There are many systemic diseases that have been linked to periodontal diseases and other dental infections over the years. These diseases are generally the direct or indirect result of the microorganisms that cause infections in the oral cavity. These diseases are generally caused by one of five mechanisms. The first two mechanisms are generally associated with larger infections such as dental abscesses, pericoronitis, or advanced periodontal disease. The third and fourth mechanisms are associated with smaller more chronic problems such as periodontal disease.
- Bacteremia – Bacteria from the oral cavity travel by way of the vascular system directly to other tissues which they infect and damage. (Ex. Bacterial endocarditis, congestive heart failure, artificial joint reinfection)
- Embolism – Microorganisms from the oral cavity spread into the venous system where they bind to various blood cells causing a large mass which forms a blockage. These blockages are called a thrombosis. If the thrombosis starts to move it is called an embolism. These blockages can block arteries causing hypoxia and tissue damage. Also, toxins and other metabolic products from microorganisms in the embolism can affect nearby tissues.(Ex. Stroke, myocardial infarction, lung cancer, and several neurological diseases.)
- Metabolic Products of Microorganisms – In this case the microorganisms themselves do not migrate to the targeted tissues. Only the metabolic products of the bacteria spread to the tissues involved. Because most of these products are proteins which are recognized as foreign protein; a second inflammatory response occurs at this sight. Because this is an inflammatory response in the absence of microorganisms; this clinical situation may easily be mistaken for an autoimmune disease. The main sights of concentration of these protein metabolic products are the three main filter sights of the cardiovascular system namely the lungs, kidneys, and liver. This is the mechanism involved in periodontal disease as well as some forms of lung, kidney, and liver diseases. It may also be one mechanism that plays a part in some cases of MS and Dementia.
- Inflammation – Microorganisms in plague can damage far away tissues indirectly through the process of inflammation. When there is a chronic infection such as periodontal disease; there is chronic inflammation attacking this infection. In this case it is the immune cells involved in inflammation that produce and release a lot of inflammatory products which are released into the vascular system and spread to other tissues where they cause problems. The products released by the inflammatory cells include prostaglandin E2, interleukin 1B,cytokines,and tumor necrosis factor(TNF). Also, prostaglandins and cytokines cause the liver to produce C-reactive protein. These products get into the blood stream and affect other tissues and organs throughout the body.(Ex. Diabetes mellitus, low birth weight babies, osteoporosis, Alzheimer’s disease, and possibly rheumatoid arthritis.)
- Cancers – Cancers can be caused by microorganisms of oral origin. If the microorganisms can produce metabolic products that are carcinogenic; then they can produce cancers. For example, E. Coli can produce polycyclic hydrocarbons from any substrate and the mold, Aspergillus Flavis can produce the carcinogen Aflatoxin. These microorganisms can easily travel to the lungs as embolisms or to the brain through the mechanism described with the neurological diseases.(Ex. Pancreatic cancer, gastric cancer, lung cancer, and various brain cancers.)