Periodontal disease is a chronic bacterial infection characterized by persistent inflammation, connective tissue breakdown, and alveolar bone destruction. It has been a great challenge in periodontology to determine biomarkers for screening and predicting the early onset of disease (prognostic tests) or evaluating the disease activity and the efficacy of therapy (diagnostic tests). Biomarkers are such substances that can be useful in predicting disease severity & its outcomes. Various diagnostic kits are also used which are mentioned elaborately in this book.