Radiation
Energy carried by waves or a stream of particles
Wilhelm Conrad Roentgen
Discovered x-rays
William H. Rollins
Developed the first x-ray unit
Tiny, negatively charged particles that have very little mass.
Electrons
Radioactivity
Process by which certain unstable atoms or elements undergo spontaneous disintergration, or decay, in an effort to attain a more balanced nuclear state
Travel in waves with a specific frequency at the speed of light
X-rays
Accelerated particles with a mass of 1 and no electrical charge
Neutrons
Has no mass or weight, no electrical charge, travels at speed of light as both a particle and a wave, propagates an electric and magnetic field at right angles has different measurable energies
Electromagnetic Radiation
Scatter Radiation
Form of secondary radiation, results from x-ray being deflected, travels to all parts of patients body and dental operatory. Detrimental to both patient and operator
Surrounds the x-ray tube and transformers inside the tubehead; prevents overheating by absorbing the heat created by the production of x-rays
Insulating Oil
Used to increase the voltage from the incoming 110 or 220 line voltage to the 65,000 to 100, 000 volts used by the high voltage circuit
Step Up
When electrons strike the tungsten target, their energy of motion (kinetic energy) is converted to x-ray energy and heat. What percent is converted to x-rays
Less than 1%...the remaining 99% is lost as heat
Density
The overall darkness or blackness of a film
Contrast
How sharpley dark and light areas are differentiated or separated on film...difference in degrees of blackness between adjacent areas
Interval of time durings which x-rays are produced; measured in impulses
Exposure Time
Restricts size of x-ray beam; lead plate with central hole, fits directly over opening of metal housing where x-ray exits
Lead Collimator
Position-Indicating Device (PID)
Aims and shapes the x-ray beam; open ended, lead lined cylinder that extends from the opening of the metal housing of the tubehead. Sometimes referred to as the cone.
Anode
Converts electrons into x-ray photons.
Quality
The mean energy, or penetrating ability of the x-ray beam
When voltage is increased electrons move from the cathode to the anode with
With more speed; voltage determines the speed of electrons that travel from the negative cathode to the positive anode.
Aims and Shapes x-ray beam
PID
Lead Collimator
Restricts size of x-ray beam
What type of radiation is most detrimental to the patient and radiographer?
Scatter Radiation
Dental Radiography requires the use of what kV
65 to 100 kV
The product of milliamperes and exposure time is
Milliampere-seconds
Difference between collimator and PID
Collimator restricts size of x-ray beam PID aims and shapes x-ray beam
Examples of nonstochastic eccetcs
Erythema, hair loss, cataract formation and decreased fertility
Total Dose
Quantity of radiation recieved
More damage occurs in cells that are sensitive to radiation, examples are
Rapidly dividing cells and young cells
Short Term Radiation Effects
Associated with large amounts or radiation absorbed in a short period of time
The more radiation and the faster the dose rate means what for the latent period
The shorter the latent period
The traditional unit of radiation measurement, unit of dose, is termed
rad - radiations absorbed dose
The cell that is most sensitive to radiation is
The small lymphocyte (blood)
Naturally occuring background radiation includes
Cosmic and terrestrial radiation
Dental x-ray machines operating above 70kVp requires a minumum total of what aluminum filtration
2.5 mm
Dental x-ray machines operating at or below 70kVp requires a minumum total of what aluminum filtration
1.5 mm
Filters out longer wavelength, low emergyx-rays from the x-ray beam
Aluminum Filters
Thyroid Collar
May exists as a separate shield or as part of a lead apron; used in intraoral films not extraoral films
When x-rays exit from the conical PID, they penetrate the plastic and produce
Scatter Radiation
The fastest intraoral film currently available is
F-speed film
The protection guidelines are based on the following rule
The dental radiographer must avoid the primary beam
Use of F-speed film reduces exposure by what percents over D-speed film
60%
The PIDs that do not produce scatter radiation are
Round and Rectangular
The permitted lifetime radiation dose is termed
MAD - Maximum accumalted dose
ALARA means
As low as reasonable achievable
Mechanism of radiation injury when x-radiation is absorbed
Ionization and free radical formation
Fast film require less than _____ of the initial exposure times used in 1920
2%
What should be placed in the area of missing teeth to support the bite-wing tab ot film holder
Cotton Roll
SLOB stands for
Same Lingual Opposite Buccal
Phalangioma
Distal phalanx of the finger is seen in the radiograph
The bite-wing tab is a/an
Alternative to a film holding device made of heavy paper board tab or loop fitted around a film and used to stabilize film during exposure
Using the bite-wing technique the film is placed
In the mouth, parallel to the crowns of both upper and lower teeth
Interproximal examination
Intraoral radiographic examination used to inspect the crowns of both the maxillary and mandibular teeth on a single film
The cause of incorrect vertical angulation
Vertical angulation was to excessive (too steep) in the bisecting technique
Incorrect vertical angulation will appear on film as
Short teeth with blunted roots
Incorrect horizontal angulation will appear on film as
Overlapped Contacts
Correct film placement for molar bite-wing radiographs will show
Both maxillary and mandibular molars; front edge of film should align with the midline of the mandibular second molar
Correct film placement for premolar bite-wing radiographs will show
Both maxillary and mandibular premolars and distal areas of both canines
If the film was creased the image will appear with
A thin radiolucent line on the film
Overexposed film will appear
Dark
Underexposed film will appear
Light
Unexposed film will appear
Clear
Light images with a herringbone pattern on a film is caused by
Reversed film
Cone-cut without film holder
PID not directed at the center of the film and the x-ray beam did not expose the entire film. Appears as a clear (unexposed) area on film
Cone-cut with film holder
PID not properly aligned with periapical film holder and appears as a clear, unexposed area on a dental radiograph and may occur with either a rectangular or round PID.
Double exposure
Double images appear on film because it was exposed twice
If the film is bent excessively the image will appear
Stretched and distorted
Blurred images on a film are caused by
Movement
Film exposed to light will appear
Black
Object film distance
Distance between film and tooth
A vertical angulation of what is recommended for the bite-wing radiograph: +10 degrees
+10 degrees
XCP
Extension Cone Paralleling
With the bisecting technique, film holders are recommended because the need for the patient to stablize the film with their fingers is eliminated. This reduces
Patient exposure to radiation
When doing maxillary premolar exposures what must be visible in the projection
The distal contact of the maxillary canine
What usually obscures the distal contact of the canine in the paralleling technique
The linqual cusp of the first premolar
What size film is used in the bisecting technique
Size two
Vertical angulation refers to
Positioning of the PID in a vertical (up and down) plane
The film type used in a interproximal exam is
Bite-wing film
Elongated images result from
Insufficient vertical angulations, teeth appear too long
Foreshortened images result from
Excessive vertical angulation, teeth appear shorter than actual tooth
Horizontal angulation refers to
Positioning of the tubehead in a horizontal (side to side) plane
The difference between bisecting and paralleling regarding film sizes
Paralleling uses size 1 for anterior and size 2 for posterior, bisecting uses size 2 for both
Number of film placements anterios paralleling technique
Seven (four maxillary exposures and three mandibular exposures)
Number of film placements anterior bisecting technique
Six (three maxillary, three mandibular)
In the CMRS, to include every tooth and all tooth bearings areas a total of
14 to 18 films may be included
What method/s for obtaining interproximal radiographs are used
Bite-wing technique
Interproximal Examination
Used to examine the crowns of both maxillary and mandibular teeth on a single film
Occlusal Examination
Used to examine large areas of the maxilla or mandible on one film
Bite-wing radiographs must show
Open contacts, or interproximal tooth surfaces, that are not overlapped
In the prescribed placements for anterior periapical films, paralleling technique the lingual cusp
Of the first premolar usually obscures the distal contact of the canine
Periapical examination
Used to examine the entire tooth (crown and root) and supporting bone
To make sure the apical structures appear on a periapical radiograph
Ensure no more than 1/8 inch of the film edge extends beyond the incisal-occlusal surfaces of the teeth
The edge of the periapical film must be placed: parallel to the incisal or occlusal surfaces of the teeth
And extend 1/8 inch beyond those surfaces
Periapical radiographs must show
The entire crowns and roots of the teeth being examined, as well as 2-3 mm beyond the root apices
Recommended Vertical Angulations for the bisecting technique for the mandibular molars is
Mandibular -5 to 0
The complete mouth radiographic series (CMRS) can be defined as
A series of intraoral dental radiographs that shows all of the tooth-bearing areas of the upper and lower jaws
The distal contact of the maxillary canine must be visible in what projection
Maxillary premolar exposure
The extraoral radiographic examination is a
Radiographic inspection of large areas of the skull and jaws
Right angle
Angle of 90 degrees formed by two lines perpendicular to each other
Perpendicular
Intersecting at or forming a right angle
Parallel
Moving or lying on the same plane, always separated by the same distance and not intersecting
Long axis of tooth
An imaginary line that divides the tooth longitudinally into two equal halves
Intersecting
To cut across or through
To achieve parallelism between the film and the tooth
The film must be placed away from the tooth and toward the middle of the oral cavity.
An example of commercially available intraoral film holders include
STABE FILM HOLDER
Radiolucent
Portion of a processed film that is dark or black, lacks density and permits the passage of the x-ray beam
Examples of of radiolucent objects on a radiograph
Air space and cavities
Radiopague
Portion of a processed film that is light or whie, dense and absord or resist passage of x-ray beam
Examples of radiopague onjects on a radiograph
Amalgam, enamel, dentin and bone
A diagnostic radiograph
Images that exhibit proper density and contrast, has sharp outlines and are of same shape and size as image radiographed
Any increase in exposure factors (mA, kVp or time) separately of combine
Increases the desity of a radiograph as well as the subject thickness influences density
Subject contrast
Determined by thickness, density and composition of subject
Sharpness
Detail, resolution and definition, capability of x-ray film to reporduce distint outlines. Influenced by Focal spot, Film compositions and movement
Penumbra
A certain lack of sharpness is present in every radiograph called
Dimensional distortion
A variation in the true size and shape of the onject being radiographed. Caused from improper film alignment or beam angulation
The type of contrast preferred in a radiograph
Compromise between short scale and long scale contrast
Magnification
Geometric characteristic that refers to an image that appears larger than its actual size
Steps in film processing
Development, rinsing, fixing, washing, drying
A safelight is
A lamp equipped with a low wattage (7.5 to 15 watts) with a filter set a min distance of 4 feet from work area
Underdeveloped film appear
Light
Overdeveloped film appear
Dark
Fixer spots appear
Light or white, if fixer levels are low may get cut off that would be a straight black border of none fixed film
A film with a damaged emulsion appears
Cracked
Scratches on film appear as
Thin white lines
Static electricity on film appears as
Black branching lines
Latent image
Pattern of stored energy on an exposed film made visible by processing
Film fog
Appears gray, lacks detail/contrast and caused from light leaks, improper film storage, outdated fil, contaiminated solutions or high developer temp
Optimal Temperature for developer solutions is
68 degrees
Calibration tests and annual tests are performed by
Calibrated = Qualified tech Annual = Dentist, hygenist, assistant or manufacturer
Fresh film appears
Clear with a slight blue tint
Film Processing
One of the most critical areas in quality control and requires daily monitoring
Reference radiographs
Monitors developer solution, used to compare film densities, must use fresh film and fresh chemicals. If unmatched densities solution is too week (lighter densities) or to strong (darker desities)
Clearing test
Monitors fixer strength
The person who is ultimatly responsible for overall quality assurance
The dentist
Dental radiograph is necessary component of patient care and is better than a written record as it enables indentity of
many conditions that may go unnoticed like diseases, lesions, conditions of teeth/bone that can not be seen and for confirming suspected diseases and locating foreign objects.
The primary benefit, most important use of radiographs is
Detection of disease
The top priorities that the dental radiographer should be concerned with is
Patient and operator protection
The dental radiograph is the property of
The dentist, patient may have reasonable access or request a copy