When I first qualified as a Dental Hygienist in 1988 the thing that gave me to most clinical trepidation was treating Periodontal Disease (PD), despite my training. I can recall my very first case as a green “rookie” hygienist they were young, a heavy smoker with established disease which was active and unstable. I did my best instrumently, following my training, and when I reviewed them, a few weeks later the resolution and repair I witnessed was astonishing. I felt quite proud of my efforts but was crestfallen to learn they had had a prescription for antibiotics for a separate health condition in the meantime. My dentist gently alluded me to the fact that my treatment alone probably wasn’t entirely responsible for the startling outcome. It became very apparent to me that the systemic benefits of medicine had enhanced the patients host response and had significantly aided his dental disease recovery. This systemic “assistance” made me reflect at quite an early stage of my career, in the complexity and ingenuity of the immune system.
Globally, PD is the sixth most prevalent disease affecting over 11% of the world, rising by 57.3% from 1990 to 2010 1. Periodontitis is a major cause of tooth loss in adults, in particular the aging population and vulnerable sections of society 2, 3, 4. The New Zealand population study, undertaken in Dunedin, indicated that untreated adult gum disease in adulthood is associated with negative childhood low economic status 5. PD is classed as a Non-Communicable Disease (NCD) and shares social determinents and risk factors with other NCDs that cause about two-thirds of causes of death such as heart disease, diabetes, cancer, as well as, more topically, respiratory related diseases 5.There is a growing body of evidence that the effects of PD reach beyond the oral cavity with bacteria and associated inflammatory by-products systemically travel from the point of origin to other parts of the body, helping, over time, to initiate various NCDs. The loss of teeth due to the PD process affects mastication, likely changing dietary habits as a consequence to a more sugar and fat based diet and less fruit and vegetables. In turn this has the potential to increase the systemic inflammatory burden further by increasing the degree of PD, tooth decay, and possibly increasing further risk of NCDs 6.
The mouth has often been described as “the window to general health” with oral systemic health, of late, being seen as the connection the oral cavity and health with overall health. The mouth hosts a unique population of microorganisms numbering between 500 -700 7. The quality of individual oral hygiene significantly impacts how they organise themselves culturally and ecologically, with better maintenance allowing beneficial varieties to thrive and dominate. This is balanced by products found in the oral cavity being regularly bathed by a complex of components from saliva and, from between the tooth and gum, crevicular fluid, both playing an important natural role, mediating and balancing the oral environment 8, 9.
Much research has investigated the relationship between PD and cardiovascular disease (CVD) and has proven diverse and varied 10, 11. CVD is amongst the most common medical problems globally, being responsible for the 33% of deaths in New Zealand and 30% in the USA 12, 13. Oral inflammation, from gingivitis, opens the systemic pathway for pathogenic bacteria to travel to blood vessels elsewhere in the body where they can cause inflammation and damage to arterial walls. The remnants of oral bacteria can be found within atherosclerotic blood vessels far from its origin in the mouth. An alternative theory is that the body’s inflammatory immune response sets off a cascade of vascular damage throughout the body, including the heart and brain. They may also be no direct connection between CVD and PD, and the process maybe mediated through other factors like smoking, negative lifestyle choices, genetics and poor nutrition 14. A large cohort study in 2018 observed nearly 1 million people in Korea of a variety of ages from 30. The conclusion demonstrated the relationship between poor oral health and coronary heart disease risk was confounded by smoking, making causation indeterminable 15.
Pulmonary diseases like pneumonia, chronic obstructive pulmonary diseases and chronic bronchitis bring bacteria from the mouth via the oropharynx into the respiratory tract 14. The immune-compromised who are critically ill and intubated are at risk from bacteria seeding of the lower respiratory tract. Multiple intervention studies have shown that improving the oral hygiene of ventilated cases decreased the risk of ventilator associated pneumonia 16, 17. Aligned with this, evidence that poor dental health is causal in such conditions is at present inconclusive, where institutionalised and ventilated patients are at high risk, those with improved oral hygiene has indicated a positive outcome to their systemic health 18. This research requires careful consideration and appropriate action regarding oral health messages given to institutions nursing and treating risk populations during flu outbreaks and the present COVID 19 global epidemic.
Diabetes is a disease of disrupted glycaemic control resulting from a lack of insulin (type 1) or systemic insulin resistance (type 2)19. Their share a bidirectional association with PD. It negatively impacts oral health but also, conversely, glycaemic control and those affected with diabetes can be up to three times a greater risk of PD than those who aren’t. Those who have well controlled diabetes comparatively have no increased risk 20, 21.
Obesity is a chronic disease affecting 42.8% of middle-age adults, is closely related to several other chronic diseases, including heart disease, hypertension, type 2 diabetes, sleep apnea, certain cancers, joint diseases, and more. Obesity is defined as excessive body fat in proportion to lean body mass, to the extent that health is impaired. It is associated with chronic low grade inflammation and both local and system oxidative stress, in which it links to PD in oral health 22. Clinical PD studies reveal significant correlations with body mass indices, insulin and lipid levels and oxidative stress markers 23.
Our systemic health can be measured, in part, by looking more closely and specifically at metabolic risk factors that includes obesity, insulin resistance, hypertension and dyslipidaemia. If these factors are dysfunctional, it is termed as Metabolic Syndrome (MetS) and is often characterized by oxidative stress, a condition in which an imbalance results between the production and activation of reactive oxygen species. MetS is thought to play a major role in the pathogenesis of a variety of human diseases, including atherosclerosis, diabetes, hypertension, aging, Alzheimer’s disease, kidney disease and cancer 24. MetS allows the a pro-oxidative state in periodontal tissue, altering antioxidant defence mechanisms, affecting its response against bacterial plaque attack 25. The components that are most closely related to the risk of periodontitis are dysglycaemia and obesity, but less from atherogenic dyslipidaemia and hypertension, with a risk of increase linked to more MetS components in an individual. However, due to the cross-sectional nature of studies, a direct relationship can’t as yet be established. However evidence suggests that a reduction in serum inflammatory mediators can be achieved through successful periodontal therapy 26. A recent systematic review and meta-analysis reinforces the association between MetS and PD demonstrating a 38% greater likelihood amongst at MetS sufferers to present with PD in relation to those who without 27.
Dental professionals can play a key role in promoting avoiding or reducing the risks to individuals with MetS. Moving from a poor diet of foods with high glycaemic index (GI) towards nutrient rich, high fibre food like fruit and vegetable, as well as maintaining good oral hygiene is fundamental for individuals with MetS. This also has a positive role on affect to improving heart health, reducing tooth loss, which in many alter masticatory function and promotes poor dietary choices 28.
It is important for dental healthcare professionals to understand the oral-systemic links to improving dental health in our patient populations, especially in our present COVID 19 era and oral hygiene recommendations to at-risk groups. I predict we will also soon see an increase in the knowledge base of the significance of the mechanisms of MetS beyond dentistry into the realms of general health. But to understand MetS better we need to take a journey with free thinking fellow healthcare professionals, key influencers, and protagonists involved in the emergence of this key medical field. This will be the theme and feature of part 8b.
So, to conclude, our current knowledge base from the preceding decades of my first clinical journey into PD to the present has and will continue to evolve. This growing body of research has enhanced the awareness of the links between PD and systemic health in general, but more importantly appropriate specific oral health interventions that can improve health outcomes. I feel the moment will soon come when as allied health professionals we will better combined, collaborative and successful approaches to the treatment of the NCDs.
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