International consensus on the assessment of bruxism: Report of a work in progress

In 2013, consensus was obtained on a definition of bruxism as repetitive masticatory muscle activity characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible and specified as either sleep bruxism or awake bruxism. In addition, a grading system was proposed to determine the likelihood that a certain assessment of bruxism actually yields a valid outcome. This study discusses the need for an updated consensus and has the following aims: (i) to further clarify the 2013 definition and to develop separate definitions for sleep and awake bruxism; (ii) to determine whether bruxism is a disorder rather than a behaviour that can be a risk factor for certain clinical conditions; (iii) to re-examine the 2013 grading system; and (iv) to develop a research agenda. It was concluded that: (i) sleep and awake bruxism are masticatory muscle activities that occur during sleep (characterised as rhythmic or non-rhythmic) and wakefulness (characterised by repetitive or sustained tooth contact and/or by bracing or thrusting of the mandible), respectively; (ii) in otherwise healthy individuals, bruxism should not be considered as a disorder, but rather as a behaviour that can be a risk (and/or protective) factor for certain clinical consequences; (iii) both non-instrumental approaches (notably self-report) and instrumental approaches (notably electromyography) can be employed to assess bruxism; and (iv) standard cut-off points for establishing the presence or absence of bruxism should not be used in otherwise healthy individuals; rather, bruxism-related masticatory muscle activities should be assessed in the behaviour's continuum.

Depressive symptoms account for differences between self-reported versus polysomnographic assessment of sleep quality in women with myofascial TMD

Patients with temporomandibular disorder (TMD) report poor sleep quality on the Pittsburgh Sleep Quality Index (PSQI). However, polysomnographic (PSG) studies show meagre evidence of sleep disturbance on standard physiological measures. The present aim was to analyse self-reported sleep quality in TMD as a function of myofascial pain, PSG parameters and depressive symptomatology. PSQI scores from 124 women with myofascial TMD and 46 matched controls were hierarchically regressed onto TMD presence, ratings of pain intensity and pain-related disability, in-laboratory PSG variables and depressive symptoms (Symptoms Checklist-90). Relative to controls, TMD cases had higher PSQI scores, representing poorer subjective sleep and more depressive symptoms (both P < 0·001). Higher PSQI scores were strongly predicted by more depressive symptoms (P < 0·001, R² = 26%). Of 19 PSG variables, two had modest contributions to higher PSQI scores: longer rapid eye movement latency in TMD cases (P = 0·01, R² = 3%) and more awakenings in all participants (P = 0·03, R² = 2%). After accounting for these factors, TMD presence and pain ratings were not significantly related to PSQI scores. These results show that reported poor sleep quality in TMD is better explained by depressive symptoms than by PSG-assessed sleep disturbances or myofascial pain. As TMD cases lacked typical PSG features of clinical depression, the results suggest a negative cognitive bias in TMD and caution against interpreting self-report sleep measures as accurate indicators of PSG sleep disturbance. Future investigations should take account of depressive symptomatology when interpreting reports of poor sleep.

Identification of a Sleep Bruxism Subgroup with a Higher Risk of Pain

Sleep bruxism research diagnostic criteria (SB-RDC) have been applied since 1996. This study was performed to validate these criteria and to challenge the hypothesis that pain is associated with lower frequencies of orofacial activities. Polygraphic recordings were made of 100 individuals presenting with a clinical diagnosis of sleep bruxism and 43 control individuals. TwoStep Cluster analyses (SPSS) were performed with sleep bruxism variables to reveal groupings among sleep bruxers and control individuals. Participants completed questionnaires during screening, diagnosis, and recording sessions. Cluster analysis identified three subgroups of sleep bruxers. Interestingly, 45 of the 46 sleep bruxers with values below SB-RDC were classified in the low-frequency cluster. These individuals were more likely to complain of pain and fatigue of masticatory muscles than were the higher-frequency sleep bruxers (odds ratios > 3.9, p < 0.01). Sleep bruxers were distributed among three heterogeneous groups. Sleep bruxers with low frequencies of orofacial activities were more at risk of reporting pain.

Could transient hypoxia be associated with rhythmic masticatory muscle activity in sleep bruxism in the absence of sleep-disordered breathing? A preliminary report

Sleep bruxism (SB) is a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth during sleep. Sleep bruxism activity is characterised by rhythmic masticatory muscle activity (RMMA). Many but not all RMMA episodes are associated with sleep arousal. The aim of this study was to evaluate whether transient oxygen saturation level change can be temporally associated with genesis of RMMA/SB. Sleep laboratory or home recordings data from 22 SB (tooth grinding history in the absence of reported sleep-disordered breathing) and healthy subjects were analysed. A total of 143 RMMA/SB episodes were classified in four categories: (i) no arousal + no body movement; (ii) arousal + no body movement; (iii) no arousal + body movement; (iv) arousal + body movement. Blood oxygen levels (SaO2 ) were assessed from finger oximetry signal at the baseline (before RMMA), and during RMMA. Significant variation in SaO2 over time (P = 0·001) was found after RMMA onset (+7 to +9 s). No difference between categories (P = 0·91) and no interaction between categories and SaO2 variation over time (P = 0·10) were observed. SaO2 of six of 22 subjects (27%) remained equal or slight increase after the RMMA/SB onset (+8 s) compared to baseline; 10 subjects (45%) slightly decreased (drop 0·01-1%) and the remaining (27%) decreased between 1% and 2%. These preliminary findings suggest that a subgroup of SB subjects had (i) a minor transient hypoxia potentially associated with the onset of RMMA episodes, and this (ii) independently of concomitant sleep arousal or body movements.

Validity of self-reported sleep bruxism among myofascial temporomandibular disorder patients and controls

Sleep bruxism (SB), primarily involving rhythmic grinding of the teeth during sleep, has been advanced as a causal or maintenance factor for a variety of oro-facial problems, including temporomandibular disorders (TMD). As laboratory polysomnographic (PSG) assessment is extremely expensive and time-consuming, most research testing this belief has relied on patient self-report of SB. The current case-control study examined the accuracy of those self-reports relative to laboratory-based PSG assessment of SB in a large sample of women suffering from chronic myofascial TMD (n = 124) and a demographically matched control group without TMD (n = 46). A clinical research coordinator administered a structured questionnaire to assess self-reported SB. Participants then spent two consecutive nights in a sleep laboratory. Audiovisual and electromyographic data from the second night were scored to assess whether participants met criteria for the presence of 2 or more (2+) rhythmic masticatory muscle activity episodes accompanied by grinding sounds, moderate SB, or severe SB, using previously validated research scoring standards. Contingency tables were constructed to assess positive and negative predictive values, sensitivity and specificity, and 95% confidence intervals surrounding the point estimates. Results showed that self-report significantly predicted 2+ grinding sounds during sleep for TMD cases. However, self-reported SB failed to significantly predict the presence or absence of either moderate or severe SB as assessed by PSG, for both cases and controls. These data show that self-report of tooth grinding awareness is highly unlikely to be a valid indicator of true SB. Studies relying on self-report to assess SB must be viewed with extreme caution.

Masticatory muscle sleep background electromyographic activity is elevated in myofascial temporomandibular disorder patients

Despite theoretical speculation and strong clinical belief, recent research using laboratory polysomnographic (PSG) recording has provided new evidence that frequency of sleep bruxism (SB) masseter muscle events, including grinding or clenching of the teeth during sleep, is not increased for women with chronic myofascial temporomandibular disorder (TMD). The current case-control study compares a large sample of women suffering from chronic myofascial TMD (n = 124) with a demographically matched control group without TMD (n = 46) on sleep background electromyography (EMG) during a laboratory PSG study. Background EMG activity was measured as EMG root mean square (RMS) from the right masseter muscle after lights out. Sleep background EMG activity was defined as EMG RMS remaining after activity attributable to SB, other orofacial activity, other oromotor activity and movement artefacts were removed. Results indicated that median background EMG during these non-SB event periods was significantly higher (P < 0·01) for women with myofascial TMD (median = 3·31 μV and mean = 4·98 μV) than for control women (median = 2·83 μV and mean = 3·88 μV) with median activity in 72% of cases exceeding control activity. Moreover, for TMD cases, background EMG was positively associated and SB event-related EMG was negatively associated with pain intensity ratings (0-10 numerical scale) on post-sleep waking. These data provide the foundation for a new focus on small, but persistent, elevations in sleep EMG activity over the course of the night as a mechanism of pain induction or maintenance.

Bruxism defined and graded: an international consensus

To date, there is no consensus about the definition and diagnostic grading of bruxism. A written consensus discussion was held among an international group of bruxism experts as to formulate a definition of bruxism and to suggest a grading system for its operationalisation. The expert group defined bruxism as a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible. Bruxism has two distinct circadian manifestations: it can occur during sleep (indicated as sleep bruxism) or during wakefulness (indicated as awake bruxism). For the operationalisation of this definition, the expert group proposes a diagnostic grading system of 'possible', 'probable' and 'definite' sleep or awake bruxism. The proposed definition and grading system are suggested for clinical and research purposes in all relevant dental and medical domains.

Bruxism physiology and pathology: an overview for clinicians

Awake bruxism is defined as the awareness of jaw clenching. Its prevalence is reported to be 20% among the adult population. Awake bruxism is mainly associated with nervous tic and reactions to stress. The physiology and pathology of awake bruxism is unknown, although stress and anxiety are considered to be risk factors. During sleep, awareness of tooth grinding (as noted by sleep partner or family members) is reported by 8% of the population. Sleep bruxism is a behaviour that was recently classified as a 'sleep-related movement disorder'. There is limited evidence to support the role of occlusal factors in the aetiology of sleep bruxism. Recent publications suggest that sleep bruxism is secondary to sleep-related micro-arousals (defined by a rise in autonomic cardiac and respiratory activity that tends to be repeated 8-14 times per hour of sleep). The putative roles of hereditary (genetic) factors and of upper airway resistance in the genesis of rhythmic masticatory muscle activity and of sleep bruxism are under investigation. Moreover, rhythmic masticatory muscle activity in sleep bruxism peaks in the minutes before rapid eye movement sleep, which suggests that some mechanism related to sleep stage transitions exerts an influence on the motor neurons that facilitate the onset of sleep bruxism. Finally, it remains to be clarified when bruxism, as a behaviour found in an otherwise healthy population, becomes a disorder, i.e. associated with consequences (e.g. tooth damage, pain and social/marital conflict) requires intervention by a clinician.

Sleep bruxism is associated to micro-arousals and an increase in cardiac sympathetic activity

Sleep bruxism (SB) subjects show a higher incidence of rhythmic masticatory muscle activity (RMMA) than control subjects. RMMA is associated with sleep micro-arousals. This study aims to: (i) assess RMMA/SB episodes in relation to sleep cycles; (ii) establish if RMMA/SB and micro-arousals occur in relation to the slow wave activity (SWA) dynamics; (iii) analyze the association between RMMA/SB and autonomic cardiac activity across sleep cycles. Two nights of polygraphic recordings were made in three study groups (20 subjects each): moderate to high SB, low SB and control. RMMA episodes were considered to occur in clusters when several groups of RMMA or non-specific oromotor episodes were separated by less than 100 s. Correlations between sleep, RMMA/SB index and heart rate variability variables were assessed for the first four sleep cycles of each study group. Statistical analyses were done with SYSTAT and SPSS. It was observed that 75.8% of all RMMA/SB episodes occurred in clusters. Micro-arousal and SB indexes were highest during sleep cycles 2 and 3 (P < 0.001). Within each cycle, micro-arousal and RMMA/SB indexes showed an increase before each REM sleep (P <or= 0.02). The cross-correlation plot for micro-arousal index showed positive association from 4 min preceding SB onset in the moderate to high SB subjects (P <or= 0.06). The cross-correlation plot revealed that SWA decreases following SB onset (P <or= 0.05). Further cross-correlation analysis revealed that a shift in sympatho-vagal balance towards increased sympathetic activity started 8 min preceding SB onset (P <or= 0.03). In moderate to severe SB subjects, a clear increase in sympathetic activity precedes SB onset.

Experimentally induced arousals during sleep: a cross-modality matching paradigm

Micro-arousals occur spontaneously or in response to exogenous and endogenous sensory input during sleep. The function of micro-arousals remains unclear, for example, whether it reflects a disturbance or a preparatory response to environmental changes. The goal of this study was to assess arousal responsiveness when two types of sensory stimulations were used: auditory (AD) alone and the addition of a vibrotactile (VT) sensation. Ten normal sleepers participated in three nights of polygraphic recordings. The first night was for habituation and to rule out sleep disorders, and the second to collect baseline sleep data. During the third night, AD and VT + AD stimuli, with three levels of intensities for auditory and vibratory signals, were randomly given to induce arousal responses in sleep stages 2, 3 and 4 and rapid eye movement (REM). The frequency of the arousal responses increased with stimulus intensity for all sleep stages and was lowest in stages 3 and 4. In non-REM (NREM) sleep, combined VT + AD stimulation induced more frequent and more intense arousal responses than AD alone. In REM sleep, more frequent micro-arousals rather than awakenings were triggered by combined stimulations. In stage 2, the response rate of total induced K-complexes did not differ between both types of stimulations while more K-complexes followed by arousals were evoked by the combined VT + AD stimulation than by the AD alone. The induced arousals were associated with an increase in heart rate in all sleep stages. An increase in suprahyoid muscle tone was observed in NREM sleep only, REM being not associated with a rise in muscle tone following experimental stimulation. Most leg and body movements occurred in response to induced awakenings. These results suggest that the cross-modality sensory stimuli triggered more arousal responses in comparison with single-modality stimuli. In an attempt to wake a sleeping subject, the addition of a tactile stimulation, such as shaking the shoulder, is an effective strategy that increases the arousal probability.

Quantitative polygraphic controlled study on efficacy and safety of oral splint devices in tooth-grinding subjects

The efficacy of occlusal splints in diminishing muscle activity and tooth-grinding damage remains controversial. The objective of this study was to compare the efficacy and safety of an occlusal splint (OS) vs. a palatal control device (PCD). Nine subjects with sleep bruxism (SB) participated in this randomized study. Sleep laboratory recordings were made on the second night to establish baseline data. Patients then wore each of the splints in the sleep laboratory for recording nights three and four, two weeks apart, according to a crossover design. A statistically significant reduction in the number of SB episodes per hour (decrease of 41%, p = 0.05) and SB bursts per hour (decrease of 40%, p < 0.05) was observed with the two devices. Both oral devices also showed 50% fewer episodes with grinding noise (p = 0.06). No difference was observed between the devices. Moreover, no changes in respiratory variables were observed. Both devices reduced muscle activity associated with SB.

Neurobiological mechanisms involved in sleep bruxism

Sleep bruxism (SB) is reported by 8% of the adult population and is mainly associated with rhythmic masticatory muscle activity (RMMA) characterized by repetitive jaw muscle contractions (3 bursts or more at a frequency of 1 Hz). The consequences of SB may include tooth destruction, jaw pain, headaches, or the limitation of mandibular movement, as well as tooth-grinding sounds that disrupt the sleep of bed partners. SB is probably an extreme manifestation of a masticatory muscle activity occurring during the sleep of most normal subjects, since RMMA is observed in 60% of normal sleepers in the absence of grinding sounds. The pathophysiology of SB is becoming clearer, and there is an abundance of evidence outlining the neurophysiology and neurochemistry of rhythmic jaw movements (RJM) in relation to chewing, swallowing, and breathing. The sleep literature provides much evidence describing the mechanisms involved in the reduction of muscle tone, from sleep onset to the atonia that characterizes rapid eye movement (REM) sleep. Several brainstem structures (e.g., reticular pontis oralis, pontis caudalis, parvocellularis) and neurochemicals (e.g., serotonin, dopamine, gamma aminobutyric acid [GABA], noradrenaline) are involved in both the genesis of RJM and the modulation of muscle tone during sleep. It remains unknown why a high percentage of normal subjects present RMMA during sleep and why this activity is three times more frequent and higher in amplitude in SB patients. It is also unclear why RMMA during sleep is characterized by co-activation of both jaw-opening and jaw-closing muscles instead of the alternating jaw-opening and jaw-closing muscle activity pattern typical of chewing. The final section of this review proposes that RMMA during sleep has a role in lubricating the upper alimentary tract and increasing airway patency. The review concludes with an outline of questions for future research.

Evidence that experimentally induced sleep bruxism is a consequence of transient arousal

Spontaneous rhythmic masticatory muscle activity (RMMA) during sleep occurs more frequently following spontaneous transient micro-arousal in patients with sleep bruxism (SB) and normal controls. Here, we tested the hypothesis that an experimental arousal would be followed by an increase in RMMA. We identified RMMA on polygraphic recordings taken before and after sensory stimulation to induce experimental arousal in eight SB patients and eight matched normal subjects. The rate of experimental arousal and the level of resting electromyographic activity in masseter and suprahyoid muscles during sleep did not differ between the groups. In both, muscle tone and heart rate increased during the experimental arousal. Although post-arousal RMMA occurred in all SB patients, it was seen in only one normal subject. Moreover, tooth-grinding occurred during 71% of the evoked RMMA in SB patients. These results support the hypothesis that SB is an exaggerated form of oromotor activity associated with sleep micro-arousal.

Lack of associations between occlusal and cephalometric measures, side imbalance in striatal D2 receptor binding, and sleep-related oromotor activities

AIMS

First, to evaluate possible orofacial morphologic differences between sleep bruxers and non-bruxers, and second, to determine possible correlations between morphologic factors and striatal D2 receptor expression in persons with sleep-related oromotor activities.

METHODS

Twenty subjects were included in this study; half of them had polysomnographically confirmed oromotor values above the cutoff points for sleep bruxism. For all participants, 26 standard occlusal measures were recorded clinically and from dental study casts. In addition, 25 standard angular and linear measures were taken from standardized cephalometric films, and variables were derived to evaluate dental and skeletal relationships. Fourteen of the 20 participants had also participated in a previous study that included iodine-123-iodobenzamide (I-123-IBZM) and single-photon emission-computed tomography (SPECT). For them, the side-to-side difference in striatal D2 receptor binding was determined as the neurochemical outcome measure.

RESULTS

Following the classical Bonferroni adjustment for multiple testing, no morphologic differences were found between the sleep bruxers and the non-bruxers. In addition, none of the morphologic variables were significantly associated with the neuroimaging data.

CONCLUSION

Taking into account the low power of this retrospective, exploratory study, the results suggest that the orofacial morphology of sleep bruxers does not differ from that of non-bruxers. In addition, morphologic factors are probably not involved in the asymmetry in striatal D2 receptor distribution that was previously observed in association with sleep bruxism.

Lower number of K-complexes and K-alphas in sleep bruxism: a controlled quantitative study

OBJECTIVES

Although patients with sleep bruxism (SB) show a higher incidence of rhythmic masticatory muscle activity (RMMA) during sleep than matched normal controls, they are good sleepers. Sleep macrostructure (e.g. total sleep time, sleep latency, number of awakenings or sleep stage shifts and sleep stage duration) is similar between groups. Differences in sleep microstructure between SB patients and normals have been investigated only in few studies. The aim of the present study was to quantify number of microarousals, K-complexes, K-alphas, EEG spindles, and the density of slow wave activity, in both groups, in order to better understand the pathophysiology of SB.

METHODS

Ten normal sleepers were matched for age and gender with 10 patients who exhibited frequent tooth-grinding during sleep. Using quantitative polysomnographic measures, we compared the above-mentioned sleep variables in both groups. Data are presented as indices for total sleep and for consecutive non-rapid eye movement (non-REM) episodes over non-REM to rapid eye movement (REM) cycles and per hour of sleep.

RESULTS

SB patients showed 6 times more RMMA episodes per hour of sleep than normals (P<0.001), with a higher frequency in the second and third non-REM to REM cycles. SB patients presented 42.7% fewer K-complexes per hour of stage 2 sleep, but only normals showed a decline from the first to fourth non-REM episode. Only 24% of SB-RMMA episodes were associated with K-complexes in 60 s. The number of K-alphas was 61% lower in SB patients, no change across non-REM episodes was noted. While no difference in electroencephalographic (EEG) spindles or slow wave activity (SWA) was observed between groups, EEG spindles increased and SWA decreased linearly over consecutive non-REM to REM cycles.

CONCLUSIONS

According to our observations, good sleep in SB patients is characterized by a low incidence of K-complexes or K-alphas and by the absence of any difference in other sleep microstructure variables or SWA.

Sleep bruxism: an oromotor activity secondary to micro-arousal

Spontaneous rhythmic masticatory muscle activity (RMMA) during sleep occurs in relation to transient activation in the cerebral and autonomic nervous systems of normal subjects and in patients with sleep bruxism (SB). In this study, we made a quantitative assessment of the sequential changes in cortical electroencephalographic (EEG) and autonomic-cardiac activities associated with micro-arousals preceding RMMA episodes. We matched 10 SB patients with 10 normal subjects. The onset of RMMA episodes was defined in terms of the onset of activation in the suprahyoid muscles. In SB patients, an increase in cortical EEG activity was observed 4 seconds before the onset of suprahyoid activity in 79% of episodes. A significant acceleration in heart rate was initiated one cardiac cycle before RMMA onset. A clear sequence of cortical to autonomic-cardiac activation precedes jaw motor activity in SB patients. This suggests that SB is a powerful oromotor manifestation secondary to micro-arousal.

Bruxism and orofacial movements during sleep

Several issues remain to be clarified in the future research and management of SB. It is important to differentiate SB from other normal sleep orofacial activities and concomitant sleep disorders. Other orofacial activities may obscure the diagnosis of SB and may give an ambiguous clinical picture when evaluating treatment efficacy. Laboratory recordings provide a more specific diagnosis. Most of the clinical signs (e.g., tooth wear, masseter hypertrophy) are not exclusive to SB but could be concomitant with other habits or activities during wakefulness. No pathologic features in the central nervous system, such as a dysfunction of the dopaminergic system, have been observed in SB patients. Recent neurophysiologic studies have suggested that SB is a powerful microarousal event associated with central and autonomic nervous system activity during sleep. The additive contribution of psychosocial stress cannot be overlooked. There have been no recent major breakthroughs in SB management. Cognitive and behavioral managements, which include stress management, lifestyle changes, or improved coping mechanisms, may be beneficial. Oral splint appliances are useful to protect teeth from damage. A few medications (e.g., benzodiazepines, muscle relaxants) may be helpful for a short-term period, particularly when there is secondary pain, but controlled studies are needed to assess their efficacy, safety, and patient acceptance and tolerance.

Variability in sleep bruxism activity over time

Sleep bruxism (SB) is an oral activity associated with jaw movements and tooth grinding. Sleep bruxism is believed to be highly variable over time, with subjects showing no activity on some nights and intense activity on others. Assessment of SB variability in individual patients is necessary for clinical trials designed to estimate the efficacy of SB management strategies. The present study analysed SB night-to-night variability over time in nine moderate to severe SB patients. Excluding the first night for habituation, a total of 37 nights were analysed, with a range of 2-8 nights per subject. The interval between the first and the last recording was between 2 months and 7.5 years. The outcomes were the number of SB episodes per hour, number of SB bursts per hour and number of SB episodes with grinding noise. The within subject variability of the three SB oromotor outcomes was evaluated using standard deviation (SD) and coefficient of variation. To verify the diagnosis of subjects over time, the values of the oromotor outcomes were compared with a standard research diagnostic cut-off: (1) Number of SB episodes per hour >4, (2) Number of SB bursts per hour >25, (3) Number of SB episodes with noise per night >1 (Lavigne et al. 1996). The mean coefficient of variation for the nine subjects was 25.3% for SB episodes per hour, 30.4% for SB bursts per hour and 53.5% for episodes with noise. Linear regression showed that the number of SB episodes per hour of stages 1 and 2 explains a large proportion of the variability. The SB diagnosis remained constant over time for every subject: 35 nights over 37 respected criteria 1 and 2, while grinding was present every night. These results indicate that while the SB diagnostic remains relatively constant over time in moderate to severe sleep bruxers, individual variability could be important in some SB patients.

Double-blind, crossover, placebo-controlled trial of bromocriptine in patients with sleep bruxism

This study was designed to assess the effects of bromocriptine, a dopamine D2 receptor agonist, on sleep bruxism. Seven otherwise healthy patients with severe and frequent sleep bruxism participated in this randomized, double-blind, placebo-controlled study. The study used a crossover design that included 2 weeks of active treatment or placebo with a washout period of 1 week. To further evaluate whether bromocriptine influences striatal D2 receptor binding, we used iodine-123-iodobenzamide single photon emission computed tomography (SPECT) under both placebo and bromocriptine regimens. Bromocriptine did not reduce the frequency of episodes of bruxism during sleep (mean +/- SEM, 9.0 +/- 1.0 and 9.6 +/- 1.5 bruxism episodes per hour for placebo and bromocriptine, respectively) or the amplitude of masseter muscle contractions (root mean square values, 48.2 +/- 15.5 microV and 46.9 +/- 12.7 microV for placebo and bromocriptine, respectively). SPECT also failed to reveal that either treatment had any influence on striatal D2 binding (values for total binding in counts/pixel, 1.80 [1.72-1.93] and 1.79 [1.56-1.87] for placebo and bromocriptine, respectively). This study shows that a nightly dose of bromocriptine does not exacerbate or reduce sleep bruxism motor activity.

Heart rate changes during sleep in response to experimental thermal (nociceptive) stimulations in healthy subjects

OBJECTIVE

During wakefulness, nociceptive thermal stimulation can trigger a rapid and transient rise in heart rate (HR). During sleep, HR variations are different across sleep stages; HR is more variable in stage 2 and in REM than in stages 3 and 4. The aim of this study was to assess the HR response to experimental thermal stimulation during different sleep stages.

METHODS

Eight young subjects free of sleep and pain problems, underwent a night of polysomnographic recording during which experimental thermal stimulations were applied. During all sleep stages (St), a series of cold, warm/control and heat pain stimulations were applied over the shoulder skin by means of a water-driven system. Variation of HR interval was measured for 6 s before and for 6 s during the thermal stimulation.

RESULTS

In comparison to control warm stimulation, experimental nociceptive thermal stimulation induced a significant rise in HR during sleep; HR increased by 7% in St 2, 5.4% in St 3&4, and by 4.3% in REM sleep.

CONCLUSION

The brief increase in cardiac activity with experimental nociceptive stimulation suggests that during sleep, the autonomic-cardiac nervous system remains reactive to external sensory inputs and is part of the physiological response to preserve body safety and sleep integrity in the face of potentially harmful stimulation.

Rhythmic masticatory muscle activity during sleep in humans

Rhythmic Masticatory Muscle Activity (RMMA) is frequently observed during sleep in normal subjects and sleep bruxers. We hypothesized that some normal subjects exhibit RMMA at a lower frequency than sleep bruxers. Polysomnographic data from 82 normal subjects were compared with data from 33 sleep bruxers. RMMA episodes were defined as three or more consecutive bursts of masseter EMG activity, with or without tooth-grinding. Such episodes were observed in nearly 60% of normal subjects. A lower frequency of episodes was noted in normal subjects than in bruxers. Sleep organization was similar between groups. Bruxers had twice as many masseter muscle bursts per episode and episodes of higher amplitude compared with controls with RMMA. The high prevalence of RMMA observed in normal subjects suggests that this activity is related to certain sleep-related physiological functions, including autonomic activation.

A controlled daytime challenge of motor performance and vigilance in sleep bruxers

Many etiological factors have been suggested for sleep bruxism. Among these, elevated mental and physical alertness has been proposed to characterize sleep bruxers. The present study tests the hypothesis that, during the day-time, sleep bruxers are more vigilant and more prone to react to a motor command than are control subjects. Seven sleep bruxers, diagnosed polysomnographically according to validated research criteria, were matched for age and gender to seven control subjects. A simple reaction time task was selected to assess daytime vigilance and motor responsiveness. The following physiological measures were recorded: reaction time, error rate, electroencephalography, electrocardiography, electromyography, and video detection of body movements. Analysis of these variables showed no differences between groups. During the test, bruxers and controls showed a parallel decrease in EEG vigilance and heart rate over time. Frequency of orofacial and body movements was the same in both groups, and no clenching activity was observed during the experimental test. Subjects' visual analog scale ratings revealed that both controls and bruxers were more competitive after the test than before, and bruxers were slightly more anxious than controls before and after the test. Together, the results indicate that sleep bruxers are neither more vigilant nor more prone to react to a motor command during the daytime than are control subjects.

Idiopathic myoclonus in the oromandibular region during sleep: a possible source of confusion in sleep bruxism diagnosis

As part of a larger study, polysomnographic and audiovisual data were recorded over 2 nights in 41 subjects with a clinical diagnosis of sleep bruxism (SB). Electromyographic (EMG) events related to SB were scored according to standard criteria (Lavigne et al. J Dent Res 1996;75:546-552). Post hoc analysis revealed that rapid shock-like contractions with the characteristics of myoclonus in the jaw muscles were observed in four subjects. EMG bursts characterized as myoclonus were significantly shorter in duration than bursts classified as SB. None of the subjects had any history of myoclonus while awake. Myoclonic episodes were more frequent in sleep stages 1 and 2 than in REM. Half of the episodes contained one or two contractions whereas the other half had three or more repetitive contractions. SB and myoclonus coexisted in one subject. To rule out sleep epilepsy, full electroencephalogram montage was done in three subjects and no epileptic spikes were noted. Our results suggest that approximately 10% of subjects clinically diagnosed as SB could present oromandibular myoclonus during sleep.

Sleep disorders and the dental patient: an overview

This article is intended to briefly describe common sleep disorders of interest to the dental profession and to render general management guidelines. Topics include sleep-related bruxism, xerostomia, hypersalivation, gastroesophageal reflux, apnea, and the effect of orofacial pain on sleep quality. The term sleep-related is used instead of the term nocturnal because some of the activities described can occur with daytime sleep.

Do bruxism and temporomandibular disorders have a cause-and-effect relationship?

Controversy continues to exist over the putative role of bruxism in the etiology of temporomandibular disorders. A commonly held concept is that bruxism leads to signs and symptoms characteristic of one or more of the subdiagnoses of temporomandibular disorders, while another hypothesis suggests that bruxism is a temporomandibular disorder itself that sometimes coexists with other forms of temporomandibular disorders. Following a thorough review of the literature in this article, it is concluded that the relationship between bruxism and temporomandibular disorders is still unclear. Future research should examine longitudinal epidemiologic and clinical/experimental data to establish or refute a cause-and-effect relationship. In doing so, the existence of various sub-groups of temporomandibular disorders should be taken into account, and sleep-related bruxism should be discriminated from its daytime variant.

Oral splints: the crutches for temporomandibular disorders and bruxism?

Despite the extensive use of oral splints in the treatment of temporomandibular disorders (TMD) and bruxism, their mechanisms of action remain controversial Various hypotheses have been proposed to explain their apparent efficacy (i.e., true therapeutic value), including the repositioning of condyle and/or the articular disc, reduction in the electromyographic activity of the masticatory muscles, modification of the patient's "harmful" oral behavior, and changes in the patient's occlusion. Following a comprehensive review of the literature, it is concluded that any of these theories is either poor or inconsistent, while the issue of true efficacy for oral splints remains unsettled. However, the results of a controlled clinical trial lend support to the effectiveness (i.e., the patient's appreciation of the positive changes which are perceived to have occurred during the trial) of the stabilizing splint in the control of myofascial pain. In light of the data supporting their effectiveness but not their efficacy, oral splints should be used as an adjunct for pain management rather than a definitive treatment. For sleep bruxism, it is prudent to limit their use as a habit management aid and to prevent/limit dental damage potentially induced by the disorder. Future research should study the natural history and etiologies of TMD and bruxism, so that specific treatments for these disorders can be developed.

Effects of the D2 receptor agonist bromocriptine on sleep bruxism: report of two single-patient clinical trials

An altered dopamine receptor status has been associated with sleep bruxism. Evidence from a functional neuro-imaging study has implicated an abnormal side imbalance in striatal D2 receptor expression in its pathophysiology. To assess the significance of this finding, we studied the effects of short-term administration of the preferential dopamine D2 receptor agonist bromocriptine on sleep bruxism in a double-blind, placebo-controlled polysomnographic and neuro-imaging study with a single crossover design. Six otherwise healthy and drug-free patients with sleep bruxism were entered into the trial. One of the patients dropped out due to an intercurrent illness, while three others were discontinued from the study due to severe adverse reactions to bromocriptine. Because of the high frequency and intensity of the side-effects, the trial was interrupted. Two patients, however, completed the trial without any adverse reactions. Their outcome measures are presented as single-patient clinical trials. Following a two-week administration of bromocriptine, both patients showed a decrease in the number of bruxism episodes per hour of sleep of about 20% to 30% with respect to the placebo. WHile no significant differences between both conditions (i.e., placebo and bromocriptine) were found for the number of bruxism bursts per episode, significantly lower root-mean-squared EMG levels per bruxism burst occurred during bromocriptine use. In association with this polysomnographically established attenuation of sleep bruxism, bromocriptine afforded a decreased normal side distribution of striatal D2 receptor binding, as was evidenced by single-photon-emission computed tomography using the radioactive D2 receptor antagonist iodine-123-iodobenzamide. This study supports previous suggestions that the central dopaminergic system may be involved in the modulation of sleep bruxism. To see if the present findings apply across a population, investigators should use a peripheral D-2 antagonist to prevent side-effects.

Motor activity in sleep bruxism with concomitant jaw muscle pain. A retrospective pilot study

In a controlled polysomnographic (PSG) study that we recently performed in our laboratory, we noticed that some patients with a chief complaint of sleep bruxism reported concomitant non-myofascial pain in their masticatory muscles. To study the influence of such pain on the pattern of bruxism motor activity, we re-assessed the 2nd out of 2 consecutive PSG and masseter electromyographic (EMG) recordings of 7 bruxers without pain and 6 bruxers with concomitant jaw muscle pain. Among others, the selection of these patients was based on reports of current jaw muscle pain intensity, using 100-mm visual analogue scales. In our sample of bruxism patients with pain, levels of pain intensity did not differ significantly between bedtime and awakening in the morning. Although there were no significant differences between both subgroups of bruxers in the number of bruxism bursts per episode and the root-mean-squared EMG level per bruxism burst, bruxers with pain had 40% less bruxism episodes per hour of sleep. This suggests that non-myofascial jaw muscle pain decreases the number of initiations of bruxism episodes, but leaves their contents unaffected.

The effect of catecholamine precursor L-dopa on sleep bruxism: a controlled clinical trial

The putative role of the dopaminergic system in sleep bruxism (SB) was studied in a double-blind clinical trial by using low doses of short-term L-dopa in combination with benserazide. We recorded 10 patients with SB in our sleep laboratory for 3 consecutive nights. The first night was for habituation to the laboratory environment. During the second and the third nights, the patients received two doses of either L-dopa or a placebo in a crossover fashion: the first dose 1 h before bedtime and the second, 4 h after the first one. The order of administration was reversed in half the patients. The efficacy of L-dopa was analyzed by using multilevel models. L-Dopa resulted in a significant decrease in the average number of bruxism episodes per hour of sleep, as well as in a significant reduction in the average value of the root-mean-square (RMS) electromyography (EMG) level per bruxism burst. This indicates that L-dopa exerts an attenuating effect on SB. In addition, L-dopa caused a reduction in the variance in RMS values, which suggests that L-dopa normalizes the EMG activity patterns associated with SB.

Relationship between sleep, neck muscle activity, and pain in cervical dystonia

OBJECTIVE

The interactions between sleep, neck muscle activity, and cervical spinal pain were examined in a controlled study with nine patients suffering from idiopathic cervical dystonia (ICD; also referred to as spasmodic torticollis), and nine gender- and age-matched controls.

METHODS

From each participant, two all-night polysomnograms with additional electromyographic recordings from the sternocleidomastoid and upper trapezius muscles were obtained. The first night was for habituation to the laboratory environment; the second night for experimental data collection. Visual analogue scales were used to collect intensity and unpleasantness ratings of cervical spinal pain before and after the second sleep recording.

RESULTS

None of the standard sleep variables showed statistically significant differences between average values of both groups of participants. However, a significantly larger variance in sleep latency was obtained for the ICD patients. In general, abnormal cervical muscle activity decreased immediately when lying down without the intention to go to sleep. Subsequently, abnormal muscle contractions were gradually abolished in all ICD patients during the transition from relaxed wakefulness to light NREM sleep. Following this transition phase, no more abnormal EMG activity was found in any of our patients. Finally, cervical spinal pain intensity and unpleasantness were reduced by about 50% overnight.

CONCLUSIONS

Both supine position and sleep can be associated with an improvement of symptoms of ICD, and this disorder does not induce any sleep perturbations.

Striatal D2 receptor binding in sleep bruxism: a controlled study with iodine-123-iodobenzamide and single-photon-emission computed tomography

The neurochemical mechanisms underlying sleep bruxism are little understood at present. However, recent pharmacologic evidence suggests that the central dopaminergic system may be involved in the pathophysiology of sleep bruxism. This possibility was further assessed by means of functional neuroimaging of dopamine D2 receptors with single-photon-emission computed tomography (SPECT). Ten controls and ten patients with polysomnographically confirmed sleep bruxism were injected intravenously with 185 MBq (5 mCi) iodine-123-iodobenzamide, a specific D2 receptor antagonist radioligand, and data acquisition was performed 90 min post-injection. Following image reconstruction, it was found that striatal D2 receptor binding potential (basal ganglia/background ratio) did not differ significantly between bruxism patients and controls. However, side-to-side differences between unilateral values of the striatal D2 binding potential ("highest side" values minus "lowest side" values) were significantly larger for the bruxism patients (p < 0.001, by two-independent-samples t test with pooled variances). It was concluded that an abnormal side imbalance in striatal D2 receptor expression can be associated with sleep bruxism. This reinforces the possibility that the central dopaminergic system plays a role in the pathophysiology of this disorder.

Pain perception in idiopathic cervical dystonia (spasmodic torticollis)

Cervical spinal pain is frequently found in conjunction with idiopathic cervical dystonia (ICD), a focal dystonia characterized by sustained deviation of the head. Since the perception of noxious stimuli has never been studied in ICD, we performed a controlled study to obtain more insight into the psychophysics of dystonia-related muscle pain by evaluating pressure-induced pain levels. In nine ICD patients and five gender- and age-matched asymptomatic control subjects, pain-pressure thresholds (PPTs) were determined in the sternocleidomastoid and upper trapezius muscles, both at resting activity and at maximal voluntary contraction (MVC). The masseter muscles served as non-pathological control regions. To determine the accuracy of PPT values, pain intensity and unpleasantness were rated at threshold on 100-mm visual analogue scales. Four replication measurements were obtained. The data were analyzed by multilevel procedures. For all muscles under investigation, average PPTs of the ICD patients were about two times lower than those of the control subjects (P < 0.001-0.0005) and showed a smaller intra-subject variance. Further, average PPTs at MVC were about two times higher than those at resting activity (P < 0.005). These results provide psychophysical evidence to suggest that, at controlled levels of muscle contraction, the threshold of pain perception is decreased in ICD. In addition, ICD patients seem to be better able to establish their own PPTs than control subjects, which might be due to a different setting of the discriminative aspect of pain in ICD. Surprisingly, lower intensity and unpleasantness scores were found in ICD patients with coinciding painful and deviated sides than in ICD patients for whom the painful side was opposite to the deviated one (P < 0.05). This finding might be of clinical importance for defining functional disability and predicting treatment outcome.

Bruxism: A factor associated with temporomandibular disorders and orofacial pain

Rhythmic masticatory muscle activities are probably part of normal jaw motor behavior. Certain factors, like disease, stress, personality, alcohol, and medication, may turn this normal activity into a condition that might include abnormal tooth wear, myofascial pain, and temporomandibular joint problems. This condition then corresponds with bruxism. Bruxism and masticatory muscle pain may reciprocally influence one another: although not a compulsory finding, bruxism may be associated with the predisposition, initiation, and perpetuation of temporomandibular disorders and orofacial pain. On the other hand, the presence of jaw muscle pain may reduce bruxism motor activity. Research on the integrity and nature of the relationship between bruxism and pain is hampered by controversies that exist regarding definition, diagnostic criteria, and measurement techniques. Moreover, the pathophysiology of bruxism and its association with other sleep-related and movement disorders are still unclear. Consequently, there is no real cure for bruxism, although several treatments may be used to control its adverse effects. However, there is very limited research to support the efficacy of behavioral, physical, dental, pharmacological, and orthopedic treatments. Probably the best current treatment modality for bruxism is the occlusal stabilization splint. Although such an orthopedic device may not actually prevent bruxism, it may help to reduce its symptoms.

Sleep bruxism: validity of clinical research diagnostic criteria in a controlled polysomnographic study

The clinical validity of diagnostic criteria for sleep orofacial motor activity--more specifically, bruxism--has never been tested. Polysomnographic recordings from 18 bruxers and 18 asymptomatic subjects, selected according to American Sleep Disorders Association criteria, were analyzed (1) to discriminate sleep bruxism from other orofacial motor activities and (2) to calculate sensitivity, specificity, and predictive values of research criteria. Clinical observations and reports revealed that all 18 bruxers reported frequent tooth-grinding during sleep. Tooth wear was noted in 16 out of 18 bruxers and jaw discomfort reported by six of them. These findings were present in none of the controls. The analysis of polysomnographic data showed that the asymptomatic subjects presented a mean of 1.7 +/- 0.3 bruxism episodes per hour of sleep (sustained or repetitive bursting activity in jaw closer muscles), while bruxers had a significantly higher level of activity: 5.4 +/- 0.6. Controls exhibited 4.6 +/- 0.3 bruxism bursts per episode and 6.2 (from 0 to 23) bruxism bursts per hour of sleep, whereas bruxers showed, respectively, 7.0 +/- 0.7 and 36.1 (5.8 to 108). Bruxism-like episodes with at least two grinding sounds were noted in 14 of the 18 bruxers and in one control. The two groups exhibited no difference in any of the sleep parameters. Based on the present findings, the following polysomnographic diagnostic cut-off criteria are suggested: (1) more than 4 bruxism episodes per hour, (2) more than 6 bruxism bursts per episode and/or 25 bruxism bursts per hour of sleep, and (3) at least 2 episodes with grinding sounds. When the polysomnographic bruxism-related variables were combined under logistic regression, the clinical diagnosis was correctly predicted in 81.3% of the controls and 83.3% of the bruxers. The validity of these clinical research criteria needs now to be challenged in a larger population, over time, and in subjects presenting various levels of severity of sleep bruxism.

Jaw pain prevalence among French-speaking Canadians in Québec and related symptoms of temporomandibular disorders

The purpose of this study was to assess the prevalence and pattern of self-reported TMD jaw pain in a randomized stratified sample from the general population living in the Province of Québec, Canada. Through a telephone survey, standardized questions were asked to 897 French-speaking respondents, aged 18 years old and over, regarding frequency, severity, daily pattern of jaw pain, presence of difficulty in opening, joint clicking, and sleeping problems. All prevalence estimates were adjusted to the sociodemographic distribution of the non-institutionalized population. The results indicate that TMD jaw pain is self-reported by 30% of the general population; however, the prevalence of cases reporting frequent episodes (quite often or very often) is estimated at 7%, with more than two-thirds (69%) of the respondents in this subgroup experiencing moderate to severe pain. The prevalence rates of frequent difficulty in opening and joint clicking were estimated at 9% and 4%, respectively. Approximately one in four subjects with frequent episodes of jaw pain also reported frequent joint clicking or difficulty in opening, and a strong association (Gamma coefficient > 0.6) was found among all three TMD symptoms. Our data suggest that the prevalence of clinically significant TMD-related jaw pain (frequent jaw pain of moderate to severe intensity) is approximately 5% in the general population of the Province of Québec. In the nine months preceding the survey, about 2% of the total population sought treatment for a TMD symptom.

Restless legs syndrome and sleep bruxism: prevalence and association among Canadians

A survey conducted through personal interviews was done in Canada to estimate the prevalence of subjective symptoms related to restless legs syndrome (RLS) and to sleep bruxism. Of the 2,019 respondents, all over 18 years of age, 15% reported leg restlessness at bedtime; 10% reported unpleasant leg muscle sensations associated with awakening during sleep and with the irresistible need to move or walk. Both these complaints are related to RLS. The prevalence of RLS-related symptoms increased linearly with age. Tooth grinding, a symptom related to sleep bruxism, was reported by 8% of the subjects; in contrast to RLS-related symptoms, the prevalence of tooth grinding decreased linearly with age. RLS-related symptoms were reported more frequently in Eastern provinces than in Ontario and Western Canada, and more frequently in Roman Catholic and French-speaking responders. This was not the case for sleep bruxism; between 14.5% and 17.3% of the subjects who reported subjective RLS-related symptoms also reported tooth grinding. Conversely, 9.6-10.9% of the tooth grinders reported RLS-related symptoms. These data suggest that both sleep movement disorders can be concomitant and that socio-geographic and age characteristics influence the prevalence of reports.

Pain responses to experimental chewing in myofascial pain patients

Although patients with myofascial pain of the masticatory muscles often report that chewing exacerbates their pain, this has never been verified experimentally. In this study, pain was assessed before and after chewing in 20 asymptomatic subjects and in 61 patients with muscle pain. First, self-reports of pain were obtained with a checklist and on five-point category scales (CAT) at the screening visit. None of the asymptomatic subjects reported that mastication or other jaw movements caused pain. On the other hand, the majority of patients reported that movements were painful (67.2%, checklist; 78.7%, CAT). Afterward, pain intensity at rest and after chewing on wax for 3 min was reported on 100-mm Visual Analogue Scales (VAS). No asymptomatic subjects had pain before or after the chewing test, while about 50% of the patients reported an increase of pain after chewing. In this subgroup, mean pain intensity increased by 102.6%. However, mean pain intensity after chewing decreased by 56.6% in about 30% of the patient sample. These patients had significantly higher resting pain than the first subgroup. These data show that a short chewing test can exacerbate pain in most myofascial pain patients but has no effect in asymptomatic subjects. Surprisingly, the exercise decreased pain in an important subgroup of patients. These results suggest that two subgroups of myofascial pain patients may exist with opposite reactions to exercise. It remains to be seen if these reactions are due to two different pathologies or to the fact that the pre-exercise pain levels were significantly different in the two groups.

A retrospective evaluation of 193 patients with oral lichen planus

One hundred and ninety-three patients with oral lichen planus were evaluated retrospectively. Women outnumbered men by more than two to one. The mean age at lesion discovery was in the sixth decade. The buccal mucosa was the most common site of occurrence. There were concomitant systemic diseases in many of the patients. The ulcerative form was the most prevalent referred form. Therapies included observation and treatment with topical and systemic corticosteroids with and without anti-fungals and immunosuppressants. Areas of discussion include lesion location, chronicity, therapeutic modalities, malignant transformation, age, gender, symptomatology and systemic disease.

Cholecystokinin type A and type B receptor antagonists produce opposing effects on cholecystokinin-stimulated beta-endorphin secretion from the rat pituitary

Cholecystokinin octapeptide (CCK-8) is a potent corticotroph secretagogue. Consistent with earlier reports, the present results demonstrate that CCK-8 administration to rats elevates circulating beta-endorphin and adrenocorticotropin, but not alpha-melanocyte-stimulating hormone concentrations. This response was blocked by dexamethasone pretreatment, but not by vagotomy, and it could not be reproduced by i.c.v. CCK-8 injection, evidence that CCK-8 exerts its effects by directly activating cholecystokinin (CCK) receptors localized on anterior pituitary corticotrophs rather than in brain or the vagus nerve. Subsequent experiments demonstrated further that type A CCK receptors primarily mediate the stimulatory effect of CCK-8 on corticotroph secretion. Thus, devazepide, a selective CCK-A receptor antagonist, produced a dose-related inhibition of the CCK-8-stimulated rise in circulating beta-endorphin concentrations. Less selective CCK-A antagonists, including proglumide and lorglumide, produced little or no effect, however. Unexpectedly, the CCK-B receptor antagonist, L-365,260, enhanced the response to CCK-8, an effect diametrically opposite to that produced by CCK-A antagonists. These observations indicate that CCK-A and CCK-B receptors mediate quite different, if not opposing, roles in regulating corticotroph secretion.

The CCK-A and CCK-B receptor antagonists, devazepide and L-365,260, enhance morphine antinociception only in non-acclimated rats exposed to a novel environment

Devazepide, a potent CCK-A receptor antagonist, and L-365,260, a selective CCK-B receptor antagonist, have been introduced as pharmacologic tools for differentiating the physiologic roles of CCK-A and CCK-B receptor subtypes. In the present study, we tested the effects of devazepide and L-365,260, on morphine antinociception in rats using the thermal sensorimotor tail flick test. Both devazepide and L-365,260 significantly enhanced the antinociceptive action of morphine, but only in rats that had not been acclimated to the laboratory environment or habituated to investigator handling. When tested with fully acclimated animals, devazepide and L-365,260 had no effect whatsoever; they neither enhanced nor attenuated morphine-induced antinociception. These observations indicate that the effects of devazepide and L-365,260, CCK antagonists, on morphine antinociception appear to be dependent on the animal's response to a new environment or to the stress induced by an unaccustomed experimental paradigm.

Muscle pain, dyskinesia, and sleep

Muscle pain and poor sleep commonly occur together. Whether pain induces poor sleep or vice versa is difficult to know. Muscle pain is also observed in the presence of some types of dyskinesia or movement disorders. The interaction between sleep, movement disorders, and some musculoskeletal pain appears to be complex and may be influenced by various concomitant psychological and (or) biological factors.

Power and sample size calculations for clinical trials of myofascial pain of jaw muscles

When a clinical trial is planned, the approximate number of subjects needed for significant differences between/among groups to be detected must be estimated. Sample-size calculations provide the investigator with this information. This paper discusses the choice of outcome measures and describes the steps used to estimate the numbers of subjects necessary for a study that compares treatments for patients with chronic myofascial pain of jaw muscles. Within- and between-subject variances were estimated for the chosen variables, the subjects' pain ratings on visual analogue scales. Sample sizes were then calculated for theoretical differences between groups by pre-treatment means and overall standard deviations (Cohen, 1977). The results of this analysis can be used by other researchers when planning studies involving these types of patients.

Cholecystokinin antagonists proglumide, lorglumide and benzotript, but not L-364,718, interact with brain opioid binding sites

It has been reported that proglumide and L-364,718 potentiate opioid-induced antinociception. However, their mode of action in pain modulation is still not understood. To evaluate a possible interaction with opioid receptors, we determined the affinities of the CCK antagonists proglumide, lorglumide, benzotript and L-364,718 on mu, delta and kappa binding sites, using guinea pig brain crude synaptosome preparations. These affinities were compared to that of the central CCK binding site, using rat brain slide-mounted sections. At 100 microM, proglumide competed for 13% and 17% of mu and kappa binding sites, but did not interact with delta and CCK sites. At this concentration, lorglumide reduced mu, delta, kappa and CCK specific binding by 44%, 69%, 35% and 88%, whereas benzotript diminished it by 16%, 13%, 38% and 48%, respectively. L-364,718 did not interact with opioid receptors (assay limit of solubility, 10 microM) but had a high affinity for CCK binding sites (IC50, 126nM). The lack of selectivity of proglumide, lorglumide and benzotript for CCK receptors suggests that their reported ability to potentiate morphine analgesia may be related to an interaction with opioid receptors.

A retrospective survey of the oral conditions of 981 patients referred to an oral medicine private practice

A retrospective survey of 981 patients seen in a private oral medicine practice from 1980-87 was conducted to gather information on several defined parameters. Inferences extracted from this information can be applied to long-range planning in clinical, educational, and research areas.

Proglumide potentiates morphine analgesia for acute postsurgical pain

Proglumide, an antagonist of cholecystokinin, has been shown to potentiate morphine analgesia in animal and human experimental pain models. This study was undertaken to determine whether proglumide enhances morphine analgesia for patients experiencing postoperative pain. At onset of pain after the removal of impacted third molars, patients (n = 60) received intravenously either 4 mg morphine, 8 mg morphine, or 4 mg morphine plus proglumide (0.05, 0.5, or 5 mg). The administration of 8 mg morphine significantly reduced pain, in comparison with baseline and 4 mg morphine, for the first 30 minutes. The addition of 0.05 mg proglumide resulted in a significant increase in the magnitude and duration of the analgesic activity of 4 mg morphine; 0.5 and 5.0 mg proglumide did not produce this effect. No difference was seen in respiratory rate or in the frequency of side effects among the various forms of treatment. These data indicate that a low dose of proglumide potentiates both the magnitude and the duration of morphine analgesia in a clinical model of acute pain, without any detectable increase in side effects.