Losing teeth can do more than affect the ability to enjoy a fresh, crunchy apple or flash a healthy smile. Research suggests that tooth loss – a marker for periodontal (gum) disease – may predict rheumatoid arthritis and its severity. 

In the study of 636 patients with early arthritis, presented at the 2012 European Congress of Rheumatology in Berlin, 24.2 percent had 10 or fewer teeth, 16.1 percent had 11 to 20, 36.3 percent had 21 to 27 teeth, and 23.3 percent had 28 or more teeth. (A full set of adult teeth, including wisdom teeth, numbers 32.)

At six months’ follow-up, 52 percent had a good response to treatment, 32 percent had a moderate response and 16 had no response. The worst prognosis was for those with the fewest teeth. People with 10 or fewer teeth had more severe arthritis – evidenced by a significantly greater erythrocyte sedimentation rate, higher tender and swollen joint counts, and a higher Disease Activity Score – than those with more than 10 teeth. 

In a separate study presented at the same meeting, Italian researchers reported that tooth loss was associated with joint symptoms in a group of 366 first-degree relatives of people with RA. Participants with one or more swollen joints had an average of 26 teeth, compared with an average of 29 teeth for those with no swollen joints. The fewer the teeth participants had the greater their risk for joint inflammation, the researchers found. Patients with fewer than 20 teeth had eight times the risk of having at least one swollen joint compared to those with all 32 original teeth.

In addition, a 2012 study published in the Annals of Rheumatic Disease showed that the 1.5 million people with RA are up to four times more likely to develop gum disease than people without RA, and that the gum disease also appears to be more severe among people with RA.

The Mouth-Joint Connection

These studies joined the growing body of research linking periodontal disease and rheumatoid arthritis. While research hasn’t proven a cause and effect, increasingly it is showing that periodontal disease in people with RA doesn’t always come after RA – in some cases it precedes it, says Jerry Molitor, MD, PhD, associate professor in the rheumatic and autoimmune disease division of the department of medicine at the University of Minnesota, Minneapolis.

Researchers studying the RA-periodontal disease connection have found likenesses in the joint and oral tissues, as well as in the inflammatory processes that affect them.

“If you look at the tissues of the mouth in periodontitis and the tissues of the joint in RA, there are a number of similarities – including the types of cells that are infiltrating tissues of the mouth in periodontitis and the tissue of the joint,” says Clifton O. Bingham III, MD, associate professor of medicine and director of the Johns Hopkins Arthritis Center at Johns Hopkins University in Baltimore. He also notes that the levels of proinflammatory proteins like tumor necrosis factor, interleukin-1 and interleukin-6 are also similar in RA and periodontitis. 

Research has also shown a genetic link between the two. In a study published in  Journal of Periodontology, scientists in Israel found HLA-DR4 – a gene that occurs more frequently in people with rheumatoid arthritis – in 8 out of 10 patients with severe, aggressive gum disease, compared to just a little over a third of a group of patients without RA.       

Such findings led doctors to believe that there may in fact be a relationship between the two driven by an underlying disease process, says Dr. Bingham.

A potential advance in the understanding of that disease process came around a decade ago when scientists began to understand that one of the early markers of RA is the development of antibodies to citrullinated peptides.