Abstract:
Dental caries is the most common infectious disease affecting humans. The
main causative agents of this disease are bacteria especially group of
streptococcal species. This study has examined the potential of using essential
oils/antioxidants to control the growth of Streptococcus mutans and
Streptococcus oralis in vitro in tryptone soya broth and a saliva medium in the
presence and absence of sodium fluoride. A total of 9 essential oils and three
antioxidants were screened using a clearing zone method. This showed that
two essential oils (clove leaf, and cinnamon oils) and two antioxidants (butyl
hydroxy anisole and propyl gallate) were the most effective. These were then
tested at up to 10% concentration for inhibition of cell viability of both S.mutans
and S.oralis. The ED50 and ED90 concentrations of these four compounds were
determined. Studies were then carried out to examine the potential of
integrating these compounds with sodium fluoride for inhibition of these two oral
bacteria. Concentrations of 0.5 and 1% of the essential oils/antioxidants +
2000ppm sodium fluoride was able to completely inhibit growth of populations of
both bacteria in TSB medium. Studies in an artificial saliva medium showed that
these mixture were still effective resulting in >75% decrease in populations after
treatment for 24 hrs. Ecological studies using the Bioscreen system showed
that S.mutans and S.oralis could grow well at pH 5-7, but much more slowly at
pH 4 as indicated by the times to detection and the increase in lag times prior to
growth initiation. An increase in NaCl concentration from 1 to 6% (=0.999 to
0.97 water activity) showed a similar result for both bacteria.
