Clinical, Microbiological and Immunological Effects of the Adjuvant Use of Systemic Antibiotics and Probiotics in the Non-surgical Treatment of Periodontitis

Inclusion Criteria: * Adults with a diagnosis of generalized periodontitis, defined as involvement of ≥30% of teeth, classified as: Stage III or Stage IV, and Grade B or Grade C, according to the 2018 classification. * Presence of at least one tooth with ≥1 interproximal site exhibiting: Probing depth (PD) ≥6 mm, and Clinical attachment loss (CAL) ≥5 mm. * Presence of at least 15 teeth, excluding third molars and teeth indicated for extraction. * Presence of at least 6 non contiguous teeth, each with ≥1 interproximal site presenting PD and CAL ≥5 mm. Exclusion Criteria: * Current smokers or former smokers who quit less than 5 years prior to enrollment. * Pregnant or breastfeeding women. * History of periodontal treatment within the previous 6 months. * Continuous use of oral antiseptics within the last 6 months. * Use of systemic antibiotics, corticosteroids, non steroidal anti inflammatory drugs, immunosuppressants, estrogen, estrogen receptor modulators, or medications affecting bone metabolism (e.g., alendronate, calcitonin) within the last 6 months. * Presence of systemic conditions that may alter the host response, including: Diabetes mellitus, HIV infection, Down syndrome. * Medical conditions requiring antibiotic prophylaxis for dental procedures (e.g., mitral valve prolapse). * Known allergy or hypersensitivity to amoxicillin, metronidazole, penicillins, or related compounds. * Use of probiotics within the last 6 months.