Ha William Nguyen, Shakibaie Fardad, Kahler Bill, Walsh Laurence James
School of Dentistry, Oral Health Centre, The University of Queensland , Herston , Queensland , Australia.
Acta Biomater Odontol Scand. 2016 Jan 1;2(1):7-11. doi: 10.3109/23337931.2015.1129611. Epub 2016 Jan 26.
Mineral trioxide aggregate (MTA) cements contain two types of particles, namely Portland cement (PC) (nominally 80% w/w) and bismuth oxide (BO) (20%). This study aims to determine the particle size distribution (PSD) of PC and BO found in MTA. The PSDs of ProRoot MTA (MTA-P) and MTA Angelus (MTA-A) powder were determined using laser diffraction, and compared to samples of PC (at three different particle sizes) and BO. The non-linear least squares method was used to deconvolute the PSDs into the constituents. MTA-P and MTA-A powders were also assessed with scanning electron microscopy. BO showed a near Gaussian distribution for particle size, with a mode distribution peak at 10.48 μm. PC samples milled to differing degrees of fineness had mode distribution peaks from 19.31 down to 4.88 μm. MTA-P had a complex PSD composed of both fine and large PC particles, with BO at an intermediate size, whereas MTA-A had only small BO particles and large PC particles. The PSD of MTA cement products is bimodal or more complex, which has implications for understanding how particle size influences the overall properties of the material. Smaller particles may be reactive PC or unreactive radiopaque agent. Manufacturers should disclose particle size information for PC and radiopaque agents to prevent simplistic conclusions being drawn from statements of average particle size for MTA materials.
三氧化矿物凝聚体（MTA）水泥包含两种类型的颗粒，即波特兰水泥（PC）（名义上占80%重量/重量）和氧化铋（BO）（20%）。本研究旨在确定MTA中PC和BO的粒度分布（PSD）。使用激光衍射法测定了ProRoot MTA（MTA - P）和MTA Angelus（MTA - A）粉末的PSD，并与PC（三种不同粒径）和BO的样品进行比较。采用非线性最小二乘法将PSD解卷积为各成分。还通过扫描电子显微镜对MTA - P和MTA - A粉末进行了评估。BO的粒度呈现近似高斯分布，众数分布峰值在10.48μm。研磨至不同细度的PC样品的众数分布峰值从19.31μm降至4.88μm。MTA - P具有由细PC颗粒和大PC颗粒组成的复杂PSD，BO处于中间尺寸，而MTA - A仅具有小BO颗粒和大PC颗粒。MTA水泥产品的PSD是双峰或更复杂的，这对于理解粒度如何影响材料的整体性能具有重要意义。较小的颗粒可能是活性PC或非活性不透射线剂。制造商应披露PC和不透射线剂的粒度信息，以防止根据MTA材料平均粒径的表述得出过于简单的结论。
