Abstract Objectives The aim of this study is to investigate the association of 25-hydroxy (25-OH) vitamin D level, FokI vitamin-D receptor (VDR) gene polymorphism, and painful temporomandibular joint (TMJ) disc displacement with reduction (DDwR). Methods This cross-sectional study comprised 49 people with temporomandibular disorders (TMDs) and 48 healthy controls of comparable age and gender. DDwR was diagnosed based on TMD diagnostic criteria (DC/TMD). Using genomic DNA extracted from blood, a genotyping analysis of the FokI (rs2228570) polymorphisms was conducted utilizing DNA sequencing and the Applied Biosystems 3130XL Genetic Analyzer (USA). The serum 25-hydroxy vitamin D levels and the FokI VDR gene polymorphism were compared between the two groups. Results There was not a noticeable distinction in the mean 25-hydroxy vitamin D levels between the two groups, the TMD group had substantially more persons with severe vitamin-D insufficiency (<10 ng) compared to the control group (p<0.05). The genotype and allele frequency of the FokI VDR polymorphism did not differ significantly between the TMD and control groups. However, The GG genotype and G allele were significantly more prevalent in the severe vitamin D deficiency (<10 ng) group than in the normal group (20–60 ng) and mild deficiency group (10–20 ng) (p<0.05). Conclusions Differences between groups in serum 25-hydroxy vitamin D levels indicate that indicating that vitamin-D insufficiency might be linked to TMD. Although the FokI (rs2228570) VDR polymorphism was associated with severe vitamin-D deficiency, no significant relationship existed between TMJ DDwR and FokI VDR polymorphism.
Ekici et al. (2026) studied this question.