<p><b>Background</b> Periodontal diseases are common and can lead to severe dental complications, with bacterial infections at their core. Dental restorations, such as crowns, can exacerbate these conditions by facilitating bacterial accumulation. Traditional therapies, including mechanical debridement and antimicrobial agents, may not fully address oral microbiome dysbiosis, potentially leading to recurrent infections and antibiotic resistance.</p><p><b>Objective</b> This study evaluated the effectiveness of a probiotic mouthwash in reducing plaque accumulation and gingival inflammation in patients with full crown anterior teeth prostheses, focusing on the impact on the oral microbiome and inflammatory markers.</p><p><b>Methods</b> A randomised, double-blind, placebo-controlled trial of 30 patients with gingivitis and 30 periodontally healthy individuals was conducted. The participants used either a probiotic or placebo mouthwash for one month. Clinical assessments, including the bleeding index (BI), plaque index (PLI) and gingival index (GI), were conducted at baseline and post-treatment. Gingival crevicular fluid was collected to measure interleukin-6 (IL-6), interleukin-1 beta (IL-1β), and tumour necrosis factor-alpha (TNF-α) by enzyme-linked immunosorbent assays. Microbial diversity was analysed using quantitative polymerase chain reaction analysis and sequencing.</p><p><b>Results</b> Probiotic mouthwash use significantly decreased BI, PLI and GI values compared to the control group. Decreases in IL-6, IL-1β, and TNF-α levels in the gingival crevicular fluid were also observed. Microbial analysis showed an improved oral microbiome health index and reduced levels of periodontal pathogens.</p><p><b>Conclusion</b> The probiotic mouthwash significantly improved gingival health and modulated the oral microbiome, suggesting its potential as an adjunct to standard periodontal treatments for patients with dental prostheses.</p>