Bacteria-laden mouths and bleeding gums are giving medical researchers plenty to think about.
Turns out gum disease is associated with a greater risk of developing diabetes, heart disease and even pregnancy complications. And a study released last week found evidence that bacteria linked to gingivitis traveled to brains afflicted by Alzheimer's disease, hinting at a role in dementia.
As the latest research deepens scientists' understanding of the link between dental health and disease, the potential implications are coming into focus. Something as simple as treating gum disease, a neglected, often painless condition, could limit damage from some of the world's most widespread and costly illnesses. About half of all adults have some form of gum disease, says Iain Chapple, a professor of periodontology at the University of Birmingham in England. That shows the potential impact of healthier mouths, he said.
"Even if it's just going to delay onset of arthritis or cardiovascular disease, if you add it up in fiscal terms, the savings would be huge," said Chapple, who co-led a recent review of research on gum disease's links with diabetes.
Heart disease and diabetes are costly illnesses and are becoming more prevalent around the world. Heart disease, the world's biggest killer, costs the U.S. alone $108.9 billion each year, according to the American Heart Association. Diabetes, which most frequently occurs in older people who are overweight and sedentary, cost $245 billion last year, according to the American Diabetes Association.
The link to an increased risk of diabetes, heart disease and pregnancy complications was highlighted in the research review organized by Chapple and other scientists from the U.S. and Europe. Colgate-Palmolive Co. funded the review.
Colgate, a New York-based maker of toothpaste and toothbrushes, and other makers of dental-hygiene products such as Johnson & Johnson, Procter & Gamble Co. and Royal Philips NV stand to benefit if more connections between oral health and disease are established.
What gum disease has in common with other illnesses is inflammation, a response by the immune system to invaders that features swelling, redness, heat and pain as fluids and white blood cells rush to the affected area.
Bugs can travel from the mouth by being swallowed, inhaled or by entering the bloodstream through the gums, according to Frank Scannapieco, chairman of the department of oral biology at the University of Buffalo's School of Dentistry. If harmful bacteria and viruses spread from the mouth, that could explain inflammation that leads to disease elsewhere in the body.
"The real question, the so-what question, is does it act as a risk factor with other medical conditions," said Ian Needleman, a professor at University College London Eastman Dental Institute. "There's a substantial body of research that connects them, but we are a long way from demonstrating causation. Can there be smoke without fire?"
To answer that question, larger and more expensive studies are needed, and funding is scarce, according to Needleman. The budget of the U.S. National Institute of Dental and Craniofacial Research is about $400 million, compared with the $30.9 billion its parent organization, the National Institutes of Health, invests in medical research each year.
"The field is wide open and the gaps in knowledge are large," Chapple's group wrote in the Journal of Clinical Periodontology in April.
Scientists are trying to fill that void. At least four trials are exploring whether dental treatment improves diabetics' control of their condition, according to clinicaltrials.gov, a U.S. government website. Colgate-Palmolive is collaborating on one of the trials.
To prevent gum disease, the American Academy of Periodontology recommends brushing both teeth and tongue after meals, flossing and rinsing with a mouthwash once daily and seeing a periodontist. Eating a healthy diet rich in vitamin C and stopping smoking also help.
"Prevention is better than intervention," said Steve Engebretson, the chairman of the department of periodontology and implant dentistry at New York University's College of Dentistry.
If the diabetes research shows a benefit, patients would have another way to improve their health in addition to diet, exercise and medication. One of the studies, a U.S. trial of about 600 people, has been completed, said Engebretson, the lead researcher. It builds on previous findings that show treating gum disease improves a measure of blood sugar.
"Our trial will be the largest to date to address the question," Engebretson said. "One large trial is often not enough to convince clinicians about usefulness of one intervention or another."
He declined to comment further on the study, which was funded by Stony Brook University, because it was submitted to a medical journal and hasn't yet been published.
Heart disease is another promising area for research. The link between it and gum disease is "robust and significant" though it isn't clear whether gum disease can cause heart disease, Chapple said. Only long-term trials can establish a connection, he said.
"I was the biggest cynic" about the link between the two illnesses, Chapple said. "But I've changed my view. The evidence is very strong now and I'll be surprised if there isn't a causal role."
The British research team behind the Alzheimer's study is seeking more funding for a larger trial that would track recently diagnosed patients, said St. John Crean, the dean of the School of Medicine and Dentistry at the University of Central Lancashire in England. The goal of the trial would be to show whether taking action against gum disease can slow the progression of the dementia, according to Crean.
People care for their teeth regardless of gum disease's links to other illnesses, Needleman said.
"There are over 1,000 different kinds of bacteria in your mouth," Chapple said.