Bruxism secondary to antipsychotic drug exposure: a positive response to propranolol

Drug-Induced Bruxism: a Comprehensive Literature Review

Bruxism is a parafunctional teeth grinding activity that is attributed to be of multifactorial origin. The aim of this article is to provide a brief overview on drug-induced bruxism, commonly associated drugs, and its possible pathogenic mechanisms. Around 43 relevant publications were selected after a comprehensive search in PubMed, Cochrane library, Science Direct, and Google Scholar with appropriate keywords to collect data and compile this review. Disturbances in the neurotransmitters and their receptors in the central nervous system may play a significant role, particularly in sleep bruxism. Drugs that interfere normal secretion and function of neurotransmitters are documented to be capable of inducing bruxism. Such psychotropic drugs are being used in clinical practice chiefly for the management of mood disorders, anxiety, and depression. Although bruxism is a well-recognized side effect of certain medications, the extent of awareness about the same is still inadequate among dental professionals.

Psychotropic drugs and bruxism

INTRODUCTION

Sleep and awake bruxism is defined as 'a parafunctional activity including clenching, bracing, gnashing, and grinding of the teeth'. Some evidence suggests that bruxism may be caused by, or associated with, alterations in the CNS neurotransmission. Several classes of psychotropic drugs interfering with CNS activity may potentially contribute to bruxism. Thus, the purpose of this study was to examine relevant peer-reviewed papers to identify and describe the various classes of psychotropic substances that may cause, exacerbate or reduce bruxism as the result of their pharmacological action in CNS neurons.

AREAS COVERED

A literature search from 1980 to the present was performed using PubMed database. The term 'bruxism' was used in association with 'psychotropic', 'dopamine (DA)', 'serotonin', 'histamine', 'antipsychotics', 'antidepressants', 'antihistaminergics' and 'stimulants'.

EXPERT OPINION

Studies on the effects of DA agonists (Levo-DOPA, psychostimulants) and antagonists (antipsychotics) identified a central role of DA in the pathogenesis of pharmacologically induced bruxism. Important information from studies on drugs acting on serotonin neurotransmission (antidepressants) was recognized. Other mechanisms involving different neurotransmitters are emerging. This is the case of antihistaminergic drugs which may induce bruxism as a consequence of their disinhibitory effect on the serotonergic system.

Sleep bruxism: a comprehensive overview for the dental clinician interested in sleep medicine

Sleep bruxism (SB) is a common sleep-related motor disorder characterized by tooth grinding and clenching. SB diagnosis is made on history of tooth grinding and confirmed by polysomnographic recording of electromyographic (EMG) episodes in the masseter and temporalis muscles. The typical EMG activity pattern in patients with SB is known as rhythmic masticatory muscle activity (RMMA). The authors observed that most RMMA episodes occur in association with sleep arousal and are preceded by physiologic activation of the central nervous and sympathetic cardiac systems. This article provides a comprehensive review of the cause, pathophysiology, assessment, and management of SB.

Antipsychotics and physical attractiveness

BACKGROUND

Antipsychotics are effective in treating the symptoms of schizophrenia, but they may induce adverse effects, some of which-those that impact negatively on physical appearance-have not been sufficiently discussed in the psychiatric literature.

AIM

Through a narrative review, to catalog antipsychotic side effects that interfere with physical attractiveness and to suggest ways of addressing them.

METHOD

PubMed databases were searched for information on the association between "antipsychotic side effects" and "attractiveness" using those two search phrases plus the following terms: "weight," "teeth," "skin," "hair," "eyes," "gait," "voice," "odor." Data from relevant qualitative and quantitative articles were considered, contextualized, and summarized.

RESULTS

Antipsychotics, as a group, increase weight and may lead to dry mouth and bad breath, cataracts, hirsutism, acne, and voice changes; they may disturb symmetry of gait and heighten the risk for tics and spasms and incontinence, potentially undermining a person's attractiveness.

CONCLUSIONS

Clinicians need to be aware of the impact of therapeutic drugs on appearance and how important this issue is to patients. Early in treatment, they need to plan preventive and therapeutic strategies.

Bruxism: a literature review

Bruxism is a movement disorder characterized by grinding and clenching of teeth. Awake bruxism is found more in females as compared to males while sleep bruxism shows no such gender prevalence. Etiology of bruxism can be divided into three groups psychosocial factors, peripheral factors and pathophysiological factors. Treatment modalities involve occlusal correction, behavioural changes and pharmacological approach. A literature search was performed using National Library of Medicine's (NLM) Medical Subject Headings (MeSH) Database, Pubmed and Google search engines. The search term 'Bruxism' yielded 2,358 papers out of which 230 were review papers. Most of the papers selected were recently published during the period of 1996-2010 and very few of them were published before 1996.

Associated conditions and clinical significance of awake bruxism

BACKGROUND

Awake bruxism is defined as an oral parafunctional activity that includes clenching and grinding of teeth during wakefulness. Confirming the possible related anatomy and the clinical significance of awake bruxism in geriatric hospitals is the aim of this study.

METHODS

We analyzed the medical records of 503 patients who were admitted to hospital from April to June 2008. After the recognition of bruxism, the clinical, brain imaging studies and statistical parametric mapping (SPM) of brain single photon emission computed tomography were performed.

RESULTS

In each disease group, five of 125 Alzheimer's disease (AD) patients (4.0%), three of 11 frontotemporal dementia (FTD) patients (27.3%), seven of 230 stroke patients (including two patients related to citalopram, 3.0%), one of 45 Parkinson's disease patients (2.2%) and four of 17 hydrocephalus patients (23.5%) had bruxism. Even though awake bruxism occurred early after stroke onset, it occurred late after AD and FTD onset. This occurred in a far advanced stage of AD, while it occurred in a moderately advanced stage of FTD. SPM analysis in AD and FTD patients with awake bruxism revealed significant hypoperfusion in frontotemporal and other subcortical structures. Surface electromyography recordings from the masseter muscle showed rhythmic regular motor activity at a rate of 1-2/s.

CONCLUSION

This study suggests that awake bruxism is encountered not infrequently in various diseases in geriatric hospitals. It is frequently observed in FTD and normal pressure hydrocephalus, which characteristically shows frontal lobe dysfunction. These facts and SPM analysis show that awake bruxism can be regarded as a frontal neurological sign of various neurological disorders.

Bruxismo na infância: um sinal de alerta para odontopediatras e pediatras

OBJETIVO: Apresentar uma revisão de literatura sobre o bruxismo na infância, abordando os fatores etiológicos, as características clínicas, os sinais e sintomas, a importância do diagnóstico por parte dos pediatras e odontopediatras e o tratamento multidisciplinar desta condição parafuncional. FONTES DE DADOS: Foram selecionados os artigos mais relevantes sobre o tema publicados desde 1907 até 2007, com pesquisa realizada no Medline, na Bibliografia Brasileira de Odontologia (BBO) e em livros de Odontologia. SÍNTESE DOS DADOS: O bruxismo é definido como um hábito não funcional do sistema mastigatório, caracterizado pelo ato de ranger ou apertar os dentes, podendo ocorrer durante o dia e durante o sono. A etiologia é multifatorial e a literatura sugere vários fatores associados: dentário, fisiológico, psicológico e neurológico. As forças exercidas pelo bruxismo podem provocar distúrbios em diferentes graus nos dentes e nos tecidos de suporte, na musculatura e na articulação têmporo-mandibular. O sinal mais comum é o desgaste nas faces incisais dos dentes anteriores e oclusais nos posteriores, além de mobilidade e hipersensibilidade dentárias, fratura de cúspides e restaurações e hipertonicidade dos músculos mastigatórios. CONCLUSÃO: O conhecimento dos fatores etiológicos e das características clínicas do bruxismo na infância é fundamental para que o diagnóstico seja precoce, permitindo que pediatras, odontopediatras e psicólogos possam estabelecer um tratamento multidisciplinar e favoreçam o desenvolvimento integral da criança para a promoção de saúde e bem-estar individual.

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.

Urinary levels of catecholamines among individuals with and without sleep bruxism

INTRODUCTION

Sleep bruxism (SB) is characterized by repetitive and coordinated mandible movements and non-functional teeth contacts during sleep time. Although the etiology of SB is controversial, the literature converges on its multifactorial origin. Occlusal factors, smoking, alcoholism, drug usage, stress, and anxiety have been described as SB trigger factors. Recent studies on this topic discussed the role of neurotransmitters on the development of SB.

OBJECTIVE

Thus, the purpose of this study was to detect and quantify the urinary levels of catecholamines, specifically of adrenaline, noradrenaline and dopamine, in subjects with SB and in control individuals.

MATERIALS AND METHODS

Urine from individuals with SB (n = 20) and without SB (n = 20) was subjected to liquid chromatography. The catecholamine data were compared by Mann-Whitney's test (p </= 0.05).

RESULTS

Our analysis showed higher levels of catecholamines in subjects with SB (adrenaline = 111.4 microg/24 h; noradrenaline = 261,5 microg/24 h; dopamine = 479.5 microg/24 h) than in control subjects (adrenaline = 35,0 microg/24 h; noradrenaline = 148,7 microg/24 h; dopamine = 201,7 microg/24 h). Statistical differences were found for the three catecholamines tested.

CONCLUSION

It was concluded that individuals with SB have higher levels of urinary catecholamines.

Alternative pathways for catecholamine action in oral motor control

Orofacial movement is a complex function performed by facial and jaw muscles. Jaw movement is enacted through the triggering of motoneurons located primarily in the trigeminal motor nucleus (Mo5). The Mo5 is located in the pontine reticular formation, which is encircled by premotor neurons. Previous studies using retrograde tracers have demonstrated that premotor neurons innervating the Mo5 are distributed in brainstem areas, and electrophysiological studies have suggested the existence of a subcortical relay in the corticofugal-Mo5 pathway. Various neurotransmitters have been implicated in oral movement. Dopamine is of special interest since its imbalance may produce changes in basal ganglia activity, which generates abnormal movements, including jaw motor dysfunction, as in oral dyskinesia and possibly in bruxism. However, the anatomical pathways connecting the dopaminergic systems with Mo5 motoneurons have not been studied systematically. After injecting retrograde tracer fluorogold into the Mo5, we observed retrograde-labeled neurons in brainstem areas and in a few forebrain nuclei, such as the central nucleus of the amygdala, and the parasubthalamic nucleus. By using dual-labeled immunohistochemistry, we found tyrosine hydroxylase (a catecholamine-processing enzyme) immunoreactive fibers in close apposition to retrograde-labeled neurons in brainstem nuclei, in the central nucleus of the amygdala and the parasubthalamic nucleus, suggesting the occurrence of synaptic contacts. Therefore, we suggested that catecholamines may regulate oralfacial movements through the premotor brainstem nuclei, which are related to masticatory control, and forebrain areas related to autonomic and stress responses.

On the pharmacotherapy of sleep bruxism: placebo-controlled polysomnographic and psychometric studies with clonazepam

OBJECTIVES

Sleep bruxism (SB) is a parasomnia defined as a stereotyped movement disorder characterized by grinding or clenching of the teeth during sleep. Pathophysiologically, SB is the result of biological and psychosocial influences. Treatment comprises behavioral, orthodontic and pharmacological interventions. While benzodiazepines and muscle relaxants have been reported by clinicians to reduce bruxism-related motor activity, placebo-controlled studies are lacking. Thus, the aim of the present study was to investigate the acute effects of clonazepam (Rivotril) as compared with placebo, utilizing polysomnography and psychometry.

METHOD

Ten drug-free outpatients (6 females, 4 males), aged 46.5 +/- 13.1 years, suffering from SB (ICD-10: F45.8; ICSD: 306.8) and having been treated by bite splints were included in the trial. Comorbidity was high: 7 patients presented nonorganic insomnia related to adjustment or anxiety disorders (5 patients) or depression (2 patients); all patients had a concomitant movement disorder (6 restless legs syndrome, 4 periodic leg movement disorder). After one adaptation night, patients received placebo and 1 mg clonazepam 1/2 hour before lights out in a single-blind, nonrandomized study design. Objective sleep quality was determined by polysomnography, subjective sleep and awakening quality by rating scales, objective awakening quality by psychometric tests. Clinical evaluation was based on the Pittsburgh Sleep Quality Index (PSQI), the Zung Depression (SDS) and Anxiety (SAS) Scales, the Quality of Life Index, the Epworth Sleepiness Scale and the International Restless Legs Syndrome Study Group (IRLSSG) Scale.

RESULTS

On admission, SB patients exhibited deteriorated PSQI, SAS, SDS and IRLSSG measures. As compared with placebo, 1 mg clonazepam significantly improved the mean bruxism index from 9.3 to 6.3/h of sleep. Furthermore, it significantly improved the total sleep period, total sleep time, sleep efficiency, sleep latency and time awake during the total sleep period, and increased stage 2 sleep and movement time. Periodic leg movements decreased significantly, while the apnea index and apnea-hypopnea index increased marginally, but remained within normal limits. Subjective sleep quality improved as well, while in mood, performance and psychophysiology no changes were observed.

CONCLUSION

Acute clonazepam therapy significantly improved not only the bruxism index but also objective and subjective sleep quality, with unchanged mood, performance and psychophysiological measures upon awakening, suggesting good tolerability of the drug.

The Primary Parasomnias

BACKGROUND

Primary parasomnias are undesirable motor or verbal phenomena which occur during sleep and result in abnormal arousals. They occur out of all sleep stages or during transitions between sleep and awake. Secondary parasomnias are sleep disturbances that are caused by disorders of other organ systems. This review addresses only primary parasomnias. Arousal disorders and the parasomnias associated with REM sleep are the primary parasomnias most likely to be seen in a neurology practice. Sleep-wake transition disorders are also discussed with nocturnal leg cramps, probably the most common in this group.

REVIEW SUMMARY

The salient clinical features of the primary parasomnias are discussed. Emphasis is placed on the differential diagnosis of the different conditions and the best management strategies. Parasomnias encountered in infancy, such as infant sleep apnea, are not discussed in this review.

CONCLUSIONS

Parasomnias are common disturbances of sleep that may significantly affect the patient's quality of life and that of the bed partner. Most parasomnias can be diagnosed with careful history taking and polysomnography, and management is usually safe and effective.

Successful electroconvulsive therapy in major depression with fluvoxamine-induced bruxism

A 61-year-old patient with major depression and selective serotonin reuptake inhibitor-induced bruxism was successfully treated with a course of bilateral electroconvulsive therapy. Both the depressive symptoms and bruxism completely remitted after six treatments. Possible mechanisms of this effect are discussed.

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.

Prevalence of bruxism awareness in a Sardinian population

1014 subjects on the island of Sardinia (Italy) were interviewed regarding the habit of clenching and grinding their teeth. They had to specify if this activity occurred during the day, during the night, or both. Other information recorded was their age, gender, marital status, and occupation. Overall prevalence of bruxism was 27.2% (276 subjects). No association was found between bruxism and age, gender and job. Even differentiating diurnal, nocturnal, diurnal and nocturnal bruxism, associations were non-significant. Marital status seems to make some difference: divorced people reported higher parafunctional activity compared to widows and widowers who reported the least. Although awareness of bruxism is not a precise measure of parafunction, based on the results we cannot support the role of stress on bruxism etiology.

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.

Sleep bruxism; an overview of an oromandibular sleep movement disorder. REVIEW ARTICLE

Sleep bruxism (SB) is a stereotyped movement disorder characterized by grinding or clenching of the teeth during sleep. The majority of the population will at some time during their lifetime grind or clench their teeth. It becomes a pathological condition when the subject presents severe tooth damage or complains of non-restorative sleep. The prevalence of SB is difficult to estimate, since quite often the subjects are unaware of having the disorder. There is no gender difference. SB is more frequent in the younger generation, with a decline over age. The symptom recognized in children can persist in adulthood. The aetio-pathophysiology is still unclear. SB has been associated with tooth interference, psychosocial and environmental factors, brain transmitters and basal ganglia dysfunction. Attempts have been made to specify the personality traits of bruxers, reported to be greater anxiety or vulnerability to stress; however, this is still controversial. SB subjects were observed to present vigilance-sleepiness and somatic problems. However, they are generally good sleepers. Some authors reported SB during all sleep stages, others observed the majority of bruxe episodes during light sleep and REM and often associated with arousal transients. No abnormalities of the autonomic nervous system could be shown in awake SB subjects. While some studies have shown an association between SB and PLM or breathing disorders, others did not confirm this. There is no specific treatment for SB: each subject has to be individually evaluated and treated. Three management alternatives are used: dental, pharmacological and psychobehavioural.

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.

Bruxism and cranial-cervical dystonia: is there a relationship?

To characterize the relationship between bruxism and dystonia, 79 patients (28 men and 51 women) with cranial-cervical dystonia were studied. Sixty-two patients (78.5%), 22 men and 40 women, had bruxism. The mean age at onset of dystonia in patients with bruxism was 52.4 +/- 12.6 years (range 14-80), similar to patients with cranial-cervical dystonia without bruxism. Involuntary oromandibular movements (46 patients) and blepharospasm (34 patients) were the most common initial symptoms among patients with dystonia. About one-fourth of bruxism patients had associated dental problems including TMD (21%) and tooth wear (5%). A majority (58%) of the bruxism patients had diurnal bruxism and 12% had nocturnal bruxism. The bruxism patients were compared to 100 patients with Parkinson's disease (PD), cervical dystonia, cranial dystonia, and normal controls, respectively. The prevalence of bruxism was much higher in the cranial-cervical dystonia patients when compared to normal controls (P < 0.001); however, this difference was not significant between other diseased groups and controls. Medications and botulinum toxin injections, used in the treatment of focal dystonia also provided effective relief of bruxism.

Occlusal disharmonies modulate central catecholaminergic activity in the rat

Occlusal disharmonies have classically been thought to be involved in the etiopathogenesis of bruxism, as have, more recently, alterations in central neurotransmission, particularly dopaminergic neurotransmission. However, the connection between these two factors has still not been established. In this study, we assessed the effects of diverse occlusal disharmonies, maintained for either 1 day or 14 days, on neurochemical indices of dopaminergic and noradrenergic activity in the striatum, frontal cortex, and hypothalamus of the rat. The in vivo activity of tyrosine hydroxylase, determined as the accumulation of 3,4-dihydroxyphenylalanine (DOPA), 30 min after the administration of 3-hydroxybenzylhydrazine, a DOPA decarboxylase inhibitor, and dopamine and noradrenaline contents were quantified by high-performance liquid chromatography with electrochemical detection. The wearing of an acrylic cap on both lower incisors for 1 day induced a significant increase in DOPA accumulation in the regions analyzed, with parallel increases in dopamine levels in the hypothalamus and dopamine and noradrenaline in the frontal cortex. After the cap was maintained for 14 days, DOPA accumulation tended to return to control values, except in the left striatum, thereby causing an imbalance between hemispheres. In contrast, 1 or 14 days after the lower left and the upper right incisors were cut, less pronounced changes in catecholaminergic neurotransmission were found in the brain areas studied. Moreover, the cutting of one lower incisor did not modify either DOPA accumulation or dopamine and noradrenaline contents in the striatum or hypothalamus. These results provide experimental evidence of a modulation of central catecholaminergic neurotransmission by occlusal disharmonies, being dependent on the nature of the incisal alteration and on the time during which it was maintained.

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.