Mineral trioxide aggregate
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Mineral trioxide aggregate (MTA) was developed for use as a dental root repair material by Dr. Mahmoud Torabinejad, DMD, MSD, PhD  Professor and Director of Advanced Specialty Education Programs in Endodontics at Loma Linda University School of Dentistry and was formulated from commercial Portland cement combined with bismuth oxide powder for radiopacity. MTA is used for creating an apical plug during apexification, repairing root perforations during root canal therapy and treating internal root resorption and can be used as both a root-end filling material and pulp-capping material. Originally, MTA was dark gray in color, but white versions have been on the market since 2002.
Portland cement is a term applied to a class of materials covering a range of compositions (between silica alumina and calcia). The composition, fineness, setting time and strength of portland cement are not controlled or guaranteed. Portland cement is an unsuitable substitute for MTA based on several characteristics that are essential to the performance: freedom from heavy metals, dimensional stability and fineness. The FDA requires dental materials to have high purity and be lead and arsenic-free, unlike commercial portland cement.
ProRoot® MTA  root canal repair material was commercialized by DENTSPLY Tulsa Dental Specialties  in 1998, in cooperation with and based on prior work by Dr. Mahmoud Torabinejad. Dr. Torabinejad had distributed his experimental material as ProRoot MTA. Unlike commercial Portland cement, ProRoot MTA is manufactured under FDA guidelin Medical Device Regulation to ensure the quality, purity and efficacy for use as a dental material. The composition is certified for purity and the absence of heavy metal contamination. The components were selected for their lack of expansion or contraction during setting to ensure that microleakage does not occur after placement. The characteristics of ProRoot MTA include a very fine particle size. Coarse particles are removed during screening, a process that is unnecessary for portland cement. This screening process improves the handling and packing ability for dentists.
MTA is composed of 1. tricalcium silicate, 2. dicalcium silicate, 3. tricalcium aluminate, 4. tetracalcium aluminoferrite, 5. calcium sulfate and 6. bismuth oxide. The later 4 phases vary among the commercial products available.
Newly developed fast set MTAs were developed by Pozzolan Cement or Zeolite Cement. These were used by pozzolanic reaction. Pozzolan Cement is a mineral aggregate with watery calcium silicate hydration.
|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|
Original ProRoot MTA is a refined, medical grade root repair material that meets dental standards (ISO 9917) for purity and performance (ISO 6876 and ADA 57). The primary components of ProRoot MTA include tricalcium silicate and dicalcium silicate naturally composed, bismuth oxide (for radiopacity), tricalcium aluminate (C3A) and tetracalcium aluminoferrite (C4AF). By composition, ProRoot MTA contains: 55% (C3S), 19% (C2S), 10% (C3A), 7% (C4AF), 2.8% MgO, 2.9% (SO3), 1.0% Ignition loss and 1.0% free CaO. A limitation on the composition is that the (C3A) shall not exceed fifteen percent.
ProRoot MTA does not contain calcium phosphate, calcium oxide or silica. (An article in the April 2003 issue of Oral Surgery, Oral Medicine and Oral Pathology inaccurately reported ProRoot MTA contains these compounds.) Calcia, alumina and silica are the primary ingredients of portland cement. The typical portland cement contains about only 0.2% of phosphate.
In response to customer requests, ProRoot MTA White was created by DENTSPLY Tulsa Dental Specialties and introduced in 2002. ProRoot White MTA was developed for reducing discoloration to the tooth structure. It eliminated C4AF (tetracalcium aluminoferrite) as iron (Fe)'s main discoloration induced element. ProRoot MTA White contains significantly lesser amount of aluminum oxide (Al2O3), magnesium oixde (MgO) and ferric oxide (Fe2O3) than ProRoot MTA Gray. ProRoot MTA White was patented in 2008 by US Patent 7,892,342.
Characteristics and products
- Biocompatible with periradicular tissues
- Non cytotoxic to cells, but antimicrobial to bacteria
- Minimal leakage around the margins.
- Very basic AKA alkaline (high pH when mixed with water).
- As a root-end filling material MTA shows less leakage than other root-end filling materials, which means bacterial migration to the apex is diminished.
- Treated area needs to be infection free when applying MTA, because an acidic environment will prevent MTA from setting.
- Compressive strength develops over a period of 28 days, similar to Portland cement. Strengths of more than 50 MPa are achieved when mixed in a powder-to-liquid ratio of more than 3 to 1.
Originally, MTA products required a few hours for the initial and final setting, which is uncommon in dental materials. Newer materials are available that set more quickly and have added characteristics. For instance, Angelus company has made MTA products similar to ProRoot MTA, but added a salicylate based sealer, have less than 20% MTA powder.
MTA Plus is washout resistant. MTA Plus may be used for 10 indications.
MTA Products: Gray: Calcium Alumino-Silicate Cement (C3S, C2S with C3A)- Portland Cement Type I with Bismuth Trioxide. (ex. ProRoot MTA, MTA Angelus) White : Calcium Carbonate alumino-silicate Cement (CaCO3 + SiO2 with Al2O3). Final phase is medical grade material similar to Portland Cement. (Limestone Portland Cement) -ex. ProRoot MTA White, MTA Angelus Blanc, EndoCem/Zr, MM MTA, Tech BioSeal MTA, Trioxident, most white MTAs.
Setting Time: Original ProRoot MTA is set by water and reaches final set in approximately 3 hours. For faster/quicker setting, there are hydration accelerants. Also Alumina more containing MTA can be set faster than less alumina containing MTA. GIC solution is polyacrylic acid. GIC is alumino-silicate (glass) bioceramic cement. As MTA is mainly composed of calcium-alumino-silicate, PAA (polyacrylic acid) is an accelerant for MTA. PAA set MTA within 15–18 minutes. More aluminate, faster set. Also high concentrated calcium chloride (CaCl2, 70% more) is well known as accelerator of Portland cement. So high concentrated -over 70%- Calcium Chloride solution sets MTA within 12 minutes. Or Pozzolanic reaction is also faster set chemical reaction of calcium silicate hydrate. By this pozzolanic reaction, MTA Agelus, MM MTA and EndoCem MTA are pozzolan-calcium carbonate with fumed silica hydration for fast set. But pozzolanic reacted cement has lower compressive strength at 15 MPa maximum. Easy broken and easily removable property of pozzolanic MTA.
Alternative to MTAs - BioA, Bioceramic Aggregate
Mineral is ceramic in nature. MTA was used by mineral aggregates from natural resources. Instead of mineral aggregate, sythetic artificial pure calcium silicate is used for dental and medical products. It is named as Bioceramic (chemically bonded cermic) cement. Recently medical graded calcium silicate based materials were developed. It can also be used as a root repair material. So it is classified as bio-aggregates (BA or BioA). Hydraulic calcium silicate cements are integrated name of calcium silicate based materials. The examples are BioDentine and BioAggregate (DiaRoot). Silicate based bioceramic is a glass ionomer cement (GIC) as restorative material. Calcium based bioceramics are calcium phosphate, calcium carbonate, calcium aluminate, calcium sulfate, calcium silicate, etc. However, as calcium phosphate, calcium sulfate and calcium carbonate are biodegradable materials, these are used for bone grafting material. As root canal filling material and root repair material is non-biodegradable material permanently, so calcium aluminate cement and calcium silicate bioceramic materials have been used for endodontic materials and restorative materials. Calcium alumino-silicate cement is a potential material. In root canal sealing/filling material, calcium based material with bioactivity is commonly used rather than alumina-based material of calcium aluminate cement because alumina is bioinert bioceramic.
BioAggregate was marketed after FDA approval in 2006. BioAggregate is medical grade calcium silicate compound containing (tricalcium silicate and dicalcium silicate) by 65% and calcium phosphate as admixture by 6% and tantalum pentoxide by 25% as radiopacifier. Mineral trioxide aggregate is ceramic in nature, bioceramic is chemically bonded ceramic, artificial sythetic pure calcium silicates. So there is no toxic heavy metals and unnecessary heavy metals of iron, manganese, nickel, copper, zinc. Also BioA is not used by bismuth trioxide, but by tantalum pentoxide, zirconia, or calcium tungstate as radiopaque material. It is a differentiation from MTA, trioxide. Before MTA was developed, calcium phosphate bioceramic materials were developed as root-end filling material. But calcium silicate bioceramic materials have been used only as bone cement or admixture. Pure calcium silicate bioceramic materials were developed for root-end and root canal filling material. After researching, BioAggregate (DiaRoot) was approved by FDA and then marketed. Biodentine material is a newer tri/dicalcium silicate powder (aluminum-free) that is made radiopaque with zirconia, and has salt and other additives for quicker setting. Biodentine is pure tricalcium silicate and dicalcium silicate with calcium carbonate by 20% and high concentrated calcium chloride solution as hydration accelerant. It is called as tricalcium biosilicate technology. Biodentine is also an alternative to BioAggregate. - aluminum-free (non-tricalcium aluminate) and zirconia (ZrO2) instead of bismuth trioxide.
Brasseler offers paste and putty versions of tri/dicalcium silicate, including sealer, which set in vivo. The Brasseler products are based on the same free-tricalcium aluminate containing powders as Diaroot BioAggregate, Bioceramic Aggregate. These powders are very white, non-discoloration and are made radiopaque by tantalum pentoxide and zirconia or any other radiopacifying agents except bismuth trioxide. Brasseler's bioceramic sealers (BC sealer, RRM and RRM putty) are different from powderic bioceramic materials. The compositions are similar to bio-Aggregate, but the material is in paste-form of bioceramic gel formation. BioAggregate is an alternative to MTA. Bioceramic pastes are higher technologies of Bio Tech, Ceramic Tech and Nano Tech integrated technology based advanced bioMaterial (esp. Bioceramic Science) for dental and medical purpose.
These hydraulic Calcium Silicate based materials are alternatives to Mineral calcium silicate cements. Alumino-silicate bioceramic, Calcium Aluminate Bioceramic, Calcium Alumino-Silicate Bioceramics are developed for Root-end filling and root canal filling materials rather than mineral aggregate based materials.
Usage in some clinical cases
Root-end Filling after Apicoectomy
In root canal therapy where an apical infection is persistent, an apicoectomy may be required. Flap[disambiguation needed] is raised over the tooth and the root tip is resected and a cavity created (3–4 mm) in the root tip removed. Retrograde application of MTA to the root tip cavity is completed.
MTA was originally developed for root-end filling. There were several different materials such as amalgam, reinforced zinc oxide eugenol cements (intrim restorative material - IRM, super ethoxy benzonic acid [EBA], glass ionomer cement and composite resin for root-end filling after apicoectomy. MTA, a refined "Portland cement" - calcium alumino-silicate cement-, was found to have less cytotoxic and better results in biocompatibility and micro-leakage sealing ability, giving it more success over root-end filling materials. But MTA is not acceptable as "ideal root-end filling material" because MTA has some drawbacks of toxic heavy metal presence, discoloration, difficult handling, short working time, long setting time, washout before setting and washout after set (calcium carbonate based MTA has solvent of carbonic acid).
For ideal Root-end filling, there are many new materials or improved materials developed. 1. Glass ionomer cement: It is based on alumino-silicate based bioceramic material. Most cytotoxicity is caused by polyacrylic acid. So current GIC as root-end filling material is reducing the cytotoxic acclerator's concentration. - calcium alumino-silicate - MTA (calcium alumino-silicate) + GIC (alumino-silicate), calcium reinforced glass ionomer cement is developed. It's a promising material.
2. Calcium phosphate cement (hydroxyapatite) bioceramic material: CPC has been studied since 1985 in the US. Bone grafting material, artificial bioceramic CPC is developed for Root-end filling or pilot material in root-end filling and root repair material.
3. Calcium silicate based material - bioceramic material: It was known as bioceramic sealers. But actual bioceramic aggregates are composed of pure medical graded calcium silicate based material. BioAggregate, Biodentine, EndoSequence RRM and RRM Putty are based on calcium silicate bioceramic material.
4. Calcium aluminate bioceramic material - (alumina cement in minerals, calcium aluminate cements in bioceramics) Alumina is an initial fast setting element and high compressive strength. It has been used as dental products as luting agent. Calcium aluminate cement (bioceramic) has been developed for dental products and root-end filling material.
These newly developed root-end filling materials are based on bioceramic, chemically bonded ceramic, not by mineral (ceramic in nature) like MTA. Even if mineral shows higher biocompatibility, minerals have potential toxic heavy metals in material. Bioceramic or bioMaterial is used for medical and dental products. BioMaterials can reduce the issues on discoloration and toxic heavy metals' presence initially.
Internal & external root resorption & obturation
In internal resorption… root canal therapy is performed, putty mixture of MTA is inserted in the canal using pluggers to the level of the defect. Gutta percha and root canal sealer are placed above the defect to complete the root canal treatment. In direct cases, the canal may be completely obturated with MTA. 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[disambiguation needed] 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 when an instrument has perforated the root 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. The perforation can be sealed with a thick mixture of an MTA-type product, 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.
Root canal sealer
Several MTA products are available as sealer. MTA Plus has the highest percentage of MTA in its formula. As calcium based materials have washout property in dam, the antiwashout agents are used. The examples are chitosan and gelatin, which has been used with injectable bone grafting paste. MTA Plus is used with gelatin complex as antiwashout agent. MTA Angelus Fillapex sealer contains less than 20% tri/dicalcium silicate powder in a salicylate carrier medium similar to Sealapex. By element analysis, there is no bismuth oxide of MTA. EndoSeal MTA, Tech BioSeal MTA are also MTA root canal sealesr. MTA is used as filler in the resin like MTA Fillapex. MTA powder is mixed with fillers in the resin. These are not MTA based root canal sealer, but resin modified root canal sealer.
Brasseler Endosequence offers a pre-mixed sealer with a non-reactive carrier medium and the product only sets in vivo. Brasseler's EndoSequence bioceramic sealers are tricalcium silicate-based materials without any calcium aluminate phase. The sealer paste or root repair putty contain a medium of organic liquids. By the diffusion of water into the paste, the materials set in vivo. Apexification (Necrotic pulp)
When the root is incompletely formed in adolescents and an infection occurs, apexification can be performed to maintain the tooth in position as the roots develop. In case of non-vital pulp: 1. Isolate the tooth with a rubber dam 2. perform root canal treatment. 3. Mix MTA and insert it to the apex of the tooth, creating a 3 mm thickness of plug. 5. Fill the canal with sealer and gutta percha. Alternatively, revascularization techniques are being used where an antibiotic is locally administered. Later a blood clot is formed in the canal and a coronal plug of MTA is placed.
Apexogenesis (Vital pulp)
The process of maintaining pulp vitality during pulpal treatment to allow continued development of the entire root (apical closure occurs approximately 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.
MTA can be used in a one step or a two step approach. It can be used as a powder or a Wet Mix. However a study found that all these approaches have shown to be equally effective.
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.
MTA Plus material is also indicated for base and liner in vital pulp therapy. In root-end filling after apicoetomy, the anti-washout agent (chitosan or gelatin) is useful to prevent from MTA washout. But in vital pulp therapy, anti-washout gel doesn't increase bioactivity or bacterial tight sealing ability of MTA. Instead, hydraulic (100% pure water) MTA shows the higher success rate than anti-washout gel or resin medium. Resin Modified MTA or Calcium Silicate Cement was marketed already. TheraCal LC is HEMA-free resin modified calcium silicate cement (MTA-like, Portland cement Type III) light-curable for base and liner in vital pulp therapy.
- http://www.llu.edu/dentistry/news/index.page?story_id=1374. Missing or empty
- "ProRoot MTA".
- "DENTSPLY Tulsa Dental Specialties".
- Formosa LM, Mallia B, Camilleri J (February 2013). "A quantitative method for determining the antiwashout characteristics of cement-based dental materials including mineral trioxide aggregate". Int Endod J. 46 (2): 179–86. doi:10.1111/j.1365-2591.2012.02108.x.
- Milani, AS; Jafarabadi, MA; Pakdel, MV (Sep–Oct 2014). "Using mineral trioxide aggregate powder as an apical barrier: a bacterial leakage study.". General dentistry 62 (5): 55–9. PMID 25184718.