TNF and Peri-Implantitis: However, Hentenaar et al. [29] found that IL-1β was significantly elevated in peri-implantitis sites, while a significant difference in the levels of TNF-α and IL-6 was failed to be found between healthy and diseased implants from 20 healthy implants (N = 17 patients) and 20 implants with peri-implantitis (N = 19 patients).