The research, from the Academic Centre for Dentistry in Amsterdam, looked at 50 people with rheumatoid arthritis and 50 with inflammatory joint pain.
They looked at bacteria on the volunteers' tongues, saliva and plaque, and compared them with 50 healthy people of a similar age.
'If this is the case, the next step for future research would be to see if the risk of rheumatoid arthritis can be lowered by targeting these bacteria.'.
Researchers found similar levels of mouth bacteria in both people with the disease, and those at risk of it, who already had joint pain and high levels of antibodies which attack healthy joints
During their study, scientists looked at 50 people with rheumatoid arthritis and 50 with inflammatory joint pain
However experts suspect it is more likely that poor tooth-brushing allows harmful bacteria to flourish and to get into the bloodstream, causing inflammation which may help to trigger rheumatoid arthritis