Initially recommended as a material for filling root end surgical preparations and for perforation repair, this material is also advocated for immediate apical sealing in teeth with open apices,⁵ pulpotomies, apexification, or apexogenesis in vital teeth with open apices,^6-9 and other endodontic and reparative procedures. The extraordinary success in perforation repair since its introduction has motivated its use in these many other areas. This article will look at the success, practicality, and scientific basis for use in pulp capping procedures, particularly in permanent teeth, as MTA has been described very recently as “the material of choice”¹⁰ for this treatment.

Properties of MTA

MTA stands for mineral trioxide aggregate, denoting the three dominant oxides in the material’s composition — namely, calcium, aluminum, and selenium. Its particle sizes are strictly controlled during manufacturing, as they all need to be less than 10 microns, so that the material may be completely hydrated. MTA has a similar mechanism of action to calcium hydroxide¹¹ in that the main component of the material, calcium oxide, when in contact with a humid environment, is converted into calcium hydroxide.¹² This results in a high pH of 12.5, making its surroundings inhospitable for bacterial growth, and producing an antibacterial effect for a long period of time. But unlike calcium hydroxide products, such as DYCAL^® (Dentsply, York, Pennsylvania), MTA Angelus (Angelus Dental Solution, Londrina,  Brazil/Clinician’s Choice Dental Products, New Milford, Connecticut) has very low solubility, so it maintains a hard, excellent marginal seal. Finally, unlike most dental materials, MTA actually needs moisture to set, so it thrives in a moist environment. Of the commercially available MTA products, MTA Angelus is well suited for pulp capping procedures due to its setting time of 10 minutes, compared with the 4-hour setting time of the other commercially available MTA. It is also packaged in airtight bottles, allowing the practitioner to use only what is exactly needed without introducing undue moisture into the remainder.