ettringite and calcium-silicate

To evaluate the effect of adding wollastonite and bioactive glass to an experimental mineral trioxide aggregate-like cement (MTA) on the dimensional stability, compressive strength, solubility, bioactivity, and marginal adaptation by scanning electron microscopy (SEM) and X-ray diffraction (XRD).. Four groups were evaluated at 7, 14, and 21 days: MTA Angelus, experimental MTA-like cement (MTA Exp), BG10 (MTA Exp+10 wt% bioactive glass), and WO20 (MTA Exp+20 wt% wollastonite). To evaluate marginal adaptation, extracted teeth were endodontically obturated and root-end cavities were prepared and filled with the tested materials.. Cements with bioactive materials showed minimal dimensional changes. Adding wollastonite or bioactive glass to MTA Exp reduces the compressive strength but does not affect solubility. Bismite (Bi. Acicular growing crystals typical of hydroxyapatite were found on the surfaces of all cements. An improved marginal adaptation was observed with the addition of wollastonite or bioactive glass.

Topics: Aluminum Compounds; Calcium Compounds; Dental Cements; Dentin; Drug Combinations; Hydroxyapatites; Materials Testing; Oxides; Root Canal Filling Materials; Silicates

Characterization and assessment of the hydration reaction of mineral trioxide aggregate (MTA) Plus exposed to different environmental conditions.. The specific surface area, surface morphology and characterization of un-hydrated MTA Plus (Avalon Biomed Inc. Bradenton, FL, USA) were investigated. The specific surface area was compared with that of ProRoot MTA (Dentsply International, Tulsa Dental Specialties, Johnson City, TN, USA). The reaction rate was determined using calorimetry, and the hydrated cement was assessed for setting time (determined using an indentation technique), and the set material was characterized using X-ray diffraction analysis, scanning electron microscopy and X-ray energy-dispersive analysis. Atomic ratio plots were drawn to establish the relationship of the hydration products. Three different environmental conditions namely dry or immersed in either water or Hank's balanced salt solution (HBSS) were used.. Mineral trioxide aggregate Plus had a higher specific surface area than ProRoot MTA. The hydration reaction was exothermic. The setting time of MTA Plus was retarded when in contact with fluids (P < 0.001). The setting time was longer when MTA Plus was in contact with HBSS than when in contact with water (P < 0.001). Hydration of MTA Plus resulted in the formation of calcium silicate hydrate, calcium hydroxide, ettringite and monosulfate phases. Bismuth was incorporated in the calcium silicate hydrate structure. The hydration of the core material was not affected by contact with the different solutions but the periphery exhibited microcracking, leaching of calcium hydroxide, partial decalcification of calcium silicate hydrate, inhibition of hydration in contact with the physiological solution.. The novel MTA Plus was finer than ProRoot MTA but had a similar chemical composition. MTA Plus in direct contact with fluids exhibited partial decalcification of calcium silicate hydrate in contact with the solution, microcracking and leaching of calcium hydroxide. Interaction with a physiological solution resulted in inhibition of hydration.

Topics: Aluminum Compounds; Bismuth; Calcium Compounds; Calcium Hydroxide; Calorimetry; Desiccation; Drug Combinations; Hardness; Humans; Isotonic Solutions; Materials Testing; Microscopy, Electron, Scanning; Minerals; Oxides; Root Canal Filling Materials; Silicates; Spectrometry, X-Ray Emission; Surface Properties; Temperature; Time Factors; Water; X-Ray Diffraction

The manufacture of prefabricated building materials containing binding products such as ettringite (6CaO·Al2O3·3SO3·32H2O) and calcium silicate hydrate (CSH) can give, in addition to other well-defined industrial activities, the opportunity of using wastes and by-products as raw materials, thus contributing to further saving of natural resources and protection of the environment. Two ternary mixtures, composed by 40% flue gas desulfurization (FGD) gypsum or natural gypsum (as a reference material), 35% calcium hydroxide and 25% coal fly ash, were submitted to laboratory hydrothermal treatments carried out within time and temperature ranges of 2h-7days and 55-85°C, respectively. The formation of (i) ettringite, by hydration of calcium sulfate given by FGD or natural gypsum, alumina of fly ash and part of calcium hydroxide, and (ii) CSH, by hydration of silica contained in fly ash and residual lime, was observed within both the reacting systems. For the FGD gypsum-based mixture, the conversion toward ettringite and CSH was highest at 70°C and increased with curing time. Some discrepancies in the hydration behavior between the mixtures were ascribed to differences in mineralogical composition between natural and FGD gypsum.

Topics: Calcium Compounds; Calcium Sulfate; Coal Ash; Construction Materials; Gases; Industrial Waste; Minerals; Silicates; Sulfur

To characterize the hydration products of white mineral trioxide aggregate (MTA).. Mineral trioxide aggregate, white Portland cement and bismuth oxide were evaluated using X-ray diffraction (XRD) analysis and Rietveld XRD. The cements were tested un-hydrated and after hydration and curing for 30 days at 37 degrees C. Analysis of hydrated cement leachate was performed weekly for five consecutive weeks from mixing using inductively coupled plasma atomic emission spectroscopy after which the cements were viewed under the scanning electron microscope to evaluate the cement microstructure. Quantitative energy dispersive analysis with X-ray was performed and atomic ratios were plotted.. Both Portland cement and MTA produced calcium silicate hydrate (C-S-H) and calcium hydroxide (CH) on hydration. The tricalcium aluminate levels were low for MTA which resulted in reduced production of ettringite and monosulphate. On hydration the bismuth level in the hydrated MTA decreased; bismuth oxide replaced the silica in the C-S-H and was leached out once the C-S-H decomposed with time. Both MTA and Portland cement released a high amount of calcium ions which decreased in amount over the 5-week period.. The hydration mechanism of MTA is different to that of Portland cement. In MTA the bismuth oxide is bound to the C-S-H and is leached out from the cement with time as the C-S-H decomposes. MTA produces a high proportion of calcium ions from CH a by-product of hydration and also by decomposition of C-S-H. The release of calcium ions reduces with time.

Topics: Alum Compounds; Aluminum Compounds; Bismuth; Calcium Compounds; Calcium Hydroxide; Dental Cements; Drug Combinations; Hydrolysis; Microscopy, Electron, Scanning; Minerals; Oxides; Root Canal Filling Materials; Silicates; Spectroscopy, Electron Energy-Loss; X-Ray Diffraction