Association of Estrogen Receptor 1 and Tumor Necrosis Factor Polymorphisms with Temporomandibular Joint Anterior Disc Displacement without Reduction.

Objectives: The aim of this study was to investigate the role of rs1643821 and TNF- rs1800629 as potential genetic factors regulating anterior disc displacement without reduction-mediated inflammatory pathway.

Background: The temporomandibular joint is a complex synovial joint that allows mandibular movement in three directions. Although temporomandibular disorders are widespread, limited data is available on the biochemical characteristics of the displaced disc and quality of the surrounding soft tissue. Changes in degenerative tissue provoke disc displacement which involves secretion of inflammatory markers and sequential conversion of fibroblast-like cells into chondrocyte-like cells. Due to the high occurrence in female adolescents, the potential role of sex hormones in temporomandibular joint disorders has been speculated. Furthermore, anterior disc displacement without reduction severely affects the quality of life.

Methods: 124 Caucasian patients with a history of at least one anterior disc displacement without reduction within 3 months were enrolled. Anterior disc displacement without reduction was diagnosed based on clinical examination, diagnostic criteria (DC)/TMD, and cone-beam computed tomography/magnetic resonance imaging (CBCT/MRI). The control group consisted of 126 patients with no temporomandibular joint disorders. Genotyping of two single nucleotide polymorphisms, estrogen receptor 1 () rs1643821, and tumor necrosis factor (TNF-) rs1800629 was performed.

Results: rs1643821 showed significant values (using chi-square analysis) revealing the difference in anterior disc displacement without reduction frequencies while TNF- rs1800629 polymorphism was found to be statistically insignificant when compared to the control group. Furthermore, patients with a genotype of rs1643821 showed a decreased probability (OR = 0.412) against anterior disc displacement without reduction when compared to the GG genotype (OR = 1).

Conclusion: rs1643821 with A allele frequency was lower in patients with anterior disc displacement without reduction compared to the control group. Thus, the rs1643821 variant is significantly associated with susceptibility to the anterior disc displacement without a reduction in European Caucasians. Conversely, TNF- rs1800629 was a statistically insignificant factor against anterior disc displacement without reduction when compared to the control group.