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Abstract
This paper reports the effect of a series of phosphate-based glasses based on the
Na(2)O-CaO-P(2)O(5) system doped with increasing amounts of copper and the effect
of this increasing copper content on the viability of an in vitro biofilm of Streptococcus
sanguis over an 8 day period in a constant depth film fermenter. The addition of copper
to the glass caused the solubility to change, so the glasses were adjusted in order
that their solubility in artificial saliva was nominally the same (0.3062 +/- 0.07
mg cm(-2) h(-1)). Initial experiments on glasses with 1.5% and 10% copper showed that
after 6 h there was no statistical difference between the copper containing glasses
and the non-copper containing glass and HA in terms of the viability of the biofilms.
However, at 24 h there was an approximately 0.8-0.9 log reduction in viability of
the biofilms grown on the 5% copper glass and an approximately 1.0-1.3 log reduction
for the 10% copper containing glass. Further experiments on the glass with 10% copper
and another glass with 15% copper were carried out in a time dependent study. For
both glasses a clear decrease in viable counts at 24 h was found but for both glasses
these returned to levels similar to those of controls. The initial decrease in viability
during the first 24 h is likely to be due to the antibacterial effect of the copper
and this could be correlated with copper content. The recovery after 24 h is probably
due to the dead cells forming a barrier, making diffusion of the antibacterial ions,
increasingly difficult. This study has shown that phosphate-based glasses could potentially
be used to deliver antibacterial ions to help combat oral infections. Copper, which
has been shown to have antibacterial properties, could be incorporated but some development
of the glasses used in this investigation may be required. Further work is needed
to determine the effectiveness of copper containing glasses on oral bacterial communities.