Physical properties, marginal adaptation and bioactivity of an experimental mineral trioxide aggregate-like cement modified with bioactive materials

PURPOSE

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).

METHODS

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.

RESULTS

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 (Bi₂O₃), larnite (Ca₂SiO₄), calcite (CaCO₃) and carbonated hydroxyapatite (Ca₅[PO₄,CO₃]₃[OH]) were identified in the four cements; ettringite (Ca₆Al₂[SO₄]₃[OH]₁₂·26H₂O) and bismutite ([BiO]₂CO₃) were only observed in MTA Exp, BG10, and WO20. Cement-dentin interfaces were not observed after 14 days on the BG10 and WO20 cement composites due to the ettringite formation.

CONCLUSION

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.

Synthesis and Characterization of an SWCNT@HKUST-1 Composite: Enhancing the CO2 Adsorption Properties of HKUST-1

Synthesis of a new HKUST-1 composite based on single-walled carbon nanotubes (SWCNTs) was successfully achieved (SWCNT@HKUST-1). SWCNTs were used as templates to grow rod-like HKUST-1 crystals over the surface of the nanotubes. N₂ adsorption properties showed an increment on the surface area and pore volume for the SWCNT@HKUST-1 composite. Furthermore, the CO₂ capture increased, from 7.92 to 8.75 mmol g^-1 at 196 K up to 100 kPa, for the SWCNT@HKUST-1 composite. This enhancement was directly associated with the increase of the surface area of the composite. Additionally, an increase in the CO₂ heat of adsorption was estimated, from 30 to 39.1 kJ mol^-1 for the SWCNT@HKUST-1 composite. In situ Raman experiments corroborated the favored CO₂ adsorption for the composite and provided an insight into the augmented hydrophobicity of the SWCNT@HKUST-1. Ethanol adsorption isotherms corroborated an increase in the hydrophobicity of the material upon the incorporation of carbon nanotubes.

Structure stability of HKUST-1 towards water and ethanol and their effect on its CO2 capture properties

Water and ethanol stabilities of the crystal structure of the Cu-based metal-organic framework (MOF) HKUST-1 have been investigated. Vapour (water and ethanol) sorption isotherms and cyclability were measured by a dynamic strategy. The ethanol sorption capacity of HKUST-1 at 303 K remained unchanged contrasting water sorption (which decreased along with the sorption experiment time). Considering the binding energy of each sorbate with the open Cu(ii) sites, obtained by the use of diffusion coefficients, we showed the superior crystal stability of the HKUST-1 framework towards ethanol. Finally, a small quantity of ethanol (pre-adsorbed) slightly enhanced CO₂ capture without crystal structure degradation.

Water Adsorption Properties of NOTT-401 and CO2 Capture under Humid Conditions

The water-stable material NOTT-401 was investigated for CO₂ capture under humid conditions. Water adsorption properties of NOTT-401 were studied, and their correlation with CO₂ sequestration at different relative humidities (RHs) showed that the CO₂ capture increased from 1.2 wt % (anhydrous conditions) to 3.9 wt % under 5% RH at 30 °C, representing a 3.2-fold improvement.

Twofold role of calcined hydrotalcites in the degradation of methyl parathion pesticide

Methyl parathion (MP) is a very toxic organophosphate pesticide used as a non-systematic insecticide and acaricide on many corps. As MP and its by-products are highly toxic, they have to be retained to avoid pollution of rivers and lakes. Highly efficient sorbents are hydrotalcites (HTs) (or anionic clays). We have correlated the degradation of an aqueous solution of MP at room temperature, with the basicity of the adsorbing materials. It was found that the metal composition of hydrotalcites determines both the surface electronic properties (basic or acidic) and the sorption capacity. Depending on the basic strength, some calcined hydrotalcites can catalyze the transformation of MP to p-nitrophenol (p-NP) and retain its by-products. Such a process has the advantage of being able to be carried out at room temperature and at the pH of the pesticide solution.

[Mexican ceramic material for skin healing]

Sixty female Wistar rats were employed and divided into three experimental groups of 20 rats each. Groups were evaluated at 15, 30, and the last at 45 days after surgery. Each group was divided into four sets of five rats each. All rats were subjected to surgery; an incision of 2 x 2 cm was done on the back of each animal, removing tissue until reaching muscular fascia, where the material was applied. Nitro-furazone was employed as positive control. Test materials were AlPO added with 0.55% wt of Zn; 0.30% wt of Ca(OH)2, and AlPO added with 0.55% wt of Zn and 0.66% wt of Ca(OH)2. Finally, as negative control no material was used. The object of this work was in the first place obtension of test materials and to evaluate the healing skin process in rats using AlPO enriched with Zn and Ca(OH)2; as indicated previously. Obtained materials were characterized employing XRD. Histologic studies tested showed that best healing process of dermal tissue corresponded to rats treated with AlPO added with 0.55% wt of Zn and 0.30% wt of Ca(OH)2. Use of AlPO ceramics to repair skin has not been reported previously.