## 4 Discussion
: not available; PPD red: periodontal pocket depth reduction; Rec: gingival recession; SS: sonic scaler; =: no difference; \(\uparrow\): (*significant) better results in the test group; \(\downarrow\): (*significant) worse results in the test group). et al. concluded that the alternative use of APWJT may lead to an enhanced BOP reduction compared to conventional measures [39; 41; 45]. Anyway, one must note that the conclusions are based on a maximum of three included studies (Table 4). Further, two of these studies used carbon curettes and 0.1% CHx rinsing as a comparison but reported on the same patient cohort [50; 51]. The other study used Er:Yag laser irradiation as a comparison [52]. The adjunctive use of APWJT was only investigated by [PERSON] et al. (2021), who could only find one study that showed no additional effect [41]. Overall, most systematic reviews were based on very few clinical studies, and all stated the need for more studies in the future. Furthermore, only one systematic review that specifically gathered data on APWJT for peri-implantitis therapy could be found. Should low-abrasive APWJT powder be used in the active or supportive treatment phase, and should it be used alone or in combination with other treatment measures? The analyzed systematic reviews for the use of APWJT in active periodontal treatment from [PERSON] et al. [37] and [PERSON] et al. [40] showed the results of four clinical trials that used the GPAP or EPAP as an adjunct to hand instruments and ultrasonic device [53; 54; 55; 56]. In general, the clinical outcome parameters improved similarly to the control groups despite the clinical attachment gain that was in favor of the APWJT test groups. In the meta-analysis by [PERSON] et al. [37], APWJT was not tested as a standalone in active periodontal treatment. In a recently published systematic review by [PERSON] and co-workers, they analyzed antiseptic methods used for implant surface decontamination [57]. It was concluded that chlorhexidine (0.2%, 0.12%), citric acid (40%) and sodium hypochlorite (1%) are used the most as an adjunct in peri-implantitis therapy and are effective in killing bacterial cells. These findings are in line with the analyzed treatment strategies in the included systematic reviews of this umbrella review, even though the included reviews also focused on abrasive devices for implant surface decontamination. Another indication for the use of APWJT devices is described in a case report of retrograde peri-implantitis by [PERSON] et al. The group treated a patient with retrograde peri-implantitis surgically and with an APWJT device with glycine powder and an Er, Cr: YSGG laser to decontaminate the implant surface [58]. After six and thirteen months, the infected peri-apical site of the implant showed re-ossification, which underlines the effectiveness of this treatment strategy. Further investigation of this specific treatment indication is needed to evaluate the use of APWJT in this field. The main advantages of the low-abrasive air powder and waterjet technology might be the enhanced patient comfort and reduced treatment time during supportive periodontal therapy. The higher patient acceptance and comfort were shown in all the included systematic reviews that evaluated this technology in the supportive therapy on teeth [37; 38; 40; 42; 43; 44]. These findings correlated with a systematic review on patient perception when using APWJT devices that was conducted by [PERSON] and co-workers in 2016 [31]. Similar findings were reported in a recent survey-based clinical study with 100 recall patients by [PERSON] et al. [4]. The mean visual analog scale after APWJT-based tooth cleaning was very low, with only 0.66, and the patient acceptance of air powder waterjet technology was higher compared to that of hand instruments and ultrasonic devices. A significantly reduced treatment time was shown in a randomized clinical trial by [PERSON] et al., where 0.5 min per side was used when using APWJT devices subgingivally versus 1.4 min/site when using curettes (\(p<0.001\)) [2].