## 4 Discussion
Considering the limited information currently available and the wide heterogeneity of clinical studies, superiority of laser treatment over conventional treatment of peri-implantitis has not been conclusive, although surgical laser therapy of peri-implantitis is able to achieve clinical improvement [31]. Controversial data may be reported because of the inherent heterogeneity in clinical and in vivo studies, although these studies are critical for the evaluation of implant cleaning procedures. The effectiveness of laser irradiation on the implant surface in non-surgical therapy may be significantly influenced by peri-implant soft tissues. Effects of peri-implant bony defect configurations on surgical therapy after flap reflection are expected to be greater than those of peri-implant soft tissues. To investigate the effects of the peri-implant soft tissues on the effectiveness of laser irradiation in non-surgical treatment, the models currently described mimicked surgical treatment situations for peri-implantitis with shallow and deep intra-bony defects. By integrating CAD and 3D-printing techniques to construct a standard in vitro laser treatment platform, this study provides an integrated process to investigate the effects of access limitation and defect configurations on the effectiveness of cleansing contaminated implant surfaces. The present study investigated the sterilization effect of Er:YAG laser irradiation in shallow and deep peri-implant intra-bony defects that simulate clinical situations. Er:YAG laser irradiation effectively sterilized implants with both shallow and deep peri-implant bony defects in these models at mandibular incisor, premolar, and molar positions. There was no significant difference of sterilization effects between shallow and deep intra-bony defects using Er:YAG laser irradiation. A slightly lower sterilization rate was observed with the wider implants in the mandibular posterior region; however, these results were not statistically significant. Few studies have investigated the influence of defect configurations on implant surface decontamination. [PERSON] et al. investigated two surface debridement/decontamination methods with intra-bony (class Ib, Ic, le) and supra-bony (class II) defects in patients with peri-implantitis [32; 33; 34]. Although these studies failed to demonstrate a significant impact of the surface decontamination method [32; 34], a potential impact of defect configuration on clinical outcome following combined surgical therapy for advanced peri-implantitis lesions was identified [33]. The results of this study coincided with literature indicating that the decontamination effects of Er:YAG lasers were similar in different peri-implant intra-bony defect configurations with a proper contact tip and parameter settings [32; 34]. In the present study, shallow (2 mm) and deep (6 mm) peri-implant intra-bony defects were created with similar crestal apical widths of 1.8 mm and 1.5 mm, respectively (Figure 1a, Table 1). Considering the similar macro- and micro-topography of the implant models and similar dimension of intra-bony defects, the differences in sterilization rates between the three types of implant specimens may have been related to differences in implant surface area, the position of implants in the dental arch or access limitation by local anatomic structures including the buccal cheek. Further investigations are necessary to evaluate the effects of implant positions in dental arches and adjacent dental/facial anatomic features. Although the clinically beneficial effects of mechanical and chemical interventions to disrupt peri-implant biofilms demonstrate convincingly that microorganisms are involved in the disease process, there is no evidence for the existence of one or a limited number of specific pathogens causing peri-implantitis.