In contrast to the past in vivo and in vitro studies, 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 and to ensure the safety of peri-implant tissue. Kreisler et al. 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. 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. 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.