ACTN3 genotype influences masseter muscle characteristics and self-reported bruxism.

OBJECTIVES: Main aim of the study was to explore the association between genetic polymorphisms in ACTN3 and bruxism. Secondary objectives included masseter muscle phenotypes assessment between bruxers and non-bruxers and according to genetic polymorphisms in ACTN3. MATERIALS AND METHODS: Fifty-four patients undergoing orthognathic surgery for correction of their malocclusion were enrolled. Self-reported bruxism and temporomandibular disorders status were preoperatively recorded. Saliva samples were used for ACTN3 genotyping. Masseter muscle samples were collected bilaterally at the time of orthognathic surgery to explore the muscle fiber characteristics. RESULTS: There were significant differences in genotypes for rs1815739 (R577X nonsense) (p = 0.001), rs1671064 (Q523R missense) (p = 0.005), and rs678397 (intronic variant) (p = 0.001) between bruxers and non-bruxers. Patients with self-reported bruxism presented a larger mean fiber area for types IIA (p = 0.035). The mean fiber areas in individuals with the wild-type CC genotype for rs1815739 (R577X) were significantly larger for type IIA fibers (1394.33 µm2 [572.77 µm2 ]) than in those with the TC and TT genotypes (832.61 µm2 [602.43 µm2 ] and 526.58 µm2 [432.21 µm2 ] [p = 0.014]). Similar results for Q523R missense and intronic variants. CONCLUSIONS: ACTN3 genotypes influence self-reported bruxism in patients with dentofacial deformity through specific masseter muscle fiber characteristics.

Single nucleotide polymorphisms in dopamine receptor D2 are associated with bruxism and its circadian phenotypes in children.

Objective: To evaluate the association of bruxism phenotypes with single nucleotide polymorphisms in FKBP5, DRD2, ANKK1, and COMT.Methods: Clinical oral examination was performed to diagnose bruxism phenotypes in 150 children. DNA was collected from saliva. Logistic univariate regression, Chi-square, and Fisher's exact tests were performed (p < 0.05).Results: Bruxism was associated with DRD2 (p = 0.02). Tooth grinding while awake was associated with ANKK1 (p < 0.001), and tooth grinding while asleep was associated with DRD2 in the additive (p = 0.030) and dominant (p = 0.008) model. Tooth clenching while awake was associated with ANKK1 in the additive (p = 0.005) and dominant (p = 0.008) models, whereas tooth clenching while asleep was associated with ANKK1 (p < 0.001) and with COMT in the additive (p = 0.001) and dominant (p = 0.003) models.Discussion: Polymorphisms in DRD2, ANKK1, and COMT are associated with bruxism phenotypes.

Polymorphic variants in genes related to stress coping are associated with the awake bruxism.

BACKGROUND: Chronic stress is one of the leading predisposing factors in bruxism aetiology, but the influence of genetic factors is also suggested. We aimed to study whether sequence variants in genes involved in stress regulation pathways: NTRK2 and BDNF, may be associated with awake bruxism susceptibility, clinical presentation, and patients' perceived stress level. METHODS: The study group included 104 patients with probable awake bruxism and 191 population controls. Patients underwent dental examination concerning the symptoms of bruxism and psychological testing. Genotyping was performed using HRMA and sequencing. Statistical analyses were conducted, and P values below 0.05 were considered statistically significant. RESULTS: We observed a positive correlation of measured stress level and pathological teeth attrition in the anterior segment (r = 0.45, P < 0.001), enamel attritions (r = 0.44, P < 0.001), tongue impressions (r = 0.50, P < 0.001) and posterior teeth attrition (r = 0.27, P = 0.005). Moreover, the c.196A variant (p.66Met) of the BDNF gene and c.1397-31392G allele of the NTRK2 gene were present with elevated frequency, comparing to controls. CONCLUSIONS: This study hence the thesis that perceived stress level is a substantial contributing factor to awake bruxism occurrence and its clinical manifestations. Moreover, sequence variants in genes related to stress coping may be correlated with awake bruxism's susceptibility via elevated perceived stress level.

STXBP1 encephalopathy is associated with awake bruxism.

Heterozygous mutations in syntaxin-binding protein 1 (STXBP1) gene are associated with early infantile epileptic encephalopathy 4 (EIEE4). This condition is characterized by epilepsy, developmental delay (DD), and various movement disorders. Herein, we will report 5 unrelated patients with different de novo mutations in STXBP1. In addition, we conducted an online survey through Facebook to identify the incidence of bruxism (BRX) in these patients. Four out of 5 patients (80%) presented with awake BRX (A-BRX). Bruxism was also reported in 81.4% (57/70) of the patients with STXBP1 encephalopathy through the online questionnaire. No consistent correlation was identified between the type of mutation and development of movement disorders or BRX. This is the first study to demonstrate A-BRX in patients with STXBP1 mutation. Given the role of STXBP1 in exocytosis of neurotransmitters and other manifestations of dopamine dysregulation in patients with STXBP1-EIEE4, we suggest that in patients with STXBP1 encephalopathy, A-BRX might be the result of the involvement of dopaminergic circuits.

Single nucleotide polymorphisms in genes of dopaminergic pathways are associated with bruxism.

OBJECTIVES: This research aimed to evaluate the frequency of single nucleotide polymorphisms (SNPs) in dopaminergic pathway genes (DRD1, DRD2, DRD3, DRD4, DRD5, and MAOB) in patients undergoing bruxism treatment and controls. SUBJECTS AND METHODS: Patients submitted to bruxism treatment were classified in awake bruxism (61 patients), sleep bruxism (26 patients), and awake-sleep bruxism (43 patients). Control group included 59 patients. Association between circadian manifestations of bruxism and SNPs was investigated using Fisher's exact test, chi-squared test, and calculating the odds ratios and their respective 95% confidence intervals. RESULTS: The G allele of DRD2 rs1800497 SNP was associated with a significant risk reduction of awake-sleep bruxism (p = 0.041), while the C allele of DRD3 rs6280 SNP was associated with increased risk of sleep bruxism (p = 0.02), and the C allele of DRD5 rs6283 SNP was associated with decreased risk of awake bruxism (p = 0.01). CONCLUSIONS: To our knowledge, this is the first report exploring the contribution of genetic variants in dopaminergic pathways to bruxism development, considering all circadian manifestations. Our findings indicate a possible genetic influence in the etiology of awake, sleep, and awake-sleep bruxism. Therefore, further research is needed to increase the current understanding of bruxism physiopathology.

Genetic polymorphisms in the serotonergic system are associated with circadian manifestations of bruxism.

Bruxism (BRX) is a condition of great interest for researchers and clinicians in dental and medical areas. BRX has two circadian manifestations; it can occur during sleep (sleep bruxism, SB) or during wakefulness (awake bruxism, WB). However, it can be suffered together. Recent investigations suggest that central nervous system neurotransmitters and their genes could be involved in the genesis of BRX. Serotonin is responsible for the circadian rhythm, maintaining arousal, regulating stress response, muscle tone and breathing. Thus, serotonin could be associated with BRX pathogenesis. The aim of this work was to evaluate the frequency of genetic polymorphisms in the genes HTR1A (rs6295), HTR2A (rs1923884, rs4941573, rs6313, rs2770304), HTR2C (rs17260565) and SLC6A4 (rs63749047) in subjects undergoing BRX treatment. Patients included were classified according to their diagnosis in awake bruxism (61 patients), sleep bruxism (26 patients) and both (43 patients). The control group included 59 healthy patients with no signs of BRX. Data showed significant differences in allelic frequencies for the HTR2A rs2770304 polymorphism, where the C allele was associated with increased risk of SB (odds ratio = 2·13, 95% confidence interval: 1·08-4·21, P = 0·03). Our results suggest that polymorphisms in serotonergic pathways are involved in sleep bruxism. Further research is needed to clarify and increase the current understanding of BRX physiopathology.

Epigenetics and Bruxism: Possible Role of Epigenetics in the Etiology of Bruxism.

Bruxism is defined as a repetitive jaw muscle activity characterized by clenching or grinding of the teeth and/or bracing or thrusting of the mandible. There are two distinct circadian phenotypes for bruxism: sleep bruxism (SB) and awake bruxism, which are considered separate entities due to the putative difference in their etiology and phenotypic variance. The detailed etiology of bruxism so far remains unknown. Recent theories suggest the central regulation of certain pathophysiological or psychological pathways. Current proposed causes of bruxism appear to be a combination of genetic and environmental (G×E) factors, with epigenetics providing a robust framework for investigating G×E interactions, and their involvement in bruxism makes it a suitable candidate for epigenetic research. Both types of bruxism are associated with certain epigenetically determined disorders, such as Rett syndrome (RTT), Prader-Willi syndrome (PWS), and Angelman syndrome (AS), and these associations suggest a mechanistic link between epigenetic deregulation and bruxism. The present article reviews the possible role of epigenetic mechanisms in the etiology of both types of bruxism based on the epigenetic pathways involved in the pathophysiology of RTT, PWS, and AS, and on other epigenetic disruptions associated with risk factors for bruxism, including sleep disorders, altered stress response, and psychopathology.

Bruxism and genetics: a review of the literature.

People who suffer from bruxism (teeth-grinding) often ask their dentists whether their condition is hereditary. The purpose of this study is to enable dentists to provide an 'evidence-based' answer to this question. The biomedical literature was searched using PubMed, and 32 publications were identified, of which nine proved relevant to the research question. The references cited by the publications identified yielded one further publication, bringing the total number of publications included in the analysis to 10. Four publications related to family studies, five related to twin studies and one related to a DNA analysis. With the exception of one of the twin studies, all the included studies concluded that bruxism appears to be (in part) genetically determined. Dentists whose patients ask them about bruxism can therefore tell them that teeth-grinding does indeed 'run in families'.

¿Es posible la contribución de factores genéticos en el bruxismo? / Are there genetic factors Involved in bruxism?

Bruxismo se define como un trastorno del movimiento mandibular que se caracteriza por apretamiento o rechinamiento dentario. Se estima que la prevalencia de éste puede variar desde un 8 por ciento a un 20 por ciento de la población adulta. Quienes padecen esta parafunción relatan manifestación en otras personas del grupo familiar. Existen teorías que buscan explicar la etiología del bruxismo, basados principalmente en estudios clínicos y encuestas a pacientes. Estas proponen que los principales factores etiológicos de Bruxismo serían estrés y alteraciones en ciertos neurotransmisores o sus vías (Dopamina, Ácido Gamma-Aminobutírico y Serotonina). La posibilidad de que alteraciones genéticas del ADN influyan en la aparición de bruxismo no ha sido considerada. Dado que no existe en la literatura consultada estudios genético-moleculares y/o funcionales que confirmen las teorías basadas en estudios clínicos, parece necesario iniciar investigaciones en esta área que lleven a una mejor comprensión de esta parafunción, con el ánimo final de aportar en el desarrollo de más y mejores terapias para el tratamiento del bruxismo...

Bruxism has been defined as a sleep-related movement disorder characterized by tooth grinding or clenching. Between 8 percent to 20 percent of adult population is affected by this parafunction. Relatives of these patients have reported to be affected by bruxism as well. There are theories that want to explain bruxism ethiology based on factors as stress and alteration in neurotransmitters (Dopamine, GABA and Serotonin). Possible epigenetic alterations in DNA influencing bruxism appearance have not been considered. It is therefore necessary to perform genetic, epigenetic and molecular research to confirm theories related to bruxism ethiology, with the aim to improve knowledge in this field as well as to contribute in the development of new and better therapies in bruxism treatment...

Genetic and environmental factors in oral health among twins.

To date, studies on the contributions of genetic factors to oral health have been inconclusive. We hypothesized that major dental diseases show a significant genetic component. The study was based on self-reported oral health among young adult twins. The data were derived from the fourth wave of the longitudinal FinnTwin16 study, in which participants completed a questionnaire in 2000-2002 enquiring about the number of filled teeth and the prevalence of gingival bleeding. We used quantitative genetic modeling, based on the genetic similarity of identical and non-identical twins, to calculate the most probable model for both filled teeth and gingival bleeding. The models revealed a strong genetic component behind the number of filled teeth, differing between males (49%) and females (68%), and a weaker genetic component affecting gingival bleeding, being similar for males and females (32%). Genetic factors contribute to inter-individual differences in oral health among young adults.

Genetic aspects and genetic epidemiology of parasomnias.

Parasomnias are undesirable phenomena associated with sleep. Many of them run in families, and genetic factors have been long suggested to be involved in their occurrence. This article reviews the present knowledge of the genetics of the major classical behavioral parasomnias as well as present results from genetic epidemiological studies. The level and type of evidence for genetic effects varies much from parasomnia to parasomnia. The genetic factors are best established in enuresis, with several linkages to chromosomal loci, but their functions are not so far known. Environmental causes and gene-environment interactions are most probably also of great importance in the origin of complex traits or disorders such as parasomnias.

Sleep bruxism based on self-report in a nationwide twin cohort.

The relative roles of genetic and environmental factors in bruxism are not known. In 1990 a questionnaire sent to the Finnish Twin Cohort yielded responses from 1298 monozygotic and 2419 dizygotic twin pairs aged 33-60 years. We used structural equation modelling to estimate genetic and environmental components of variance in the liability to bruxism. There was a significant gender difference both in childhood (P = 0.001) and adult (P = 0.007) bruxism. Females compared to males reported childhood bruxism 'often' 5.2% vs 4.1% and 'sometimes' 17.4% vs 17.3%, and as adults 'weekly' 3.7% vs 3.8% and 'monthly' 3.9% vs 4.6%, respectively. Bruxism in childhood and adulthood is highly correlated (0.86 in males and 0.87 in females). The proportion of total phenotypic variance in liability to bruxism attributed to genetic influences in childhood bruxism was 49% (95% CI 37-60%) in males and 64% (55-71%) in females, and for adults 39% (27-50%) among males and 53% (44-62%) among females. The correlation between the genetic effects on childhood bruxism and the genetic effects on adult bruxism was estimated in a bivariate model to be 0.95 (95% CI 0.94-0.96) in males and 0.89 (0.88-0.90) in females. Bruxism appears to be quite a persistent trait. There are substantial genetic effects on bruxism both in childhood and as adults, which appear to be highly correlated.