Abstract
Commercial formulations based on 80:20 mixtures of Portland cement and bismuth oxide (a radiopacifying agent) are used in dentistry as root-filling materials. This study compares the impact of two alternative radiopacifiers, barium sulphate and zirconium oxide, with that of bismuth oxide, on the setting times and bioactivity of white Portland cement. The findings indicate that bismuth oxide prolongs both the initial and final setting times of the cement, and that barium sulphate and zirconium oxide have no effect on this parameter. Hydroxyapatite (HA) formed on the surfaces of all test samples within 7 days of exposure to simulated body fluid, indicating that they possess the potential to stimulate new hard tissue formation. Fourier transform infrared spectroscopy, the traditional technique for the identification of HA, was not appropriate for the analysis of these cement systems owing to the overlap of signals from each of the radiopacifiers with the characteristic P-O bending modes of HA in the 570 – 610 cm-1 region. In this respect, the P-O band at 965 cm-1 of HA in the Raman spectrum was found to be a suitable means of detection since it is discrete with respect to all signals arising from the radiopacifying agents and cement phases.
Highlights
Mineral trioxide aggregate (MTA) is a commercial dental cement comprising a mixture of 80 wt% Portland cement and 20 wt% bismuth oxide (Bi2O3), a radiopacifying agent, which has been used in endodontic restorations for the past two decades [1]
These data demonstrate that the presence of 20 wt% bismith oxide significantly increases both the initial and final setting times of white Portland cement (WPC) by 105 min and 145 min, respectively; whereas, barium sulphate and zirconium oxide have no impact on either setting time
This paper reports the comparative impact of 20 wt% of barium sulphate, zirconium oxide or bismuth oxide on the setting times and in vitro bioactivity of white Portland cement
Summary
Mineral trioxide aggregate (MTA) is a commercial dental cement comprising a mixture of 80 wt% Portland cement and 20 wt% bismuth oxide (Bi2O3), a radiopacifying agent, which has been used in endodontic restorations for the past two decades [1]. Barium sulphate (BaSO4) and zirconium oxide (ZrO2) are among a range of alternative radiopacifying agents with potentially superior chemical, mechanical and biological properties that are currently under investigation for use in hydraulic calcium silicate cements for dental restorations [4,5,6,7]. Both barium sulphate and zirconium oxide, by virtue of their low solubilities, are currently used as radiographic contrast agents in a number of biomaterials [5, 8]. The impact of the various radiopacifiers on initial and final setting times were determined using a Vicat apparatus
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