The Adjunctive Effect of Soft Tissue Augmentation Procedures of Moderate-severe Peri-implantitis

Inclusion Criteria: 1. Age \> 18 years old (UZH, FRA) or \> 21 years old (SIN), male and female. 2. Diagnosed with periimplantitis of at least 1 implant in function for at least 1 year Diagnostic criteria * Presence of bleeding and/or suppuration on gentle probing. * Probing depths of ≥6 mm. * Bone levels ≥3 mm apical of the most coronal portion of the intraosseous part of the implant. 3. Periodontal health (including previously treated periodontitis patients with reduced but healthy periodontium) 4. Good oral hygiene (full mouth plaque score \<25%) 5. Adequate control of inflammation (full mouth BOP \<25%) 6. Signed informed consent form Exclusion Criteria: 1. Pregnant or lactating female patient at inclusion 2. Allergy or objection to porcine and bovine implantable biomaterials 3. Allergy to Penicillin or NSAIDs 4. Known or suspected non-compliance, drug or alcohol abuse 5. Inability to follow the procedures of the study, e.g. due to language/ comprehension problems, psychological disorders, dementia, etc. of the participant 6. Smoking \> 15 cigarettes a day 7. Active periodontal disease