SHMT1 and temporomandibular joint disorder: From the four polymorphisms studied on the cytoplasmic SHMT1 in TMD patients, a significant increase was observed of the G allele of the polymorphism rs1979277 (Leu435Phe) when compared with controls (OR = 3.99; 95% CI 1.72, 9.25; p = 0,002).