- Mineral trioxide aggregate
Mineral trioxide aggregate is a material used to fill the root canals of teeth as part of root canal therapy. It has the ability to encourage hard tissue deposition similar to Calcium hydroxide effect. Also both have the same biological and histological properties.
Components (phases) in MTA Tricalcium silicate (CaO)3.SiO2 Dicalcium silicate (CaO)2.SiO2 Tricalcium aluminate (CaO)3.Al2O3 Tetracalcium aluminoferrite (CaO)4.Al2O3.Fe2O3 Gypsum CaSO4 · 2 H2O Bismuth oxide Bi2O3
It was developed by the research pioneer and Endodontist, Dr. Mahmoud Torabinejad at Loma Linda University, and his patient Dean White (US Patents 5,769,638 and 5,415,547).
MTA has the same composition as Portland cement but has added bismuth oxide for radiopacity - making it visible on an x-ray. However, dental materials are required to have high purity and be lead and arsenic free, unlike portland cement. Two brands are commonly available ProRoot MTA. Another brand is MTA-Angelus (not sold in the USA due to the patent). Both materials contain roughly 20% bismuth oxide.
Properties & Deficiencies
1.Biocompatible with periradicular tissues, 2.non-toxic, 3.non-resorbable and 4.minimal or no leakage around the margins. 5.Very alkaline material (high pH when mixed with water). 6. As a root-end filling material MTA shows less leakage than other commonly used root-end filling materials, which means bacterial penetration will be less when using MTA. 7. You need to be infection free when applying MTA to clear the acidic environment, because acidic infections will prevent MTA from setting.. compressive strength is develops over a period of 28 days, like portland cement, and when mixed in a powder to liquid ratio of more than 3 to 1- strengths of more than 50 MPa are achieved.
MTA material requires a few hours for the initial and final setting, which is not common in dental materials. Also the material has a tendency to washout when rinsed by a dentist. These problems have not been addressed in commercial products, although research has been published.
Several authors have published papers complaining about the high cost of ProRoot MTA- which has prevented wider use.
Usage in some clinical cases
In case of mechanical exposure that occurs during cavity preparation and not a pathological exposure due to caries . Proper isolation should be completed using a rubber dam and cotton pellet.Disinfection of the cavity with sodium hypochlorite. then application of MTA over the exposure area. restoration of the cavity with amalgam or composite is done. MTA provides a higher incidence and faster rate of reparative dentin formation without the pulpal inflammation.
Internal and external root resorption
In internal resorption… root canal therapy is performed, putty mixture of MTA is inserted in the canal using gutta percha. The MTA will provide structure and strength to the tooth by replacing the resorbed tooth structure. In external resorption… after root canal therapy is performed. Flap is raised over the tooth and the defect removed from the root surface with a round bur. Retrograde application of MTA to the root surface is then completed.
Lateral or furcation perforation
Lateral perforation occurs due to wrong direction of instrumentation during cleaning & shaping of the canal by the dentist. If it happens, one should finish cleaning & shaping of the canal , irrigate the canal with sodium hypochlorite to disinfect it and dry it with a paper point. When the perforation occurs at the furcation (between roots)… it can be healed by using MTA material in the perforation to seal it from the coronal area- thus preventing bacterial ingress. 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.
Apexification (Necrotic pulp)
When the root is not completely formed in adolescents, but an infection occurs with a no vital pulp. In case of non-vital pulp: 1. Isolate the tooth with a rubber dam 2. perform root canal treatment. 3. Mix the MTA and plug it down to the apex of the tooth, creating a 2 mm thickness of plug. 5. Wait for it to set; then fill in the canal with cement and gutta percha.
Apexogenesis (Vital pulp)
The proces of maintaining pulp vitality during pupl treatment to allow continued development of the entire root (apical closure occurs appeoximately 3 years after eruption). 1. Isolate the tooth with a rubber dam 2. Perform a pulpotomy procedure. 3. Place the MTA material over the pulp and close the tooth with temporary cement until the apex is completely formed.
Contraindication: 1. Avulsed teeth 2. Unrestorable teeth 3. Severe horizontal fracture teeth 4. Necrotic teeth
Prognosis: Good when pulp capping or shallow pulpothomy is done correctly; conventional pulpotomy is slightly less successful.
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