Genetic polymorphisms in Dopaminergic pathways are associated with Bruxism

Objectives: Bruxism (BRX) is characterized by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible. BRX can occur during sleep (SB) or during wakefulness (WB). However, it may be suffered together (W&SB). Relatives of people suffering BRX are affected by this parafunction. Possible genetic factors are involved in BRX. Mandibular movements observed in BRX have been compared to the movement patterns of Parkinson´s disease. Theories that explain BRX etiology include alcohol consumption, smoking and alteration in neurotransmitters. Dopamine was proposed as a possible neurotransmitter associated to BRX. Genetic variants in Dopaminergic pathways (DP) are involved in Parkinson´s disease, alcohol consumption and nicotine dependence. Thus, there is a possible association in genetic variants in DP genes and BRX. This investigation aimed to evaluate the frequency of genetic polymorphisms in DP genes (DRD1, DRD2, DRD3, DRD4, DRD5 and MAOB) in patients under BRX treatment and a control group.
Methods: Subjects undergoing BRX treatment were classified in WB (61 patients), SB (26 patients) and W&SB (43 patients). The control group included 59 patients. A blood sample was obtained, and genomic DNA was extracted. Genotypes were determined using TaqMan® SNP genotyping assay in a StepOne^TM Real-Time PCR system. Statistical analysis was made using R software.
Results: Were found significant differences in polymorphism rs1800497; G allele was associated with a significant decreased risk of W&SB (OR 0.50, 95% CI = 0.26 – 0.95, p=0.041). To polymorphism rs6280 were found differences comparing BS and controls to genotypic (p= 0.0009) and allelic frequencies; C allele was associated to a increased risk of BS (OR 2.11, 95% CI = 1.08 – 2.61, p=0.02). In rs6283 polymorphism were found differences in genotypic frequencies when comparing BS (p=0.01), BV (p=0.0009) and W&SB (p=0.016) to a control group. C allele was associated to a decreased risk of WB (OR 0.49, 95% CI = 0.29 – 0.84, p=0.01).
Conclusions: This is the first research exploring if genetic variants of DP are associated to BRX. Our findings suggest a possible genetic contribution to the etiology of WB, SB and W&SB. Hence, it becomes necessary to continue research in this area to increase the current understanding of BRX physiopathology.