Peri-implantitis was defined as bleeding on probing (BOP) with or without suppuration (Supp) in addition to changes in the radiographic bone level. Interproximal bone level changes were estimated on intraoral radiographs. In the absence of available baseline radiographs taken at prosthesis installation, “a threshold vertical distance of 2 mm from the expected marginal bone level” was used to assess bone loss [3].

The identified patients with a history of grafting had received the following treatment protocols:

Simultaneous grafting (one stage) of dehiscence-type defects, employing a particulated bone substitute, and collagen membrane (2 patients; 3 implants)

Grafting and staged implant placement at 6 months (two stage) employing a particulated bone substitute and collagen membrane (3 patients; 3 implants)

External grafting (lateral window) employing a particulated bone substitute and collagen membrane and implant placement (2 patients; 3 implants)

External grafting (lateral window) employing a particulated bone substitute and collagen membrane and staged implant placement at 6 months (4 patients; 7 implants)

To be included, the radiographic bone loss at baseline (i.e., prior to treatment) in respective patients had to extend to the formerly grafted area.

After an initial course of non-surgical therapy, each subject had received a combined (i.e., implantoplasty + augmentative therapy) surgical treatment procedure [14] at respective implant sites (Fig. 1). This procedure included open flap debridement and a meticulous granulation tissue removal using conventional plastic curets (Straumann Dental Implant System; Institut Straumann AG, Basel, Switzerland) and an implantoplasty at both buccally (i.e., Classes Ib and Ic) and supracrestally (i.e., class II) (Fig. 1) exposed implant surfaces. This was accomplished using diamond burs (ZR Diamonds; Gebr. Brasseler GmbH & Co. KG, Lemgo, Germany) and Arkansas stones under copious irrigation with sterile saline. The remaining unmodified implant surfaces at the respective intrabony defect areas (i.e., classes Ib, Ic, and Ie) were decontaminated using either an Er:YAG laser device (energy density of 11.4 J/cm2, 10 Hz) (elexxion delos; elexxion AG, Radolfzell, Germany) or debrided using plastic curetes and cotton pellets soaked in sterile saline (Straumann Dental Implant System). Respective intrabony defect compartments were homogeneously filled using NBM (BioOss spongiosa granules, particle size 0.25–1 mm; Geistlich, Wolhusen, Switzerland) and were covered with CM (BioGide; Geistlich). Transmucosal healing was supported by a peri- and postoperative antibiotic medication for 5 days.