Diederik Hentenaar

8 Chapter 1 Over the past decades, dental implantology has been successfully integrated into the field of modern dentistry (Buser et al. 2017). Dental implants have shown good long term results with survival rates of 93% and 84% after 20 and 25 years (Bakker et al. 2019, Jemt 2018). In addition, dental implant placement is considered a feasible treatment in almost any medically compromised patient, when the required preventive measures are taken and follow-up care is at a high level (Doll et al. 2015, Vissink et al. 2018). Although accurate data about the number of implants placed worldwide is lacking, a yearly increase in the U.S. between 1999 and 2016 of 14% is reported (Elani et al. 2018). Moreover, an increasing trend of implant placement ranging from 6% to 23% up to 2026, has been estimated (Elani et al. 2018). Despite the increased popularity of dental implant placement, challenges in regard to preservation of hard and soft tissue health around the implant are seen (Lang et al. 2019). Characterized by inflammatory processes affecting these tissues, one of the biggest challenges clinicians are facing today are peri-implant diseases, specifically known as peri-implant mucositis and peri- implantitis (Lang & Berglundh 2011). Anatomical comparisons and differences between implants and teeth Following implant placement, peri-implant hard and soft tissues are formed as a result of a wound-healing process (Eggert & Levin 2018). The formation of new bone (hard tissue) in contact with the implant is recognised as osseointegration, while the establishment of peri-implant mucosa (soft tissue) includes the build-up of a junctional epithelium and a connective-tissue zone in contact with components of the implant/suprastructure (Albrektsson et al. 1981). Osseointegrated implants are directly anchored to the bone and hence, compared to the presence around natural teeth, lack periodontal ligament (PDL). As a result, blood supply is limited to the supraperiostal vessels, thereby restricting the amount of nutrients and immune cells that may extravasate to tackle bacterial infection. Both the natural tooth and the implant show equivalence in the form of presence of junctional epithelial attachment, however, a major difference between teeth and implants is the absence around implants of organized groups of collagenous connective tissue fibers that insert into root cementum, bone, and soft gingival tissues (Eggert & Levin 2018). Instead, connective tissue fibers around implants/ suprastructures are organized in a vertical manner (see figure 1).