Mineral Trioxide Aggregate (MTA) is a bioactive dental material widely used in endodontics for its excellent sealing ability, high biocompatibility, and regenerative potential. Derived from Portland cement, MTA sets in moist environments, releases calcium ions, and forms hydroxyapatite, promoting tissue healing and hard tissue formation. Its applications include pulp capping, pulpotomy, apexification, root-end filling, perforation repair, and regenerative procedures. MTA's physical and biological properties-such as high pH, low solubility, and antimicrobial action-make it ideal for clinical use. Despite drawbacks like long setting time and discoloration, ongoing innovations have improved its performance. This book provides an in-depth analysis of MTA's composition, mechanism, properties, modifications, and clinical relevance.