This document provides an overview of the history and properties of dental radiography. It discusses how Wilhelm Roentgen's discovery of x-rays in 1895 built upon prior work in electricity and magnetism. It then summarizes key developments in dental radiography, including Dr. C. Edmund Kells performing the first dental x-ray in 1899. The document also outlines the electromagnetic spectrum and defines x-rays as weightless energy packets that travel in straight lines. It describes the physical, chemical, and biological properties of x-rays and their interaction with matter, such as their ability to penetrate tissues and induce ionization.

1. Presented by:
Sharanya Majumdar
Final BDS
Bapuji Dental College & Hospital

2.  History of dental radiography
 Highlights in the history of dental radiography
 Electro magnetic Spectrum
Introduction
Properties of electromagnetic radiation
 Properties of X-rays
Definition
Physical properties
Effect of interaction of x-rays with Matter
Chemical properties
Biological properties
Physiochemical properties

3. Nothing materializes as if magic by overnight.
Even Roentgen’s discovery depended upon
the development and application of three
converging thoughts; Electricity, Vacuum and
Magnetism

4.  Sir William Morgan unknowingly was the first
man to produce x-rays while conducting one
of his experiments.

5.  Professor Wilhelm Conrad Roentgen made the
most important discovery striking and
outstanding property of cathode ray.
 Dr. C. Edmund Kells (1880) known as the
Father of Dental Radiography, was the first
dentist to practice radiography in root canal
therapy on May10,1899.

7.  Introduction
Electromagnetic radiation can be defined as the
propagation of wave like energy (without mass)
through space or matter.
Electromagnetic radiations are arranged according
to their energies in what is termed Electromagnetic
spectrum

9.  They travel through space in a wave motion
along a straight line.
 They travel at the speed of light in vacuum,
i.e. 3x10 m/sec or 186,000 miles/second.
 As they travel through space they give off an
electric field at right angles to the path of
propagation and a magnetic field at right
angles to both.
8

10.  In passing through matter the intensity of
radiation is reduced both because energy is
taken up by the material and some energy is
deflected from its original path to travel in a
new direction.

11.  Definition:
X-rays are defined as weightless packages of pure
energy that are without electrical charge and that
travel in waves along a straight line with a specific
frequency and speed.
The properties of X-rays may be classified as:
 Physical
 Chemical
 Biological
 Physiochemical

12.  X-rays belong to a family of electromagnetic
radiations having a wavelength between 10Å
and 0.01Å.
 They travel with the same speed as that of
visible light (i.e. 1,86,000 miles per second)
 They are invisible to the eye and cannot be
seen; heard or smelt (they remain undetected
by the human senses)

13.  They cannot be reflected, refracted or
deflected by a magnet or electric field as they
do not possess any charge.
 X-rays are pure energy, no mass and they
transfer energy from place to place in the
form of quanta (photons).

14.  X-rays are produced by the collision of
electrons with tungsten atoms. The collisions
which occur are of two types, thus giving rise
to two types of spectra:
 Continuous spectra (General radiation,
Bremsstrahlung radiation or braking radiation)
 Characteristic spectrum or line spectrum

15.  X-rays can penetrate various objects and the
degree of penetration depends upon the
quality of the X-ray beam, and also on the
intensity and wavelength of the X-ray beam.

16.  In the case of diagnostic X-ray beam there
are three X-ray mechanisms by which these
processes take place:
1. Coherent Scattering
2. Photoelectric Scattering
3. Compton Scattering

17. Photon
Matter
Compton scatter
High speed electrons
Matter
Excitation
Chemical effects
Biological effects
HeatHeat
Ionization
RecombinationX-rays
Bremsstrahlung
Scattered
Radiation
Characteristic
Radiation
Photoelectric
effect
Pair production
Annihilation
radiation

20.  X-rays induce colour changes of several
substances:
a. Methylene blue gets bleached
b. Sodium platinocyanide, which is apple green in
colour turns darker green then to light brown and
finally to dark brown
 X-rays bring about chemical changes in
solutions which are otherwise completely
stable
 X-rays cause destruction of fermenting
power of enzymes

21.  When x-rays are incident on a atom, one of
the reaction it produces is ‘excitation’.
 These state of ‘excitation’ in biological
materials enable it to take part in a chemical
process into which in the normal state it
would not enter.
 This is an important cause of biological
damage produced by radiation.
 Biological effect of X-rays may be classified
into two types
1. Somatic effect
2. Genetic effect

23.  The photographic paper or film when exposed
to X-ray radiation and then developed will be
found blackened.
 This blackening is known as ‘film density’ & the
degree of blackening depends upon:
a. Amount of radiation
b. Quality of radiation
c. Characteristic of a film
d. Concentration and age of developing solution
e. Length of developing time
f. Use of intensifying screens

24.  X-rays travel in straight line.
 X-rays can penetrate liquids, solids & gases.
The composition of the substance determines
whether the X-rays penetrate or are absorbed.
 X-rays are absorbed by matter, the absorption
depends on the atomic structure of the matter
& the wavelength of the X-ray.
 X-rays interact with materials they penetrate
and cause ionization, dissociate silver ions in
film emulsions.

25.  X-rays can cause substances to fluorescence
or emit light radiation in longer wavelengths.
 X-rays can produce an image on a
photographic film.
 X-rays cause biological changes in living
things.

26.  ‘Essentials of Oral and Maxillofacial
Radiology’ by Freny R. Karjodkar
 ‘Oral Radiology-Principles & Interpretation’
(6th Edition) by White & Pharoah