200 patients with ≥1 molar presenting with a furcation defect degree II will be included and randomized to either control (open-flap debridement) or test treatment (open-flap debridement + bone substitute material). The primary outcome of the study is furcation closure defined as absence of clinically detectable furcation involvement degree \>I. Secondary outcomes include changes in bleeding on probing, probing depth, vertical and horizontal attachment levels, soft tissue level, marginal bone level, need for surgical retreatment, tooth loss, patient-reported outcomes and adverse events. A composite outcome based on furcation closure (degree ≤I) in combination with shallow probing depth (≤5 mm) and absence of bleeding on probing will also be evaluated. conditions: Periodontitis conditions: Furcation Defects studyType: INTERVENTIONAL phases: NA allocation: RANDOMIZED interventionModel: PARALLEL interventionModelDescription: The project will be conducted as a two-armed randomized controlled trial in multiple clinical centers. The primary outcome will be assessed at 1 year post-surgery with a subsequent follow-up of 10 years. primaryPurpose: TREATMENT masking: SINGLE maskingDescription: Clinical assessments following intervention will be conducted by assessors unaware of group allocation. whoMasked: OUTCOMES_ASSESSOR count: 200 type: ESTIMATED name: Access flap & surgical debridement name: Application of bone substitute material (BioOss Collagen) measure: Proportion of patients/teeth displaying furcation closure. measure: Proportion of patients/teeth displaying furcation closure. measure: Proportion of patients/teeth displaying furcation closure. measure: Proportion of patients/teeth displaying furcation closure. measure: Proportion of patients/teeth displaying furcation closure. measure: Proportion of patients/teeth displaying furcation closure. measure: Changes in probing pocket depth. measure: Changes in probing pocket depth. measure: Changes in probing pocket depth. measure: Changes in probing pocket depth. measure: Changes in probing pocket depth. measure: Changes in probing pocket depth. measure: Changes in bleeding on probing. measure: Changes in bleeding on probing. measure: Changes in bleeding on probing. measure: Changes in bleeding on probing. measure: Changes in bleeding on probing. measure: Changes in bleeding on probing. measure: Changes in vertical and horizontal clinical attachment level. measure: Changes in vertical and horizontal clinical attachment level. measure: Changes in vertical and horizontal clinical attachment level. measure: Changes in vertical and horizontal clinical attachment level. measure: Changes in vertical and horizontal clinical attachment level. measure: Changes in vertical and horizontal clinical attachment level. measure: Changes in marginal soft tissue levels. measure: Changes in marginal soft tissue levels. measure: Changes in marginal soft tissue levels. measure: Changes in marginal soft tissue levels. measure: Changes in marginal soft tissue levels. measure: Changes in marginal soft tissue levels. measure: Changes in radiographic bone levels. measure: Changes in radiographic bone levels. measure: Changes in radiographic bone levels. measure: Changes in radiographic bone levels. measure: Patient satisfaction assessed by visual analogue scale. measure: Patient satisfaction assessed by visual analogue scale. measure: Patient discomfort as expressed on a visual analogue scale. measure: Patient discomfort as expressed on a visual analogue scale. measure: Esthetic appreciation as expressed on a visual analogue scale. measure: Esthetic appreciation as expressed on a visual analogue scale. measure: Rate of adverse events. measure: Rate of adverse events. measure: Tooth loss. measure: Tooth loss. measure: Tooth loss. measure: Tooth loss. measure: Tooth loss. measure: Need for retreatment. measure: Need for retreatment. measure: Need for retreatment. measure: Need for retreatment. measure: Need for retreatment. measure: Change of inflammatory markers. measure: Change of inflammatory markers. sex: ALL minimumAge: 18 Years stdAges: ADULT stdAges: OLDER_ADULT facility: Department of Periodontology, Institute of Odontology city: Göteborg zip: 40530 country: Sweden name: Jan Derks, PhD role: CONTACT phone: 0046 76 618 3124 email: jan.derks@odontologi.gu.se name: Jan Derks, PhD role: PRINCIPAL_INVESTIGATOR name: Karolina Karlsson, PhD role: SUB_INVESTIGATOR name: Kostas Bougas, PhD role: SUB_INVESTIGATOR lat: 57.70716 lon: 11.96679 hasResults: False