The aim of the present investigation will be evaluated the healing of suprabony defects following surgical flap elevation and hyaluronic acid application respect to surgical flap elevation alone.

A total of 80 patients will be enrolled, selected by inclusion and exclusion criteria and randomly divided in two groups: hyaluronic acid group and no-hyaluronic acid group.

The objective of the study will be compare the healing of suprabony defects following treatment with either open flap debridement (OFD) and application of hyaluronic acid (HA) with OFD alone.

Eighty patients with suprabony periodontal defects will be randomly assigned to treatment with open flap debridement and application of hyaluronic acid (HA Group) or open flap debridement alone (No-HA Group).

Primary outcome will be Clinical Attachment Level (CAL) gain, while the secondary outcomes will be Probing Depth (PD) and Gingival Recession (GR).

After local anesthesia, an access flap will be prepared. Depending on the mesiodistal width of the interproximal space, two different incision techniques will be selected to access the suprabony defect area. The modified papilla preservation technique (MMPT) will be used at sites with an interproximal width > 2 mm, whereas the simplified papilla preservation technique (SPPT) will be applied at sites with an interproximal width ≤ 2 mm. Then, a mucoperiosteal flap will be reflected.

Scaling and root planning will be performed combining the use of metal curettes and power-driven instrumentation by means of ultrasonic scaler.

Hyaluronic acid will be applied to exposed roots surface only in HA Group followed, for both groups, by a tension-free primary closure of the interdental papillae and of the mucoperiostal flaps by means of 5-0 monofilament (polypropylene) non-resorbable suturing material.

Inclusion Criteria:

• Patients diagnosed with periodontitis
• Age ≥ 18 years old
• Single-rooted and multi-rooted teeth
• Presence of suprabony periodontal defects at a minimum of two adjacent teeth and a maximum of 7 adjacent teeth in either the maxilla or the mandible with a PD ≥ 5 mm after completion of non-surgical periodontal treatment and re-evaluation
• Intrabony defect with an intraosseous component < 2 mm

Exclusion Criteria:

• Patients with systemic diseases
• Prolonged antibiotic or anti-inflammatory treatment within 4 weeks prior to surgery
• Pregnant or lactating
• Tobacco smokers (≥ 10 cigarettes per day)
• Multi-rooted teeth with furcation involvement
• Increased tooth mobility (grade II and III)

Only patients will be unaware of the type of treatment performed, with prior written informed consent. So, they will be divided in the two groups of study after a process of randomization