Background: The aim of this study was to investigate vitamin D receptor (VDR) gene polymorphism as a risk factor associated with chronic periodontitis (CP) and to determine the effect of VDR gene polymorphism on phenotypic CP.Methods: This study is a case-control design that included 162 adults divided into two groups: patients with CP (case group) and patients without CP (control group). Venous blood and DNA were obtained from individual samples. The gene polymorphism was determined using

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... icted Fragment Length Polymorphism-Polymerase Chain Reaction (RFLP-PCR) and DNA sequencing to identify endonuclease restrictions in exon 9 (TaqI). The data were analyzed using an independent t-test and Fisher's exact test. The odds ratio (OR) was used to calculate the risk of VDR gene polymorphism in CP. Results: VDR gene polymorphism was detected in patients with CP and a TT genotype (86.4%), Tt genotype (12.4%), and tt genotype (1.2%). The case group with TT and Tt genotypes had an OR of 12.5 (95% CI:1.6–99.8) of having CP compared to the control group (P<0.05).Conclusions: VDR gene polymorphisms (the TT and Tt genotypes) are risk factors associated with individual susceptibility to CP.