Moreover, Heidari et al[27] found that IFN-γ +874A/T genetic polymorphism was linked with susceptibility to periodontitis in Iranian population, and the T allele was less frequent in the periodontitis compared with control subjects.[27] However, in this meta-analysis, the TT genotype distribution and T allele in the periodontitis patients had no difference compared with the control subjects (TT vs AA: OR  =  1.07, 95% CI: 0.87–1.32, P  =  .537; T vs A: OR  =  1.01, 95% CI: 0.90–1.13, P =.878; Table 2). Here, IFNG is linked to periodontitis.