Diederik Hentenaar

151 General discussion and conclusions Previously, studies evaluating the influence of acids on titanium implant surfaces were mainly performed in an in-vitro or animal setting mainly focused on the use of citric acid (Zablotsky et al. 1992, Dennison et al. 1994, Mouhyi et al. 2000, Htet et al. 2016, Dosti et al. 2017). Clinically, phosphoric acid was, as far as we know, only used in a peri-implant maintenance study (Strooker et al. 1998) and a case series by Wiltfang et al. (2012) on the surgical regenerative treatment of peri-implantitis. Hence, our study is the first to show that the use of phosphoric acid as implant surface decontaminant did not seem to enhance clinical outcomes on a 3-month follow-up more than sterile saline. However, our findings are in line with previous studies on acid decontamination showing an antibacterial potential of phosphoric acid. A recent in-vitro study by Dosti et al. (2017), which for the first time evaluated SLA implant disks with multilayer and multi-species 3-week-old biofilm, found that when the implant surface was rinsed twice with sterile saline (i.e., pre-rinse, followed by 2 minute rinsing) this ‘double rinse group’ was the only group to have significantly more bacteria removed from the SLA disks than a single rinse control group. The use of phosphoric acid in that study did not appear to result in a superior effect compared to the ‘double rinse group’. In addition, a study by Wheelis et al. (2016) found noticeable morphological changes when the synergistic effect of acidic environments ( i.e. citric acid, 15% hydrogen peroxide, tetracycline, peroxyacetic acid) and mechanical forces (rubbing with cotton swabs) were applied. To which extent implant surface changes affect the biological response in terms of peri-implant hard and soft tissue cell (i.e., fibroblast, epithelial cells and/or osteoblasts) re-attachment, remains to be found. However, considering the possible detrimental effect of mechanical and chemical combined influences on the implant surface, it seems advisable that care should be taken applying such combinations on the implant surface. Randomized clinical trials are needed to evaluate the influence of different combinations in different approaches. Hence, until no superior decontaminating approach has been appointed, one might advocate the use of only sterile saline as implant surface decontaminant. Treatment considerations Titanium particle release In recent years, studies increasingly focused on evaluating implant surface physical and chemical properties (Kotsakis et al. 2016, Wheelis et al. 2016). It is expected that, as a result of synergism between different wear factors (e.g., cyclic implant loading, implant maintenance/cleaning procedures, oral biofilm and friction at the implant- abutment interface) there is an increased risk that the implant surface titanium dioxide layer might get damaged to such an extent that it diminishes the corrosion resistance. Subsequently, titanium particle release and ion leakage can occur, a phenomenon which is called bio-tribocorrosion (Kotsakis et al. 2021). Titanium particle release and ion leakage in turn have been suggested as triggers for marginal bone loss and peri- 7