the subjects' maximum bite-force levels. Thus, bite forces exerted to incise different foods probably depend more on the food than on the individual's bite capabilities. There was variability within this range, although, as expected, bite forces were least for chocolate and greatest for apple and toffee.

Adult↗

PubMed1994

Effect of denture adhesive on the retention and stability of maxillary dentures.

This study used quantitative methods to measure the effects of a denture adhesive on the retention and stability of the maxillary denture. Denture movements were measured on 20 patients during standardized chewing, swallowing, and speaking activities, first with no adhesive, and then at 0, 2, 4, 6, and 8 hours after application of an over-the-counter cream adhesive. The major findings were that the denture adhesive produced a statistically significant improvement in the retention and stability of the maxillary denture during the various chewing, swallowing, and speaking activities, for up to 8 hours; there were no statistically significant differences in improvement between a poorly fitting and well-fitting denture; and patients were able to produce significantly greater levels of incisal bite force with the use of the adhesive.

Adhesives↗

PubMed1994

Coordination of oral cavity and laryngeal movements during swallowing.

In this study, dynamic imaging was used to track the movements of oral cavity and laryngeal structures during swallowing in 10 normal adults subjects. The movements of tiny lead pellet markers attached to the lips, tongue, mandible, and soft palate, as well as anatomic landmarks on the hyoid bone, were measured in relation to a reference pellet affixed to the upper central incisors. Sagittal views of the oral cavity were obtained using standard videofluorography. Each subject produced 10 swallows of 12 ml of tap water followed by 5 swallows with a bite block placed between the molars. The recorded video images were input to a microcomputer where the x- and y-coordinates of the pellets were measured. Results of the analyses revealed considerable temporal overlap in the timing of oral cavity and laryngeal movements, widespread individual variability in coordination patterns and movement trajectories, and selective effects of the bite block. These data suggest the existence of individual adaptive strategies in the programming and control of swallowing movements.

Adult↗

PubMed1994

Oral and laryngeal muscle coordination during swallowing.

The objective of this experiment was to determine the relative contributions and patterns of activity of different muscles involved during the oral phase of swallowing. Electromyographic (EMG) signals were recorded from the orbicularis oris inferior, masseter, palatal elevator, anterior and posterior genioglossus, mylohyoid, anterior belly of the digastric, and vocalis muscles of 12 normal adult subjects. Each subject swallowed 15 mL of water, under normal and bite block conditions, 15 to 20 times. The integrated EMG signals for each subject's swallows were ensemble averaged. The results of the analyses showed that swallowing function varies from individual to individual in terms of the specific muscles used and how the various muscle activity patterns are coordinated. These results suggest that swallowing is a highly complex adaptive motor activity which probably relies more on higher-level control mechanisms than previously believed.

Adult↗

PubMed1994

Activation and coordination patterns of the suprahyoid muscles during swallowing.

This study was undertaken to determine the activation and coordination patterns of the three suprahyoid muscles--geniohyoid, mylohyoid, and anterior belly of the digastric muscle--in elevating the larynx during swallowing. Electromyographic activity was also recorded from two intrinsic laryngeal muscles (vocalis and lateral cricoarytenoid) and the anterior genioglossus. Ten adults served as participants. Each participant produced 15 swallows of 15 mL of tap water both normally and with a 12-mm bite block placed between the molars. The electromyographic data were ensemble-averaged with a laboratory computer. Analyses showed that the three suprahyoid muscles were used selectively by different participants. Some participants used all three muscles for hyoid elevation, while others used different pairs of two of the muscles. The activation patterns of the suprahyoid muscles during swallowing also varied with respect to each other and the onset of the laryngeal constrictor muscles; however, use of at least one suprahyoid muscle always preceded the onset of the laryngeal adductors, indicating that larynx elevation consistently preceded glottal adduction. The way in which the muscles responded to the bite block varied considerably both within and among participants. Some maintained temporal stability but increased overall muscle activity; others reorganized temporal relations either with or without corresponding muscle activity adjustments. These findings suggest that the laryngeal elevation system is an adaptive function rather than an immutable action.

Adaptation, Physiological↗

PubMed1993

Use of sodium hyaluronate in treating temporomandibular joint disorders: a randomized, double-blind, placebo-controlled clinical trial.

This study assessed the efficacy of high-molecular-weight sodium hyaluronate as a treatment for certain intracapsular temporomandibular joint (TMJ) disorders. One hundred twenty-one patients were studied at three test sites using a randomized, double-blind, placebo-controlled experimental design. Patients were selected on the basis of 1) confirmed diagnosis of either degenerative joint disease (DJD), reducing displaced disc (DDR), or nonreducing displaced disc (DDN); 2) nonresponsiveness to nonsurgical therapies; and 3) severe dysfunction as established by the Helkimo indices (HI), visual analog scales (VASs), and physical measurements of joint movement and joint noise (arthrophonometry [APM]). Subjects received a unilateral upper joint space injection of either 1) 1% sodium hyaluronate in physiologic saline (MedChem Products, Woburn, MA) or 2) USP physiologic saline. Clinical evaluations were performed using HI, VAS, and APM at weekly intervals for the first month and then at monthly intervals up to 6 months postinjection. Statistical analyses for both categorical and continuous variables were performed for each diagnostic category at each examination interval. For DJD, no difference in outcome was seen between treatment groups. For DDN, significant between-group differences were seen through 1 month; however, beyond this time point, the number of DDN patients was insufficient to draw meaningful conclusions concerning efficacy. For DDR, statistically significant within-group and between-group improvement in all three measures (HI, VAS, APM) was seen for the hyaluronate group compared to the saline group throughout the 6-month test period. At the month-2 and month-3 examination intervals, twice as many patients treated with hyaluronate (90%) showed improvement compared to patients given placebo. Further, only 3% of patients with DDR who were treated with hyaluronate relapsed compared with 31% of patients with DDR given placebo.

Adult↗

PubMed1993

Effect of jaw opening on masticatory muscle EMG-force characteristics.

This study was designed to evaluate the way in which changes in vertical jaw opening affected the relative contributions of various masticatory muscles to bite force production. EMG activity was recorded simultaneously from the masseter, and anterior, middle, and posterior temporalis muscles, during controlled isometric biting at different force levels and vertical jaw openings. EMG-force characteristics were compared between muscles and bite openings. All but the posterior temporalis muscle displayed significant increases in muscle activity with increased bite force production; the masseter muscle demonstrated the largest activity increments. Statistically significant changes in muscle function due to jaw opening were demonstrated only for the masseter muscle, though similar trends were observed for the anterior and middle temporalis muscles. Minimum increases in muscle activity associated with increases in bite force occurred between 9 and 11 mm of opening, measured at the first molar, for all three muscle groups. The results of this study suggest that changes in masticatory muscle length resulting from vertical jaw opening cause alterations in muscle contractile properties, but the relative contributions of various masticatory muscles toward bite force production may also be affected by biomechanical factors and neural control adaptations.

Biomechanical Phenomena↗

PubMed1992

Masticatory muscle fatigue: endurance times and spectral changes in the electromyogram during the production of sustained bite forces.

The purpose of this experiment was to determine if the characteristics of fatigue observed in the limb muscle system are also evident in the muscles of mastication, specifically, the masseter and temporalis. Surface electrodes were placed bilaterally over the masseter and temporalis muscles of 10 adults. Each subject was instructed to maintain maximal and six levels of submaximal incisal bite forces for as long as possible. The power density spectrum of the electromyographic signals for each muscle was calculated at the onset and failure of the task. The decrease in endurance time with an increase in bite force followed a pattern similar to that in limb muscles, and each muscle was characterized by a consistent reduction in the mean power frequency of the power density spectrum and a variable change in r.m.s. power. The variability of changes in r.m.s. power (which is inconsistent with changes found in the limb muscles) was explained in terms of either changes in motor-unit firing rate or the muscle's relative contribution to the generation of bite force. The analyses also demonstrated a curvilinear relationship between bite force and r.m.s. power, but no relationship between bite force and the mean power frequency of the power density spectrum.

Adult↗

PubMed1992

Orthodontic treatment and temporomandibular joint disorders.

The overall objective of this project was to study the relationship between orthodontic treatment and temporomandibular joint (TMJ) disorders. This relationship has been and remains an important and complex issue in orthodontics. The objectives of the study were to determine the incidence of TMJ pain and dysfunction in a group of orthodontic patients who were symptom-free on entering treatment, and to assess and characterize the level of pain and dysfunction in patients with symptoms, and track changes in these parameters during the course of orthodontic treatment. Standardized functional indices and physical measurements were used to describe and assess TMJ pain and dysfunction. The results of this study showed that of 451 patients without symptoms undergoing treatment at our university clinic during the 18-month project, no patient developed signs and symptoms of TMJ disorders during that time. In addition, for the 11 patients who presented with signs and symptoms of TMJ disorders at the time of their entry into the treatment program, no clear or consistent changes in levels of pain and dysfunction occurred longitudinally during the treatment period followed in this study. On the basis of these findings, a relationship between either the onset of TMJ pain and dysfunction and the course of orthodontic treatment or the change in TMJ pain and dysfunction and the course of orthodontic treatment could not be established in this particular patient population.

Adolescent↗

PubMed1992

Acoustic and perceptual effects of changes in vocal tract constrictions for vowels.

The purpose of this study was to use vocal tract simulation and synthesis as means to determine the acoustic and perceptual effects of changing both the cross-sectional area and location of vocal tract constrictions for six different vowels: Area functions at and near vocal tract constrictions are considered critical to the acoustic output and are also the central point of hypotheses concerning speech targets. Area functions for the six vowels, [symbol: see text] were perturbed by changing the cross-sectional area of the constriction (Ac) and the location of the constriction (Xc). Perturbations for Ac were performed for different values of Xc, producing several series of acoustic continua for the different vowels. Acoustic simulations for the different area functions were made using a frequency domain model of the vocal tract. Each simulated vowel was then synthesized as a 1-s duration steady-state segment. The phoneme boundaries of the perturbed synthesized vowels were determined by formal perception tests. Results of the perturbation analyses showed that formants for each of the vowels were more sensitive to changes in constriction cross-sectional area than changes in constriction location. Vowel perception, however, was highly resistant to both types of changes. Results are discussed in terms of articulatory precision and constriction-related speech production strategies.

Adult↗

PubMed1991

Electromyographic-force characteristics in the assessment of oral function.

The purpose of this investigation was to examine the utility of EMG-force characteristics as reliable and valid parameters by which to assess oral function. Masseter-muscle activity was recorded during controlled isometric biting exercises performed at various bite openings and force levels on two separate occasions. Measured muscle-activity levels, as well as the EMG-force characteristics of slope and y-intercept, were compared between bite openings and experimental trials. Sensitivity, assessed as the ability to detect statistically significant differences in muscle function due to changes in muscle length, was found to be acceptable for all measurements, except the y-intercept parameter, and during production of minimal forces. Reproducibility, evaluated as the correspondence between values recorded at different experimental sessions, was best for the EMG-force parameter of slope and during production of higher forces. The results from this study support the following conclusions: (1) Substantial variations in muscle function exist between individuals; (2) acceptable reliability and sensitivity of quantitative EMG values can be achieved, especially at higher muscle-activity levels, by rigidly controlling and quantifying functional activities during experimental trials; (3) the slope of an EMG-force curve is a reproducible, quantitative, and functionally sensitive measurement for assessment of muscle function; and (4) the EMG-force y-intercept is not a reliable quantity by which muscle-function characteristics may be studied.

Adult↗

PubMed1988

The acoustical characteristics of the normal temporomandibular joint.

Both clinical and empirical evidence suggests that the "normal" temporomandibular joint produces noise during function. The purpose of this study was to determine the conditions under which these noises might arise. Joint sounds and mandibular movements were recorded simultaneously from 200 adults who had no previous history or present symptoms of TMJ pain or dysfunction. The joint sounds were recorded bilaterally by means of two separate miniature vibration transducers mounted on a common headband, and incisal point mandibular movements were measured by a magnetometer tracking system. Recordings were made while each subject opened and closed the mouth, first in a natural and comfortable manner, and then to maximum displacement. Two types of measurements were made: the appearance, onset, and duration of joint-propagated sounds in relation to relative mandibular position; and the spectral properties of the detected sounds. The results of this study showed that for natural opening and closing movements of the mandible, the "normal" TMJ was silent for all age groups. However, for the maximum displacement condition, detectable sounds appeared at the points of maximum displacement in both the opening and closing phases of the cycle in over 80 percent of the subjects. However, these sounds were, as a class, substantially longer than, and spectrally distinct from, abnormal joint sounds, suggesting that they arise from a distinct physical substrate.

Adolescent↗

PubMed1987

The acoustical characteristics of the normal and abnormal temporomandibular joint.

This paper describes the results of a clinical study that recorded and analyzed sounds emitted from the temporomandibular joint (TMJ) during simple function as a means for differentially diagnosing disorders of the joint. The technique is based on the principle that each different disorder of the TMJ produces a different effect on the mechanical relationship between the articulating surfaces of the joint, and that these mechanical effects can be determined by analyzing joint sounds in relation to joint movement. A total of 79 patients (101 joints) were studied; 32 (46 joints) were diagnosed as having extracapsular disorders, (primarily MPD), 27 (32 joints) were diagnosed as having a displaced disc with reduction, nine (10 joints) were diagnosed as having a displaced disc without reduction, and 11 (13 joints) were diagnosed as degenerative disease (osteoarthritis/arthrosis). In addition, 25 adults (50 joints) with normal TMJs were included as controls. The results of this study demonstrated that each specific disease of the TMJ is characterized by a unique relationship between the sounds propagated by the joint and the movement of the joint. Essentially, an extracapsular disease was characterized by acoustic quiescence during natural (as opposed to maximal) jaw movement, an internal derangement by a usually symmetrical short duration click/reciprocal click, or random click complex, depending on the subcategory of the disorder, and a degenerative disease by a long duration noise during either or both jaw opening and closing. The data further suggest that the technique serves to reflect the mechanical events (and abnormalities) that are involved in function of the diseased joint and has potential for use as a clinical diagnostic tool.

Acoustics↗

PubMed1987

Non-pulmonary Rhodococcus equi infections in patients with acquired immune deficiency syndrome (AIDS).

Rhodococcus equi, formerly known as Corynebacterium equi, was isolated repeatedly from the blood of two patients with the acquired immune deficiency syndrome (AIDS). Neither of the patients had pneumonia while they were bacteraemic, whereas pneumonia has been present in all previously reported cases of human infection with R equi. One of our patients had diarrhoea and the organism was isolated from a stool culture; the other patient had a large granulomatous soft tissue mass in his pelvis caused by R equi. Both isolates were resistant to penicillin and one produced a beta-lactamase. Both patients were treated with vancomycin but only one recovered.

Acquired Immunodeficiency Syndrome↗

PubMed1987

The spectral properties of temporomandibular joint sounds.

Spectral analyses were performed on sounds recorded from TMJ's that had previously been classified into different intracapsular categories, in an attempt to determine whether the inherent properties of these sounds were unique for each different disorder. A total of 55 joints was studied: 32 were diagnosed as displaced disc with reduction [DDR], 10 were diagnosed as displaced disc without reduction [DDN], and 13 were diagnosed as degenerative joint disease [DJD]. The spectral analysis for each recorded joint sound was performed using a Fast Fourier transform routine, the results of which were plotted as a frequency vs. amplitude envelope. These analyses showed that different intracapsular TMJ disorders were characterized by sounds whose energy distribution patterns, while showing certain across-group differences, usually shared significant common spectral properties. The joint-propagated noises associated with DDR, DDN, and DJD were each characterized by a spectral envelope whose primary band of energy was centered around a peak at approximately 1 kHz, and which dropped off from that point to background levels. These patterns presumably reflect the resonance characteristics of the disordered joint as defined by the mass and stiffness of its articulating surfaces. Based on the findings of this study, it would appear that comparisons of the spectral envelopes of joint-propagated sounds would have only limited application in the differential diagnosis of intracapsular TMJ disorders.

Adolescent↗