Oral Health Group
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ENDODONTICS: Mineral Trioxide Aggregate (MTA): Sealing the Pathways of Communication

July 1, 2000
by Gary Glassman, DDS, FRCD(C)


Pulpal and periradicular pathology develop when the dental pulp and periradicular tissues become exposed to microorganisms. In experimental germ free conditions pulpal and periradicular tissues fail to show the development of pathosis and associated lesions when exposed to bacteria.1,2 The conclusion: microorganisms are the main irritants of the dental pulp and periodontium, and sealing the pathways of communication between the root canal system and the periradicular tissues is imperative if bacterial leakage is to be prevented.

Mineral trioxide aggregate (MTA) has been investigated as a material to seal off the pathways of communication between the root canal system and surrounding tissues, significantly reducing bacterial migration.3 It is made up of fine hydrophilic particles that set in the presence of water, and is composed of, tricalcium silicate, bismuth oxide, dicalcium silicate, tricalcium aluminate, tetracalcium aluminoferrite, and calcium sulfate dihydrate (gypsum).4

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Historically, amalgam, composite resins, glass ionomer cements, Cavit (ESPE America, Norristown, PA), and zinc-oxide-eugenol based materials such as Super-EBA (Bosworth Co., Skokie, IL) and IRM (Dentsply Milford, DE), have all been advocated at one time or another to seal the pathways of communication between the root canal system and the oral cavity, as well as the periradicular tissues. The main disadvantages with these materials include microleakage, sensitivity to moisture, and varying degrees of toxicity.5

Resistance to marginal leakage translates to reduced bacterial migration. In dye leakage studies conducted by Torabinejad et al.,5,6 the sealing ability and marginal adaptation of MTA, amalgam and Super EBA cement were compared. Their results showed that MTA allowed significantly less dye leakage and had better adaptation to the root canal walls than the other test materials. In addition, other studies reinforced MTA’s resistance to leakage by showing less bacterial migration with MTA compared to the other root repair materials.5,7,8

MTA has shown to allow a normal healing response including the formation of new cementum over the restored root interface and excellent biocompatibility when communicating with vital tissues.9 Torabinejad et al. have well documented histological evidence showing MTA to have a good clinical response when used as a root-end filling and root repair material10 (Fig. 1).

Many of the materials previously used for root repair and root-end filling have shown to be moisture sensitive, seriously affecting their integrity as good barriers thereby allowing bacterial migration and contamination. In the clinical environment where complete removal of moisture is not always possible, MTA uses it hydrophilic chemistry to its advantage where setting to a solid barrier is necessary to be an effective root repair and root end material.5

MTA is indicated for repair of root perforations during root canal therapy, root-end fillings, repair of root resorptions, pulp capping and pulpotomies in teeth with immature apices, and providing for an apical plug during apexification procedures. There are no known contraindications for its use, no known side effects, and no known interactions with other dental materials.11 (Figs. 2A-2D)

MTA powder easily mixes with sterile water and has a working time of approximately five minutes. Its setting time is four hours, so any definitive restorations must be done after this period so as not to disturb the seal of the MTA.

MTA is manufactured and distributed as ProRoot MTA by Dentsply Tulsa Dental, Tulsa OK (Fig. 3).

r. Glassman is the Endodontic consultant for Oral Health’s Editorial Board.

Oral Health welcomes this original article.

REFERENCES

1.Kakehashi S, Stanley HR, Fitzgerald RJ. The effects of surgical exposures of dental pulps in germ-free and conventional laboratory rats. Oral Surg Oral Med Oral Pathol 1965; 20; 340-9.

2.Moller AJR, Fabricius L Dahlen G, Ohman A, Heyden G. Influence of periapical tissues of indigenous oral bacterial and necrotic pulp tissue in monkeys. Scand J Dent Res 1981; 89; 475-84.

3.Torabinejad M, Hong OU, Pitt Ford TR. Physical properties of a new root end filling material. J Endodon 1995; 21; 349-53.

4.Dentsply Tulsa Dental. ProRootTM MTA Root canal repair material; Material safety data sheet (MSDS).

5.Torabinejad M, Watson TF, Pitt Ford TR. The sealing ability of a mineral trioxide aggregate as a retrograde root filling material. J Endodon 1993; 19; 591-5.

6.Lee SJ, Monsef M, Torabinejad M. Sealing Ability of a Mineral trioxide aggregate for repair of lateral root perforations. J Endodontics 1993; 19; 541-544.

7.Torabinejad M, Smith PW, Kettering JD, Pitt Ford TR. Comparative investigation of marginal adaptation of mineral trioxide aggregate and other commonly used root-end filling materials. J Endodontics 1995; 21; 295-299.

8.Fischer EJ, Arens DE, Miller CH. Bacterial leakage of mineral trioxide aggregate as compared with zinc-free amalgam, intermediate restorative material, and super EBA as a root end filling material. J Endodontics 1998; 24; 176-9.

9.Torabinejad M. Hong CU, Lee SJ. Investigation of mineral trioxide aggregate for root-end filling in dogs. J Endodontics 1995; 21; 603-8.

10.Torabinejad M, Pitt Ford TR, McKendry DJ. Histologic assessment of mineral trioxide aggregate as a root-end filling in monkeys. J Endodontics 1997; 23; 225-8.

11.Torabinejad M, Chivian N. Clinical applications of mineral trioxide aggregate. J. Endodontics, 1998; 25; 197-205.


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