Although robust evidence supports the benefits of antibiotics in periodontal treatment, the potential adverse effects of this therapy cannot be overlooked. These include concerns regarding the emergence of antimicrobial resistance and the non-ecological impact of antimicrobials on the gut microbiome, which may be closely linked to the etiopathogenesis of periodontitis and to the maintenance of long-term periodontal treatment outcomes. In this context, probiotics may represent a promising alternative strategy to reduce the need for antibiotics, particularly in severe cases of periodontitis.

Scaling and root planing (SRP) is the most widely used treatment modality in periodontal therapy. However, a subset of periodontal sites does not respond adequately to this approach, and certain individuals exhibit susceptibility patterns that limit their response to initial treatment. Therefore, to overcome the limitations of SRP alone, adjunctive therapies-such as antibiotics and probiotics-may be employed.

The aim of this randomized, controlled, double-blind clinical trial is to evaluate the effects of adjunctive therapies (antibiotics and probiotics) associated with non-surgical periodontal therapy in individuals diagnosed with periodontitis stages III or IV, grades B or C. A total of sixty individuals with a clinical diagnosis of periodontitis will be treated with SRP alone or SRP combined with antibiotics or probiotics. Participants will be randomly allocated into three groups: Control (SRP), Test 1 (SRP + amoxicillin and metronidazole), and Test 2 (SRP + probiotics).

The adjunctive agents evaluated in this study will be a combination of systemic antibiotics (amoxicillin and metronidazole) and the probiotic Bifidobacterium animalis subsp. lactis HN019. Antibiotics will be administered for 14 days, three times daily, whereas probiotics will be administered for 90 days, twice daily. Adjunctive therapies will commence immediately after the first week of periodontal instrumentation.

Clinical follow-up will be conducted at baseline (pre-intervention), and at 3, 6, 9, and 12 months post-treatment. At baseline, 6 months, and 12 months, gingival crevicular fluid, subgingival biofilm, peripheral blood, and fecal samples will be collected, along with the assessment of periodontal clinical parameters. Levels of the cytokines IL-6, TNF-α, IFN-γ, IL-10, IL-1β, and IL-8 will be quantified in gingival crevicular fluid and peripheral blood samples using enzyme-linked immunosorbent assays.

Subgingival biofilm and fecal samples will be subjected to 16S ribosomal RNA gene amplification by PCR and sequenced using Illumina technology (MiSeq or MiniSeq; Illumina, San Diego, CA, USA). Sequencing data will be analyzed using reference databases of the human oral and intestinal microbiomes. Statistical analyses will be performed using an alpha level of 0.05 (p < 0.05).

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.

The study protocol will be shared as a guide for further research.

After the publication of the study

Open access