Systemic diseases caused by oral microorganisms.

Human endodontic and periodontal infections are associated with complex microfloras in which approximately 150, (in apical periodontitis) and 350 (in marginal periodontitis) bacterial species have been encountered. These infections are predominantly anaerobic, with gram-negative rods being the most common isolates. The anatomic closeness of this microflora to the bloodstream can facilitate bacteremia and systemic spread of bacterial by-products and immunocomplexes. A variety of clinical procedures such as tooth extraction, periodontal and endodontic treatment, may cause translocation of microorganisms from the oral cavity to the bloodstream. The microorganisms that gain entrance to the blood circulate throughout the body, but are usually eliminated by the host (reticuloendothelial system) within minutes. However, in patients with ineffective heart valves or vascular diseases, bacteremia can be a potential danger, leading most commonly to infective endocarditis and myocardial or cerebral infarction. Other forms of systemic diseases such as brain abscesses, hematological infections and implant infections have also been related to oral microorganisms.