Effect of parafunctional clenching on temporomandibular disorder pain and proprioceptive awareness.

This study tested the hypothesis that parafunctional clenching increases pain, can lead to a diagnosis of temporomandibular disorder (TMD) pain, and can produce reductions in proprioceptive awareness. Twenty individuals participated in EMG biofeedback training sessions on the left and right temporalis and masseter muscles. No subjects had TMD prior to training. Subjects were randomly assigned to either a Decrease group, who were instructed to maintain EMG activity below 2 microV during training, or an increase group, who were instructed to maintain EMG activity above 10 microV. To test the impact of parafunctional clenching on proprioceptive awareness, all subjects were instructed to barely touch their teeth together while EMG activity was recorded pre- and post-training. Three subjects assigned to the Increase group and no subjects assigned to the Decrease group were diagnosed with TMD pain following training. Self-reported pain post-training was significantly higher for the Increase group. Parafunctional clenching did not affect performance in the proprioceptive test.

A meta-analysis of EMG biofeedback treatment of temporomandibular disorders.

AIMS: Outcome evaluations of treatments incorporating electromyographic (EMG) biofeedback for temporomandibular disorders (TMD) have been conducted for more than 2 decades. The purpose of this study was to review the available literature to determine the efficacy of biofeedback-based treatments and to estimate treatment effect sizes. METHODS: A literature search located 13 studies of EMG biofeedback treatment for TMD, including 6 controlled, 4 comparative treatment, and 3 uncontrolled trials. Three types of outcome were examined: patient pain reports, clinical exam findings, and ratings of global improvement. RESULTS: Five of the 6 controlled trials found EMG biofeedback treatments to be superior to no treatment or psychologic placebo controls for at least 1 of the 3 types of outcome. Data from 12 studies contributed to a meta-analysis that compared pre- to posttreatment effect sizes for EMG biofeedback treatments to effect sizes for control conditions. Mean effect sizes for both reported pain and clinical exam outcomes were substantially larger for biofeedback treatments than for control conditions. In addition, 69% of patients who received EMG biofeedback treatments were rated as symptom-free or significantly improved, compared with 35% of patients treated with a variety of placebo interventions. Follow-up outcomes for EMG biofeedback treatments showed no deterioration from posttreatment levels. CONCLUSION: Although limited in extent, the available data support the efficacy of EMG biofeedback treatments for TMD.

In vivo comparison of synthetic osseous graft materials. A preliminary study.

The purpose of this study was to compare the in vivo osseous healing response of 4 commercially-available synthetic bone grafting materials; hydroxylapatite (HA), calcium sulfate (CaSO4) plus autogenous bone, or a bioactive glass ceramic: with particle size of 300-360 microm (BG1) or 90 to 710 microm (BG2). 4 osteotomy sites were prepared in each tibia of 10 adult male rabbits. One unfilled osteotomy site served as negative control (NC) and another site filled with autogenous bone was the positive control (PC). All animals received BG1 in 2 sites and BG2 in 2 sites. 5 animals received HA and five CaSO4 plus autogenous bone in the remaining 2 sites. Animals were sacrificed at 28 days post-surgery, histologic sections obtained and the % surface area of new bone formation for each material was determined by computerized image analysis. All graft sites showed evidence of bone formation, i.e., (NC) 41.95%; (PC) 50.41%; (BG1) 41.82%; (BG2) 40.36%; (HA) 41.83% and (CaSO4) 58.83%. Statistical analysis using an ANOVA with repeated measures on the materials common to all animals (excluding HA and CaSO4 groups) showed significant differences between materials in surface area of bone, with positive controls better than negative controls, and BG1 and BG2 not significantly different from the negative control. These results indicate that synthetic graft materials can support new bone formation in surgically prepared defects. The utility of a rabbit model for studying physiologic osseous turnover and healing is questioned for studies of slowly resorbing synthetic graft materials.

Effect of parafunctional clenching and estrogen on temporomandibular disorder pain.

To test the hypothesis that the pain-producing effect of parafunctional clenching is mediated by oral contraceptive use and estrogen levels, eight premenopausal women participated in daily (five days/week) 20-minute-long EMG biofeedback training sessions (on the left and right temporalis and masseter muscles) structured as a two-phase cross-over study. Four subjects used oral contraceptives, and four did not. Subjects were instructed to maintain temporalis and masseter activity below 2 microV during decrease training and above 10 microV during increase training. All subjects began their participation at the start of menses. The initial week of training was followed by a week of rest and then a second week of training at mid-cycle. Preliminary screening examinations showed that none of the subjects had TMD. One subject was diagnosed with TMD pain during increase training, and no subjects were diagnosed with TMD during decrease training. Self-reported pain following training increased significantly during increase training. No effects on pain were observed for oral contraceptive status. We conclude that chronic, low-level parafunctional clenching may be a factor producing temporomandibular disorder pain and that oral contraceptive status does not play a role in the TMD pain produced by the experimental protocol.

Effect of parafunctional clenching on TMD pain.

Parafunctional activities are assumed to play an important role in temporomandibular disorders (TMD), but experimental data in support of this hypothesis are lacking. This study examined the role of parafunctional clenching on various measures of TMD pain. Five subjects participated in daily 17-minute electromyogram biofeedback training sessions structured in three phases. Subjects were instructed to maintain temporalis and masseter muscle activity below 2 microV in the first (decrease) phase of training (10 sessions), above 10 microV in the second (increase) phase (1 to 8 sessions), and below 2 microV in the third (decrease) phase (10 to 15 sessions). Preliminary screening examinations showed that none of the subjects had TMD. Two subjects reported intolerable pain during increase training, and both were diagnosed with a TMD during this phase. No subject was diagnosed with TMD pain during either decrease training phase. The authors conclude that chronic, low-level parafunctional clenching may be a factor in the cause of TMD pain.

Myofascial pain dysfunction: treatments used by ADA members.

A survey of 10,000 members of the American Dental Association was conducted in order to identify the most commonly used treatments for myofascial pain dysfunction (MPD). A questionnaire was used in which MPD was defined, all treatments (including referral) were listed, and a percentage-of-use estimate for each treatment was requested. Results from 2,544 questionnaires showed that the most commonly used treatments are: flat plane splints with anterior/canine guidance or posterior group function, occlusal equilibration, thermal packs, relaxation/stress management training, diet counseling, and medications with anti-inflammatory (nonopioid) analgesic and muscle relaxant properties. The results also showed considerable variation in the ways common treatments are performed. A call is issued for systematic and careful research on the outcomes of these and other treatments and their major variations.

EMG biofeedback and discriminative muscle control.

The awareness model of biofeedback suggests that training teaches new skills or enhances performance at old skills, while the cognitive or feed-forward models suggest that biofeedback brings attention to the response of interest but does not actually increase task skill. In a test of the predictions made by these models, subjects were tested on one or more cross-modal matching tasks, provided brief training, and retested on the task(s). Thirty subjects participated in integer-matching tasks in which they were instructed to produce various levels of frontalis activity corresponding to the levels of a ratio scale. Forty-five subjects participated in a tone-matching task in which they tried to match their frontalis tension to the pitch of a tone. The results indicated that the groups receiving biofeedback training improved at the more difficult integer task and at the tone task. Subjects performed better on the integer tasks than at the tone task. Our findings suggest that an awareness model accounts for changes occurring during biofeedback training. However, an awareness model may be applicable only for tasks of moderate difficulty; for relatively easy tasks, a feed-forward model may be more appropriate. The clinical utility of cross-modal matching tasks is also described.

Feedback delays and relaxation expectancies in EMG biofeedback.

The use of noncontingent feedback controls in studies of the efficacy and process of electromyographic (EMG) biofeedback may yield results confounded by differential expectancies for relaxation. Furthermore, the role of expectancies in producing psychological and physical relaxation as well as reducing muscle activity is unclear. This study investigated the effects of feedback delays and induced relaxation expectancies on EMG activity and experienced relaxation. One hundred four non-clinical subjects participated in one auditory frontal EMG biofeedback training session. Subjects were assigned to one of four computerized feedback delay conditions (0.0037, 0.7493, 2.2481, 6.7444 s) and to one of two relaxation expectancy conditions (positive or negative). During 20 minutes of biofeedback training, all groups decreased frontal activity. Feedback delays interacted with training epochs in affecting EMG; the longest delay group reduced frontal activity more slowly than the shortest delay group during training. Positive relaxation expectancies produced greater experienced relaxation than did negative relaxation expectancies. Instrumental and expectancy factors in EMG biofeedback appear to operate independently of each other by reducing physiological activity and producing psychological relaxation respectively.

Subvocal motor activity and contextual processing.

Twenty male and female subjects listened for mispronounced words while minimizing either subvocal or frontalis electromyographic activity. Stimuli were varied on size of the distortion, lexical constraint, and contextual constraint, all known to influence detections. Analysis of both the reaction time and detection data indicated that the minimization of subvocal EMG activity reduced or eliminated the effect of contextual constraint, effect. Results indicate that subvocal activity is related to contextual processing. Additionally, reaction time data are reported that indicate that although low contextual constraint greatly slows the decision process, detectability is actually superior. A possible underlying mechanism for this reversal of the speed-accuracy trade-off is discussed.