Purpose of Review <p>The primary etiological factor of periodontal disease is microbial dental plaque. The techniques used for identifying microorganisms have significantly advanced over time. In parallel with these developments, our perspective on the nature and causes of periodontal disease has also begun to evolve. In our review, the role of the microbiota in periodontal disease from past to present and the current approaches to this subject have been addressed.</p> Recent Findings <p>The advancement of sequencing-based techniques has enabled the analysis of bacterial species that cannot be isolated through traditional culture methods, facilitating the detection of their presence and proportions in disease states. The role of bacteria such as <i>P. gingivalis</i> and <i>T. forsythia</i> in periodontal disease has been studied for a long time. Through sequencing systems, these bacteria, along with others in the subgingival area or oral region, have been examined comprehensively. This has allowed for the investigation of bacterial co-occurrence patterns, shifts in bacterial species and proportions from health to disease, and the identification of new bacteria that may contribute to disease alongside those traditionally associated with periodontal disease. Furthermore, research has not been limited to the mere presence of bacteria in these environments but has also extended to their metabolism and activity in both health and disease states.</p> Summary <p>Although established pathogens continue to retain their significance as causative agents of periodontal disease, advances in metagenomic methods may offer promising insights into the discovery of new microorganisms involved in disease pathogenesis.</p>