Re-discoveries about RA and the role of oral health

We all know that it’s important to brush our teeth for the sake of our oral health. But did you know that it can also be important for health in general? There is a link between inflammation of the gums and diseases like diabetes, cardiovascular disease, Alzheimer’s and RA.

The ancient Greeks knew…

Was Hippocrates right? His theory around 400 BC was that pulling out bad teeth could cure swollen, tender joints. An article on the subject was also published in 1918. It describes how, after “sterilization of the gums” and “polishing the root surfaces,” a patient recovered from both periodontitis and arthritis (1). It may sound wild, but the hypothesis isn’t as far off base as you might initially think.

Today we know that patients with periodontitis are overrepresented among people with RA (2), and meticulous research is underway to try to understand why.

Researchers at Karolinska Institutet in Stockholm, Sweden, are investigating whether it could be related to the bacteria in our mouths.

Bacteria – friend or foe?

There are over 100 billion bacteria in the human body. Most of them are in the gut, but fully six billion are in the mouth. We actually have more bacteria in our bodies than cells. That might sound scary, but for the most part, bacteria are good for us. The bacterial community is an ecosystem that helps us take advantage of the nutrients in the food we eat, protects us from chemicals we consume, and trains our immune system (3).

At the same time, bacteria are a constant threat. Disruptions to the ecosystem can lead to so-called dysbiosis. Put simply, dysbiosis is a disruption in the balance between good and bad bacteria, and the bad bacteria take over. One of these bad bacteria is Porphyromonas gingivalis, which we will come back to.

Periodontitis – among the most common diseases in the world

When bad bacteria increase in number, our immune system is activated, just as it is programmed to do with external threats. A complex cascade of biological reactions that cause inflammation begins, with the goal of eliminating the danger. But for some people, it is as if the immune system’s brakes don’t work, which entails a significant risk of the inflammation becoming chronic – and that is what happens with periodontitis.

The first symptom is bleeding gums. At a later phase, the teeth may become loose, because the jawbone is breaking down. Periodontitis affects up to 50% of adults with varying degrees of severity. Treatment involves mechanical teeth cleaning by a dental hygienist or dentist, or through surgery.

Can gum bacteria trigger RA?

Studies now show dysbiosis in the oral cavity of people with RA (4). Dysbiosis is also present in people who run an increased risk of developing RA (5, 6). These high-risk individuals don’t have joint inflammation, but they do have the same kind of antibodies as people with RA, i.e., antibodies targeting the body’s own tissue.

These antibodies can be measured in the blood and are very helpful when diagnosing RA. In addition, they are thought to be directly involved in the disease process. Experimental studies show, for example, that the antibodies may cause pain and activate cells that break down the bone (7, 8). However, we do not know how or why these antibodies form. One hypothesis of researchers at Karolinska Institutet is that the bacteria we mentioned earlier, P. gingivalis, is involved.

In an earlier analysis of blood samples from nearly 2,000 individuals recently diagnosed with RA, the researchers discovered a link between the presence of P. gingivalis and RA antibodies (9). In an ongoing project, they are studying gum biopsies to determine whether P. gingivalis might trigger the cells in the oral cavity to produce antibodies that then interact with the body’s tissue, which could lead to autoimmune diseases, as in the case of RA.

An opportunity for influence

The current research supports the idea of a connection between gum bacteria and arthritis. This information raises the question of whether you can influence the course of disease by restoring the balance between good and bad bacteria in the mouth.

There are not currently any large controlled studies, but overall, a number of smaller studies show promising results for people with RA. By mechanically removing tartar and bacteria, people have been able to reduce disease activity and levels of inflammatory markers in the blood (10-12). It has also been observed that RA patients with periodontitis do not respond as well to RA treatment as those without periodontitis (13).

We may not need to be as drastic as they were in antiquity, but it can’t hurt to pay attention to your oral health and start flossing.

Sources

1. Sturridge. Case of rheumatoid arthritis treated by ionization of periodontal membrane. Proc R Soc Med 1918, 11 (Odontol Sect): 112–4.

2. Fuggle et al, Hand to Mouth: A Systematic Review and Meta-Analysis of the Association between Rheumatoid Arthritis and Periodontitis. Front Immunol. 2016, 2;7:80

3. Deo and Deshmuk. Oral microbiome: Unveiling the fundamentals. J Oral Maxillofac Pathol. 2019, 23(1): 122–128.

4. Zhang et al. The oral and gut microbiomes are perturbed in rheumatoid arthritis and partly normalized after treatment. Nat Med. 2015, 21(8):895-905.

5. Tong et al. Oral Microbiota Perturbations Are Linked to High Risk for Rheumatoid Arthritis. Front Cell Infect Microbiol. 2020, 22;9:475

6. Cheng et al. Dysbiosis in the oral microbiomes of anti-CCP positive individuals at risk of developing rheumatoid arthritis. Ann Rheum Dis. 2021, 80(2):162-168.

7. Wigerblad et al. Autoantibodies to citrullinated proteins induce joint pain independent of inflammation via a chemokine-dependent mechanism. Ann Rheum Dis. 2016, 75(4):730-8.

8. Krishnamurthy et al. Identification of a novel chemokine-dep. Molecular mechanism underlying RA-associated autoantibody-mediated bone loss. Ann Rheum Dis. 2016, 75(4):721-9.

9. Kharlamova et al. Antibodies to Porphyromonas gingivalis Indicate Interaction Between Oral Infection, Smoking, and Risk Genes in Rheumatoid Arthritis Etiology. Arthritis Rheumatol. 2016, Mar;68(3):604-13

10. Ortiz et al. Periodontal therapy reduces the severity of active rheumatoid arthritis in patients treated with or without tumor necrosis factor. J Periodontol. 2009, 80(4):535–540.

11. Białowąs et al. Periodontal disease and influence of periodontal treatment on disease activity in patients with rheumatoid arthritis and spondyloarthritis. Rheumatol Int. 2020, 40(3):455-463

12. Moura et al. Clinical and microbiological effects of non-surgical periodontal treatment in individuals with rheumatoid arthritis: a controlled clinical trial. Odontology. 2021, 109(2):484-493.

13. Tachibana et al. Does periodontitis affect the treatment response of biologics in the treatment of rheumatoid arthritis? Arthritis Res Ther. 2020, 25;22(1):178.