1. Introduction to Dental Radiography and Equipment21
Introduction to Dental
Radiography and Equipment

2. Discovery of the X-Ray Roentgen 1895 Walkoff Kells Anode Cathode
Dental Radiograph
Kells
Intraoral Radiograph
William Conrad Roentgen discovered x-rays in 1895 by using a glass vacuum tube with an electrical circuit connected to each end.
The stream of electrons traveled from the cathode end to the anode end.
Also in 1895, Dr. Otto Walkoff was the first to use the x-ray to take the first dental radiograph.

3. Discovery of the X-Ray Rollins Coolidge Victor X-Ray Corporation (GE)
First dental x-ray unit
Coolidge
Cathode x-ray tube
Victor X-Ray Corporation (GE)
Dental x-ray machine
In 1896, Dr. C. Edmund Kells took the first intraoral radiograph and Dr. William Rollins, the inventor of the first dental x-ray unit, reported effects of radiation exposure.
In 1913, Dr. William Coolidge invented the hot cathode x-ray tube.
Victor X-Ray Corporation, later known as General Electric Corporation, developed a dental x-ray machine known as the Coolidge tube.

4. X-Ray Techniques Bisecting technique Parallel technique
Panoramic technique
Tomography
Digital Imaging
A variety of techniques were discovered in an effort to capture dental x-rays.
In 1905, Dr. Howard Robert and A. Cieszykski developed the bisecting technique, in which isometry is employed.
The parallel technique, developed by Frank McCormack in 1920, used the right angle technique to expose dental x-rays.
The panoramic technique was discovered in 1959 by a team of doctors and Dr. Paatero was credited with developing the first unit to capture an x-ray of the entire dental arch on one film.
Currently, mouth structures can be visualized using tomography in which certain planes are selected for view.

5. Radiation Physics and Biology
Electromagnetic energy
Travels in waves moving in straight line
Travels at the speed of light
Has no mass
Travels through space as transverse waves
Energy travels in waves that move in straight lines at the speed of light (186,000 miles per second).
There is no mass involved and it travels through space in the form of transverse waves.

6. Wavelength Cycle Short wavelength Long wavelength
Distance between peaks
Short wavelength
Long wavelength
Wavelength is measured in cycles: the measurement between two peaks of adjacent waves.
Longer wavelengths include visible light, television, and radio waves.
Shorter wavelengths are x-rays and gamma rays.
The more cycles that pass a given point in a specified time frame, the higher the frequency.
More energy is given by shorter wavelengths with higher frequency and less energy is emitted when the wavelength is long and has lower frequency.

7. Radiation Types Hard radiation Soft radiation Four types of radiation
Primary
Secondary
Scatter
Leakage
Dental radiographs employ hard radiation, which is in the form of short wavelengths that have high frequency and high energy, and therefore a higher penetrating power.
Soft radiation, called Grenz rays, is a longer wavelength with low energy due to lower frequency.
There are four types of radiation; primary, secondary, scatter, and leakage.
Primary radiation is a high energy, short wavelength that is the central beam originating from the x-ray tube head.
Secondary radiation waves are often transformed into longer wavelengths that lose their energy as they form when primary x-rays contact matter.
Radiation deflected from its path as it strikes matter is called scatter radiation and is dangerous to anyone in its path.
It is recommended that operators stand at least six feet from the patient while conducting radiographs.
Leakage radiation is the radiation that escapes from the tube or tube head.

8. Radiation Units of Measurement
Roentgen R
Radiation absorbed dose
Rad or Gray (GY)
Roentgen equivalent man
Rem or Sievert (SV)
The amount of radiation that ionizes one cubic centimeter of air is called a roentgen (R).
The radiation absorbed dose (rad) or Gray (GY) refers to the amount if ionizing radiation absorbed into a substance.
The dose to which body tissues are exposed is called the roentgen equivalent man (rem) or sievert (Sv), and is measured in terms of its estimated biological effects in relation to an exposure dose of one R or x or gamma radiation.

9. Radiation Units of Measurement
Milliroentgen mR
Relative biological effectiveness
rbe
A milliroentgen (mR) is one one thousandth (1/1,1000) of an R. The measurement unit used to compare the biological effects of different tissues compares effects of different forms of energy on different tissues is called relative biological effectiveness (rbe).

10. Structure of Atom Ionization Atoms make up all matter Protons Neutrons
Electrons
Hadrons
Leptons
Quarks
Ionization is the process in which atoms change into negatively or positively charged ions during radiation.
All matter is composed of atoms, which are composed of electrons, protons, and neutrons.
The protons are positively charged particles inside the nucleus.
Negatively charged particles orbiting the nucleus are called electrons and are comprised of tinier particles called hadrons, leptons, and quarks. The neutrons have no charge.

11. Biological Effects of Radiation
Somatic and genetic effects
Radiosensitive cells
Biological harm can result from exposure to X-rays resulting in the death of a cell or change to its makeup.
Somatic effects (all cells excluding reproductive) may occur in the form of cataracts, cancer, or leukemia.
Genetic effects can be passed on to future generations and are irreversible.
Some cells are more radiosensitive than others, such as immature cells, rapidly dividing cells, and those cells without specialized functions.

12. Radiation Exposure Occupational exposure
Maximum Permissible Dose (MPD)
Daily radiation exposure
Natural
Artificial
Accumulation of radiation
The maximum permissible exposure (MPD) is the maximum dose of radiation that is an allowable exposure not expected to harm an individual.
Most individuals are exposed to natural and artificial radiation.
Natural radiation, such as the radiation produced by the sun and atmosphere, comprises about 55 percent of the daily radiation exposure.
Artificial radiation contributes almost 41 percent of the daily radiation exposure and comes from x-rays and consumer products.
Because the effects of radiation are cumulative, long-term effects of exposure can result.

13. Components of the Dental X-Ray Unit
Control Panel
Milliamperage
Kilovoltage (KV)
Electronic Timer
Milliamperage Seconds
Contrast
Density
The dental assistant should understand the components that make up the dental x-ray unit.
Settings, adjustments, and selections of milliamperage, kilovoltage, and the electric timer are made on the control panel.
The amount or quantity of electrons is determined by the milliamperage.
The quality or penetrating power of the central beam is determined by kilovoltage (KV).
The higher the KV, the greater the penetrating power of the x-rays, and therefore, less exposure time is necessary.
The electronic timer controls the total time rays flow from the x-ray tube.
It is located in a safe area outside the room or behind a lead barrier to keep the operator safe.
The amount of radiation exposure a patient receives is determined by milliamperage seconds (mAs).
Contrast is indicated on an x-ray by differing shades of gray.
The degree of darkness on an x-ray is referred to as density, and is affected by distance to the x-ray tube, patient tissue thickness, and amount of radiation reaching the film.

14. Components of the Dental X-Ray Unit
Arm assembly and tubehead
Arm Assembly
Tubehead
X-ray Tube (Coolidge Tube)
Filter
Central Beam
Collimator
The arm assembly is a flexible extension attached to the x-ray room wall that enables the operator to position the unit as needed. The x-ray vacuum and the step-up (high voltage) and step-down (low voltage) transformers are located in the tubehead.
X-rays travel through the x-ray tube to a metal filter, known as an inherent filter, which separates hard and soft x-rays.
Hard x-rays, called the central beam, pass through the collimator, a lead disc used to filter out weaker x-rays.

15. Safety Precautions Responsibilities for safety Manufacturers Dentist
Dental Assistant
Patient
Precautions to ensure safety for staff and patients are necessary to ensure safety.
The federal government has mandated that all manufacturers ensure that their x-ray units have separate control switch to cut power and also have an electric timer to stop electricity automatically.
The PID must be lead lined and the x-ray tube sealed according to guidelines.
Indicators displaying mA, kV, and impulses [per exposure time are to be set in the control panel and the collimator is to be fitted directly over the tubehead where the x-ray beam exits.
Additionally, film head of 2.5 mm of aluminum must be built into the head of all x-ray machines operating at kV higher than 70.
It is the responsibility of the dentist to have all x-ray equipment installed and maintained properly.
He or she must prescribe x-rays responsibly and train staff accordingly.
The dental assistant must be trained to understand safety as well.
Finally, it is the patient’s responsibility to notify staff of physical conditions, such as pregnancy, that may affect the prescription of x-rays.

16. Radiation Production Thermionic Emission
Electrons given off when the filament is heated to a certain temperature
Electrons travel from cathode to anode
X-rays produced when electrons collide
Thermionic emission occurs as the filament is heated by electricity, sending electrons through the tube.
The X-ray is produced at the exact moment the electrons collide.

17. Dental X-Ray Film Composition Film speed Film size Dental film pack
Dental film storage
Halide crystals suspended in gelatin store energy when exposed to x-rays, thus forming a black mark on the film.
There are several speeds used by dentists; D-speed (Ultraspeed), E-speed, (Ektaspeed), and F-speed (InSight).
Five basic sizes are used in intraoral x-rays, depending on the size of the patient’s oral cavity and the area to be radiographed.
Film is placed in the intraoral film packet, which is sealed in plastic wrap and backed with lead foil.
Dental film should be stored carefully to prevent exposure to stray radiation.