138 142 pihlstrom feb centennial commentary.rev.qxp:layout 1

JADA LANDMARK SERIESSpotlighting articles from past ADA Journals that have achieved landmark status thanks to their lastingimpact on dental care and the dental profession

Originally published March 1920,The Journal of the NationalDental Association, Vol. 7,No. 3, 241-272;forerunner to The Journal ofthe American Dental Association

To read full article, visitwww.ada.org/centennial

138 JADA 144(2) http://jada.ada.org February 2013

The X-ray in dentistry,and the legacy of C. Edmund KellsA commentary on Kells CE. The X-ray in dental practice. J Natl Dent Assoc1920;7(3):241-272.Peter H. Jacobsohn, DDS; Mel L. Kantor, DDS, MPH, PhD; Bruce L. Pihlstrom, DDS, MS

Many pioneers in dentistry and scienceforged the future of modern health care.We shall always be indebted to dentists

such as Horace Wells and William Morton, whoare credited with the discovery of anesthesia;Greene Vardiman (G.V.) Black for his many con-tributions to dentistry; Willoughby Miller, whoproposed that oral bacteria produce acids that dis-solve tooth structure; Robert Ledley, who devel-oped the first whole-body computed tomographic(CT) scanner; and biochemist William Gies, whochampioned a scientific basis for dentistry anddental education.1-4 These, and many others,helped shape dentistry and medicine into whatthey are today.

138_142_Pihlstrom_Feb_Centennial_Commentary.rev.qxp:Layout 1 1/10/13 3:50 PM 38

J A D A L A N D M A R K S E R I E S

JADA 144(2) http://jada.ada.org February 2013 139

This commentary focuses on C. Edmund Kells,who was among the pioneers of modern healthcare. He not only introduced radiography todentistry, but he also held dozens of patents onmedical, dental and household devices. Dr. Kellswas a true dental pioneer and scientific genius.

In 1895, Wilhelm Conrad Roentgen discov-ered the X-ray, and the following year Dr. Kellsintroduced this new and revolutionary tech-nology to dentistry.5 This 1920 landmarkarticle,6 highlighted here in the centennial yearof The Journal of the American Dental Associa-tion (JADA), was published in the Journal of theNational Dental Association, a precursor toJADA. It is the publication of a paper read byDr. Kells at the 1919 Association meeting inNew Orleans. Inthis article, hemodestly refers tohis introduction ofthe X-ray to den-tistry in 1896 at ameeting of theSouthern DentalAssociation held inAshville, N.C., justa few months afterDr. Roentgen’s discovery.

When Dr. Kellsread this paperbefore the NationalDental Association(NDA) in 1919, hehad been using“the rays” for 23years. He initiallyused a Ruhmkorffinduction coil andHittof-Crookestubes to generate X-rays and recorded theimages on glass photographic plates. By 1919,General Electric had invented a self-containedshockproof dental X-ray unit, and EastmanKodak had introduced “Regular” film, amachine-manufactured dental film packet.7

Notwithstanding these technical improve-ments and others yet to come, Dr. Kells and hiscontemporaries lived in a two-dimensional X-ray world. Radiographs, or skiagraphs as theywere known at the time, are two-dimensionalrepresentations of three-dimensional patients;the third dimension is represented as varyingshades of gray caused by the differential attenu-ation of anatomic structures in the X-ray beam.Therefore, either two radiographs taken at rightangles to one another or stereoscopic views are

needed to fully appreciate the three-dimensionalrelationships among teeth and their supportingstructures. In the words of Dr. Kells, “…for athoro [sic] diagnosis in some cases, some teethneed to be rayed from two or three angles… .”6

Despite improvements in dental X-ray units andimage receptors, including the introduction ofdental digital imaging in the late 1980s, two-dimensional geometric projection of intraoralradiographs was a limitation that had to be con-tended with for the first half of the 20th century.

Much of the Dr. Kells’ article deals with the“crime,” as he put it, of focal infection. Thearticle provides a window into a segment ofmedical and dental thinking and practice of thetime, and gives us Dr. Kells’ view of how to

make meaningfulchange. Thearticle focuses onhow the X-ray wasbeing used to sup-port a flawed con-cept of diseaseorigin—the theoryof focal infection.Focal infectiontheories were verymuch in vogueduring a timewhen the originsof disease werenot as well under-stood as they aretoday. Interestedreaders arereferred to anexcellent histor-ical review of focalinfection by Pal-lasch and Wahl.8

Briefly stated, focal infection theory is theconcept that a local infection in a small area ofthe body can lead to subsequent infections inother parts of the body, due either to the spreadof the infectious agent itself or to toxins pro-duced by the infection. The focal infectiontheory, popular in the late 19th and early 20thcenturies, had oral health in its cross-hairs. Dr.William Hunter, a British physician, claimedthat poor dental health or “oral sepsis” fromperiodontal disease or “pyorrhea alveolaris,” asit was called at the time, could cause systemicdiseases such as gastritis, “nervous disorders,”meningitis, ulcerative endocarditis, osteomyel -itis and “other septic conditions.”9

In 1915, Dr. Frank Billings introducedAmerican physicians to focal infection theory in

138_142_Pihlstrom_Feb_Centennial_Commentary.rev.qxp:Layout 1 1/10/13 3:51 PM Page 139



lectures at Stanford University and advocatedtonsillectomies and dental extractions as rem-edies for focal infection.10 Many physicians anddentists were convinced. Even such prominentphysicians as Dr. Charles Mayo promoted thetheory. In 1916, Dr. Mayo stated that chronicdiseases and diseases such as neuritis, sciatica,

acute paralysis, appendicitis, gall bladder dis-eases and stomach ulceration were caused bylocal infections and “while there are severalsources in the body for the entrance of bacteriaand their culture in a local focus, the mouth isfar the most common situation.”11 Dr. Mayo alsostated that “the bulk of the dentist’s workshould be referred work of physicians versed inthe rudiments of dentistry.”11 Physicians withlittle else to go on, and often after X-raying theteeth, would make a diagnosis that necessitatedremoval of the teeth. Patients were referred todentists for extraction and untold millions ofteeth were needlessly removed.

Dr. Kells was an early critic of the theory offocal infection, and in his presentation to theNDA he condemned the mass extraction ofteeth. He was adamant that dentists mustrefuse to extract teeth based merely on requestsfrom physicians. It must be remembered thatDr. Kells was not a lightweight inmedical/dental circles; he had attained consider-able prominence through his many contribu-tions and accomplishments. When he spoke,people listened. We remember him mainly forhis efforts to bring the X-ray to dental practice.However, among his many other accomplish-ments were patents for the first electric air com-pressor, the first electric dental unit, the firstelectric mouth lamp and the first “electrified”dental office.

Some have claimed that perhaps his most sig-

nificant contribution was his invention of anelectric suction apparatus for the irrigation andaspiration of fluid during surgery. Dr. RudolphMatas, one of the world’s most renowned sur-geons, paid tribute to Dr. Kells: “The suctionapparatus is sufficient to immortalize the nameof C. Edmund Kells. He has won the eternalgratitude of every working surgeon in theworld.”12 Every dentist owes him the same grati-tude, and it is little wonder that he was held inhigh esteem by both professions.

This article6 makes it quite clear that Dr.Kells’ innovation, namely the application of theX-ray in dentistry, was state-of-the-art in 1919.He stated, “The Roentgen Ray is an absolutenecessity to a high class dental practice” and“the general practitioner of dentistry is not fullycapable of rendering his patients THE VERYBEST SERVICES unless his equipmentincludes an X-ray machine.” Furthermore, hewanted it understood that the X-ray was to beused to enhance the practice of dentistry andnot to encourage the “mania for extracting devi-talized teeth, whether good, bad or indifferent”in the name of focal infection. He wanted to“check the evil” of focal infection by speakingout. The article often repeats his commitment tothe preservation of oral health and the denti-tion. He was very concerned that incompetentand inexperienced persons were misinterpretingwhat they saw on dental radiographs andthereby causing untold harm. He advocated therestoration of teeth even though, on X-ray, theymay appear “infected.” He also stated that devi-talized teeth should be saved and not neces-sarily labeled infected and, therefore, extracted.

Dr. Kells placed the blame for dental mutila-tion squarely on physicians who ordered massextractions and dentists who complied withoutquestion. A recommendation to help curtail the“crime” was to educate physicians in oral healthby including lectures by dentists in medicalschool curricula. His recommendation to thedental profession was that no dentist “willextract a tooth upon orders of a physician.”6

Gradually over time, the focal infection theoryfell out of favor. Clinicians came to realize thatthe removal of teeth, or tonsils for that matter,did not usually relieve the symptoms theirpatients presented. No doubt, Dr. Kells’ earlyadmonitions played a significant role in thedemise of the theory of focal infection.

By the 1950s, the theory of focal infection wasall but dead as more and more clinicians spokeout against it and as advances in medical sci-ence provided explanations for the etiology ofmany diseases. An entire issue of JADA in 1951



JADA 144(2) http://jada.ada.org February 2013 141

was devoted to a review of focal infection thatalso could be considered a “landmark” JADAarticle.13 After evaluating the evidence for focalinfection it was concluded that “over the years,close observation of the benefits derived fromthe promiscuous removal of teeth led membersof both the dental and medical professions toquestion the soundness of the theory. Manyauthorities who formerly felt that focal infectionwas an important etiologic factor in systemicdisease have become skeptical and now recom-mend less radical procedures in the treatmentof such disorders.”13(p694) However, to a minorextent, the theory of focal infection lingered onfor many years. When one of the authors of thisCommentary (PHJ) started his oral surgerypractice in the late 1960s, he occasionally hadphysicians refer patients to him for removal ofteeth to treat various nonoral diseases.

Dr. Kells died in 1928, but his spirit of inno-vation lived on as the mid-20th century wit-nessed the development of panoramic radio-graphy, based on principles first described byDr. Hisatsugu Numata in the 1930s and Dr. YrjöV. Paatero in the 1940s.7 A patent for an “Appa-ratus for producing radiographs of selectedstructures within a subject” was issued in 1957to Drs. Donald C. Hudson and John W.Kumpula on behalf of the U.S. Secretary of theArmy.14 The military’s interest in developingpanoramic radiography was in the rapid assess-ment of large numbers of recruits for militarypreparedness and to have records for post-mortem identification when necessary. The S.S.White Co. produced the first commercially avail-able panoramic machine in the 1960s andopened a new window onto the oral and maxillo-facial region. The curved surface tomogram fol-lows the shape of the dental arches and displaysthe teeth, jaws and surrounding structures thatlie within the U-shaped focal trough as a flatimage. As with two-dimensional projectionradiography, panoramic radiography hasenjoyed significant technological refinementsover the last 50 years, including the replace-ment of film with digital sensors that allowimages to be stored, manipulated and trans-mitted with relative ease.

The latest development in oral and maxillofa-cial radiology involves acquiring three-dimensional or volumetric images with cone-beam computed tomography (CBCT). Althoughmany CBCT machines look like panoramicmachines, the images produced are akin to thecross-sectional images produced by a medicalCT machine. Unlike plain radiography andpanoramic radiography that started out using

film and migrated to a digital environment,CBCT is inherently a digital technology. With asingle sweep around the patient’s head, CBCTacquires a three-dimensional volumetric map ofthe head that can be manipulated and displayedin any plane of space, including a U-shapedpanoramic-like curved surface. CBCT has beenespecially useful in presurgical implant siteassessment, evaluation of the temporoman-dibular joints, investigation of pathology andtrauma in the maxillofacial region, and evalu-ation of developmental disturbances of the facialregion.

In addition to these quintessential dentalradiographic techniques—intraoral, panoramicand CBCT imaging—oral and maxillofacialradiology and other dental specialties haveadopted medical imaging technologies for theirown purposes. Orthodontists adopted conven-tional head and neck radiographs and generatecephalometric radiographs for morphometricmeasurements to evaluate growth and develop-ment and to assess orthodontic treatment out-comes. Contrast agents—mentioned by Dr.




Kells: “the ingenious Roentgenologist gives hispatient a free lunch of bismuth and then takesmoving pictures of it as it travels down the ali-mentary canal”6 —have been used in sialog-raphy and temporomandibular arthrography.Imaging modalities such as CT, magnetic reso-nance imaging (MRI), nuclear medicine, ultra-sound, positron emission tomography (PET),and single photon emission computed tomog-raphy (SPECT) all have applications in the oraland maxillofacial region.

When the 200th anniversary of JADA is cele-brated in 2113, there will be as yet unimaginedadvancements in diagnostic imaging that will bechampioned by as yet unborn pioneers—pio-neers in the tradition of C. Edmund Kells, wholived for the betterment of the profession andthe alleviation of suffering. ■

Dr. Jacobsohn is an adjunct professor of oral and maxillofacial sur-gery, and the curator, Englander Dental Museum, School of Den-tistry, Marquette University, Milwaukee. Address reprint requests toDr. Jacobsohn at 3819 W. LeGrande Blvd., Mequon, Wis. 53029, e-mail [email protected].

Dr. Kantor is a professor, Department of Oral Health Practice, Col-lege of Dentistry, University of Kentucky, Lexington.

Dr. Pihlstrom is a professor emeritus, Department of Surgical andDevelopmental Sciences, School of Dentistry, University of Min-

nesota, Minneapolis. He also is guest editor for The Journal of theAmerican Dental Association centennial year features and associateeditor, Research, for JADA, as well as an independent oral healthresearch consultant.

1. Gutmann JL. The evolution of America’s scientific advancementsin dentistry in the past 150 years. JADA 2009;140(9 suppl):8S-15S.

2. Snead ML, Slavkin HC. Science is the fuel for the engine of tech-nology and clinical practice. JADA 2009;140(9 suppl):17S-24S.

3. Zero DT, Fontana M, Martínez-Mier EA, et al. The biology, pre-vention, diagnosis and treatment of dental caries: scientific advancesin the United States. JADA 2009;140(9 suppl):25S-34S.

4. Hendee WR. Cross sectional medical imaging: a history. Radio-graphics 1989;9(6):1155-1180.

5. Jacobsohn PH, Fedran RJ. Making darkness visible: the dis-covery of X-ray and its introduction to dentistry. JADA 1995;126(10):1359-1367.

6. Kells CE. The x-ray in dental practice: the crime of the age. J Natl Dent Assoc 1920;7(3):241-272.

7. Goaz PW, White SC. Oral Radiology: Principles and Interpreta-tion. 2nd ed. St. Louis: Mosby; 1987:1-17.

8. Pallasch TJ, Wahl MJ. Focal infection: new age or ancient his-tory? Endodontic Topics 2003;4(1):32-45.

9. Hunter W. Oral sepsis as a cause of disease. Br Med J 1900;2(2065):215-216.

10. Billings F. Focal Infection: The Lane Medical Lectures. NewYork City: D. Appleton; 1916.

11. Mayo CH. Dental research, its place in preventive medicine. Off Bull Natl Dent Assoc 1916;3(2):167-171.

12. Matas R. Tribute to C Edmund Kells: An address by RudolfMatas. Am Dent Surgeon 1927;47:205-215.

13. Easlick K. An evaluation of the effect of dental foci of infectionon health. JADA 1951;42(6):615-697.

14. Glenner RA. The Dental Office: A Pictorial History. Missoula,Mont.: Pictorial Histories; 1984:127-146.


138 142 pihlstrom feb centennial commentary.rev.qxp:layout 1

Documents