This randomized controlled clinical trial evaluates the adjunctive effect of subgingival administration of Lactobacillus reuteri probiotics in diabetic patients with Stage III Grade B or higher periodontitis receiving non-surgical periodontal therapy. Forty periodontal sites were randomly assigned to either a test group treated with scaling and root planing (SRP) plus subgingival Lactobacillus reuteri or a control group treated with SRP plus saline irrigation. Clinical periodontal parameters, microbiological outcomes, and glycated hemoglobin (HbA1c) levels were assessed at baseline, 1 month, and 3 months. The study aims to determine whether locally delivered probiotics provide additional clinical, microbiological, and glycemic benefits compared with SRP plus saline irrigation.

Periodontitis is a chronic inflammatory disease associated with dysbiotic subgingival biofilms and is strongly influenced by diabetes mellitus. Chronic hyperglycemia may impair immune function and wound healing, resulting in increased periodontal destruction and poorer treatment outcomes. Non-surgical periodontal therapy based on scaling and root planing (SRP) remains the standard treatment; however, residual periodontal pockets may persist after therapy.

Lactobacillus reuteri probiotics have demonstrated antimicrobial, anti-inflammatory, and host-modulatory properties and may enhance periodontal healing. This randomized controlled clinical trial evaluated the adjunctive effects of subgingival administration of a liquid probiotic preparation containing Lactobacillus reuteri in diabetic patients with Stage III Grade B or higher periodontitis.

Forty periodontal sites were randomly allocated to either a test group receiving SRP plus subgingival Lactobacillus reuteri probiotics or a control group receiving SRP plus saline irrigation. A second application was performed at the 1-month visit. Clinical outcomes included plaque index, gingival index, bleeding on probing, probing pocket depth, and clinical attachment level. Glycemic control was evaluated using HbA1c levels, and microbiological analysis was performed using real-time PCR for Porphyromonas gingivalis, Tannerella forsythia, and Fusobacterium nucleatum.

Assessments were conducted at baseline, 1 month, and 3 months. The primary objective was to evaluate changes in clinical outcomes. Secondary objectives included microbiological and glycemic outcomes.

Inclusion Criteria:

• Age ≥18 years.
• Diagnosed with diabetes mellitus according to WHO criteria.
• Stage III Grade B periodontitis or higher according to the 2017 AAP/EFP classification.
• At least 15 remaining teeth.
• Periodontal pockets ≥5 mm with bleeding on probing.
• Clinical attachment loss ≥5 mm.

Exclusion Criteria:

• Current smokers.
• Pregnant or lactating women.
• Use of antibiotics or anti-inflammatory medications within 1 month before enrollment.
• Periodontal therapy within the previous 3 months.
• Undergoing orthodontic treatment.
• Presence of pulpal lesions or severe occlusal trauma.

Individual participant data will not be made publicly available

Participants, investigators, and outcome assessors were blinded to treatment allocation. The clinician administering the intervention was not involved in outcome assessment.