Researchers found that of more than 3,400 U.S. adults, those who rated their oral health as "poor" to "fair" were more likely to have an oral infection with human papillomavirus (HPV), which, in certain cases, can eventually lead to cancer.
Overall, 10 percent of people with tooth or gum disease tested positive for oral HPV. That compared with 6.5 percent of those who rated their dental health as "good" to "excellent."
The results, reported Aug. 21 in the journal Cancer Prevention Research, do not actually prove that diseased teeth and gums cause HPV infection.
"We don't know if poor oral health led to the HPV infection," said Christine Markham, one of the researchers on the study.
Her team tried to account for other factors that could affect dental health or the odds of having HPV -- such as smoking or multiple oral sex partners. And poor oral health was still linked to a 56 percent increase in the risk of having oral HPV.
But there could be other explanations for the connection, and more research is needed, said Markham, an associate professor at the University of Texas Health Science Center in Houston.
Still, she said, there are already plenty of reasons to take care of your teeth and gums. "Good oral health care is important for your health in general," Markham said. This study just offers some more incentive, she added.
HPV, which can cause genital and anal warts, is the most commonly transmitted sexual infection in the United States. Usually, the immune system clears the infection, but in some cases the virus persists in the body. And persistent infection with certain HPV strains can eventually lead to cancer -- with cervical cancer the best known.
HPV can also invade the mouth during oral sex. Those infections usually cause no symptoms, but a lingering infection with a cancer-linked strain can lead to oropharyngeal cancer, which affects the back of the throat, base of the tongue and tonsils.
It's a rare cancer, but cases tied to HPV are on the rise in the United States. No one knows why.
It's already known that poor oral hygiene is tied to a heightened risk of oropharyngeal cancer, even when smoking and heavy drinking -- two big risk factors for the cancer -- are taken into account.
But it has not been known whether dental health matters in the risk of oral HPV infection, Markham noted.
This study, however, does not answer that question, according to a specialist in head and neck cancers.
The study is hampered by some limitations, said Dr. Amy Chen, a professor of otolaryngology, head and neck surgery at Emory University in Atlanta.
The findings come from a large federal health survey that included more than 10,500 Americans. But Markham's team had to exclude two-thirds of them from the analysis because the participants lacked key information -- such as an HPV test result.
Paring down the group like that is problematic because it can bias the results, Chen said.
The "take-away," she said, is that people should be aware of the already-known link between oral health and cancers of the mouth and throat.
Anna Giuliano, of the Moffitt Cancer Center in Tampa, Fla., agreed that the study leaves questions -- including whether people with poor oral health have a higher risk of a long-lasting HPV infection, which is the real concern.
If unhealthy gums and teeth do raise the odds of oral HPV infection, it's not certain how. But Markham said it's possible that diseased gums offer an "entry portal" for the virus.
Fewer than 12,000 cases of oropharyngeal cancer occur among Americans each year, according to the U.S. Centers for Disease Control and Prevention. But it's thought that HPV causes nearly three-quarters of them. So preventing the infection is key to preventing the cancer.
There are two vaccines available against the most common cancer-linked strains of HPV (Gardasil and Cervarix). Experts advise vaccination for girls, boys and young adults.
Of course, that would not be of help to most of the people in this study, the majority of whom were aged 30 or older, said Dr. Dennis Kraus, director of the Center for Head and Neck Oncology at North Shore-LIJ Cancer Institute in Lake Success, N.Y.
Oral hygiene, on the other hand, is something we all can pay attention to, Kraus noted. "Taking care of your teeth, taking care of your gums -- it makes sense," he said.
To help keep your mouth healthy, the American Dental Association recommends dental visits at regular intervals determined by your dentist.
Learn more about HPV and cancer from the U.S. National Cancer Institute.