Peri-implant disease is an infectious inflammatory disease that occurs in the soft and hard tissues surrounding dental implants and includes two types of diseases: peri-implant mucositis and peri-implantitis. At the First European Symposium on Periodontology in 1993, peri-implant mucositis was defined as a reversible inflammatory reaction limited to the soft tissues around the implant, without destruction of bone tissue, and at the Sixth European Symposium on Periodontology in 2008, peri-implant mucositis was defined as inflammation of the mucosa around a functioning implant, without loss of supporting bone; The term “reversible” was eliminated to avoid any misinterpretation as implying that peri-implantitis is irreversible and untreatable. The term “peri-implantitis” first appeared in the French scientific literature in 1965 and two decades later in the English scientific literature to describe the pathological state of peri-implant tissue infection in the oral cavity. In 1993, the First European Symposium on Periodontology defined “peri-implantitis” as a destructive inflammatory process in the tissues surrounding a functioning implant, resulting in peri-implant pocket formation and loss of supporting bone. This definition indicates that an implant with peri-implantitis has acquired osseointegration and that the bone loss at the apex of the alveolar ridge due to infection should be distinguished from the normal bone remodeling at the apex of the alveolar ridge after the superstructure has been installed. The bone remodeling often caused by two-part implants after abutment placement is not related to infection, and the marginal bone resorption in this case is usually limited to the first few weeks after abutment attachment and is not necessarily the initial stage of peri-implantitis. The onset of peri-implantitis begins at the top of the marginal bone ridge on the crown side around the implant, while the osseointegration on the root side is good. If left untreated, it can lead to a complete loss of implant-bone contact, loosening and dislodging of the implant. Clinically, peri-implantitis results in implant loss (dislodgement or complete failure) of close to 4% and is one of the leading causes of dental implant failure.