midterms Flashcards
X-ray Machine Components
Tube-head
P.I.D. (Position Indication Device)
Extension Arm
Control Panel
radiation
A form of energy carried by waves or a stream of particles
x-radiation
A high-energy radiation produced by the collision of a beam of electrons with a metal target in an x-ray tube
x-ray
A beam of energy that has the power to penetrate substances and record image shadows on photographic film or digital sensors
radiograph
An image or picture produced on a receptor by exposure to ionizing radiation. A two-dimensional representation of a three-dimensional object
Radiology
The science or study of radiation as used in medicine; a branch of medical science that deals with the use of x-rays, radioactive substances and other forms of radiant energy in the diagnosis and treatment of disease
Radiography
The art and science of making radiographs by the exposure of film to x-rays
The ATOM consist of a central nucleus and orbiting
electrons
Nucleus contains
Protons: positively charged particles, Accelerated particles, specifically hydrogen nuclei
Neutrons: carry no electrical charge, Accelerated particles with mass of 1 and no electrical charge
The____ is located closest to the nucleus and has the _____ level
K shell
highest energy
Ionization Radiation
Radiation that is capable of producing ions by removing or adding an electron to an atom
Particulate radiation:
tiny particles of matter that possess mass and travel in straight lines at high speeds
Beta particles:
: fast moving electrons emitted from the nucleus of radioactive atoms
Cathode rays:
streams of high-speed electrons that originate in an x-ray tube
Alpha particles
Emitted from the nuclei of heavy metals and exist as two protons and neurons, without electrons
Wavelength
is the distance between the peaks or crest of a wave frequency
Energy moving through space
Frequency
= the number of crest in a given period of time determines the energy
The longer the wavelength
the less energetic the wavelength
The shorter the wavelength the
more energetic the wavelength.
- Control Panel
On and off switch
Indicator light
Exposure button
Controls for kVp and mA
- Extension Arm
Suspends the x-ray tube-head
Houses electrical wires
Allows movement of tube-head
- Tube Head
Where x-rays are produced
Tube- head contains
Metal Housing Insulating oil Tubehead seal X-ray tube Transformer Aluminum disks Lead collimator Position-indicating device (PID)
X-ray Tube
Heart of x-ray generating system
Leaded glass housing (envelope)
Prevents x-rays from escaping in all directions
Cathode
Purpose is to supply the electrons necessary to generate x-rays
Anode
purpose is to convert electrons into x-ray photons
Production of dental x-rays
- Filament circuit is activated, filament heats up and thermionic emission occurs
- Exposure button is pushed
- Electrons strike the tungsten target, and their kinetic energy is converted to x-rays and heat
Primary radiation (primary beam):
refers to penetrating x-ray beam
Secondary radiation
X-radiation that created when primary beam interacts with matter (less penetrating than primary beam)
Scatter radiation
A form of secondary radiation
X-ray has been deflected from its path by interaction with matter
Is detrimental to both patient and radiographer
X-ray film used in dentistry has four basic components
A film base
An adhesive layer
Film emulsion
A protective layer
Film Base
Is a flexible piece of polyester plastic
0.2mm in thickness
Constructed to withstand heat, moisture, and chemical exposure
Purpose : to provide a stable support for the emulsion and strength
Adhesive layer
Purpose: attaches the emulsion to the base
Added to the film base before the emulsion is applied
Film Emulsion
A homogeneous mixture of gelatin and silver halide crystals
Purpose: to give the film greater sensitivity to x-radiation
Gelatin
Used to suspend and evenly disperse millions of microscopic silver halide crystals over the film base.
During film processing, the gelatin absorbs the processing solutions and allows the chemicals to react with the silver halide crystals
Halide
a chemical compound that is sensitive to radiation or light
Silver halide crystals absorb radiation during
x-ray exposure and store energy from the radiation
Protective layer
Purpose: to protect the emulsion surface from manipulation, as well as mechanical and processing damage
latent image
image is not visible before processing
Latent Image Formation
When radiation interacts with the silver halide crystals in the film emulsion, the image on the film is produced
three types of x-ray film
Intraoral film
Extraoral film
Duplicating film
Intraoral Film
Film used to examine teeth and supporting structures
X-ray film
A double-emulsion film
Requires less radiation exposure to produce image
Paper Film Wrapper
Protective sheet that covers film
Shields the film from light
Lead Foil Sheet
Protects film from backscattered (secondary) radiation that results in film fog.
Contain an embossed pattern on foil sheet
Will appear on x-ray is it was positioned in mouth backwards
Outer Package Wrapping
Protects film from exposure to light and saliva
Label Side of Film Packet Contains the following information
A circle or dot that corresponds with the raised identification dot on the film
The statement “opposite side toward tube”
The manufacturer’s name
The film speed
The number of films enclosed
Periapical Film
Used to examine the entire tooth (crown and root) and supporting bone
Bite-Wing Film aka inter proximal film
Used to examine the crowns of both maxillary and mandibular teeth on one film
Occlusal Film
Used for examination of large areas of the maxilla or mandible
Periapical film sizes
Size 0 is smallest intraoral film
Size 1 is used primarily to examine anterior teeth of adults
Size 2, also know as the standard film, is used to examine the anterior and posterior teeth in adults
Bite-wing film sizes
Size 0 is used to examine posterior teeth of small children
Size 2, is used to examine posterior teeth of adults. This is the most frequently used bite-wing
Size 3 is longer and narrower that the standard size 2, shows all posterior teeth in an arch.
Occlusal film size
Size 4, is the largest intraoral film, used to show large areas of the maxilla and mandible
Intraoral Film Speed
Film speed refers to the amount of radiation required to produce a radiograph of standard density
Film speed or sensitivity is determined by
Size of the silver halide crystals (Larger =Faster)
Thickness of the emulsion
Presence of special radiosensitive dyes
Speeds of X-ray films are given alphabetical classification :
A speed (slowest) to F speed (fastest)
Only _ and _ speeds are used for intraoral radiography
D and F
Extraoral Film
Are used to examine large areas of the skull and jaws
Common extraoral film include:
panoramic and cephalometric
Panoramic film
Shows a panoramic (wide) view of maxilla and mandible and surrounding structures
Cephalometric film
Shows the bony and soft tissue areas of the facial profile
Screen film
Requires intensifying screens and cassettes
Intensifying screens transform x-ray energy into visible light, which exposes the film
Requires less radiation = less patient exposure
Nonscreen film
Not recommended for use in dentistry
Slower = more patient exposure
Duplicating Film
A type of photographic film used to make an identical copy of an x-ray
Used in a darkroom setting and is not exposed to x-radiation
Duplicating film has emulsion on one side only
Emulsion side appears dull
Non –emulsion side appears shiny
The emulsion side must contact the radiograph to duplicate it
Films are adversely affected by
heat, humidity, and radiation
film Must be stored away from radiation sources at
500 to 700 F
film storage:
Relative humidity of 30% -50%
Dark room requirements
Conveniently located Adequate size Equipped with correct lighting Arranged with ample work space with adequate storage Temperature and humidity controlled
dark room Location and Size
Should be near, where x-ray units are installed
Accommodate film processing equipment
Allow ample work space
At what distance from the working area should the safelight be place?
(Four feet.)
Why does the safelight need to be placed at this distance?
To decrease the intensity of the light reaching the indeveloped film. Safelight will still expose a film if left long enough or help close enough
Safelight filter
Removes short wavelengths in the blue-green portion of the visible light spectrum
Darkroom work space
Must include an adequate counter area where films can be unwrapped
Must be kept clean, dry, and free from processing chemicals
Darkroom storage space
Humidity level
Darkroom plumbing
Steps that produce a visible image on a dental radiograph
Convert the latent image to a visible image
Preserve the image so it is permanent
The film used in dentistry has three primary components
Emulsion = photosensitive crystals that ultimately form the radiographic image
Base = made of polyester plastic providing support for the emulsion
Gelatin = the specialized “glue” that holds the emulsion to the base.
The ___form a pattern and creates an invisible image within the emulsion on the exposed film.
silver halide crystals
Silver halide crystals
Absorb x-radiation during x-ray exposure
The Emulsion of the film:
Is composed of crystals of silver halide (AgBr2, AgCl2)
Reduction
The halide portion of the exposed, energized silver halide crystal is removed.
This results in a precipitated black metallic silver
Selective Reduction:
The energized, exposed silver halide crystals are black
The unenergized, unexposed crystals are removed from the film
Resulting in the latent (visible) image
From Latent Image to Visible Image
The film is placed in developer solution.
The film is placed in fixer solution.
The film is washed in water.
The film is dried.
The Visible Image
Made of black, white, and gray areas
Radiolucent
Readily permits passage of the x-ray beam
radiolucent appears what color
black
Radiopaque
Resists passage of the x-ray beam
Radiopaque appears what color
white
Film Processing Solutions May be obtained as:
Powder
Ready-to-use liquid (Automatic Processors)
Liquid concentrate
___ ___ is by far the most commonly used solution.
Ready-to-use liquid
What would films look like if the developer solution was not diluted?
(The film would appear overdeveloped.)
Film Processing Solutions (Automatic Processor) To maintain freshness:
Must be checked for replenisher daily.
Must be replaced every 2 to 6 weeks (or manufacturer’s recommendations).
May need to change more frequently when large numbers of films are processed.
The purpose of the developer is to
chemically reduce the exposed silver halide crystals to black metallic silver.
The developer solution also____ the film emulsion during this process.
softens
Developer Solution
Developing agent
Hydroquinone: black tones and sharp contrast
Elon: shades of gray
Preservative – sodium sulfite
Accelerator – sodium carbonate
Restrainer – potassium bromide
Fixer Solution
Fixing agent
Sodium thiosulfate or ammonium thiosulfate
Commonly called “hypo”
Preservative – sodium sulfite
Hardening agent – potassium alum
Acidifier – acetic acid or sulfuric acid
The purpose of the __ ___ is to remove or clear all unexposed and underdeveloped silver halide crystals from the film emulsion.
fixer solution
Automatic Film Processing
Often preferred over manual film processing
Less processing time required
Time and temperature automatically controlled
Less equipment used
Less space required
Daylight loader
May be used in a room with white light
What beam alignment devices may be used with the paralleling technique?
Rinn XCP instruments Precision Film Holders Stabe Bite-Block EEZEE-Grip Film Holder Hemostat with Bite-Block
What are the advantages of the paralleling technique?
The primary advantage of the paralleling technique is that it produces a radiographic image without dimensional distortion.
- Accuracy
- Simplicity
- Duplication
What are the disadvantages of the paralleling technique?
Receptor placement
Discomfort
What are the basic principles of the paralleling technique?
- The receptor is placed in the mouth parallel to the long axis of the tooth being radiographed.
- The central ray of the x-ray beam is directed perpendicular to the film and the long axis of the tooth.
- A beam alignment device must be used to keep the receptor parallel with the long axis of the tooth.
Object-receptor distance (tooth – film)
Must be increased to keep the receptor parallel with the long axis of the tooth
Target-receptor distance (x-ray beam-film)
Must be increased to ensure that only the most parallel rays will be directed at the tooth
Beam Alignment Devices
A device used to position the receptor in the mouth and retain the receptor in position during exposure
How do film holders reduce exposure?
(In two ways: by preventing cone cuts, thus reducing retakes; and by allowing the film to be held in place without the aid of the patient’s finger in the field of radiation.)
What does XCP stand for?
(extension-cone paralleling.)
Rules for Paralleling Technique
Receptor placement Receptor position Vertical angulation Horizontal angulation Film receptor exposure
Receptor Placement for Paralleling Technique
The specific area where the receptor must be positioned before exposure
Dictated by teeth and surrounding structures
Modifications in Paralleling Technique
Shallow Palate
Bony Growths
Mandibular Premolar Region
What factors influence film density?
Milliamperage
Operating kilovoltage
Exposure time
Subject thickness
Density
Refers to the overall darkness or blackness of a dental radiograph
influencing factors of contrast?
Increasing the kilovoltage affects image contrast by increasing the mean or average energy of the x-rays and by producing higher energy x-rays.
what controls contrast
kilovoltage
Short-scalecontrast (high contrast)
A radiograph with only two densities, black and white
Occurs with machines functioning at low kVp
Long-scale contrast (low contrast)
A radiograph with many densities, many shades of gray
Occurs with machines functioning at high kVp
Long-scale contrast (low contrast)
A radiograph with many densities, many shades of gray
Occurs with machines functioning at high kVp
A lack of ____ can change a diagnosis dramatically. It may cause a problem to be undetected in a early stage when the prognosis would have been more favorable
sharpness
_____ is especially important when measuring the length of a tooth during root canal therapy.
Magnification
_____ occurs when a radiograph is taken at a vertical angle that is greater than or less than necessary, resulting in a film image that appears either stretched out or shorter than it really is.
Distortion
Sharpness
is the capability of the x-ray receptor (film) to reproduce the distinct outlines of an object.
Is the fine outline of the image on a radiograph
penumbra.
A certain lack of image sharpness is present in every radiograph;
Penumbra is the fuzziness of an outline.
sharpness is influenced by 3 factors
focal spot size
film composition
movement
Film speed may affect sharpness due to
the different sizes in silver bromide crystals. The faster the film speed, the larger the crystals.
Magnification
Results from the divergent paths of the x-ray beam as they radiate from the focal spot
The object size appears larger on the film than its’ actual size.
Influencing factors of magnification
Target-receptor (Source (PID) to film) distance
Object-receptor (Tooth to film) distance
Object-receptor (Tooth to film) distance
An increase in object-receptor distance results in an increase in image magnification.
Target-receptor (Source (PID) to film) distance
A longer PID and target-receptor distance results in less image magnification.
Distortion
Results from unequal magnification of different parts of the same object because of improper receptor alignment or angulation of the x-ray beam
Misshape of images on a radiograph
influencing factors of distortion
Object-film alignment
Object-film alignment
The object and film must be parallel to each other or there will be distortion.
The x-ray beam must be directed perpendicular to the tooth and film.
Periapical Examination
Purpose:Used to examine the entire tooth and supporting bone
Type of imaging receptor: Periapical receptor
Technique:Paralleling and bisecting
Interproximal Examination
Purpose: To examine the crowns of both the maxillary and mandibular teeth on a single film
Type of imaging receptor: Bite-wing receptor #2 is standard (Premolar/Molar Views) #3 premolar and molar on single film
Technique: Bite-wing technique
This type of film is most often taken to check for cavities between teeth.
Interproximal
Occlusal Examination
Purpose:Used to examine large areas of the maxilla or the mandible on one film
Type of imaging receptor: Occlusal receptor
Size #2 or #4
Technique:
Occlusal technique
This type of film is most commonly seen in pediatric dental offices.
Occlusal film
full-mouth series or complete series.
This series can include only periapicals or be a combination of periapicals and bite-wings.
A total of 14 to 20 films may be taken.
Film size selection is important.
Used to detect disease, foreign objects, retained roots.
Patients usually have a full-mouth series of x-rays taken every 3 to 5 years.
full-mouth series or complete series.
This series can include only periapicals or be a combination of periapicals and bite-wings.
A total of 14 to 20 films may be taken.
Film size selection is important.
Used to detect disease, foreign objects, retained roots.
Patients usually have a full-mouth series of x-rays taken every 3 to 5 years.
Diagnostic Criteria for Intraoral Images
- Images must have optimum density, contrast, definition, and detail.
- Images must have the least amount of distortion possible.
- The CMS must include images that show all tooth-bearing areas.
- Periapical images must show the entire crowns and roots of teeth being examined
- Bite-wing images must show open contacts.
Not all patients need a CMS.
CMS is appropriate when a new adult patient presents with clinical evidence of generalized dental disease or a history of extensive dental treatment.
Otherwise, a combination of bite-wings, selected periapicals, and/or a panoramic image should be prescribed on the basis of a patient’s individual needs.
