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Scientific
Publications - Work Done by Microbiology Reader
P. Khalichi, D.G. Cvitkovitch and J.P. Santerre, Modulation of oral streptococcal growth by composite resin degradation by-products, The IADR/AADR/CADR 80th General Session (March 6-9, 2002), San Diego, California, USA ABSTRACT Studies have confirmed that activities present in human saliva
can catalyze the degradation of the constitutive monomers (bis-GMA, bis-EMA, and
TEDGMA) used in dental restorative composites, forming by-products such as
bis-hydroxy-propoxyphenyl propane, ethoxylated bisphenol A, methacrylic acid
(MA), and triethylene glycol (TEG). Few studies have yet examined the effects of
such products on oral bacterial function. Objective: To study the effects
of MA and TEG on the growth S. mutans strains NG8 and JH1005, and S.
salivarius AT2. Methods: Bacterial growth rates were measured at 37
° C using a Bioscreen C (Lab Systems, Finland) microbial growth reader and
analyzer. The growth medium used was tryptone yeast extract plus 0.1% glucose at
pH 5.5 or 7.0. Bacterial growth rates at concentrations of 0-50 mmol/L for MA
(Sigma, US) and 0-100 mmol/L for TEG (Sigma, US) were studied. Results:
At pH 5.5 TEG significantly stimulated the growth of both S. mutans
strains (p<0.05) at the concentration range of (0.5-10.0) mmol/L and
stimulated the growth of S. salivarius AT2 for the entire concentration
range tested (p<0.05). TEG did not significantly affect the doubling times of
S. salivarius at pH of 7.0 and slowed the growth of both S. mutans
strains above 50 mmol/L. At pH 5.5 MA inhibited the growth of all three strains
with increasing concentration. At neutral pH, the growth of S. mutans NG8
strain was significantly reduced by MA (p<0.05) above 10 mmol/L. Conclusions:
These results indicate that TEG and MA modulate the activity of important oral
bacteria. The concentrations of the degradation by-products likely reach these
significant levels at the plaque/surface interface in marginal gaps where
microbial leakage is common, potentially increasing the growth and accumulation
of these bacteria. Therefore further analysis of the impact of these products in
the plaque environment is warranted.
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