Diederik Hentenaar

98 Chapter 4 approach is able to stop progression of bone loss. In addition to the previous 6-month results, possibly up to 1-year after therapy as shown in our study. On the other hand, the sensitivity of BoP in the present study seemed quite low to predict further bone loss. It could therefore be questioned if the total absence of BoP as part of the success criteria used in previous studies, is not too strict. In order to truly evaluate the influence of BoP on therapy success on the long term, future studies should consider to present a more detailed overview of BoP levels (at implant level). Furthermore, the absence of relevant changes in radiographic marginal bone levels between the 3-month intervals suggest that future studies should extend this radiographic evaluation interval to justify a balanced risk (radiation exposure) to benefit ratio. Only recently, a similar comparison of decontamination methods was evaluated in an in- vitro setting by the group of Amate-Fernandez, et al. (2021). It was shown that erythritol had the same antibiofilm and antibacterial capacity on a 14 day grown multi-species biofilm as mechanical removal with saline-soaked gauzes which might be an explanatory basis of the clinical findings in the present study. Translation of these preclinical findings to a clinical situation should however be done with utmost care, considering that in- vitro studies using specimens and biofilm contaminants may not simulate actual clinical situations. Patients characteristics, the presence of suprastructures and anatomical limitations of the oral cavity (e.g. the tongue) are confounders in a clinical setting which could overshadow possible beneficial in-vitro effects. Hence, this might also explain why the favorable in-vitro effects of eryhtritol/chlorhexidine powder, in terms of bacterial growth suppression (e.g., P. gingivalis and S. gordonii ) (Soderling, et al., 2010; Hashino, et al. 2013) and prevention of bacterial regrowth (Drago, et al. 2017, Amate- Fernandez, et al. 2021) could not be clinically underlined by the present study. Namely, microbiologically, erythritol air-polishing did not lead to significantly lower bacterial counts 12 months after therapy. One could however advocate that earlier sampling should have been performed to find a related effect, however the present findings indicate that even though there might be a beneficial effect on bacterial suppression/ regrowth (on the short term) it does not lead to a clinically relevant effect. The exact mechanism underlying the antibiofilm activity of eryhtritol remains poorly understood. Up to date, it remains unknown which powder is favorable in terms of cleaning efficacy, surface change and the ability to restore the biocompatibility. A myriad of in-vitro studies evaluating different powders (e.g., sodium bicarbonate, glycine, erythritol, calcium carbonate, calcium phosphate, hydroxyl apatite, tricalcium phosphate etc.) having different sizes, forms and hardness, used with different devices (in different settings) in custom made defect models with different morphologies have emerged in the recent literature (Moharrami, et al., 2019). Both larger particles (i.e. sodium