Inclusion Criteria:  > 18 years; Untreated AO after extraction of a permanent tooth (excluding wisdom teeth);  Diagnosis of AO based on the criteria of Blum (Blum 2002)  Exclusion Criteria:  Patients with chronic diseases and/or taking any medication, influencing hard and soft tissue healing; Pregnancy; History of hypersensitivity or allergy to HY; Inability to attend follow-up appointments; Intake of preoperative antibiotics.