VDR and leukoplakia: The aim of the study was to analyze three single nucleotide polymorphisms (SNPs) in vitamin D receptor gene (VDR)—rs7975232 (Apa I), rs2228570 (Fok I) and rs1544410 (BsmI)—combined with oral health assessment—pH, GI (gingival index), dry mouth, periodontitis, dry socket, redness of oral cavity mucosa, leukoplakia—in a group of cigarette smokers and in controls.