Comparison of the GTR Procedure Alone and in Combination With Immediate OTM

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 mo…