Thiobarbituric acid-reacting substances (TBARS) are widely used as markers of oxidative stress and lipoperoxidation. Salivary TBARS are affected by age, smoking and periodontal status. The origin of these compounds in saliva is unknown, but microbial factors and inflammation have been previously postulated as potential candidates. Virulence factors of Enterococcus faecalis include resistance to oxidative stress and the production of extracellular free radicals. E. faecalis has been linked to the pathogenesis of caries and periodontitis, both associated with oxidative stress. It is hypothesized that E. faecalis produces an extracellular superoxide causing oxidative damage to membranes of host cells. This lipoperoxidation leads to increased salivary TBARS levels. The hypothesis should be tested in future studies.