MTA Mineral Trioxide Aggregate

Most General Dentists have heard of MTA (Mineral Trioxide Aggregate) but few are familiar with its properties and use. Endodontists have been using this material for about 10 years and have found it to have amazing properties. In this month's EndoFiles Fax we will examine this material and see how it can be incorporated into your practice. This information has been copied from an internet article, published by Dr. Yosi Nahmias and Dr. Paul Bery. It is an excellent synopsis of the uses of MTA and I thank them for allowing me to use it in this month's EndoFax.

MTA- what is it? 

 Used with permission but edited

MTA was developed by Dr. Mahmoud Torabinejad at Loma Linda University in 1993. It is a compound mixture of hydrophilic tricalcium silicate, tricalcium oxide, and tricalcium aluminate with some other oxides. An independent analysis revealed that MTA is identical to Portland Cement with the addition of bismuthoxide. Because MTA has a pH of 12.5, some of its biological and histological properties can be compared to those of Ca(OH)2. The material sets in a moist environment and has low solubility. The compressive strength of MTA is equal to that of IRM and Super EBA but less than that of amalgam (Nahmias and Bery).

An ideal root repair material should be non-toxic, bacteriostatic, and non-resorbable. It should also promote healing and provide a good apical seal. Compared to other materials, MTA shows less microleakage, less toxicity, and better bacteriostatic effect. Histologic examination has revealed that it has actually induced cementogenesis, and bone deposition with minimal or absent inflammatory response. 

 MTA is hydrophilic and requires moisture to set, making absolute dryness not only unnecessary but also contraindicated. Some techniques require the placement of a moist cotton pellet directly in contact with the MTA in order to allow proper setting. It takes an average of four hours for the material to completely solidify. MTA's consistency is that of very hard cement and it can be compared to "concrete"! Torabinejad and others have widely and extensively documented the response of connective tissue in contact with MTA. When studied as a root-end filling material, MTA has shown to be better than amalgam. Histologic examination revealed that it had actually induced cementogenesis, and bone depositin with minimal or absent inflammatory response. Holland showed that the histological responses of MTA were similar to those induced by Calcium Hydroxide after six months. Dye and bacterial leakage studies have shown the sealing ability of MTA to be superior to amalgam and equal to or better than Super EBA. It has also been shown to be less cytotoxic than IRM and Super EBA. As a retrofilling material, MTA fulfills many of the requirements of the ideal material such as biocompatibility with periradicular tissues. It is non-toxic, non-resorbable and displays minimal or no leakage around the margins. MTA is now the material of choice in the non-surgical treatment of furcal and radicular strip perforations! 

Here are a few of the clinical situations that benefit from the use of MTA and the treatment methods for each case.

Pulp Capping

Internal & External Root Resorption

In the case of internal root resorption, isolate the tooth and perform RCT in the usual manner. Once the canal has been cleaned and shaped, prepare a putty mixture of MTA and fill the canal with it, using a plugger or gutta-percha cone. Next insert a 25/.08 instrument down the canal to spread the cement laterally and create a new canal. Flood the canal with EZ-Fill cement (EDS Dental) and obturate it with a single gutta-percha cone. The MTA will provide structure and strength to the tooth by replacing the resorbed tooth structure. In the case of external resorption, complete the root canal therapy for that tooth. Next raise a flap and remove the defect on the root surface with a round bur. Mix the MTA in the same manner as above and apply it to the root surface. Remove the excess cement and condition the surface with tetracycline. Graft the defect with decalcified freeze-dried bone allograft and a calcium sulfate barrier.

Lateral Perforation and Strip Perforation

If you happen to cause a strip or lateral perforation during instrumentation, first finish cleaning and shaping that canal. Irrigate the canal really well with sodium hypochlorite and dry it with a paper point. The paper point will allow you to see where the perforation is located. If the perforation is down at the mid to apical third, then follow the directions for treating an internal resorption, above. The MTA will seal off the perforation as it is spread laterally by the 25/.08 file and the gutta-percha cone. If the perforation is closer to the coronal third, then fill the canal up with EZ-Fill cement and gutta percha as usual. Next, remove the gutta percha about 23 mm below the perforation using the Peeso reamer. (Be careful not to perforate again!) Now mix the MTA and fill the rest of the canal up with a plugger.

Furcal  Perforation

Apexification

Vital pulp: Isolate the tooth with a rubber dam and perform a pulpotomy procedure. Place the MTA over the pulp stump and close the tooth with a strong temporary cement until the apex of the tooth closes up. 

Non-vital pulp: Isolate the tooth with a rubber dam and perform root canal treatment. Once the canal has been cleaned and shaped, irrigate it and dry it with a paper point. Mix the MTA and plug it down to the apex of the tooth, creating a 2 mm thickness of plug. Check for proper set (I prefer to bring the patient back the next day) then fill in the canal with cement and gutta percha.

Dr. Kaufmann's Comments:     How to Apply It

MTA has a consistency that is unlike any other dental material that you are currently using and it has correctly been described as "difficult to handle" in many circumstances. When properly mixed it resembles wet sand and therefore is not easily condensable. You use it similarly to loose, wet cement in that it must be teased into place and should NOT be "packed" with a plugger. Removal of too much of the moisture can adversely affect the set. Several devices can be used to apply it. A Messing Gun or specially designed Dovgan Carriers are best. When using it as a canal filling or in apexification - low powered ultrasonics can often be helpful in getting rid of voids and helping the material flow into place. (Similar to when vibrators are used in the concrete industry!)