Now, Marquis and others have vindicated Bibby by showing that fluoride does affect bacteria directly. In his laboratory, Marquis has shown that fluoride and food preservatives knock out bacteria by pushing them to exhaustion. Though bacteria like streptococcus mutans thrive in the high-acid environment that they create along the surface of teeth and in dental plaque, the bacteria must maintain a lower acidity level within themselves. But fluoride and food preservatives make this difficult. Both take molecular actions that lower the pH within bacteria by continually bringing protons into the cells. Bacteria pump these protons back out, but like an athlete who continually must toss a heavy medicine ball over a fence, the cell soon uses up all its energy pumping the protons back out. Without energy, the cell shuts down and stops producing acid.
"The acid from these bacteria is what causes enamel to dissolve," says Marquis, professor of microbiology and immunology. "Fluoride and preservatives like benzoate prevent the bacteria from acidifying the plaque and causing cavities. The bacteria are still there -- you have to take a tooth brush to get rid of them -- but they're not causing damage."
In his laboratory, Marquis has also shown that the common medicine ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), also acts like fluoride and food preservatives in the way it inhibits bacteria. Again picking up on that basic research, Bowen's team has just published results showing that ibuprofen also enhances fluoride's action, dramati
Contact: Tom Rickey
University of Rochester