Oral Supplementation of Bacillus subtilis Attenuated Alveolar Bone Loss in a Mouse Model of Ligature-Induced Periodontitis

Background/Objectives: This study aimed to investigate the effects of oral Bacillus subtilis (BS) on alveolar bone loss, intestinal morphology, and gut microbiota in a mouse model of ligature-induced periodontitis. Methods: A total of 24 male C57BL/6J mice (6 weeks old) were allocated to control, periodontitis (P), BS, and BS+P groups. Periodontitis was induced by bilateral ligation of maxillary second molars, and BS was orally administered for 18 consecutive days. Gut microbiota composition was analyzed by 16S rDNA sequencing, alveolar bone loss and gut morphology were evaluated using ImageJ version 1.54g, and ELISA-detectable serum vitamin D metabolite concentrations were measured using an enzyme-linked immunosorbent assay. Results: Compared with the P group, the BS+P group showed reduced bone loss. Serum vitamin D metabolite concentrations, small-intestine villus height, and villus height-to-crypt depth ratios were higher in the BS+P group. In gut microbiota, alpha diversity differed significantly among groups based on the Shannon index. Bray–Curtis-based beta diversity differed significantly among groups. Conclusions: Oral supplementation of BS attenuated the progression of ligature-induced periodontitis in a mouse model, and changes in gut microbiota may be associated with this effect.