The aim of this clinical trial is to evaluate and compare the effect of a newly designed air-polishing device (APD) using Erythritol, Glycine, and Trehalose air-polishing powders in nonsurgical periodontal therapy with control (conventional scaling and root planning) following the concept of guided biofilm therapy (GBT) as an adjunctive to subgingival instrumentation (SI) in nonsurgical periodontal therapy for Stage II and III periodontitis patients both clinically and microbiologically.

Inclusion Criteria:

1. Individuals of both sexes with an age between 30 and 65 years, having at least 16 natural teeth in function,
2. Stage II and III (moderate to severe) periodontitis, having at least 16 teeth with the need for SI
3. Interproximal plaque index (API) ≤ 35%; patients with Good oral hygiene.
4. No history of systemic disease that may influence periodontal disease

Exclusion Criteria:

1. Pregnancy or breastfeeding,
2. Smokers with more than seven cigarettes per day
3. Patients that had a treatment with antibiotics within six months before the study
4. Need for periodontal surgery or adjunctive antibiotic treatment to the SI
5. Patients who had any periodontal treatment during the last year before the study.
6. Patients with known systemic or autoimmune disease.

six month