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? (From http://www.endoweb.com/) - 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 deposition 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.
If you happen to cause a mechanical perforation, immediately place a rubber dam over the tooth for proper isolation. Rinse the cavity with sodium hypochlorite to disinfect the area and wash it with water. You do not have to completely dry the area since MTA sets in a moist environment. Mix the MTA powder with enough sterile water to give it a putty consistency. Apply it over the exposed pulp and remove the excess. Blot the area dry with a cotton pellet and restore the cavity with an amalgam or composite filling material. MTA provides a higher incidence and faster rate of reparative dentin formation without the pulpal inflammation that is seen when Dycal is used.
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.
If you create a furcal perforation while accessing the tooth, there are two ways to repair it: If you can finish the root canal in one visit, then do that first. Next remove the excess gutta percha in the chamber and soak it for 5 minutes with sodium hypochlorite. Now mix the MTA and fill the chamber with it. Using a moist cotton pellet, plug the MTA down into the perforation site and remove the excess cement from the chamber. Place a moist cotton pellet in the chamber to help with the setting of the MTA and close the tooth up with a temporary cement of your choice. If you cannot do a one-visit root canal, then first seal the perforation with the MTA mixture. Make sure that you can locate the canal while the MTA has not set and remove the excess material from the area. Close the tooth as above and do the root canal the next visit.
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!)
Where to Get It
MTA is currently being sold under the trade name Pro Root (Dentsply Tulsa Dental). ($351.00 CDN) for 5 packets. Technically this works out to $70 per application -> IF you discard the unused portion. Most clinicians are keeping the remaining portion in the foil packets and then re-using the rest. (Not recommended by the manufacturer). This material will probably NOT gain wide use by General Dentists until a special Dental Insurance Code is made to allow them to recoup the cost of its use. The original "Dark Grey" formula could potentially cause staining of the root and was discontinued in favor or a more aesthetic tooth colored "White" formula. There have been some reports of "lack of set" with this newer white material but they are anecdotal. Overall this material represents a huge leap in our ability to treat cases that had been thought to be untreatable. MTA - Expensive but worth it!