Up to now, MTA has been used mainly by specialists, mostly endodontists, as a restorative material for root end fillings (apico retrofills) and root perforation repair. However, new applications for MTA may put it in the hands of a wider variety of practicioners.
MTA is a bioactive silicate cement. It is essentially a medical grade portland cement. There are several properties of MTA that make it such an ideal material. It has small particle size, alkaline pH when set and slow release of calcium ions. It is known for its sealing ability. It has also been reported to induce cell proliferation, cytokine release, hard tissue formation and an interface with dentin resembling hydroxyapatite. It is non-absorbable and requires moisture to set. In short, its sealing ability, biocompatibility & hydrophilic nature make it an excellent repair material.
Endodontists have been using MTA for pulp capping, apexification/apexogenesis for all of the properties described above. The recent article by Bogen, Kim & Bakland provide evidence that supports the use of MTA as a direct pulp capping agent.
The authors selected 53 teeth that had deep caries with vital pulpal tissue and no prior restorations. Caries were removed under magnification and NaOCl was used to obtain hemostasis within a short period of time (1 to 10 min.). 1.5-3.0mm thick layer of MTA was placed over the exposure. The teeth were restored provisionally with unbonded resin restoration. At a subsequent visit, the teeth were restored with a bonded restoration.
Over a 9 year period of observation, the authors found that 49 of 53 had a favorable outcome on the basis of radiographic appearance, subjective symptoms & cold testing. All teeth (15 of 15) in younger patients with open apices showed completed root formation (apexogenesis).
Many are reluctant to perform direct pulp capping procedures due to unpredictable outcomes with traditional materials. MTA may be a more predictable and successful material for direct pulp capping teeth with a pulpal condition no more severe than reversible pulpitis.
(Source: Bogen, George, Kim, Jay, Bakland, Leif. "Direct Pulp Capping with Mineral Trioxide Aggregate", JADA 2008, 139:3, p 305-315.)