Composition
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. Original ProRoot MTA is a refined Portland Cement with Bismuth Trioxide as radiopacifying agent. ProRoot MTA is especially made by Portland Cement Type I, 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. Main constituents of MTA are tricalcium silicate and dicalcium silicate naturally composed. MTA contains innated tricalcium aluminate (C3A)and tetracalcium aluminoferrite(C4AF). These constituents are determined to Portland Cement Type (I to V). White MTA was developed for reducing of discoloration to tooth structure. It was eliminating C4AF (tetracalcium aluminoferrite) as iron (Fe)'s main discoloration induced element. The initial White MTA contained significantly lesser amount of aluminum oxide (Al2O3), magnesium oixde (MgO) and ferric oxide (Fe2O3) than grey MTA. The current White MTA was developed by Dr. Carolyn Primus in 2008 with White Portland Cement. - White Portland Cement - Limestone Silica Compounding Cement, main consitituent is Calcium Carbonate Cement of Limestone.
Rawmix formulation
"The characteristic greenish-gray to brown color of ordinary Portland cement derives from a number of transitional elements in its chemical composition. These are, in descending order of coloring effect, chromium, manganese, iron, copper, vanadium, nickel and titanium. The amount of these in white cement is minimized as far as possible. Cr2O3 is kept below 0.003%, Mn2O3 is kept below 0.03%, and Fe2O3 is kept below 0.35% in the clinker. The other elements are usually not a significant problem. Portland cement is usually made from cheap, quarried raw materials, and these usually contain substantial amounts of Cr, Mn and Fe. For example, limestones used in cement manufacture usually contain 0.3-1% Fe2O3, whereas levels below 0.1% are sought in limestones for white manufacture. Typical clays used in gray cement rawmix may contain 5-15% Fe2O3. Levels below 0.5% are desirable, and conventional clays are usually replaced with kaolin. Kaolin is fairly low in SiO2, and so a large amount of sand is usually also included in the mix. Iron and manganese usually occur together in nature, so that selection of low-iron materials usually ensures that manganese content is also low, but chromium can arise from other sources, notably from the wear of chrome steel grinding equipment during the production of rawmix. See rawmill. This wear is exacerbated by the high sand-content of the mix, which makes it extremely abrasive. Furthermore, to make a combinable rawmix, the sand must be ground to below 45 μm particle diameter. Often this is achieved by grinding the sand separately, using ceramic grinding media to reduce contamination."
Also 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 |
MTA 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). White MTA was developed by Dr. Carolyn Primus (US Patent 7,892,342). It was made from White Portland Cement (Limestone - Calcium Carbonate - Silica compounding Cement).
Originally, MTA was formulated from commercial Portland cement combined with bismuth oxide powder for radiopacity, to make the material visible on a dental x-ray. However, dental materials are required to have high purity and be lead and arsenic-free, unlike portland cement, and dental companies have created materials to meet the dental standards (ISO 9917) for purity and performance (ISO 6876 and ADA 57). The original MTA was dark gray in color, but white versions have been on the market since 2002. ProRoot® MTA and MTA Angelus® brands are based on the original formulas for white and gray MTA, contain roughly 20% bismuth oxide, and are available as white or gray. Source: Current tooth-colored MTA was marketed in 2008 by US Patent 7,892,342. Original MTA was formulated form Ordinary Portland Cement as Calcium Silicates, but current White MTA was developed by White Ordinary Portland Cement as different manufacturing process and different raw material of Calcium Carbonate (Limestone). Though chemical compositions are similar, the properties and activities are different by the raw materials' compounding technology. Oridnary Portland Cement is made by long-term natural process of heat and compression. But limestone silica compounding cement is artificially compounded by decarbonation and mixturing process of Lime (CaO) and Silica (SiO2) with Alumina (Al2O3).
Aluminum-containing phases, and calcium sulfate are minor phases present in some MTA products. Although some studies have shown an increased risk of developing Alzheimer's disease with environmental factors such the intake of metals, particularly aluminium, ; the neurotoxicity of calcium aluminate compounds has not been demonstrated.
a search on neurotoxicity of aluminum of the PubMed database listed 328 individual articles, as of 8 Feb 2013.
Read more about this topic: Mineral Trioxide Aggregate
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