Regarding the air abrasives, the cleansing effect in the SEM analysis was also as considerable as that achieved by the ultrasonic scaler in the present study, in contrast to the results of the aforementioned study. Louropoulou et al. [29] also stated in their systematic review that an air-powder abrasive system with sodium bicarbonate powder could cleanse contaminated rough/smooth implant surfaces without losing biocompatibility compared with a plastic scaler, metal curette, rotating titanium brush, and ultrasonic scaler. In the present study, the air abrasive showed fair to good cleansability with glycine powder but did not achieve the best result among the tested decontamination methods. The reason for this difference may be associated with the different experimental conditions (e.g., cleaning time, powder, power setting, and nozzles). Although free access to the genuine implant surface in the present study allowed us to evaluate the efficacy of each decontamination method, glycine powder as an air abrasive may not have the best cleansing potential among the tested methods. In the present study, the Er:YAG laser generally showed inferior cleansability. Er:YAG lasers have also been used in non-surgical [27] and surgical [30] peri-implantitis treatment. It was previously reported that implant surface decontamination by Er:YAG lasers demonstrated good cleansability of the contaminated implant surface compared with other decontamination methods [31,32,33]. The reason for the inferior cleansability of the Er:YAG laser observed in this study compared with the other decontamination methods is discussed below; however, dense biofilms remained on rough surface implants in particular after decontamination by the Er:YAG laser.

A rotary stainless steel instrument has a small head composed of stainless steel that allows clinicians good accessibility to deep intrabony defect areas. To the best of our knowledge, no study has clarified the cleansability of this rotary stainless steel instrument. In the present study, it was shown that it might be useful for cleansing contaminated implant surfaces. However, the rotary stainless steel instrument created numerous shallow scratches, especially on machined surface implants. John et al. [12] compared the supragingival plaque cleansability of a rotary titanium instrument to that of a stainless metal curette on contaminated titanium disks. The residual biofilm area left on implant treated with the rotary titanium instrument was significantly lower than in the stainless metal curette, and the surface alteration of the titanium disks could not be shown in SEM analysis. Although the cleansability of the rotary stainless steel instrument in the present study is superior and advantageous, the downside of the surface alteration is an issue to consider.