Diederik Hentenaar

9 General introduction Figure 1. Schematic illustration of hard and soft tissue around a tooth and an implant. Copyright Renvert-Giovannoli Periimplantitis, Quintessence International, 2012 It is thought that the absence of the perpendicular attached connective tissue fibers cause the implant to have a weaker defence mechanism i.e., weaker peri-implant soft tissue seal/cuff to bacterial invasion and places peri-implant tissues in an ‘open wound’ conformation (Kim et al. 2019). Histologically, it has been shown that inflammatory reactions of peri-implant lesions extend apical of the junctional epithelium and become larger around implant sites than those around natural teeth (Berglundh et al. 2011). In addition, a faster progression of disease is observed with the occurrence in a non-linear and accelerating pattern (Fransson et al. 2010). Classification and definition of peri-implant diseases and conditions A classification of peri-implant diseases and conditions was for the first time addressed in the 2017 World Workshop (Berglundh et al. 2018). Although definitions of peri- implant diseases had been previously presented, the term ‘definition’ often provoked misunderstanding. Therefore the aim was to distinguish disease definition from case definition. Disease definitions are descriptive and present the typical characteristics of the disease, whereas case definitions should provide the clinical guidelines for diagnosis, 1