The further evaluation of maximum PD reduction did not indicate a significant difference between the two groups (i.e., grafted vs. non-grafted), with the range of 1.57 to 2.20 mm at the patient level analysis and 1.31 to 2.10 mm at the implant level. These results are in concurrence with data from the previous studies, where mean PD reduction amounted from 0.74 to 2.55 mm [16], up to 3 [18], and > 4 mm [17] following surgical regenerative peri-implantitis therapy. To the authors’ best knowledge, this is the first clinical study to evaluate peri-implantitis treatment outcomes at formerly grafted and non-grafted implant sites. Therefore, the results (e.g., disease resolution, changes in mean BOP, and maximum PD) cannot be compared to those from previous studies.

A recent systematic review and meta-analysis indicated lateral bone grafting procedures (both simultaneous with implant placement and staged) to be associated with peri-implant tissue stability [19]. Particularly, the results, which were based on eight clinical investigations, addressed that different surgical interventions (i.e., GBR and autogenous, allogeneic, or xenogeneic bone blocks) resulted in low and similar BOP values, along with comparable PD, marginal bone and plaque levels at both short-term (1–3 years) and long-term (> 3 years) follow-ups [19]. Moreover, the occurrence of peri-implant diseases or a progressive marginal bone loss was reported to be low and also comparable between different lateral hard tissue grafting protocols [20]. However, the data on whether former bone grafting procedures influence peri-implantitis treatment outcomes has not been reported in the literature.

Based on the findings of the current investigation, combined surgical treatment was associated with clinically important reduction in BOP and PD values and was not influenced by the presence or absence of the grafting procedure at the implant site. When interpreting these results, the relatively small number of patients in the group with grafted implant sites should be taken into consideration. Additionally, it should be noted that two different decontamination protocols (i.e., Er: YAG laser or debriding with plastic curettes and cotton pellets soaked in sterile saline) were applied. Nevertheless, according to the findings from the randomized clinical trial, the method used to decontaminate the implant surface had no impact on the clinical outcomes of the combined surgical therapy of peri-implantitis [16].