Mineral Trioxide Aggregate (MTA) is a material used in endodontics for a number of different procedures. MTA is an aggregate of several different trioxides. The original grey material with “wet sand” consistency has been on the market for several years. A new, more esthetic yellowish version is now available and preferred.
MTA is also indicated for perforation repairs that are below the crest of the bone. It will not work for perforations that are exposed to the oral cavity. That is because MTA does not bond to tooth structure, and takes about 7 hours to set, so it can be easily washed out. Glass-ionomer based materials are better for these cases. The material can also be dislodged even after it has set. That’s why after a perforation repair has been made, it’s best to leave the filling alone, and just place the build up material over it, without disturbing the MTA.
MTA does require moisture to set. For this reason, a damp cotton ball is placed on top of the MTA filling. In apical retro fillings, moisture in the bony crypt is sufficient to hydrate the material.
It is also used for apexification (to induce the closure of an open apex) and as a pulp capping material. The latter does not cause the chronic pulpal inflammation that Dycal and other materials do. MTA can stimulate reparative dentin formation in a healthy pulp, hopefully preventing endodontic involvement.