A proposed mechanism for diurnal/nocturnal bruxism: hypersensitivity of presynaptic dopamine receptors in the frontal lobe

Actual state of the diurnal masseteric electromyogram: Differences between awareness and non-awareness of awake bruxism

PURPOSE

This study aimed to elucidate the relationship between diurnal masseter muscle activity and awareness of diurnal awake bruxism (d-AB) by conducting a comparative analysis of electromyographic (EMG) data from individuals with and without awareness of diurnal awake bruxism (d-AB), utilizing EMG data gathered from multiple subjects.

METHODS

Unilateral masseter electromyography (EMG) recordings were performed during the daytime using an ultraminiature wearable EMG device. A total of 119 participants (59 with awareness of diurnal tooth clenching [d-TC] and 60 without awareness of d-TC) were included. Waveforms longer than 0.25 s with the two amplitude conditions, exceeding twice the baseline and >5% of maximum voluntary clenching, were extracted. In addition, the number of bursts and episodes (groups of bursts), burst duration, and burst peak amplitude were calculated for each participant.

RESULTS

There were no significant differences in the EMG parameters between the groups with and without awareness of d-TC. Additionally, the frequency distribution of the number of EMG waveforms exhibited wide ranges and substantial overlap between the two groups.

CONCLUSIONS

The variability in the number of bursts and episodes, burst peak amplitude, and burst duration among subjects suggests the need for an objective classification of d-AB severity based on EMG values. The absence of significant differences and large overlap in frequency distributions between the groups with and without awareness of d-TC indicate difficulty in predicting muscle activity solely based on awareness of d-AB.

Attention-deficit hyperactivity disorder and psychostimulant use in patients seeking dental care-Associations with common orofacial pain complaints

BACKGROUND

Dental medicine should expand its scope to properly assess medical and psychosocial factors that might have an impact on patients' oral health. Based on previous literature and clinical experience, attention-deficit/hyperactivity disorder and psychostimulant medications might represent factors associated with orofacial pain symptoms.

OBJECTIVE

The aim of the study was to assess whether common orofacial pain complaints such as jaw pain, jaw clicking, teeth clenching and headaches are more prevalent in dental patients who have an ADHD diagnosis and/or use psychostimulant medications.

METHODS

Orofacial pain symptoms prevalence was compared among four groups from a sample of new patients seeking dental care at Tufts University School of Dental Medicine (n = 11 699) based on ADHD diagnosis and psychostimulants intake: G1: no ADHD, no stimulants; G2: yes ADHD, yes stimulants; G3: yes ADHD, no stimulants; G4: no ADHD, yes stimulants.

RESULTS

In multivariable logistic regression models adjusting for age, gender, tobacco use, and alcohol consumption, significant differences were found for clenching (p < .0001), jaw pain (p < .0001), and headache (p < .0001). Compared to G1, two groups (G2 and G4) exhibited significantly higher odds of clenching and headaches, whereas only G2 exhibited significantly higher odds of jaw pain.

CONCLUSIONS

In comparison with patients without ADHD and not taking psychostimulants medications, dental patients using psychostimulants with and without ADHD diagnosis report headaches and teeth clenching more frequently, while jaw pain is reported more frequently only by those taking psychostimulants with an ADHD diagnosis. Further research is necessary to assess the nature of these associations and their clinical relevance.

Immediate Evaluation of the Effect of Infrared LED Photobiomodulation on Childhood Sleep Bruxism: A Randomized Clinical Trial

The gold standard for the management of sleep bruxism (SB) is the use of a rigid occlusal splint; however, there are limitations for its use in children and alternatives to the management of SB are needed. Photobiomodulation therapy has been used with positive results in temporomandibular disorders. This study aimed to evaluate the effects of photobiomodulation therapy with infrared LED in children with SB. Thirty children were divided into three groups: Group 1: control/absence of bruxism (n = 10); Group 2: SB treated with infrared LED (n = 10); Group 3: SB treated with occlusal splint (n = 10). Electromyographic evaluation of masseter, anterior temporalis, and upper trapezius, and salivary dopamine levels were assessed before and after treatments. Data were statistically analyzed using two-way mixed model ANOVA. An increase in the temporalis and right masseter EMG activity at rest was observed in Group 3, with large effect size (p < 0.05). Left masseter and temporalis EMG activity did not differ over time in the LED group, similar to the control group. Moreover, the EMG activity of masticatory muscles during chewing and upper trapezius muscle did not differ over time in all groups. The results also pointed to a difference in the levels of dopamine between children with and without SB, with Group 3 showing higher levels in the pre-treatment time compared to controls (p < 0.025). In conclusion, an increase in the masticatory muscles activity at rest was observed in children undergoing splint therapy. Moreover, a difference in the levels of salivary dopamine was found between children with and without SB.

Long-term follow-up of a patient with venlafaxine-induced diurnal bruxism treated with an occlusal splint: A case report

BACKGROUND

Bruxism is a jaw-muscle activity characterized by the clenching or grinding of teeth. It can be divided into nocturnal bruxism and diurnal bruxism (DB). DB secondary to antidepressants is rare and refractory. Reports associated with antidepressant-induced DB are mostly anecdotal without long-term follow-up. The effect of drug intervention on antidepressant-induced DB is still contested. We herein report the first case of successful treatment of venlafaxine-induced DB with an occlusal splint.

CASE SUMMARY

This case report describes detailed 7-year follow-up of a patient with venlafaxine-induced DB treated with an occlusal splint. The patient who complained about involuntary daytime tooth grinding after taking venlafaxine for a period of 4 mo and was diagnosed with venlafaxine-induced DB. Subsequently, an occlusal splint with modified bilateral buccal-pterygoid pads was used to treat his tooth grinding and to protect the dental structures from tooth wearing. The patient reported remission of symptoms after several months of treatment. His grinding activity was gradually and stably controlled after 2 years, with an almost complete recovery from DB after 6 years.

CONCLUSION

The maxillary buccal-pterygoid splint can be used as a noninvasive approach to treat venlafaxine-induced DB.

Methylphenidate-Induced Nocturnal Bruxism Alleviated by Adjunctive Clonidine

Stimulants-related bruxism has been previously reported; both diurnal and nocturnal. Here, authors report on a case of methylphenidate (MPH)-treated attention-deficit/hyperactivity disorder that developed nocturnal bruxism and failed multiple pharmacologic trials. Add-on clonidine has successfully helped with bruxisms while augmenting MPH response. This was achieved with great tolerability. This remains a viable option to deploy in such unusual clinical scenarios.

[Sleep bruxism in children]

Bruxism is defined as repetitive activity of the masticatory muscles, characterized by clenching the teeth or teeth grinding and/or by tapping and swaying. This study investigated sleep bruxism. The etiology is multifactorial: mainly central (neuropathic disorder, anxiety) but also genetic and local (posture, mouth breathing). The diagnosis is based primarily on the anamnesis and examination of dental wear and progression over time (photos and dental castings). A diagnostic guide is proposed in this article. Frequently found in children, bruxism is not always considered pathological. The severity criteria relate intensity (number of dental attrition facets) as well as the context found in children: anxiety, ventilation disorders, and fragile dental structures. Management is multidisciplinary and depends on the etiologic diagnosis.

Reevaluating Antidepressant Selection in Patients With Bruxism and Temporomandibular Joint Disorder

Temporomandibular joint disorder (TMD) is a broad pain disorder that refers to several conditions affecting the temporomandibular joint of the jaw and the muscles of mastication. As with most pain disorders, a high prevalence of depression and anxiety is associated with TMD. Research has shown that selective serotonin reuptake inhibitors (SSRIs), the first-line drug therapy for major depressive disorder, may not be suitable for TMD patients because SSRIs can induce teeth-grinding, otherwise known as bruxism. This is problematic because bruxism is believed to further exacerbate TMD. Therefore, the purpose of this literature review is to better understand the mechanism of SSRI-induced bruxism, as well as discuss alternative antidepressant options for treating depression and anxiety in patients with bruxism and TMD. Alternative classes of antidepressants reviewed include serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, atypical antidepressants, and monoamine oxidase inhibitors. Findings indicate that dopamine agonists and buspirone are currently the most effective medications to treat the side effects of SSRI-induced bruxism, but results regarding the effectiveness of specific antidepressants that avoid bruxism altogether remain inconclusive.

Evaluation of genetic factors involved in nocturnal electromyographic activity of masticatory muscles in twins

OBJECTIVES

The objectives of this study were to assess sleep bruxism events by directly recording electromyographic activity during sleep and to reveal the relative importance of genetic and environmental factors involved in sleep bruxism in twins.

MATERIAL AND METHODS

The subjects consisted of 108 twins (mean age 22.2 ± 6.4 years). Electromyographic activity of temporalis muscles during sleep was evaluated using a portable automatic sleep bruxism analyzer (Grindcare 3.0, Medotech A/S), and recordings were carried out for at least three consecutive nights. Quantitative genetic statistics based on structural equation modeling was utilized to estimate variance components.

RESULTS

Monozygotic twin-pair correlation for the number of nocturnal electromyographic activities recorded in this study (r = 0.463, P = 0.009) was higher than dizygotic twin-pair correlation (r = 0.103, P = 0.725). The proportion of total phenotypic variance in the liability of sleep bruxism to attribute to genetic influences, related to the electromyographic activities, was 48 % (95 % CI 17-95 %) and to unique environmental influences was 52 % (95 % CI 28-82 %).

CONCLUSIONS

Additive genetic effects may be a contributing factor to the occurrence of nocturnal EMG activity associated with sleep bruxism.

CLINICAL RELEVANCE

A greater understanding of the contribution of genetic factors could have beneficial uses, including enhanced accuracy of sleep bruxism diagnosis, management of sleep bruxism, and enhanced estimation of the prognosis for patients suffering from sleep bruxism. In addition, it could be also important to adequately evaluate the environmental factors in patients with sleep bruxism.

GABA and glutamate levels in occlusal splint-wearing males with possible bruxism

OBJECTIVE

The inhibitory neurotransmitter γ-aminobutyric acid (GABA) plays an important role in the pathophysiology of anxiety behavioural disorders such as panic disorder and post-traumatic stress disorder and is also implicated in the manifestation of tooth-grinding and clenching behaviours generally known as bruxism. In order to test whether the stress-related behaviours of tooth-grinding and clenching share similar underlying mechanisms involving GABA and other metabolites as do anxiety-related behavioural disorders, we performed a Magnetic Resonance Spectroscopy (MRS) study for accurate, in vivo metabolite quantification in anxiety-related brain regions.

DESIGN

MRS was performed in the right hippocampus and right thalamus involved in the hypothalamic-pituitary-adrenal axis system, together with a motor planning region (dorsal anterior cingulate cortex/pre-supplementary motor area) and right dorsolateral prefrontal cortex (DLPFC). Eight occlusal splint-wearing men (OCS) with possible tooth-grinding and clenching behaviours and nine male controls (CON) with no such behaviour were studied.

RESULTS

Repeated-measures ANOVA showed significant Group×Region interaction for GABA+ (p = 0.001) and glutamate (Glu) (p = 0.031). Between-group post hoc ANOVA showed significantly lower levels of GABA+ (p = 0.003) and higher levels of Glu (p = 0.002) in DLPFC of OCS subjects. These GABA+ and Glu group differences remained significant (GABA+, p = 0.049; Glu, p = 0.039) after the inclusion of anxiety as a covariate. Additionally, GABA and Glu levels in the DLPFC of all subjects were negatively related (Pearson's r = -0.75, p = 0.003).

CONCLUSIONS

These findings indicate that the oral behaviours of tooth-grinding and clenching, generally known as bruxism, may be associated with disturbances in brain GABAergic and glutamatergic systems.

Ketotifen-induced nocturnal bruxism

Nocturnal bruxism is a common oromandibular movement disorder highly prevalent in children, but its pathophysiological mechanism has not been fully explained. Iatrogenic sleep bruxism has been described following treatment with several psychotropic medications. However, no case of antihistamine-induced bruxism has been reported to date. Herein, we describe a 4-year-old child who experienced nocturnal bruxism during treatment for bronchospasm and rhinitis with the antihistamine ketotifen. Drug rechallenge was also performed.

CONCLUSION

The present case adds useful information to our knowledge of bruxism. Complex and poorly understood interactions between multiple central nervous system neurotransmitters, such as histamine, serotonin, and dopamine, are involved.

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.

Trial of oral metoclopramide on diurnal bruxism of brain injury

Bruxism is a diurnal or nocturnal parafunctional activity that includes tooth clenching, bracing, gnashing, and grinding. The dopaminergic system seems to be the key pathophysiology of bruxism and diminution of dopaminergic transmission at the prefrontal cortex seems to induce it. We report two patients with diurnal bruxism in whom a bilateral frontal lobe injury resulted from hemorrhagic stroke or traumatic brain injury. These patients' bruxism was refractory to bromocriptine but responded to low-dose metoclopramide therapy. We propose that administering low doses of metoclopramide is possibly a sound method for treating bruxism in a brain injury patient with frontal lobe hypoperfusion on positron emission tomography imaging.

Genetic factors account for half of the phenotypic variance in liability to sleep-related bruxism in young adults: a nationwide Finnish twin cohort study

OBJECTIVES

The aim of the present study was to examine the role of genetic and environmental factors in the phenotypic variance of bruxism in a large population-based cohort of young adult twins in Finland.

METHODS

The material of the present study derives from the FinnTwin16 cohort study consisting of five birth cohorts of twin pairs born in 1975-1979 who completed a questionnaire (at mean age 24, range 23-27 years) with data on frequency of sleep-related bruxism in 2000-2002. We used quantitative genetic modeling, based on the genetic similarity of monozygotic and dizygotic twins, to estimate the most probable genetic model for bruxism, based on decomposition of phenotypic variance into components:additive genetic effects (A), dominant genetic effects (D), and non-shared environmental effects (E).

RESULTS

On average, 8.7% experienced bruxism weekly, 23.4% rarely, and 67.9% never, with no significant gender difference (p = .052). The best fitting genetic model for bruxism was the AE-model. Additive genetic effects accounted for 52% (95% Cl 0.41--0.62) of the total phenotypic variance. Sex-limitation model revealed no gender differences.

CONCLUSIONS

Genetic factors account for a substantial proportion of the phenotypic variation of the liability to sleep-related bruxism, with no gender difference in its genetic architecture.

Delayed-onset diurnal bruxism, psychic akinesia and depression after carbon monoxide poisoning: a case report

Diagnosing the delayed neuropsychological sequelae of carbon monoxide (CO) poisoning is a clinical challenge because of its varied presentations. Pallidal lesions, the most common site of involvement in CO poisoning [Clin Radiol. 2000;55(4):273-80] can cause psychic akinesia [Mov Disord. 2001;16(5):810-4; J Neurol Neurosurg Psychiatry 1984;47(4):377-85]. We present a patient with diurnal bruxism, psychic akinesia and depression that were delayed manifestations of CO poisoning.

Bruxism is associated with nicotine dependence: a nationwide Finnish twin cohort study

OBJECTIVES

To investigate the association of smoking with bruxism while controlling for genetic and environmental factors using a co-twin-control design. Especially, the role of nicotine dependence was studied in this context.

METHODS

The material derives from the Finnish Twin Cohort consisting of 12,502 twin individuals who responded to a questionnaire in 1990 (response rate of 77%). All were born in 1930-1957, the mean age being 44 years. The questionnaire covered 103 multiple choice questions, 7 dealing with tobacco use and 22 with sleep and vigilance matters, including perceived bruxism. In addition, a subsample derived from the Nicotine Addiction Genetics Finland Study containing 445 twin individuals was studied.

RESULTS

In age- and gender-controlled multinomial logistic regression, both monthly and rarely reported bruxism associated with both current cigarette smoking (odds ratio [OR] = 1.74 and 1.64) and former cigarette smoking (OR = 1.64 and 1.47). Weekly bruxism associated with current smoking (OR = 2.85). Current smokers smoking 20 or more cigarettes a day reported weekly bruxism more likely (OR = 1.61-1.97) than those smoking less. Among twin pairs (N = 142) in which one twin was a weekly bruxer and the cotwin a never bruxer, there were 13 monozygotic pairs in which one twin was a current smoker and the other twin was not. In all cases, the bruxer was the smoker (p = .0003). Nicotine dependence associated significantly with bruxism.

CONCLUSIONS

Our twin study provides novel evidence for a possible causal link between tobacco use and bruxism among middle-aged adults. Nicotine dependence may be a significant predisposing factor for bruxism.

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.

ADHD, bruxism and psychiatric disorders: does bruxism increase the chance of a comorbid psychiatric disorder in children with ADHD and their parents?

There is an association between bruxism and ADHD. No published data on psychiatric comorbidities in attention-deficit/hyperactivity disorder (ADHD) children with bruxism were found. There is no satisfying treatment method for children with bruxism. If we understand its comorbidities well, a better treatment method could come out. This study was conducted to compare the frequency of comorbid psychiatric disorders in the parents and their ADHD children with and without teeth grinding. It was hypothesized that there is no association between bruxism and prevalence of comorbid psychiatric disorders in children with ADHD and their parental psychopathology. Eighty-nine ADHD children without teeth grinding were compared with 32 ADHD children with teeth grinding. Their parental psychiatric disorders were also compared. Structured interviews were used to diagnose comorbid psychiatric disorders. The demographic characteristics of the children and their parents were not different between the groups. The only psychiatric disorder in children, which was associated with the groups was oppositional defiant disorder. The rate of conduct disorder, tic disorder, major depressive disorder, separation anxiety disorder, generalized anxiety disorder, enuresis, and obsessive compulsive disorder were not different between the two groups of children. The rate of major depression was more in the mothers of children with teeth grinding than those without such children. These finding were not reported before. ADHD children with teeth grinding have a high prevalence of oppositional defiant disorder. Lack of association between anxiety disorder and presence of teeth grinding might not support the idea that anxiety is associated with teeth grinding. The association of ODD and teeth girding might be a clue about etiology of bruxism. Perhaps, this clue can probably lead to the development of a more satisfying treatment. With consideration of this clue, further studies should survey if there is any association between ODD and sleep micro-arousals.