Mineral trioxide aggregate: present and future developments

Portland cement is used in the building industry to make concrete. It is hydraulic and thus it develops its properties well in the presence of moisture. The oral environment is inherently wet, however, all dental materials need a dry field for optimal performance. A mixture of Portland cement and bismuth oxide was developed and marketed as mineral trioxide aggregate (MTA). The first formulation was gray in color followed by a white version and eventually by various similar materials, which are all composed of a tricalcium silicate-based cement and radiopacifier. The MTA was originally suggested for particular clinical uses, such as root-end filling and perforation repair, where maintenance of a dry field is difficult. The suggested uses were extended to apexification and dressing over pulpotomies, pulp capping and also as a sealer cement. The multipurpose use of MTA necessitated the development of improved formulations where material additives were included to the original cement/radiopacifier formulation. These additives supposedly enhance the material's properties and improve its function. Furthermore, the original Portland cement formulation was replaced with tricalcium silicate to avoid the inclusion of an aluminum phase and eliminate the inclusion of trace elements. The bismuth oxide was also replaced with alternative radiopacifiers. The multifaceted use of MTA allows the material to come into contact with different oral environmental conditions, including blood, saliva, tissue fluids, dental restorative materials, tooth structure and even air. These different conditions affect the properties and setting of the material. Future developments should further investigate the material's interactions and strive to create materials which are suited to a specific use.