Diederik Hentenaar

16 Chapter 1 In addition to mechanical approaches, chemical agents to disinfect the implant surface such as chlorhexidine digluconate 0.2%/0.12%, sodium hypochlorite and hydrogen peroxide 3% have also previously been studied in different clinical trials (Gosau et al. 2010, Heitz-Mayfield et al. 2012, De Waal et al 2013, De Waal et al. 2015). However, no superior clinical effectiveness has been shown in a single study for a specific chemical decontamination protocol (Ntrouka et al. 2011, Subramani & Wismeijer 2012, Meyle 2012). Studies using acids at low pH (< 2) have shown potentially beneficial antiseptic effects (Zablotsky et al. 1992, Dennison et al. 1994, Strooker et al. 1998, Wohlfahrt et al. 2012, Wiltfang et al. 2012, Htet et al. 2016). For example, animal studies showed re- osseointegration and direct bone-to-implant contact when acids were used (Kolonidis et al. 2003, Alhag et al. 2008). Also, acid-etching might positively influence the epithelial seal around dental implants (An et al. 2012). Clinical studies that evaluated the use of phosphoric acid (pH 1) showed an instant greater reduction of colony forming units (Wiltfang et al. 2012, Strooker et al. 1998). However, use of phosphoric acid etching gel as decontaminating agent has not been evaluated in a randomized controlled trial. Conclusively, a number of mechanical intervention methods, solely or in combination with chemical agents, have been described over the years in in vivo and in vitro studies, as well as in a non-surgical and surgical setting (Leonhardt et al. 2003, Máximo et al. 2009, Serino & Turri 2011, Heitz-Mayfield et al. 2012, De Waal et al. 2013, Bassetti et al. 2014, De Waal et al. 2016, Riben-Grundstrom et al. 2015, Ramanauskaite et al. 2016). Due to the frequently combined different regimens, evaluation of the true impact of the single implant surface decontaminating agent on clinical outcomes remained difficult to identify. Hence, a gold standard debridement regimen in the treatment of peri- implantitis did not exist before the start of this thesis (Esposito 2012, Subramani & Wismeijer 2012, Louropoulou et al. 2014, Schwarz et al. 2015). Therefore, an ongoing search to find potential alternative therapies or effective combination of therapies seemed imperative. Moreover, research on previously not well researched therapies was needed.