Diederik Hentenaar

148 Chapter 7 and movement of the air-polishing nozzle, as well as device settings such as drive air- pressure, water ejection and powder emission are factors which seems to be related to the clinical effect of an air polisher (Tastepe et al. 2017). Moreover, according to the manufacturer’s manual, particles should impact at an angle of 30–60° at an ideal working distance of 3−5 mm for the kinetic energy of the powder to remove the biofilm. Considering that suprastructures were not removed during non-surgical therapy and during the surgical intervention cemented restorations were kept in place, the insertion of the cleaning devices into the peri-implant pocket might have been hampered and proper working angel and distance might not have been achieved in every situation. We found no indications that the pre-treatment composition of the bacterial biofilm could be indicative for the treatment outcome. Furthermore, the effectiveness of air-polishing seems to depend on the abrasiveness of the powder particles used (hardness, size, and shape) (Cobb et al. 2017) and the shape of the bone defect (Sahrmann et al. 2015, Ronay et al. 2017, Keim et al. 2019, Tuchscheerer et al. 2021). Larger, coarser powder types (atrium bicarbonate ±70μ) seem to provide a higher cleaning efficacy than finer ones, but at the same time do cause more alterations of the implant surface (crater-like defects, rounding or removal of sharp edges). Smaller particles (e.g. erythritol ±14μ and glycine ±25μ) on the other hand, are less damaging and exert only a minor effect on the implant surface topography. However, although these smaller particles were more likely to reach areas in the rough implant surface inaccessible by larger particles, reduced capacity to remove implant contaminants was seen when using these smaller particles (Cha et al. 2019, Matsubara et al. 2020). Hence, this reduced capacity might have played a role in the limited clinical effects found in our studies. Regardless of the type of bone defect (30, 60 or 90 degrees), the effect of an air polisher in a laboratory open/surgical approach seems to be significant over a closed/non-surgical approach (Tuchscheerer et al. 2021). Wider implant bone defects (60,90 degrees) seem to be more effectively cleaned than narrow defects (30 degrees) but no differences between intraosseous (30, 60 degrees) and supraosseos defects (90 degrees) in a surgical approaches were found (Sahrmann et al. 2015, Keim et al. 2019, Tuchscheerer et al. 2021). One might argue that the implants were not cleaned long enough. It appeared that when the treatment time was increased from 5 to 45 seconds, considerable more efficient implant cleaning was achieved with an air-polishing device in a pre-clinical setting (Mensi et al. 2020). During the non-surgical intervention, implants were cleaned up to 30 seconds in total (5 seconds per site) and during surgery the therapy was applied until the implant surface was assessed as visually clean. Compared to the literature, a non-surgical treatment study by Renvert et al. 2011, evaluating the use of glycine