Periodontal Regeneration With Hyaluronic Acid or Enamel Matrix Derivatives

Inclusion criteria: * Diagnosis of stage III-IV periodontitis. * Completed steps I-II periodontal therapy. * FMPS \<15% at 3-month re-evaluation. * FMBS \<15% at 3-month re-evaluation. * At least one site with intrabony defects and residual PPD ≥ 6 mm at re-evaluation, with a radiographic intrabony component ≥ 3 mm, and limited to no extension of the defect on the lingual or palatal side as assessed by preoperative bone sounding. * Intrasurgically, the defect has to present a non-supporting anatomy (1-2 residual walls in its most coronal portion) and it needs to be accessible by flap elevation only on one side (either buccal or oral). * Signed informed consent. Exclusion criteria: * Compromised general health which contraindicates the study procedures (ASA III-VI patients). * Systemic diseases/medications which could influence the outcome of the therapy (e.g. uncontrolled diabetes mellitus, non-plaque-induced gingival diseases, antiepileptic drugs (phenytoin and sodium valproate), certain calcium channel-blocking drugs (e.g., nifedipine, verapamil, diltiazem, amlodipine, felodipine), immunoregulating drugs (e.g., ciclosporine), and high-dose oral contraceptives). * Current smokers (self-reported, ≥ 10 cigarettes a day), users of chewing tobacco, and drug/alcohol abusers. * Pregnant or nursing women. * Presence of furcation involvement ≥ II degree (Hamp 1975) at the affected teeth.