Diederik Hentenaar

146 Chapter 7 Furthermore, it is interesting to note that significant higher levels of PICF volume were found at peri-implantitis sites compared to healthy implant sites. This finding corroborates the results of the studies by Bevilacqua et al. (2016) and Tözüm et al. (2007) who also showed significant elevated levels of fluid in a diseased state compared to health, as well as around natural teeth compared to implants. Moreover, in the study by Bevilacqua et al. (2016), in a periodontal and peri-implant healthy state the probing pocket depth seemed directly related to the amount of fluid produced (up to 3 mm pocket depth). Although this relation was however not present in the case of active peri-implant disease, this might suggest that a volumetric threshold level might exist that could be of importance in assisting in the (early) diagnosis of peri-implant disease. In chapter 2 , the influence of the non-surgical peri-implantitis therapy on immunological biomarker levels present in PICF at 3 month follow-up was additionally evaluated. The study showed that none of the biomarker levels had significantly improved after non- surgical therapy and levels of IL-1β and MMP-8 remained high. This finding seems in accordance with a previous non-surgical study by Renvert et al. (2011) who neither found any differences in the majority of the studied cytokines (6 out of 9) when using either an air-abrasive device or Er:YAG laser. A surgical intervention study performed by Thierbach et al. (2016), also did not show a difference in MMP-8 levels 6 months after the treatment when compared to baseline, in smokers and non-smokers. Hence, after treatment of peri-implantitis, MMP-8 levels still seems to reflect an intensified host response around implants and immunologically indicate the challenge of controlling peri-implantitis. It therefore might be speculated that the limited clinical effect of a non-surgical therapy seems to be immunologically underlined. However, with our study, it seems not possible to truly support or deny the potential use of a change in biomarker as a monitor to assess the effectiveness of a peri-implantitis treatment with PICF analysis. Collectively, the outcomes of the study presented in chapter 2 seem to demonstrate capacity for biomarkers to improve clinical diagnosis of peri-implant conditions and indicate a role of tissue fluid volume in the diagnosis of peri-implant disease. Interpretation of the study results should be done cautiously since the results are based on a limited sample size, on which no sub-analyses could be performed for several possible confounding factors (e.g., smoking, age, gender). Clinical evaluation of peri-implant tissues and radiographic assessment still form the foundation for detection of peri-implant disease. However, although the evidence is still limited, a shift from clinically based towards a more biologically supported definition of peri-implant conditions seems to be imminent.