IL4 and Peri-Implantitis: Given the scarcity of information about peri-implant infections and the suppositionthat a foreign body reaction to titanium would cause peri-implantitis, this studyaimed to evaluate the levels of IL-4, MIP-1α, and MMP-9 expression in an endeavor toinvestigate the occurrence of a foreign body reaction in peri-implant tissuesaffected by peri-implantitis and compare these levels with those in tissues free ofperi-implant infections.