The key objective of the study is to compare the effects of soft tissue augmentation using a volume stable collagen matrix or autogenous connective tissue graft or no soft tissue augmentation in addition to bone grafting/implantoplasty in patients who undergo surgical therapy of peri-implantitis with respect to clinical resolution of the infection.

The global burden of periimplantitis is expected to rise with the increasing popularity of dental implants as a replacement option. While many therapeutic interventions have been proposed, none have been proven superior. Surgical therapy is often indicated to gain access to the plaque infected implant threads and bone defects. Implantoplasty of suprabony defects have shown good results although adverse effects like soft tissue recession are common.

Thin mucosa results in compromised outcomes following various surgical interventions around implants with increased recession and aesthetic failures. It has also been associated with increased marginal bone loss and severity of periimplantitis. Application of autogenous connective tissue grafts during surgical therapy of periimplantitis to increase the keratinised mucosa widths or attenuate post-implantoplasty recession showed promising results.

No randomized controlled clinical trials investigating the effects of additional soft tissue augmentation with implantoplasty on periimplantitis lesions have been done so far. In addition, few have evaluated patient reported outcome measures, included non-European subjects and none reported on soft tissue alterations. The effect of soft tissue substitutes on surgical periimplantitis therapy remains unknown.

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

Masking is not possible for the intended interventions, as the harvest of the SCTG requires an additional surgical site at the palate, which will be recognized by the patient. The investigators will also be aware of the type of procedure, as both follow different operation procedures.