Thus, the present study demonstrated an association between the DNMT3B -283T/C SNP and an increased risk of cancer in the oral cavity (OR = 2.436; 95% CI = 1.39–4.25; p = 0.001), pharynx (OR= 2.12; 95% CI = 1.02–4.41; p = 0.045), and larynx (OR = 2.16; 95% CI = 1.21–3.85; p = 0.006); however, DHFR 19-pb ins/del polymorphisms were associated with a protective effect against oral cavity cancer (OR= 0.53; 95% CI = 0.35–0.80; p = 0.003) (Table 2). This evidence concerns the gene DHFR and oral cavity cancer.