Inclusion Criteria:  Patients elder than 18 years; uni- or bilateral vertical or mesioangular complete impaction of the LM3 classified to: group II- or III- B or C according to Pell-Gregory (1933); a distance ≥ 5 mm from the CEJ to marginal bone level at the distal aspect of the second molar.  Exclusion Criteria:  Patients with chronic diseases and/or taking any medication, influencing hard and soft tissue healing; acute pain/infection of the surgical region; untreated periodontal disease; patients smoking > 10 cigarettes per day; pregnancy; history of hypersensitivity or allergy to HY; absence of an adjacent second molar; presence of caries or restoration on the distal aspect of the adjacent second molar; and inability to attend the follow-up appointments.