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.

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La anquilosis de la articulación temporomandibular (ATM) corresponde a un trastorno temporomandibular clasificado dentro de la hipomovilidad mandibular crónica. La literatura define anquilosis como una inmovilidad anormal de la mandíbula, desorden que lleva a una restricción de la apertura bucal con reducción parcial de los movimientos mandibulares o una completa inmovilidad de la mandíbula. El objetivo del presente artículo es realizar una revisión en cuanto a la clasificación, epidemiología, etiopatogenia, diagnóstico y tratamiento de la anquilosis de la articulación temporomandibular. Palabras clave: Articulación temporomandibular, trastornos temporomandibulares, anquilosis temporomandibular. SUMMARY Ankylosis of the temporomandibular joint (TMJ) corresponds to a temporomandibular disorder classified into chronic mandibular hypomobility. Ankylosis defines literature as an abnormal jaw immobility disorder that leads to a restriction of mouth opening with partial reduction of mandibular movement or complete immobility of the jaw. The aim of this article is to review the classification, epidemiology, etiology, diagnosis and treatment of temporomandibular joint ankylosis.

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.