HISTORY, HAZARDS, AND PROTECTION
Section I. INTRODUCTION
Radiography is a highly technical field, indispensable to the modern dental
practice; but it also presents many potential hazards. The dental radiographic specialist
must be thoroughly familiar with the procedures necessary to produce radiographs of
diagnostic quality. He must also have a thorough knowledge of the hazards associated
with the use of radiation and how to protect himself and the patient against those
hazards. This lesson deals with the production, characteristics, and effects of radiation
and how it may be used safely in dentistry.
DISCOVERY OF X-RAYS
In 1895, Wilhelm Konrad Roentgen was searching for invisible light by
experimenting with a Crookes vacuum discharge tube. This is a glass tube in which the
vacuum is nearly complete, having a negative electrode (cathode) and a positive
electrode (anode). Many investigators believed that invisible light rays were emitted
from the negative electrode when a high voltage current was sent through the tube.
With the room darkened and the tube covered with black paper, Roentgen passed a
high voltage current through the Crookes tube and was surprised to observe that a
fluorescent screen lying on a table at some distance was glowing brightly. He then
noted that a shadow was produced when an object was placed between the tube and
the screen. Further experimentation revealed that the rays that caused the fluorescent
screen to glow also acted upon the emulsion on photographic plates in the same
manner as light. Thus, it was shown that the rays produced would pass through some
substances through which light would not pass. Since Roentgen was unable to
determine the exact nature of the rays produced, he referred to them as x-rays (x being
commonly used to denote an unknown factor). In later years, scientists have referred to
them as Roentgen rays.
a. Radiograph. An exposed and processed film (roentgenograph,
roentgenogram). Also known as an x-ray negative.
b. Roentgenology. The study and use of x-rays (radiology).
c. Roentgen Ray. Electromagnetic radiation of pure energy and extremely
short wavelength (x-ray), sometimes referred to as x-ray photons.