The dental radiograph fundamentally changed the practice of dentistry, shifting it from a purely visual craft to one guided by internal diagnostic information. Before this technology, dentists relied entirely on surface examination and palpable signs to assess the health of teeth and jawbone. The ability to create an image that penetrated tissue to reveal underlying structures like roots, bone, and hidden decay revolutionized treatment planning. This breakthrough allowed for the precise identification of abscesses, impacted teeth, and early-stage periodontal disease, paving the way for modern dental care.
The Foundational Discovery of X-rays
The possibility of dental radiography began with the accidental discovery of a new form of energy by German physicist Wilhelm Conrad Röntgen in late 1895. Working in his laboratory at the University of Würzburg on November 8, 1895, Röntgen was experimenting with a Crookes tube, a partially evacuated glass tube through which an electrical current was passed. He observed a faint, fluorescent glow on a barium platinocyanide screen located a meter away, even though the tube was completely shielded by thick, black cardboard. This suggested the emission of a highly penetrating, unknown form of radiation.
Röntgen named this mysterious energy “X-radiation,” with “X” representing the unknown mathematical variable. He found that these rays could pass through most substances, casting shadows of denser materials like bone and metal. As evidence of his discovery, Röntgen created the first human radiograph—an image of his wife Anna Bertha’s hand, clearly showing her skeletal structure and the ring on her finger. This image, presented publicly on December 28, 1895, captivated the scientific community and the general public, launching a global race to explore the medical applications of the new ray.
Identifying the First Dental Radiograph Pioneer
The person who first applied Röntgen’s discovery directly to dentistry was Dr. Otto Walkhoff, a German dentist practicing in Braunschweig. Just fourteen days after Röntgen published his initial report, Walkhoff decided to expose the first dental radiograph. This experiment took place in January 1896, officially introducing radiography to dental practice.
To accomplish this, Walkhoff enlisted physicist Fritz Giesel and performed the experiment as a self-exposure. He placed a small piece of photographic glass plate, wrapped in black paper and covered with a rubber dam, directly into his own mouth against his lower molars. The rudimentary technology required an extremely long exposure time of approximately 25 minutes to capture an image.
Walkhoff endured the lengthy exposure, later describing it as “a real torture” but expressing joy upon seeing the result. This pioneering, self-inflicted exposure came at a personal cost. The high dose of radiation caused significant side effects, including a radiation burn and hair loss. Despite the risks, Walkhoff’s successful, albeit crude, image demonstrated the potential of X-rays to visualize internal dental anatomy.
Transition to Clinical Dental Radiography
While Dr. Walkhoff achieved the first experimental exposure, the technology quickly transitioned from a scientific curiosity to a practical clinical tool through the work of other pioneers. The challenge remained in adapting the dangerous, lengthy exposures into a safe, routine procedure for patients. Another German scientist, Wilhelm Koenig, also made a series of self-exposures in February 1896, taking 14 dental images of his own jaws, each requiring about nine minutes of exposure time.
In the United States, New Orleans dentist Dr. C. Edmund Kells was instrumental in integrating the technology into routine patient care. Kells, working with a Tulane University physicist, acquired the necessary equipment and began experimenting with intraoral radiography on living subjects in the spring of 1896. He is credited with taking one of the first intraoral radiographs on a live patient—his dental assistant—and demonstrating the technique at a professional meeting in July 1896.
Kells also focused on making the procedure safer and more practical, developing an early film holder that allowed the patient to keep the film in place during the lengthy exposure, which could still last 15 minutes. He unknowingly created one of the first X-ray filters by placing a thin board between the tube and the patient’s face to stabilize the head, likely preventing severe skin damage. Unfortunately, the lack of understanding of radiation hazards meant that Kells and other early adopters suffered repeated, high-dose exposure. Kells himself developed severe radiogenic lesions, enduring over 40 operations and multiple amputations to his fingers, hand, and arm over the last two decades of his life.