Periodontitis and atherosclerosis are highly prevalent chronic inflammatory conditions with complex and multifactorial etiology. The association between the two has been studied extensively over the last few decades. In recent years, an accumulating amount of studies support an association between Porphyromonas gingivalis and atherosclerosis. With new animal research also providing preliminary evidence of how oral bacteria can change to avoid host immune detection and establish infection.
Background
Periodontitis is initiated by the accumulation of dental plaque with a subsequent gingival inflammatory immune response that may progress to the destruction of connective tissue and alveolar bone.
Atherosclerosis, on the other hand, is characterised by initial endothelial injury followed by invasion of macrophages, accumulation of lipids and calcification of the subendothelial layer, which often results in significant morbidity and mortality.
Indeed, atherosclerosis is the leading cause of disabling and life-threatening conditions such as myocardial infarction and stroke in the developed world, accounting for one in three of all deaths worldwide. Each year an estimated 124,000 deaths are caused by cardiovascular disease in England and Wales alone.
Risk factors such as smoking, hypertension, obesity and hypercholesterolemia were traditionally thought to be associated with atherosclerosis. However, observational studies have found that these risk factors do not appear to fully account for the development of the condition. Evidence is now accumulating that demonstrates a positive correlation between periodontal disease and atherosclerosis. The current data is still insufficient to support a causal
relationship, but it is believed the host immune response plays a significant role in the pathogenesis of atherosclerosis.
Innovative research
Porphyromonas gingivalis is one of the main periodontopathogens responsible for inducing a local inflammatory response that results in oral bone destruction and manifests as periodontal disease. In addition to inflammation induced at the primary site of infection, P. gingivalis has been detected and shown to be viable in atherosclerotic lesions and tissue.
Porphyromonas gingivalis accelerates vascular inflammation through several mechanisms including the activation of toll-like receptors, increasing the production of pro-inflammatory mediators and the expression of cellsurface adhesion molecules, hence causing the apoptosis of vascular cells and triggering blood clots. Inflammatory responses are the driving force of atherosclerosis, a process that involves the hardening and thickening of artery walls due to excess fatty deposits.
Similar to other gram-negative bacteria, P. gingivalis has an outer layer that consists of sugars and lipids. The immune system can detect parts of the bacterial coating via the host recognition of atypical lipopolysaccharide (LPS) expressed on the bacterial membrane by the innate immune receptor, toll-likereceptor-4 (TLR4). This then triggers a multi-pronged immune reaction that eradicates the pathogen from the host.
In a study, published in July 2014, scientists revealed how the pathogen, P. gingivalis, evades the immune system in mice to induce inflammation beyond the oral cavity. Like several other successful pathogens, P. gingivalis has evolved mechanisms to avoid the host immune defence, resulting in the establishment of persistent and chronic infections. This is achieved by modifying their lipid A structure, which is the component of bacterial LPS that directly activates the TLR4 complex. Therefore, the gram-negative oral anaerobe can evade the immune response and establish local and systematic infection.
Prevention
As periodontal disease has been associated with higher risks of several different conditions, good dental health is imperative to reduce the build-up of dental biofilm.
Employing the use of adjuncts, such as the Waterpik Water Flosser, can help improve oral health and prevent the build-up of plaque and the on-set of gingivitis. The innovative product has been shown to reduce the proinflammatory mediators in the gingival crevicular fluid and serum.
Evolving research continues to support a correlation between the periodontitis and atherosclerosis and further highlights the importance of preventing periodontal disease by maintaining an effective oral health routine. Practitioners are encouraged to educate patients on oral hygiene and offer easy-to-use adjuncts.
References available on request.