For you hard-core research junkies, you can read about the entire study--methodology, hard data, etc.--HERE. But here's a quick summary....
Three separate population-based studies were conducted in the U.S., England, and France. The incidence of in viridans group infective endocarditis (IVG-IE) was compared between dental patients who premedicated and those who didn't. The groups showed remarkably similar infection rates (although one of the non-medicated groups did show an increase in staphylococcal infective endocarditis.
The Journal Watch summary observed: "Clearly, decreased use of dental antibiotic prophylaxis in the three populations studied has not resulted in increases in IE caused by oral bacteria. That such prophylaxis has never been helpful cannot be proven. But given the current findings and the fact that antimicrobial resistance is a major health problem, it seems prudent to reinforce guidelines that restrict antibiotic overuse."
Study and debate are sure to continue. In the meantime, though, I guess I'll follow my docs instructions.