Mineral Trioxide Aggregate (MTA) is a great material for retrofills, root perforation repair, direct pulp capping, apexification & apexogenesis. This material is mostly used by specialists, under a microscope. However, new applications, such as direct pulp capping, will make this material more commonplace.
Unlike most dental materials, MTA requires moisture to set up. Since moisture control is one of the largest challenges in working with most dental materials, this actually is a positive characteristic of this material.
Using this material is like playing with wet sand. You can add or remove water to the consistency that you like. If you put too much water in it, it runs. If you put too little water in it or it dries out, it crumbles. If you put just the right amount of water in it, it becomes packable, just like wet sand. It takes a little practice, but once you learn how to manage the moisture, it's great to work with. The material does dry out while you use it, so additional water can be added to return it to your desired consistancy.
There are few specialized instrument that aid in the placement of MTA. Carriers are made in all shapes and sizes. These work just like an amalgam carrier on a much smaller scale.
Another useful carrier is made from a plastic block and a simple hand instrument.
Handling MTA will take a little practice, but once you learn how to mix and handle it, you will find it is a great material to work with.
The following video clip shows the placement of MTA as a retrofill during an apicoectomy surgery.