Focal infection theory(병소감염이론)

Focal infection theory

From Wikipedia, the free encyclopedia

Jump to: navigation, search

For the epidemiology concept, see Focus of infection

Focal infection theory (FIT) describes a localized site of infection that disseminates microorganisms or their toxins to distal locations, which thereupon host secondary infections that initiate, sustain, or worsen systemic diseases, usually chronic, such as atherosclerosis or arthritis or cancer.^[1][2][3][4] (The criterion of spread to distant sites distinguishes focal infection from infectious spread by progressively expanding invasion of local tissues.)^[5][6] Such idea is ancient, yet took modern form around 1900, and was widely accepted in Anglosphere medicine by the 1920s.^[4][6][7][8]

In the theory, the focus of infection is often unrecognized, while secondary infections might occur at sites particularly susceptible to such microbial species or toxin.^[6] Several locations were commonly claimed as foci—appendix, bladder, gall bladder, kidney, liver, prostate, and sinuses—but most commonly oral tissues. Not only dental decay, but also sites of dental restoration and root canal therapy were indicted as the foci.^[4][6] The putative oral sepsis was countered by tonsillectomies and tooth extractions, including of endodontically treated teeth and even of apparently healthy teeth, newly popular approaches—sometimes leaving individuals toothless—to treat or prevent diverse chronic diseases.^[4]

Drawing severe criticism in the 1930s, focal infection theory, whose popularity far outstripped evidence, was generally discarded in the 1940s amid overwhelming evidence of its general falsity, whereupon dental restorations and root canal therapy became again favored.^[4][6] Untreated endodontic disease retained recognition as fostering systemic disease,^[4][6] but only alternative medicine and later biological dentistry continued highlighting sites of dental treatment—root canal therapy, dental implant, and, as newly claimed, tooth extraction, too—as foci of infection promoting systemic diseases.^[9] The primary recognition of focal infection is endocarditis if oral bacteria enter blood and infect the heart, perhaps its valves.^[5]

Entering the 20th century, scientific evidence supporting general relevance of focal infection theory remained slim, yet evolved understanding of disease had granted the theory a third possible mechanism—altogether, metastasis of infection, metastatic toxic injury, and, recently revealed, metastatic immunologic injury—that might occur simultaneously, even interacting.^[5][10] Meanwhile, focal infection theory has resurged, as dental infections apparently are widespread and significant contributors to systemic diseases, but mainstream attention is on ordinary periodontal disease, not hypotheses of stealth infections at sites of dental treatment.^[11][12][13] Despite some doubts renewed from dentistry's fringe since the 1990s, dentistry scholars maintain that endodontic therapy can be performed without creating focal infections.^[4][6]