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Biomedical subjects

G T Clark

Publications and source records attributed to G T Clark.

At least 19 recordsLinked to original sources
PubMed1997

The validity and utility of disease detection methods and of occlusal therapy for temporomandibular disorders.

Our evaluation of the clinical usefulness or devices for the diagnosis or treatment of temporomandibular disorders (TMD) led to the conclusion that the only current gold standard for TMD is a global clinical examination, because none of the instruments can be said to provide more than ancillary documentation and none have proven diagnostic validity or utility. Regarding the therapeutic efficacy of occlusal adjustment, we could find no comparative studies that test the efficacy of occlusal adjustment in preventing TMD. The studies we reviewed on the relationship of occlusion to TMD are not convincing, powerful, or practical enough to make any recommendations about a causal association.

Centric Relation↗
PubMed1997

Detecting and treating oral and nonoral malodors.

This article suggests methods on how to detect and treat the various oral and nonoral malodor conditions with which patients present. These conditions are separated into those emanating from the nasal passage, sinuses and upper respiratory sources; the mouth; the tongue; the oropharynx; the lower respiratory tract; and the lungs. Foul odors also develop as a result of systemic and gastrointestinal disorders and diseases, as well as the normal breakdown of odiferous ingested foods. The available detection methods are described and future methods are suggested. The overall conclusions made from this review are that currently available management methods will be able to treat most cases. A careful, knowledgeable clinician can usually determine the patient's problem by the use of a thorough history and examination. Occasionally medical consults will be needed; and, in these cases, the approach that must be taken is a combined treatment approach. For example, effective therapy might require a combination of periodontal disease treatment, correction of dental restoration-based food traps and a rigorous daily mechanical debridement of the tongue. The above treatments will often have to be supplemented by the most appropriate mouthwash for the patient's specific condition. Finally, this article hopes to encourage manufacturers of "halitosis products" to support and conduct well-designed clinical trials on their products so that the field is advanced and treatments become more predictable.

Breath Tests↗
PubMed1996

Haemodynamic changes induced by submaximal isometric contraction in painful and non-painful human masseter using near-infra-red spectroscopy.

Although mechanisms underlying chronic muscle pain are poorly understood, one prevalent theory is that it is due, in part, to localized hypoxia. The purpose of this study was to evaluate this theory using non-invasive near-infra-red spectroscopy that monitors relative changes in intramuscular haemoglobin (Hb) concentration and oxygen saturation levels. Data were collected for the human masseter muscle during and following three isometric 30-s trials at 50% maximum voluntary contraction. Ten females, with a history of chronic muscle pain in the jaw, and eight matched healthy females without muscle pain (controls) participated. Results showed that, upon initiation of masseter muscle contraction, there was a rapid reduction in the intramuscular Hb concentration concomitant with a reduction in oxygen saturation levels. After cessation of the contraction, the Hb concentration increased rapidly and then fell toward the baseline. Significant differences in the recovery profile for oxygen saturation were found between the first trial and the following two trials for both the muscle pain- and control group. Looking at the first trial only, and adjusting for covariates of height, weight and bite-force in the analysis, revealed a marginally significant postcontraction difference between the two groups with a lower level of oxygen saturation during recovery in the group with chronic muscle pain. Significant group differences were found in Hb concentrations without any significant trial effect. It is likely that the well-known changes in intramuscular blood flow that occur during and after contraction in human muscles are reflected in these altered relative Hb concentrations. The group with chronic muscle pain showed a clearly reduced magnitude of the Hb concentration change in the postcontraction recovery period. The results support the concept that patients with chronic muscle pain have a slower intramuscular reperfusion during the recovery phase after sustained isometric contractions.

Adult↗
PubMed1996

A crossover study comparing the efficacy of continuous positive airway pressure with anterior mandibular positioning devices on patients with obstructive sleep apnea.

OBJECTIVE: This study compared the efficacy of a removable anterior mandibular positioning (AMP) device to continuous positive airway pressure (CPAP) in patients with obstructive sleep apnea (OSA) using a fully balanced crossover design. DESIGN: Twenty-three male subjects with confirmed OSA were recruited from the Technion Sleep Laboratory in Haifa, Israel, from February 18, 1991 to December 17, 1992. Twenty-one of the 23 subjects enrolled completed all aspects of the study. RESULTS: The mean apnea-hypopnea index (AHI) before treatment was 33.86 +/- 14.30. The mean AHI decreased with CPAP to 59.50%, but decreased only 38.91% with the AMP device. The lowest mean recorded oxygen saturation level for the 21 subjects was 84.30 before treatment, 91.10 after CPAP treatment, and 90.20 after AMP treatment. Sleep data revealed a significant decrease in stage 1 and 2 (p=0.0088) and an increase in rapid eye movement percent (p=0.0066) for both treatments when compared with baseline. Three- to 10-month posttreatment phone interviews showed that 1 subject was not using either device, 1 subject was using CPAP, and 2 subjects were using the AMP device intermittently due to occasional temporomandibular joint pain symptoms. The remaining 17 subjects were all using the AMP device nightly. The symptoms of excessive daytime sleepiness also decreased significantly by both AMP and CPAP. CONCLUSIONS: The AMP device achieved substantial success in most cases, but was less effective than CPAP, especially for the more severe cases. In general, the AMP device was strongly preferred over the CPAP by the subjects of this study.

Adult↗
PubMed1996

Effect of jaw position and posture on forced inspiratory airflow in normal subjects and patients with obstructive sleep apnea.

OBJECTIVE: This study evaluated whether substantial airflow changes occur by changing both body posture and jaw position in normal subjects and patients with obstructive sleep apnea (OSA). DESIGN: A case-control design was utilized to assess group differences (OSA vs control) and each subject served as his/her own control subject to assess condition differences (jaw position and body posture changes). Subjects included 16 male patients with OSA (aged 33 to 71 years) whose conditions were diagnosed at the UCLA Sleep Disorders Laboratory with a polysomnographic recording, and 9 male non-OSA subjects (aged 22 to 52 years). The experimental intervention in the study involved alterations in body posture and jaw positioning. Airflow changes were determined using a spirometer that assessed the velocity of airflow during a forced inspiration. Subjects in this study all had the middle portion (25 to 75%) of their maximum forced inspiratory flow (FIF25-75) curve measured in three positions; (1) normal jaw position-upright body posture (N-U); (2) normal jaw position-supine body posture (N-S); and (3) protrusive jaw position-supine body posture (P-S). SETTING: The study was conducted at the UCLA Dental Clinical Research Center. RESULTS: Both groups had a significant decrease in their FIF25-75 upon reclining, and there were no significant group differences regarding the magnitude of this change. Both groups also had a nearly full recovery of their FIF25-75 airflow when their jaws were positioned forward while reclining. CONCLUSIONS: These data document that when a patient is in a supine position, a 100% protrusive jaw position allows significantly more inspiratory airflow to occur.

Adult↗
PubMed1996

Mandibular advancement and sleep disordered breathing.

The term "sleep disordered breathing" encompasses several conditions. This article gives definitions for and discusses the types of sleep disordered breathing. It also looks at the use of prosthetic devices and surgery to treat those problems and provides a suggested treatment algorithm.

Adult↗
PubMed1996

Criteria for the detection of sleep-associated bruxism in humans.

Surface electromyography of the masseter and electrocardiogram recordings of heart activity during sleep were performed on nine subjects who suffer from an oral motor dysfunction (bruxism during sleep. Signals were monitored in the subject's home sleeping environment over 4 consecutive nights. A total of 36 nights of data were analyzed to perform the following: (1) describe the nature and magnitude of total masseter muscle electromyographic activity above a minimum threshold of 3% of each subject's individually established maximum voluntary contraction level; and (2) describe electrocardiograph rate changes (using the R-R interval) that occurred in relation to these electromyographic elevations. From these data, criteria for detection of bruxism events were established and combined into a fully automated event detection algorithm. The mean number and duration of the detected bruxism events are reported. The underlying logic for the criteria selected, and what effect other possible criteria would have on the separation of abnormal from normal motor events, is also presented and discussed.

Adult↗
PubMed1996

Temporomandibular dysfunction, chronic orofacial pain and oral motor disorders in the 21st century.

This article describes the various sensory and motor disorders which afflict the orofacial region. Such information is essential to the modern dentist who wishes to be proficient in the diagnosis of patients with these problems. These abnormalities are broadly separated into three groups of pathologic conditions: Temporomandibular disorders; chronic orofacial pain disorders; and oral motor disorders. Although much more can be said about each reviewed condition, this article focuses on the diagnostic features of each specific disorder within each of these 3 groups. It suggests alternate nomenclature for each disorder, where appropriate. Due to space limitations the article does not cover the procedures for management of each disorder, however, the reader is referred to appropriate references in this regard. The overall intent of the article is to help the dental practitioner recognize and differentiate the above conditions.

Chronic Disease↗
PubMed1995

[Treatment of obstructive sleep apnea with anterior mandibular positioning device].

The efficacy of the anterior mandibular positioning (AMP) device in obstructive sleep apnea syndrome was assessed. This device advances the mandible anteriorly by approximately 5-7 mm. 29 patients were examined and questioned about temporomandibular (TM) and facial pain before and after treatment with the device. Polysomnographic sleep studies were performed on all before, and 2 weeks after continuous use of the AMP device. 10 of the patients also underwent polysomnographic follow-up after 1 year. The mean apnea index (AI) before treatment was 40.1, which decreased to 24.3 (p < 0.0001) after 14.3 days of treatment with the AMP device. O2 saturation also increased, from 84.2% before, to 89.2% after treatment (p < 0.002). In 10 patients the mean AI after 1 year was 24.9, not different from that after only 2 weeks of treatment, but significantly different from their mean AI before treatment (39.8). Use of the AMP device did not change blood saturation levels; neither did it affect dental status, action of the masticatory muscles, nor did it cause TM joint dysfunction. 21 patients (72.4%) have now been fitted with an AMP device, and the mean follow-up is 13.4 months (range 2-22); 3 have been using the AMP only intermittently for TM joint pain or discomfort. We conclude that the AMP device helps the majority of patients and is an alternative, nonsurgical method for treating obstructive sleep apnea syndrome.

Follow-Up Studies↗
PubMed1995

Electromyographic signal changes during exercise in human chronic jaw-muscle pain.

Twelve individuals (2 males, 10 females) with chronic masticatory muscle pain and 11 individuals (2 males, 9 females) without, had their bite force and surface electromyography from the right and left superficial masseter and anterior temporalis muscles recorded before, during and after a 30-s sustained submaximal clenching task. This task was performed at 50% of the force level of each subject's maximum voluntary contraction (MVC) for 30 s. Brief (3 s) 50% MVC efforts were recorded at 15-s intervals, three times before and six times after the sustained clench. Each subject performed this pattern of activities three times with a 15-min rest between each trial. The centre frequency (CF) of the electromyographic power spectrum was calculated by fast Fourier transformations. The mean CF at the end of the 30-s clench and the rate of change at the CF during the clenching task were analysed between groups, sides and muscles. The data indicated that the masseter CF decreased at a significantly faster rate for the first clenching trial in the muscle-pain group. Conversely, the rate of change of the temporalis CF did not significantly differ for the two groups during the three clenching trials. By the third trial the CF of the exercised masseter in the non-pain group exhibited a similar rate of change to that in the pain group. This suggests that both repeated exercise and the presence of chronic inflammation increase the rate of change of the electromyographic signal of the contracting masseter. The mechanism underlying this increased change is unknown.

Adult↗
PubMed1995

Cross-correlation between stress, pain, physical activity, and temporalis muscle EMG in tension-type headache.

Thirty-six tension-type headache subjects and 36 non-headache matched controls recorded their temporalis muscle electromyographic (EMG) activity and their pain intensity, stress and physical activity levels in a daily diary. Measurements were performed every 30 min for 6 days (EMG 3 days only). A time-lagged cross-correlational analysis between pain, stress, physical activity, and EMG shows that the highest correlation coefficient values occurred between pain and stress at the same (r = 0.33) and at the two preceding 0.5 h time points (r = 0.21 and r = 0.26) in the headache group. Virtually no correlation was found between pain, stress, or physical activity with EMG for either group. These data show that temporalis muscle activity levels were not related to the rise and fall of the subjects' pain or stress levels. Conversely, elevated stress appeared to be highly related to pain; it occurs as both an antecedent and simultaneous event with elevated headache pain.

Adolescent↗
PubMed1995

Temporomandibular dysfunction, chronic orofacial pain and oral motor disorders in the 21st century.

This article describes the various sensory and motor disorders that afflict the orofacial region. These abnormalities are broadly separated into three groups of pathologic conditions: temporomandibular disorders; chronic orofacial pain disorders; and oral motor disorders. This article focuses on the diagnostic features of each specific disorder, suggesting alternate nomenclature for each disorder.

Bruxism↗
PubMed1995

Temporomandibular joint derangement with multiple surgical interventions: a case report.

This case report describes the experience of a 26-year-old woman who underwent multiple jaw surgeries. An initial 22 months of unsuccessful nonsurgical therapy was followed by a 7-year period during which the following were performed: 12 surgeries of her right temporomandibular joint; one surgery of her left temporomandibular joint; bilateral coronoidectomies; one surgery of her right mandible; and three surgeries of her left mandible. This case is important because although the existence of multiple jaw surgery cases are widely noted throughout the literature, this is the first case report that presents in-depth prospective documentation.

Adult↗
PubMed1994

Validity of a brief questionnaire in screening asymptomatic subjects from subjects with tension-type headaches or temporomandibular disorders.

Clinical investigations of temporomandibular disorders require objective, repeatable methods for screening diseased subjects from non-diseased control subjects. This study evaluated whether information gathered from a short, public domain questionnaire was useful in distinguishing temporomandibular disorder subjects (n = 216) from non-temporomandibular disorder controls (n = 69) and tension-type headache subjects (n = 22). The questionnaire consisted of eight questions relating to jaw pain (i.e., location of pain, precipitating factors, and temporal pattern of pain) and five questions relating to jaw function (i.e., joint noises, locking, and difficulty in opening). There were five possible answers to each question which ranged from 0 (no symptoms) to 4 (unbearable or constant symptoms). The total scores for the eight pain questions and the five jaw function questions were used to determine the questionnaire's sensitivity and specificity in each group, and ROC curves were plotted to identify the best cutoff point for disease presence or absence. Results showed that the questionnaire reliably distinguished between the control group and temporomandibular disorder group with 90.3%-97.7% sensitivity and 95.7%-100% specificity at cutoff values between 5 and 9. These results support the use of the questionnaire as a primary screening tool for general practice and as a supplementary screening tool for clinical temporomandibular disorder studies. However, results also showed that the questionnaire was unable to distinguish easily between TMD subjects and temporalis region tension-type headache subjects.

Adult↗
PubMed1994

A cognitive-behavioral approach to temporomandibular dysfunction treatment failures: a controlled comparison.

The effects of cognitive-behavioral treatment for patients with temporomandibular disorders were studied by comparing active treatment to a wait-list control condition. Patients were predominantly women and had been referred to the study after having poor response to dental/physical medicine care. Patients' conditions were evaluated pretreatment and posttreatment based on self-report measures of pain, distress, and jaw function problems. They were examined by a dentist who assessed pain-free opening, muscle palpation pain, and tenderness of the temporomandibular joints. The 5-week cognitive-behavioral treatment included relaxation training, self-monitoring of stressors, and cognitive coping strategies. Treatment had its greatest impact on improving mood, especially anxiety; however, there were some effects on the patients' experiences of pain.

Adult↗
PubMed1993

Electromyographic turns analysis of sustained contraction in human masseter muscles at various isometric force levels.

The jaw-closing muscles differ from peripheral limb muscles in that the maximum attainable force does not decline following a sustained isometric contraction. Also, the averaged electromyographic (EMG)/force ratio in these muscles does not change with sustained contraction, whereas it increases in fatiguing limb muscles. The present study analysed EMG records from masseters in healthy male subjects. No statistically significant difference was seen between average rectified EMG signals at the beginning or the end of a sustained isometric contraction at 25-100% of maximum voluntary contraction (MVC). However, when the number of turns, or reversals of direction, was taken at various percentage MVC levels, a significant decrease was seen after 60s or at the end of the contraction. The turns/force ratio decreased monotonically with percentage MVC, but the ratio was not significantly different at the end of a contraction from that at the beginning. This result confirms an earlier suggestion that neuromuscular fatigue does not accompany sustained contractions of these muscles.

Adult↗
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↗