Sahrmann et al. [15] tested three instruments (ultrasonic scaler, Gracey curette, and air abrasive device with glycine powder) on rough surface implants stained with indelible ink used as artificial plaque. There was a statistically significant difference in terms of stain removal rate. The air abrasive device showed the best result among the tested instruments. The result of this study is in line with our result showing the superiority of the air abrasive compared with the ultrasonic scaler.

Widodo et al. [14] evaluated the efficacy of different methods used to cleanse titanium disks contaminated by S. aureus biofilm in vitro. They used the following methods: (i) rinsing with phosphate-buffered saline, (ii) rinsing with chlorhexidine digluconate 0.2%, (iii) application of photodynamic therapy (iv), use of a cotton pellet, (v) use of a titanium brush, and (vi) the combination of a titanium brush and photodynamic therapy. The results showed that the use of a titanium brush with/without photodynamic therapy was more effective in reducing the bacterial load on both polished and rough titanium implant surfaces than the other methods. Our results are also in accordance with their results in terms of the high cleansability of the rotary metal instrument. In addition, the cotton pellet showed moderate cleansability among the tested methods, but the cleansing time for the cotton pellet (60 s) was shorter than that of the titanium brush with (120 s + 60 s)/without (120 s) photodynamic therapy. If adjusting the difference of cleansing time, the cotton pellet might show equivalent cleansability to the titanium brush.

In contrast to the past in vivo and in vitro studies [35, 36], the Er:YAG laser demonstrated an inferior cleansability on the contaminated implant surfaces. The Er:YAG setting (60 mJ/pulse, 10 pps) in the present study was within the normal recommended range for cleansing an implant surface without causing damage to the implant surface or the peri-implant tissue cells [37,38,39] and to ensure the safety of peri-implant tissue [37]. Kreisler et al. [11, 37] used the same setting to cleanse a contaminated implant surface but without water coolant and demonstrated a good result. The reason why we could not achieve the same result might be associated with the water coolant used for further safety reasons in our study. In the clinical setting, the Er:YAG laser has been applied to treat peri-implantitis [27, 30, 40]. However, one report cautioned that the use of Er:YAG laser treatment as a non-surgical therapy had previously led to trauma of the peri-implant soft tissue, thereby causing unnecessary recession of the peri-implant mucosa [30]. In this context, when the Er:YAG laser is applied to the treatment of peri-implant disease, water coolant should be considered for safety. There are many aspects that contribute to the efficacy of the Er:YAG laser (e.g., setting, coolant, tip distance from the tip to the contaminated implant surface). Such differences should be investigated in future studies.