Exploring the latest evidence on the link between oral health and systemic diseases

Q & A with Prof. David Williams


FDI published a briefing note entitled “WHY and HOW to integrate oral health into the NCD and UHC responses” for policymakers in October 2021 under the guidance of the Science Committee, which is chaired by Prof. David Williams. We sat down with Prof. Williams to discuss the latest evidence and how the implementation of the five action-orientated key messages could safeguard the health and well-being of our communities.

David Williams interview

The link between oral diseases and other health conditions has been a topic of interest for many years with the issue of causation versus association being hotly debated. For which conditions is the evidence the strongest and what does it show?

The relationship between oral and systemic disease is well established; they share the same social determinants and common modifiable risk factors. The issue of causation versus association has been hotly debated and, whilst evidence for the former is weak, there is good evidence for the existence of important associations between periodontal disease with diabetes, cardiovascular disease, and kidney disease.

The association between diabetes and periodontal disease is well established. Poorly controlled diabetes affects both the development and often rapid progression of periodontal disease, whereas well-controlled diabetes is not associated with an increased risk.

What is some of the emerging evidence that links oral health with other diseases?

Recent research has implicated subgingival inflammation in the pathogenesis of diabetes. This is a fast-moving area of research, and the evidence is sometimes conflicting. However, it does appear clear that subgingival inflammation is associated with the development of diabetes and, in those who already have diabetes, severe periodontitis is associated with a higher prevalence of complications such as cardiovascular disease, retinopathy and kidney disease. This means that it is critically important that patients with diabetes receive appropriate oral healthcare to manage their periodontal health appropriately. Promisingly, there is early evidence that treating periodontal disease can lower haemoglobin A1c levels, which has important implications for diabetic control.

Good oral health is also particularly important in those with kidney disease. What might be a minor infection for a healthy person could be major problem for someone with kidney disease, because serious dental infections can delay, and even prevent, patients being approved for a renal transplant.

There is also evidence of associations between oral disease – particularly periodontal disease – and Alzheimer’s disease, rheumatoid arthritis, and adverse pregnancy outcomes. The emerging evidence for these associations between oral and systemic disease is being carefully studied by the FDI Science Committee, because it may have important implications for treatment and policy. 

How does understanding the links between oral health and other systemic diseases help to improve the health and well-being of people?

The emerging evidence that I have described is already having important implications for patient care. The need for close cooperation between the oral healthcare team and the medical team in the care of patients with diabetes is already established, and it is crucial that these patients have good periodontal health. I have already mentioned the importance of good oral health in patients with kidney disease and in the US the National Kidney Foundation recommends that oral examination should be part of the kidney transplant evaluation process.

These are two examples of why it is so important that oral and general healthcare are integrated, and we will be watching out for others. It is evidence such as this that supports the case for closer integration of oral and general healthcare, which is one of the key pillars of FDI’s Vision 2030: Delivering Optimal Oral Health for All.

Are we having the wrong debate? Oral health is a key indicator of general health, well-being and quality of life and with dental caries (tooth decay) in permanent teeth being the most prevalent disease worldwide, affecting more than one in four people and a shocking 520 million children suffering from caries of primary teeth why does the oral health community have to fight so hard for oral diseases to be prioritized by individuals and governments?

I don’t think we are having the wrong debate, but we need to do better at showing our patients and the population at large why oral health is important. Once people understand this, they will become more demanding of governments and policymakers to address their concerns. When talking about disease associations, our aim is not to highlight why oral diseases should be prioritized over other conditions, rather that they SHOULD be prioritized and to provide solutions on how this could be done. For governments this is through demonstrating how oral health can be integrated into existing health responses. And for individuals it’s about improving oral health literacy and highlighting how adopting good oral hygiene routines and managing risk factors not only benefits their oral health but their overall health and well-being too.    

The health community is getting better at breaking down silos and working together to focus on treating the person not the disease, to preserve overall health. This is clearly demonstrated, for example, by the strong partnership FDI has developed with the NCD Alliance with whom we work closely to push for common goals and the implementation of evidence-based strategies to protect population health. Such strategies are highlighted in the new policy brief, we developed jointly with them. This outlines solutions for the integration of oral health promotion and oral healthcare into noncommunicable disease (NCD) strategies and universal health coverage (UHC) benefit packages.

Traditionally, we have talked about taking a Common Risk Factor Approach (CRFA) to tackling oral diseases and other NCDs. However, poor oral health can in itself be a risk factor for other NCDs. Can you please explain this?

The fact that oral diseases and the other major NCDs share the same social determinants and common modifiable risk factors such as unhealthy diets – high in sugar, tobacco and alcohol use, is well established. Indeed, it is the justification for creating comprehensive cross-disciplinary health promotion programmes and uniting efforts across sectors.  

However, a lesser-known fact is that poor oral health is itself a risk factor for other NCDs. I have already mentioned that poor oral health is an established risk factor for diabetes, cardiovascular disease and kidney disease. There is accumulating evidence for its importance in Alzheimer’s disease and rheumatoid arthritis too. And there is evidence that implicates periodontal disease in the causation of adverse pregnancy outcomes, including pre-term birth and low birth weight, although the evidence for this is contentious. The common factor in all of these diseases is a pathogenic shift in the oral microbiome causing inflammation that results in the release of a range of inflammatory factors into the circulation. These in turn affect the target organs of these diseases and exacerbate the condition. Therefore, it makes sense that oral health is integrated into NCD and UHC responses.

What is the role of the oral microbiome in health and disease not just of the mouth but systemic health?

The normal microbiome comprises a stable population of microorganisms which exist in harmony with each other and with us. The composition of the microbiome is specific to the body site that it colonizes, so the oral microbiome differs in composition of the skin or the gut. Our microbiome is essential for the maintenance of our health and preventing the colonization by pathogenic invasive bacteria and other microorganisms. When this fails there may be a pathogenic shift in the oral microbiome called dysbiosis. Interestingly the keystone periodontal pathogen Porphyromonas gingivalis is being heavily implicated in this shift. This results in the generation of range of inflammatory factors that modulate the local disease process. However, these factors may also enter the circulation and affect remote sites causing disease.

What is the role of the dentist in educating their patients on the link between poor oral/gum health and poor systemic health?

The maintenance of good health depends on a partnership between us as clinicians and our patients. And for this to be achieved our patients need to have a sufficient understanding of how to care for their own health. In other words, they need to have a sufficient level of health literacy. This is true both of oral as well as general health, so we have a responsibility to ensure that our patients, or their carers, are oral health literate for this partnership to be effective.

If we meet again, one year from now what progress do you hope to have been made towards securing oral health for all?

The new resolution on Oral health adopted by WHO’s World Health Assembly in May 2021, provides an opportunity to make great strides in the prevention and control of oral diseases. This resolution puts oral health back on the global health agenda, and it formally recognizes the need to address oral health as an integral element of both the NCD and UHC responses. It is an implementation-oriented document that asks WHO to develop a 2022 Global strategy on tackling oral diseases, a 2023 Action plan for public oral health with 2030 targets, technical guidance, and NCD “best buys”.

FDI, its members and other health partners are already contributing to progress being made, by, for example, providing input into the draft WHO Global strategy on tackling oral diseases, where 65 organizations supported FDI’s response. By speaking with one voice and calling for the same priorities our messages will be heard more loudly and hopefully make a bigger impact to effect positive change. The draft strategy’s vision also fully aligns with FDI’s own Vision 2030, which again amplifies our messages.

If we were to meet again in a year, I would hope that WHO Member States and governments have worked with our national dental organizations and member associations in the development of their local oral health action plans that are integrated within the NCD and UHC responses and include achievable targets. I would also hope that we have built even stronger collaborations across health conditions, sectors, and professions to work towards the common goal of protecting the health and well-being of our communities.


Read the briefing note