This randomized controlled clinical trial aims to evaluate the effectiveness of using nano-hyaluronic acid (nano-HyA) gel alongside a minimally invasive non-surgical technique (MINST) to treat deep intrabony defects in patients with Stage II and III periodontitis. While MINST is a proven method for cleaning deep periodontal pockets without the need for traditional surgery , the addition of nano-HyA may further enhance soft tissue healing, reduce inflammation, and promote regeneration. Participants in the study will be randomly assigned to one of two groups. The test group will receive the MINST procedure combined with the application of nano-HyA gel into the periodontal pocket, while the control group will receive the MINST procedure alone. The primary goal of the study is to measure the decrease in probing pocket depth over a 6-month follow-up period to determine if the adjunctive use of nano-HyA provides superior clinical and radiographic outcomes compared to non-surgical treatment alone

Inclusion Criteria:

1. Males and females aged ≥ 18 years.
2. Patients with a diagnosis of periodontitis (stage II or III).
3. At least one tooth with ≥5 mm PPD and CAL and evidence of radiographic bone loss.
4. Presenting with at least 1 intrabony defect, with a radiographic intra-bony component ≥3 mm.

Exclusion Criteria:

1. Patients with systemic diseases.
2. Pregnant or lactating females.
3. Tobacco smokers (≥ 10 cigarettes per day).
4. Multi-rooted teeth with class II and class III furcation defects.
5. Third molars.
6. Teeth with grade III mobility.
7. Peri-apical pathology and acute abscess.
8. Non-surgical or surgical periodontal treatment in the past 12 months.
9. Prolonged treatment with antibiotics or anti-inflammatory agents within 6 months before periodontal therapy.