1. Radiation Safety Dental Assistant Registration Course
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2. Radiation Physics and Biology
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

3. Wavelengths
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.

4. Structure of Atom
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.

5. Radiation Types
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.
Leakage radiation is the radiation that escapes from the tube or tube head.
It is recommended that operators stand at least six feet from the patient while conducting radiographs.

6. Radiation Measurements
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.
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).

7. Radiation Exposure
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.

8. Safety Precautions
Precautions to ensure safety for staff and patients are necessary to ensure safety.
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.
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.

9. Safety Precautions
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.

10. References
Dental Assisting: A Comprehensive Approach, Phinney, D.J., Halstead, J.H. (3rd. Ed.) Thomson /Delmar Learning,2008
Dental Radiography: Principles & Techniques, 3rd Ed; Iannucci & Howerton, Elsevier, St. Louis, 2006