DNMT3B and systemic lupus erythematosus: Genotypic frequencies are in accordance with HWE for both studied polymorphisms: MTHFR (rs1801133): Control (p=0.57), Periodontitis (p=0.13), SLE (p=0.25) and SLE + periodontitis (p=0.27), and DNMT3B (rs2424913): Control (p=0.54), Periodontitis (p=0.89), SLE (p=0.72) and SLE + periodontitis (p=0.80).