TNF and Peri-Implantitis: Petkovic-Curcin et al, in a Serbian population (n = 98), investigated susceptibility to peri-implantitis through the polymorphisms of the CD-14 (−159), TNF-α −308), IL genes, IL-6 (−174) and IL-10 (−1082), and IL-1ra genes and found that the frequencies of the genotypes were significantly different between patients with and without peri-implantitis.