VDR and periodontitis: The aim of the study was to analyze three SNPs in vitamin D receptor gene—rs7975232 (ApaI), rs2228570 (FokI) and rs1544410 (BsmI)—combined with oral health assessment—pH, gingival index, dry mouth, periodontitis, dry socket, redness of oral cavity mucosa, leukoplakia—in a group of cigarette smokers and in non-smokers.