<p>Periodontal diseases, including gingivitis and periodontitis, are among the most prevalent oral health problems worldwide and are associated with chronic inflammation and tooth loss. Increasing attention has been directed toward the role of the human microbiota, particularly the oral microbiota, in influencing periodontal health and disease. This manuscript presents a narrative review that synthesizes and critically evaluates the available evidence on the therapeutic potential of diverse bacterial strains, with special emphasis on probiotics, as adjunctive agents in the management of periodontal disease. Literature was identified through searches of PubMed and Google Scholar, with priority given to more recent studies. The review discusses host–microbiota interactions, oral microbiome characteristics, immunomodulatory effects of probiotics, and strain-specific outcomes related to periodontal indices. While a number of bacterial strains, including <i>Lactobacillus reuteri</i>, <i>Lactobacillus rhamnosus</i>, <i>Bifidobacterium</i>, and selected <i>Streptococcus</i> species, demonstrate potential benefits in reducing plaque accumulation, inflammation, and clinical attachment loss, the findings across studies remain heterogeneous. Overall, probiotics and related microbial strategies represent a promising adjunct to conventional periodontal therapies; however, more standardized and long-term clinical trials are required before firm conclusions can be drawn.</p>