Mouth-Bacteremia Relationships

(Oral Bacteria Entering the Circulatory System)

The prevalence of blood entering the blood stream (bacteremia(s)) following dental procedures such as tooth extraction, endodontic treatment, periodontal surgery, and root scaling has been well studied and well documented. Bacteremias have been observed in;

  • 100% of the patients following a dental extraction,
  • 70% following dental scaling,
  • 55% following third-molar surgery, and
  • 20% following endodontic (root canal) treatment.

In a report of a study that treated 735 children for extensive dental caries, it was reported that 9% of the children had detectable bacteremias prior to any initiation of dental treatment. In addition, a variety of oral hygiene and other conservative procedures, such as tooth brushing, increased bacteremia prevalence to 17 – 40%.

Researchers have traced microorganisms released into the bloodstream during and after root canal treatment back to their recognized source, the root canal. The collected bacteria samples from root canals and blood of these individuals revealed that all root canals contained anaerobic bacteria (bacteria that don’t like oxygen). When bacteria samples were collected at a level 2 mm beyond the end of the tooth root, PropionibacteriumacnesPeptostreptococcus prevotii,Fusobacterium nucleatumPrevotellaintermedia, andSaccharomyces cerevisiae were recovered from the blood. When root canal instrumentation ended inside the roo tcanal, P. intermedia,Actinomyces israeliiStreptococcus intermedius,and Streptococcus sanguis were isolated from the blood. This study showed that distribution of oral microorganisms into the bloodstream is common and occurred less than 1 min after an oral procedure. These bacteria can be transported to the heart, lungs, and peripheral blood capillary system.

In the 19 and early 20 centuries, the hypothesis of focal infection was presented, which stated that “foci” of sepsis were responsible for the initiation and progression of a variety of inflammatory diseases such as arthritis, peptic ulcers, and appendicitis. Consequently, in the oral cavity, therapeutic edentulation was common, due to the popularity of the focal infection theory. Since many teeth were extracted without evidence of infection, and provided no relief for systemic complaints and symptoms, this theory was discredited, and for the most part ignored for many years. However, more recently, improvement in the classification and identification of oral bacteria, along with the understanding that certain bacteria are by and large only found in the oral cavity, initiated a more reasonable evaluation of the significance of oral ‘focal’ infection. It then became clearer that the oral cavity can act as the site of origin for the spreading of pathogenic organisms to distant body sites, especially in immuno-compromised hosts, such as patients suffering from malignancies, diabetes, or rheumatoid arthritis, or having corticosteroid or other immunosuppressive therapy. Several epidemiological studies then suggested that oral infection, especially those associated with periodontitis, may be a risk factor for systemic diseases.

Millions of microorganisms are present on all body surfaces; however the underlying tissues and bloodstream are typically sterile. Several barriers exist in the oral cavity that helps to prevent bacterial infiltration from dental plaque into the surrounding tissues. These systems work together to reduce and eliminate invasive bacteria. They include:

  • a physical barrier, the surface epithelium;
  • defensins, which are host-derived peptide-antibiotics located in the oral mucosal epithelium;
  • an electrical barrier that reflects the electrical diversity between the host cell and bacteria;
  • an immunological barrier of antibody-forming cells; and
  • the reticuloendothelial system (a phagocyte barrier).

If this balance is disturbed by an apparent breaking; the physical system (e.g., trauma to the epithelium), the electrical system (e.g., through hypoxia), or immunological barriers (e.g., through neutropenia, AIDS, or immunosuppressant therapy), bacterial organisms can then proliferate, causing both acute and chronic infections with increased regularity and severity.

Bacterial levels on the teeth can reach millions of microorganisms per mg of dental plaque, and human root canal and periodontal infections are associated with complex microfloras in which approximately 200 species (in apical periodontitis) and more than 500 species (in marginal periodontitis) have been identified. These infections are predominantly anaerobic (don’t like oxygen) gram-negative rods, however other bacteria are also present. The anatomic proximity of these bacterial species in relation to the bloodstream can facilitate bacteremia and the systemic spread of bacterial products, components, and immunocomplexes.

In normal oral health and adequate dental care, only small numbers of mostly facultative (oxygen tolerant) bacterial species gain entrance into the bloodstream. Poor oral hygiene, considerably increases the numbers of bacteria colonizing the teeth, especially supragingivally (above the gums), by 2- to 10-fold and could perhaps introduce more bacteria into the surrounding tissues and the bloodstream, leading to an increased frequency and degree of bacteremia.