Inclusion Criteria:  Periodontitis with intrabony defect (Intrabony component ≥ 4mm, defect radiological angulation > 25°, 1 or max. 2 bony walls (no buccal bony wall), non-containing defect), no class III. furcation involved teeth Selected tooth must be in a traumatic occlusion or not in a gnathologically correct bite (migrated, elongated, tilted tooth, etc.). Patients must not be heavy smokers (<5 cigarettes/day). Full mouth plaque and bleeding scores (FMPS and FMBS) of <20% (O'Leary et al. 1972). The patient is able to comply with the study -related procedures (i.e. good level of oral hygiene, follow-up procedures). The patient is able to fully understand the nature of the study, signed informed consent.  Exclusion Criteria:  Pregnant women. Participation in another clinical study within 30 days prior to study start. Alcoholism, drug dependency, heavy smoking (>5 cigarettes/day). Known infection with HIV, HBV, or HCV. Patients requiring chemo- or radiotherapy. Previous or current radiotherapy of the head. Uncontrolled or insulin-dependent diabetes mellitus Clinically relevant osteoporosis or systemic disease affecting bone metabolism Clinically relevant cardiovascular disease e.g., decompensated cardiac insufficiency, hemodynamically relevant heart valve defects, or myocardial infarction during the last three months. Clinically relevant blood coagulation disorder. Previous or current treatment with systemic corticosteroids (within 2 months prior to screening visit) of more than 5 mg/day prednisone equivalent. Previous or current therapy with bisphosphonates at least for 30 days within the last 12 months before screening visit.