For each radiograph, the width of the implant was used for image calibration.

The defect height was measured from a well-defined reference point at the most coronal part of the implant body, on radiographs taken at baseline, 12 months and 7 years. The radiographic measurements were performed by one investigator (AMA), blinded to the examination timepoint. The changes in vertical defect depth were also calculated. To analyse the radiographs taken, Image J, 1.42q, US National Institutes of Health, Research Services Branch was used.

The radiographic measurements were repeated twice, after 1 week and after 10 weeks, and calculated with Pearson correlation coefficient. A strong positive correlation was demonstrated (r = 0.99–0.93).

The study population of the follow-up study did not reach statistical power due to the many drop-outs; the calculations were therefore limited to descriptive findings applied on the clinical and radiographic data assessed at baseline, 12-month examination and after 7 years.

Continuous variables were expressed as means and standard deviation.

Seven years (7.3 years [6.7–8]) after surgical treatment of peri-implantitis, 17 individuals met for the follow-up examination.

During 2008–2015, five subjects had died and ten subjects were lost to follow-up for various reasons. Among individuals accepting the invitation for the follow-up, three subjects, all in the PTG group, had lost their treated implants. Two subjects were excluded due to technical complications with the supraconstructions; one patient had received a new cemented single crown, and one subject had an overdenture impossible to remove.

In total, 12 individuals were finally included (Fig. 1).

The majority (10/12) of the subjects in the present study were smokers or former smokers, and 8/12 subjects had a history of periodontitis. The characteristics and demographic data of the groups are presented in Table 1. Most implants had screw-retained supraconstructions and had a mean function time of 14 years and were in the anterior region of the maxilla and mandibula.