Diederik Hentenaar

147 General discussion and conclusions Treatment of peri-implantitis In pursuit of the main objective of this thesis we performed three peri-implantitis treatment studies on different implant surface decontamination methods. Two studies were performed with the aim to evaluate mechanical implant surface decontamination (efficacy of air-polishing), in a non-surgical and surgical setting, and one with the aim to evaluate chemical decontamination (phosphoric acid). Mechanical implant surface debridement: air-polishing Given the scarcity of clinical trials on the single use of air-polishing in the treatment of peri-implantitis (Schwarz et al. 2016), including the identified sources of bias in previously performed studies on peri-implantitis treatment using air-polishing, we decided to conduct two large sample size randomized controlled trials comparing erythritol air-polishing with conventional debridement methods in both a non-surgical and surgical setting. From the non-surgical study ( chapter 3 ) results it was concluded that air-polishing (EMS, Airflow Master Piezon) is as effective as ultrasonic scaling (piezo-electric ultrasonic scaling with PEEK plastic tip) in the improvement of clinical parameters. However, in both groups only a limited number of patients could be considered successfully treated. No effect on marginal bone levels or microbiology was noticed and low pain scores were reported for both interventions (mean VAS scores < 3), without one being less painful than the other. At 3 month follow-up, patients who were considered unsuccessfully treated were invited to participate in a surgical follow-up study (see chapter 4) . The aim of that randomized controlled trial was to compare the effect of erythritol air-polishing as mechanical implant surface cleansing method to saline during a resective surgical protocol. It was concluded that erythritol air-polishing was as effective as saline in terms of clinical, radiographical and microbiological parameters. At 1-year follow-up, a successful treatment outcome (PPD<5mm, max 1 out of 6 sites BoP, no suppuration and no progressive bone loss >0.5mm) was only rarely attained (19%). During 1 year follow-up a total number of 16 implants (17%) were lost due to persistent signs of severe inflammation. Air-polishing did not appear to be significantly more successful. It is hard to explain the variation in treatment outcome between patients. The great variety of implant and patient characteristics as well as device specific parameters may possibly account for these observations. For example, implant thread geometry seems to influence the access of decontamination devices and in turn its efficacy (Steiger- Ronay et al. 2017). The most favorable implant characteristic for optimal mechanical biofilm removal was recently shown to be low thread pitch and low thread depth (Sanz- Martin et al. 2021). Also, the design of the air-polishing tip/nozzle, the insertion depth 7