focal infection theory focal infection theory focal infection theory is the historical concept that many chronic diseases, including systemic and common ones, are caused by focal infections. in present medical consensus, a focal infection is a localized infection, often asymptomatic, that causes disease elsewhere in the host, but focal infections are fairly infrequent and limited to fairly uncommon diseases. (distant injury is focal infection's key principle, whereas in ordinary infectious disease, the infection itself is systemic, as in measles, or the initially infected site is readily identifiable and invasion progresses contiguously, as in gangrene.) focal infection theory, rather, so explained virtually all diseases, including arthritis, atherosclerosis, cancer, and mental illnesses. for the epidemiology concept, see focus of infection. an ancient concept that took modern form around 1900, focal infection theory was widely accepted in medicine by the 1920s. in the theory, the focus of infection might lead to secondary infections at sites particularly susceptible to such microbial species or toxin. commonly alleged foci were diverse—appendix, urinary bladder, gall bladder, kidney, liver, prostate, and nasal sinuses—but most commonly were oral. besides dental decay and infected tonsils, both dental restorations and especially endodontically treated teeth were blamed as foci. 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 diseases. drawing severe criticism in the 1930s, focal infection theory—whose popularity zealously exceeded consensus evidence—was discredited in the 1940s by research attacks that drew overwhelming consensus of this sweeping theory's falsity. thereupon, dental restorations and endodontic therapy became again favored. untreated endodontic disease retained mainstream recognition as fostering systemic disease. but only alternative medicine and later biological dentistry continued highlighting sites of dental treatment—still endodontic therapy, but, more recently, also dental implant, and even tooth extraction, too—as foci of infection causing chronic and systemic diseases. in mainstream dentistry and medicine, the primary recognition of focal infection is endocarditis, if oral bacteria enter blood and infect the heart, perhaps its valves. entering the 21st century, scientific evidence supporting general relevance of focal infections remained slim, yet evolved understandings of disease mechanisms had established a third possible mechanism—altogether, metastasis of infection, metastatic toxic injury, and, as recently revealed, metastatic immunologic injury—that might occur simultaneously and even interact. meanwhile, focal infection theory has gained renewed attention, as dental infections apparently are widespread and significant contributors to systemic diseases, although mainstream attention is on ordinary periodontal disease, not on hypotheses of stealth infections via dental treatment. despite some doubts renewed in the 1990s by conventional dentistry's critics, dentistry scholars maintain that endodontic therapy can be performed without creating focal infections. rise and popularity (1890s–1930s) germ theory hippocrates, in ancient greece, had reported cure of an arthritis case by tooth extraction. yet focal infection, as such, appeared in modern medicine in 1877, when karl weigert reported "dissemination of 'tuberculosis poison' ". the prior year's breakthrough by robert koch, a fellow german, had launched medical bacteriology—a set of laboratory methods to isolate, culture, and multiply a single bacterium of one species—whereby koch announced discovery of the "tubercle bacillus" in 1882, fully premising the modern principle of focal infection. in 1884, william henry welch, tasked to design the medical department at the newly forming johns hopkins university, imported the german model, "scientific medince", to america. as progressively more diseases drew an infectious hypothesis that led to a pathogen discovery, conjectures grew that virtually all diseases are infectious. in 1890, german dentist willoughby d miller attributed a set of oral diseases to infections, and attributed a set of extraoral diseases—as of lung, stomach, brain abscesses, and other conditions—to the oral infections. in 1894, miller became the first to identify bacteria in samples of tooth pulp. miller advised root canal therapy. yet ancient and folk concepts, entrenched as galenic principles of humoral medicine, found new outlet in medical bacteriology, a pillar of the new "scientific medicine". around 1900, british surgeons, still knife-happy, were urging "surgical bacteriology". autointoxication in 1877, french chemist louis pasteur adopted robert koch's bacteriology protocols, but soon directed them to developing the first modern vaccines, and ultimately introduced rabies vaccine in 1885. its success funded pateur's formation of the globe's first biomedical research institute, the pasteur institute. in 1886, pasteur welcomed to paris the emigration from russia by international scientific celebrity elie metchnikoff—discoverer of phagocytes, mediating innate immunity—whom pasteur granted an entire floor of the pasteur institute, once it opened in 1888. later the institute's director and a 1908 nobelist, metchnikoff believed, as did his german immunology rival paul ehrlich—theorist on antibody, mediating acquired immunity—and as did pasteur, too, that nutrition influences immunity. metchnikoff brought to france its first yogurt cultures for probiotic microorganisms to suppress the colon's putrefactive microorganisms, which allegedly fostered the colon's toxic seepage causing degenerative disease, the putative phenomenon termed autointoxication. metchnikoff reasoned that the colon functions as a "vesitigal cesspool" that stores waste but is unneeded. abdominal surgery's pioneer, sir arbuthnot lane, based in london, drew from metchnikoff and clinical observation to identify "chronic intestinal stasis"—in lay terms, intractable constipation—presumably, "flooding of the circulation with filthy material". reporting surgical treatment in 1908, lane eventually offered total colon removal, but later favored simply surgical release of colonic "kinks", and in 1925, abandoning surgery, began promoting prevention and intervention by diet and lifestyle, how lane secured his contemporary reputation as a crank. since 1875, in the american state michigan, physician john harvey kellogg had targeted "bowel sepsis"—an allegedly prime cause of degeneration and disease—at his health resort, battle creek sanitarium. having, in fact, coined the term sanitarium, kellogg yearly received several thousand patients, including us presidents and celebrities, at his huge resort, advertised as the "university of health". but in the 1910s, as north american medical schools emulated the german model—that is, "scientific medicine"—medical doctors who recognized "focal infection" were hinting a scientific basis versus the older, alleged "health faddists" like medical doctor kellogg and like minister sylvester graham. hunter on "oral sepsis" in 1900, british surgeon william hunter blamed many disease cases on oral sepsis. in 1910, lecturing in montreal at mcgill university, hunter declared, "the worst cases of anemia, gastritis, colitis, obscure fevers, nervous disturbances of all kinds from mental depression to actual lesions of the cord, chronic rheumatic infections, kidney diseases are those which owe their origin to or are gravely complicated by the oral sepsis produced by these gold traps of sepsis." thus, he apparently indicted dental restorations. incriminating their execution, rather, his american critics lobbied for stricter requirements on dentistry licensing. still, hunter's lecture—as later recalled—"ignited the fires of focal infection". ten years later, he proudly accepted that credit. and yet, read carefully, his lecture asserts a sole cause of oral sepsis: dentists who instruct patients to never remove partial dentures. billings & rosenow focal infection theory's modern era really began with physician frank billings, based in chicago, and his case reports of tonsillectomies and tooth extractions that apparently cured infections of distant organs. replacing hunter's term oral sepsis with focal infection, billings in november 1911 lectured at the chicago medical society, and published it in 1912 as an article for the american medical community. in 1916, billings lectured in california at stanford university medical school, this time printed in book format. billings thus popularized intervention by tonsillectomy and tooth extraction. a pupil of billings, edward rosenow held that extraction alone was often insufficient, and urged teamwork by dentistry and medicine. rosenow developed the principle elective localization, whereby microorganisms have affinities for particular organs, and also espoused extreme pleomorphism, whereby a bacterium can drastically change form and perhaps evade conventional detection methods. preeminent recognition since 1889, in the american state minnesota, brothers william mayo and charles mayo had built an international reputation for surgical skill at their mayo clinic, by 1906 performing some 5,000 surgeries a year, over 50% intra-abdominal, a tremendous number at the time, with unusually low mortality and morbidity. though originally distancing themselves from routine medicine and skeptical of laboratory data, they later recruited edward rosenow from chicago to help improve mayo clinic's diagnosis and care and to enter basic research via experimental bacteriology. rosenow influenced charles mayo, who by 1914 published to support focal infection theory alongside rosenow. at johns hopkins university's medical school, launched in 1894 as america's first to teach "scientific medicine", the eminent sir william osler was succeeded as professor of medicine by llewellys barker, who became a prominent proponent of focal infection theory. although many of the hopkins medical faculty remained skeptics, barker's colleague william thayer cast support. as hopkins' chief physician, barker was a pivotal convert propelling the theory to the center of american routine medical practice. russell cecil, famed author of cecil's essentials of medicine, too, lent support. in 1921, british surgeon william hunter announced that oral sepsis was "coming of age". although physicians had already interpreted pus within a bodily compartment as a systemic threat, pus from infected tooth roots often drained into the mouth and thereby was viewed as systemically inconsequential. amid focal infection theory, it was concluded that that was often the case—while immune response prevented dissemination from the focus—but that immunity could fail to contain the infection, that dissemination from the focus could ensue, and that systemic disease, often neurological, could result. by 1930, excision of focal infections was considered a "rational form of therapy" undoubtedly resolving many cases of chronic diseases. its inconsistent effectiveness was attributed to unrecognized foci—perhaps inside internal organs—that the clinicians had missed. dental reception in 1923, upon some 25 years of researches, dentist weston andrew price of cleveland, ohio, published a landmark book, then a related article in the journal of the american medical association in 1925. price concluded that after root canal therapy, teeth routinely host bacteria producing potent toxins. transplanting the teeth into healthy rabbits, price and his researchers duplicated heart and arthritic diseases. although price noted often seeing patients "suffering more from the inconvenience and difficulties of mastication and nourishment than they did from the lesions from which their physician or dentist had sought to give them relief", his 1925 debate with john p buckley was decided in favor of price's position: "practically all infected pulpless teeth should be extracted". as chairman of the american dental association's research division, price was a leading influence on the dentistry profession's opinion. into the late 1930s, textbook authors relied on price's 1923 treatise. in 1911, the year that frank billings lectured on focal infection to the chicago medical society, unsuspected periapical disease was first revealed by dental x-ray. introduced by c. edmund kells, dental radiography to feed the "mania of extracting devitalized teeth". even price was cited as an authoritative source espousing conservative intervention at focal infections. kells, too, advocated conservative dentistry. many dentists were "100 percenters", extracting every tooth exhibiting either necrotic pulp or endodontic treatment, and extracted apparently healthy teeth, too, as suspected foci, leaving many persons toothless. a 1926 report published by several authors in dental cosmos—a dentistry journal where willoughby miller had published in the 1890s—advocated extraction of known healthy teeth to prevent focal infection. endodontics nearly vanished from american dental education. some dentists held that root canal therapy should be criminalized and penalized with six months of hard labor. psychiatric promulgation near the turn of the 20th century, psychiatry's predominant explanations of schizophrenia's causation, besides heredity, were focal infection and autointoxication. in 1907, psychiatrist henry andrews cotton became director of the psychiatric asylum at trenton state hospital in the american state new jersey. influenced by focal infection theory's medical popularity, cotton identified focal infections as the main causes of dementia praecox (now schizophrenia) and of manic depression (now bipolar disorder). cotton routinely prescribed surgery not only to clean the nasal sinuses and to extract the tonsils and the teeth, but also to remove the appendix, gall bladder, spleen, stomach, colon, cervix, ovaries, and testicles, while cotton claimed up to 85% cure rate. despite cotton's death rate of some 30%, his fame rapidly spread through america and europe, and the asylum drew influx of patients. the new york times heralded "high hope". cotton made a european lecture tour, and princeton university press and oxford university press simultaneously published his book in 1922. despite skepticism in the profession, psychiatrists sustained pressure to match cotton's treatments,