Protective Effects of Mixed Probiotics, Oralis SB®, on the Ligation-Induced Experimental Periodontitis and Alveolar Bone Loss in Rats

The present study evaluated the protective effects of Oralis SB® (Osb), a commercial multi-strain probiotic formulation, in a ligature-induced experimental periodontitis (EPD) Sprague–Dawley rat model. Male rats were subjected to ligature placement and orally administered Osb (1.25 × 108, 1.25 × 109, and 6.25 × 109 CFU/head) or received single-strain treatments with each of the four constituent strains (1.25 × 109 CFU/head) for 10 days. Periodontal changes were assessed by microbiological, biochemical, histological, and bone-related analyses. Ligature placement markedly increased anaerobic bacterial counts, neutrophil-associated myeloperoxidase activity, and inflammatory mediator production in gingival tissues, accompanied by elevated gingival IgA levels and impaired expression of epithelial tight junction-related genes, including claudin-1, claudin-5, occludin, and zonula occludens-1. Osb administration significantly attenuated bacterial overgrowth, restored gingival IgA contents, and suppressed the production of inflammatory mediators. Osb also reduced malondialdehyde level and inducible nitric oxide synthase activity, as markers of oxidative and nitrosative stress, and decreased metalloproteinase-8 expression in gingival tissue. In addition, Osb effectively prevented alveolar bone deterioration by improving focal bone mineral density, reducing osteoclast numbers, and restoring the receptor activator of nuclear factor-κB/osteoprotegerin balance. Histological evaluation further confirmed that Osb alleviated gingival inflammation and alveolar bone loss. Notably, the lowest dose of Osb (1.25 × 108 CFU/head) consistently produced significantly greater protective effects than each of the four individual component strains across all measured parameters. Osb exerted protective effects against EPD by modulating anaerobic microbial overgrowth, inflammatory and oxidative responses, epithelial barrier integrity, and alveolar bone resorption. These findings support the therapeutic potential of Osb in periodontitis.