The purpose of the study is to evaluate if surgical treatment of peri-implantitis with enamel matrix derivative (Emdogain®, EMD) will have an additional effect on the healing outcome, changes in the peri-implant microflora and on the inflammatory response in the periimplant pocket at 12 months.

This is a randomised controlled clinical trial. Recruiting 31 patient with periimplantitis at one or more implants in need for surgical treatment.

Randomisation to test group (EMD) with surgical treatment and additional application of enamel matrix derivative (Emdogain®) or surgical treatment alone in the control group (non-EMD).

Treatment of existing periodontitis performed before recruitment. Baseline examination including samples of microbiota and peri-implant fluid followed by surgical treatment. Access surgery to remove chronic inflammatory tissue and clean the implant surface from biofilm and implant stone with hand instrument and ultrasonic device with special tips for implants, followed by polishing the implant surface with a gauze, super floss and rinsing with saline. Allocation with a performed block randomisation at the stage of surgery, after cleaning of implant surface. Application of enamel matrix derivative (Emdogain®) or not, just before closure of flap. After surgery rinsing with chlorhexidine 0.2% twice a day in 6 weeks. No systemic antibiotic used in this study.

Supportive care program, including hygiene instructions and professional cleaning supragingival at implants and teeth at 2 weeks, 3, 6, 9 and 12 months after treatment.

Examination with measurements of pocket depth and bone levels at radiographs at baseline just before surgery and 12 months and prevalence of bleeding on probing, pus or recession as well as full mouth plaque score and full mouth bleeding score at 3, 6, 9 and 12 months.

Microbial sampling performed with endodontic paper points at baseline and 2 weeks after surgery as well 3, 6 and 12 months from implant site with at baseline the deepest pocket.

Sampling of the peri-implant fluid from the peri-implant pocket at baseline, 3, 6, and 12 months from implant site with at baseline the deepest pocket.

Removal of bridges performed to give accessibility at baseline examination/surgery and at 12 months.

Inclusion Criteria:

• peri-implant angular bone loss ≥3 mm, measured at radiographs
• deep pocket ≥5 mm combined with bleeding and/or pus

Exclusion Criteria:

• individuals with uncontrolled diabetes (HbA1c > 7,0%)
• individuals where prophylaxis of antibiotic is indicated
• medication with prednisolon or other anti-inflammatory drug
• medication with gingival hyperplasia known as a side effect
• systemic antibiotic intake the last 3 months