In the early part of the twentieth century, many people believed that RA was caused by dental infections. Infections of the teeth and gums were thought to spread to the joints, causing inflammation and other symptoms of RA. For example, researchers made correlations between increases in the rate of diagnosis of RA and increases in sugar consumption (a factor in periodontal disease) in England and the United States between the years 1765 and 1859.
This belief was so common that, when a patient was diagnosed with RA during this era, dentists were often employed to find and treat the dental infections that supposedly were causing it. Often, all of a patient's teeth would be removed in an effort to eradicate the infection and “cure” the arthritis. While this procedure wasn't effective in curing RA, belief in the infectious theory of RA persisted. Over time, interest in this theory eventually waned as studies revealed that RA was controlled by the body's immune system. Therapy was then directed at controlling the inflammation rather than looking for dental infections.
Studies of large populations still show an association between RA and diseases of the teeth and gums, however. Medical researchers, however, have proposed alternative theories about the source of this observed association of RA and diseases of the teeth and gums. Perhaps gum disease and RA occur together because RA makes using a toothbrush difficult. Tooth and gum disease might result from being unable to effectively brush and floss one's teeth. Furthermore, patients who have RA take many medications that can affect the teeth.
Many studies have been undertaken to compare the rates of tooth plaque and dental caries (cavities) in two populations—one group consisting of patients with RA and the other group consisting of age- and sex-matched people without RA. While researchers found that the rates of dental caries and plaque were the same, RA patients had a higher level of periodontal disease and a higher rate of tooth loss. Based on these findings, some scientists have suggested that bacterial infections around the teeth can trigger a chain of events in genetically susceptible individuals that ultimately results in RA. The bacteria interact with proteins and white blood cells in the body, “tricking” the white blood cells into creating an inflammatory reaction with the body's connective tissue.
Connective tissue
The material that holds various body structures together. Cartilage, tendons, ligaments, and blood vessels are composed entirely of connective tissue.
While some intriguing evidence supports this theory, the jury is still out on whether it is a significant cause of RA.