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.

Back to the Dental Materials: V - Polymer Materials-Chemistry Program
Back to the IADR/AADR/CADR 80th General Session (March 6-9, 2002)

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