MTA Obturation
Mineral Trioxide Aggregate is one of the brightest innovations in the field of endodontics over the last fifteen years.
The material developed in Loma Linda, California is a mainly a combination of tri and dicalcium silicates or essentially 80 percent Portland Cement and 20 percent Bismuth Oxide. Portland cement itself is a mixture of dicalcium silicate, tricalcium silicate, tricalcium aluminate, gypsum, and tetracalcium aluminoferrite. MTA was originally designed for perforation repairs however its use as a material in endodontics has greatly expanded over the years. When hydrated, MTA has a high PH which creates an antimicrobial environment along its surfaces. The antimicrobial properties of MTA may provide its biggest advantage relative to other similar materials available in the market. Another large benefit of the material is the strong seal created when MTA is placed along root dentin. MTA can take 2 to 3 hours to set, however once the material hardens studies show less micro leakage than traditional materials used to repair root perforations (amalgam, IRM, composite resin). A minimum of three millimeters of MTA is recommended for the best seal. Studies have also demonstrated a high degree of biocompatibility which makes the material desirable when placed against the periradicular tissue.
Historically, clinicians have searched for a material to help seal undeveloped root apices or root ends subjected to significant inflammatory resorption. MTA has proven an excellent material for these tough to manage situations. In the past, Calcium Hydroxide was used over multiple visits to help form a dentinal bridge. The bridge served as an apical stop to prevent gutta percha from extruding beyond the root end. Now with MTA, we can obturate these cases more predictably and without the many visits that were required with the Calcium Hydroxide technique. I have included two recent cases below where MTA was used as the apical seal and the canal was subsequently backfilled with Gutta Percha. I believe MTA allows the clinician to manage these cases more predictably.
Case One: A fifty two year old male, presented to our office with acute discomfort localized to tooth #18. Our initial pre-operative radiograph revealed a resorbed distal root apex. The patient has a history of orthodontics, however I am not sure of the exact etiology of the resorption as the distal root was the only root demonstrating significant resorption. I placed my first file to length and could immediately sense that the root end was wide open. In order to provide a proper seal I opted to seal the root apex with Grey MTA. After determining my exact working length, I placed CAOH to the root apex to help with disinfection and tissue dissolution along the apical third of the root. After three weeks of disinfection, the patient returned to complete the case. In order to position the MTA to the terminus, I placed my first increment of material on an endodontic plugger to 2.0 mm short of working length. Under the microscope, my assistant activated the MTA by touching my plugger with an ultrasonic tip. The ultrasonic activation helps prevent voids and slowly works the MTA to desired position (similar to concrete). Ideally an apical plug of 3.0 mm or more is desired. Once I can confirm MTA is placed to the desired position (with a radiograph), the canal space is coated with sealer and backfilled with Gutta Percha.
Case Two: This case demonstrates the use of MTA in retreatment endodontics. As can be seen in the preoperative radiograph, obturation material is extruded well beyond the root apex. The apical third of the root demonstrates reverse architecture and a wide open apex. Even a large diameter gutta percha would not properly seal the apical third of this root. Dr. Brown removed the endodontic filling material and sealed the apex with MTA before backfilling with Gutta Percha. This procedure was performed over two visits with interim CAOH therapy utilized to disinfect the canal space prior to the final obturation. Historically, CAOH would have placed to the apex over multiple visits and many months with the hopes of achieving an apical stop. The use of MTA allows this case to be predictably treated over 2-3 visits.
Both articles below were utilized as references when writing this blog:
Camilleri J, Montesin FE, Brady K, Sweeney R, Curtis RV, PittFord TR. The constitution of mineral trioxide aggregate. Dent Mater 2005;21:297–303.
Mineral trioxide aggregate material use in endodontic treatment: A review of the literatureHoward W. Robertsa, Jeffrey M. Tothb, David W. Berzinsc, David G. Charltond
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