| Summary: | Addition of CaF2 to a silicate bioactive glass
favours formation of fluorapatite, which is less soluble
in acidic environment than hydroxyapatite. However, excess
CaF2 in the glass is problematic, owing to the formation
of crystalline calcium fluoride rather than fluorapatite
on immersion. In this paper we investigate chloride
as an alternative to fluoride in bioactive silicate glasses
and in particular their bioactivity for the first time. Meltderived
bioactive glasses based on SiO2-P2O5-CaO-CaCl2
with varying CaCl2 contents were synthesised and characterised
by DSC. Chemical analysis of the chloride content
was performed by using an ion selective electrode.
Glass density was determined using Helium Pycnometry.
The glass bioactivity was investigated in Tris buffer. Ion release
measurements were carried out by using ICP-OES.
The chemical analysis results indicated that the majority
of the chloride is retained in the Q2 type silicate glasses
during synthesis. Tg and glass density reduced with increasing
CaCl2 content. Apatite-like phase formation was
confirmed by FITR, XRD and 31P MAS-NMR. The results
of the in vitro studies demonstrated that the chloride containing
bioactive glasses are highly degradable and form
apatite-like phase within three hours in Tris buffer and,
therefore, are certainly suitable for use in remineralising
toothpastes. The dissolution rate of the glass was found
to increase with CaCl2 content. Faster dissolving bioactive
glasses may be attractive for more resorbable bone grafts
and scaffolds.
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