As the AIDS epidemic began to take hold in the 1980s, researchers began to notice a connection between HIV and periodontal disease. Patients with HIV were found to have more gum disease than healthy people. Some experts believe that this is because their immune systems have been weakened by the infection. The link between HIV and gum disease is so strong that dentists now routinely offer HIV testing as a routine part of a dental exam.

But the relationship between HIV and periodontal disease is more complicated than simply a link between a weakened immune system and the loss of gum tissue. There are many steps in the process by which HIV damages the immune system. Researchers think that periodontal disease may damage the immune system in ways that make HIV easier to spread.