Association of oral behaviours and psychological factors with selected genotypes in pain‐related TMD.

Objectives: To investigate frequency of single nucleotide polymorphisms (SNPs) in pain‐related temporomandibular disorders (TMDp) and to determine whether specific SNPs, psychological, psychosomatic and behavioural characteristics are predictive for pain existence and intensity (low pain intensity (LPI)/high pain intensity (HPI)). Methods: Genomic DNA was extracted from buccal mucosa swabs (85 TMDp;85 controls) for evaluating frequency of selected SNPs: catechol‐O‐methyltransferase (rs4680, rs4818), opiorphin (rs1387964), alpha subunit of voltage‐gated sodium channel Nav1.1 (rs6432860) and voltage‐gated sodium channel Nav1.9 (rs33985936). Participants completed questionnaires on somatosensory amplification, anxiety and depression symptoms and oral behaviours (OB). Results: Sleep‐related OB frequency was higher in TMDp patients compared to controls (p = 0.008). Compared to LPI, HPI patients had higher depression (p = 0.020) and anxiety scores (p = 0.017). TMDp group showed higher frequency of CC genotype (rs1387964) than controls (12.9% vs. 3.5%, p = 0.025). Following adjustments for age, sex and sleep‐related OB, the significance of the recessive model (CC vs. TC + TT) between TMDp patients and controls was retained (OR = 5.783; 95%CI: 1.454–23.004). Frequency of GG genotype (rs4680 and rs4818) was higher in HPI compared to LPI patients (40% vs. 11.4%, p = 0.006; 24% vs. 3%; p = 0.012, respectively). The difference remained significant after adjusting for age, sex, depression, anxiety and sleep‐related OB (rs4680: OR = 3.621; 95%CI: 1.580–8.297; rs4818: OR = 4.919, 95%CI: 1.641–14.746). Conclusion: This study has demonstrated that rs1387964 CC genotype was associated with TMDp while rs4680 GG and rs4818 GG genotypes contributed to HPI. [ABSTRACT FROM AUTHOR]