The recommended beam alignment device for use with the paralleling technique when taking periapical images is?
XCP
Which of the following is NOT a criteria for diagnostically acceptable films?
high density and high contrast
In the canine periapical (PA), which contacts must be open?
Between canine and lateral
The mid-sagittal plane does what?
Divides the body into equal right and left halves
What are advantages of the bisecting angle technique?
Easier to use Less equipment Adapts better to anatomy
Considering paralleling and bisecting techniques, which applies to the paralleling technique?
More accuracy in diagnosis of films
When exposing radiographs, which of the following is true about the central ray?
Aimed through the contact points
Which intraoral exposure technique is more suited to radiographing edentulous ridges?
Bisecting the angle
In which technique is the central beam set at 90 degrees to the imaginary line bisecting the angle formed by the long axis of the tooth and the film packet?
Bisecting the angle
When the beam of radiation does not cover the entire film, the resultant radiograph will exhibit what?
Cone cut
What is the primary use of bite-wing radiographs?
Examination of the interproximal areas of the teeth.
For all bite-wings, where should the central ray be aimed?
Occlusal plane
The paralleling technique using the long cone, compared with the bisecting angle technique using a short cone uses
greater object-film distance greater anode (source)-film distance
The up and down tilting of the PID is called what?
Vertical angulation
When the horizontal angle of the x-ray beam is not directed interproximally, the teeth on the radiograph will appear what?
Overlapped
In which technique are x-rays perpendicular to the long axis of the tooth and film?
Paralleling
What is elongation caused by?
Too little vertical angulation
While taking intraoral radiographs, the midsagittal plane of the patient's head is where?
Perpendicular to the floor
Are horizontal bite-wings the recommended type for patients with moderate-to-severe bone loss?
No
Premolar films are positioned so that the anterior border of the film includes what?
Distal half of the canine
In bisecting, an imaginary line (plane) is drawn halfway between what structures?
The tooth and the receptor
Excess vertical angulation in relation to the bisecting line will result in what?
Foreshortening
Where should the identification dot on intraoral films be?
Raised dot facing the operator Dot always toward the occlusal For bite-wings, dot down
A herringbone appearance on a radiograph is indicative of what?
Reversed (backwards) film
The swiveling, side to side movement of the PID is what?
Horizontal angulation
What is the correct order for the first 5 steps in exposing intraoral radiographs?
1. Position patient 2. Position film 3. Position vertical angulation 4. Position horizontal angulation 5. Position central ray
What structure would NOT be found on a mandibular film?
Hamular process
What is a radiolucent area below the posterior mandibular roots, due to loss of trabecular bone, referred to as?
Physiologic thinning of the mandible
The hamular process radiographically appears to hang from which structure located distal to the maxillary process and superior to the hamular process?
Pterygoid process
When using the dot up to mount films, what is true about the orientation of the films
You are using labial mounting and the client's right is your left
The nasal fossa appears on which films?
Maxillary central Maxillary canine
How does the periodontal ligament appear on radiographs?
As a dark line surrounding the root of the tooth
Is the nasal septum radiolucent or radiopaque?
Radiopaque
What does the nasal septum do?
Divides the nasal cavity
Helpful hints for mounting radiographs
Longer side of film is usually horizontal for posterior teeth and vertical for anterior teeth Mandibular teeth usually have smaller crowns and shorter roots Maxillary molars usually have 3 roots and mandibular molars usually have 2 roots
Radiolucent is a term that describes what?
Dark areas of the film
The image of the coronoid process appears in which film?
Maxillary molar
The small, bony, radiopaque structure that encircles the lingual foramen in the mandibular central incisor radiograph is what?
genial tubercles
The greater palatine foramen is another name for the incisive or nasopalatine foramen - T or FTrue False
False
The "U" of "J" shaped radiopaque structure found in the maxillary molar proejction is what?
Zygomatic process
What is a radiolucent, diffuse, semi-oval area located below the internal oblique ridge and posterior to the mental foramen?
Submandibular fossa
A small, radiolucent, round structure seen between the mandibular premolars, that is often mistaken for pathology
Mental foramen
The incisive canal forman is located between which teeth?
Maxillary central incisors
What is the inverted "Y" formation and where is it found?
The intersection of the anterior wall of the sinus and lateral wall of the nose Seen on canine or premolar projections
What factor has the greatest effect on image sharpness?
Movement
High energy X-rays have what?
Short wavelength and high frequency
Based on the inverse square law, what happens to the intensity of the x-ray beam when the target-film distance is doubled?
Intensity is 1/4 as great
The negatively charged electrode of the x-ray tube is called what?
Cathode
Thermionic emission refers to what?
Process by which electrons leave the filament
Electrons are driven at a high rate of speed across the tube gap from what?
Cathode to anode Negative to positive
As a result of the multiple Bremsstrahlunjg (general radiation) reactions what occurs?
Heterogeneous x-ray spectrum is produced Succeeding x-rays produced will have less energy Later x-rays produced have less penetrating ability Wavelengths are different
What is a characteristic of duplicating film?
Emulsion on only one side
Which speed of film has the greatest sensitivity to radiation?
F speed
What factors degrade film sharpness?
Larger silver halide crystal size Larger focal spot
What are #4 intraoral film packets most likely used for?
Occlusal radiographs
The closer the object-film distance, the better detail and less enlargement of the image occurs - T or FTrue False
True
69 kV is the same as what?
69,000 volts
What is NOT a property of x-rays?
Travel at the speed of sound
An increase in ___ will result in a film with increased density.
Development temperature
What type of film is used to copy a radiograph?
Duplicating film
Who discovered x-rays and when?
Wilhelm Conrad Roentgen November 8, 1895
What is an example of a beam alignment device?
Precision film holders
What is the function of the lead foil in the x-ray packet?
Absorb backscatter radiation
When high speed electrons strike the anode, their kinetic energy is transformed into what?
about 1% x-rays, and the rest in heat
Features of the Stabe bite block
Disposable Slot for film retention
What is the "half value layer?"
The thickness of aluminum placed in the path of the x-ray beam that reduces the intensity by half
What is Dr. Kells known for?
Producing the first dental radiographs in the United States, April 1896
The closer the target (source of radiation) is to the film, the more magnification occurs - T or FTrue False
True
What is an exposure time of 20 impulses?
1/3 second
What will intensifying screens do?
Reduce exposure time
Increasing the current through the filament will do what?
Heat up the filament Boil off more electrons Increase the number of electrons in the electron cloud
What is the major advantage in using the fastest speed film and high kilovolt peak?
Reduces radiation exposure to the patient
The dental radiograph will appear more dense if one decreases what?
Subject thickness
What does the term "focal spot" refer to?
The spot on the tungsten target that is struck by electrons
When does distortion result?
Using a long object-film distance
On earth, what 3 basic states does matter exist in?
Solid, gas, liquid
When a high operating kVp (>90) is used there is low/high subject contrast and many shades of gray/areas of black and white seen on the radiograph
low subject contrast many shades of gray
Why is a 16-inch cylinder used in the paralleling technique?
To avoid magnification of the image
The degree of blackening on an x-ray film is known as what?
Density
What is the formula for determining mAs factors?
mA x (time) x # of films
What provides support for the fragile film emulsion on a film?
Base
What are the main parts of the cathode?
Filament and focusing cup
What term best describes a fuzzy shadow around the outline of the radiographic image?
Penumbra
What does the term "x-ray" refer to?
High-energy, ionizing electromagnetic radiation
When does the latent image on a film become evident?
Upon development
As crystals in the film emulsion increase in size, what happens to the radiographic image sharpness?
Decreases
As crystals in the film emulsion increase in size what happens to the amount of radiation needed to expose the film at acceptable density?
Decreases
When replacing a 16-inch PID with an 8-inch, the impulse setting will change from 20 to what?
5 Inverse law, halve the distance cut down impulses by 4, double the distance increase the impulse by a factor of 4
A stepwedge will reveal that radiographs taken at a lower kVp will have ___ than radiographs taken at a higher kVp
Higher contrast
What is Compton effect?
Bombarding electron collides with outer shell electron and gives up part of its energy Results in negatively charged ejected Compton electron, photon of scatter radiation and positively charged atom Ionization Occurs about 62% of the time
What is a collimator?
Lead washer that reduces the size of the beam leaving the cone, thus reducing exposures of the patient
If the intensity of a film taken at a distance of 8 inches is 8 mR, what will the intensity be if taken at 16 inches?
2 mR
Who regulates the manufacture and installation of dental x-ray equipment?
The federal government
What is considered a screen film?
Panoramic
What controls the QUALITY of radiation
Kilovoltage
How does filtration of the x-ray beam protect the patient?
Eliminating long wavelength x-rays from the x-ray beam
What is the appearance of a radiograph with long-scale contrast (low contrast)?
Many shades of gray
What does sodium carbonate do?
Softens film
Where is the thermometer kept?
In the developer
What is sudden temperature change called?
Reticulation
Underdeveloped film has what kind of image?
Thin
Excessive fixing does what?
Clears the film
What substance serves as a "vehicle" for the developing and fixing chemicals to spread them evenly over the film?
Water
A dark image may be due to what faulty darkroom procedures?
Developing temperatures too high Developing time too long Overexposure of the film
How is developing time determined when using the wet tank?
Temperature of the developer
What step is taken after developing and before placing the film in the fixer?
Rinse the films for 20 seconds with water
What wet tank condition will result in a too light radiograph?
Developing solution too weak
To ensure complete fixation of the radiograph, how long should films be left in the fix solution?
Double the time the film was in the developer, or approximately 10 minutes
What tools are necessary and required for manual processing of radiographs?
Thermometer Timer Time/temperature chart Film hanger
If a film is not fixed for a long enough period of time, what will happen to the film over time?
It will turn brown
Unexposed dental x-ray film should be stored away from what conditions?
Heat Scatter radiation Humidity Light
What should be done to determine a safelight is safe?
Perform a coin test
What factors should be considered when setting up an ideal darkroom?
Color of walls Location Size Lighting
What is the action of the fixer on unenergized silver halide crystals in emulsion?
Remove them from the film
What will over development of a film result in?
Darker radiographic image
What are sulfuric acid and acetic acid used in the fixer for?
Acidifiers
Which chemical is present in both the developer and fixer and acts as a preservative?
Sodium sulfite
What wattage of bulb should be used in a darkroom?
7.5-10
A light image resulting from a darkroom procedure error could be due to what?
Using old or weak solutions
Developer and fixer solutions, with regards to infection control
Do not act as sterilizing agents Promote bacterial and viral growth due to warm, wet environment
What chemical acts as a restrainer by controlling the activity of the developing agent?
Potassium bromide
A film processed in a contaminated solution will have what type of appearance?
Cloudy with poor density
If the film is outdated how may the resultant image look?
Fogged
When processing traditional film, what are the 2 sources of residual silver?
Exhausted developer Old radiographs
Which chemical will change energized silver halide crystals to silver?
Hydroquinone
What is the appearance of developer cutoff?
Straight white border
What is the appearance of fixer cutoff?
Straight black border
Which term describes the process by which the latent image becomes visible?
Reduction
What term describes the does of radiation that the body can endure with little or no chance of injury?
Maximum permissible dose (MPD)
Cells from which types of tissue are the most radiosensitive?
Small lymphocytes Bone marrow Reproductive cells Intestinal mucosa
Maximum protection of the patient requires that the x-ray beam pass through what?
shielded, open-ended cone, appropriate filtration
Radiation from medical and dental procedures accounts for what percentage of the yearly radiation exposure to the US public?
36%
What should be used to protect the patient from unnecessary radiation?
Fast film speed Rectangular collimator Increased source-to-film distance Higher kVp (70-90) Quality assurance program Lead apron Thyroid collar
What are the types and quantity of radiographs to be taken on a patient determined by?
The professional judgment of the dentist based on the patient's individual needs
What factors reduce the radiation exposure of the OPERATOR?
Stand at least 6 feet away from the radiation source Stand behind a protective barrier Avoid the primary beam Positioned 90-135 degrees to the beam
What is NOT a contraindication to taking dental radiographs?
Previous films, type of films and date of exposure unavailable
Federal regulations require the circular size of the beam at the patient's face to be collimated to what size?
2.75 inches
The maximum permissible dose for each dental staff member must not exceed what?
5.0 rem/year
What unit is most commonly used to measure the amount of ionizing radiation in the air that is produced by an x-ray machine?
roentgen
What is the poison water theory of biological effects of radiation?
The production of free radicals which can then combine to form chemicals that are potentially toxic to cells
What is the formula for the maximum accumulated lifetime of radiation for occupational workers?
5.0 rem x (age - 18)
What radiation unit describes the dose or amount of radiation absorbed by the tissue?
Gray
In dentistry, if the localized exposure is 3 rads,, what is the approximate total body exposure?
3 rads divided by 10,000
Are all radiation induced changes in tissue cells permanent?
No
What factors determine the cells ability to repair itself from radiation?
Time interval Dose Tissue sensitivity
Where should radiation badges be worn?
At waist level
What is the most effective way to reduce patient exposure to radiation?
Digital sensor or F speed film (fast film)
What unit of radiation measures the dose equivalent of radiation?
Gray
A tumor forming at the site of radiation exposure is an example of what effect of radiation?
Delayed somatic
A miscarriage is an example of what effect of radiation?
immediate genetic
In radiation biology, what does the "latent period" refer to?
The period of time between the initial exposure to ionizing radiation and the appearance of clinical symptoms
What cells are the most radioresistant?
Muscle tissue Nerve tissue
What is a noncritical organ exposed during dental radiographs?
Masseter muscle
What are critical organs exposed during dental radiographs?
Skin of the cheek Thyroid gland Lens of the eye
What concept is critical to implement in order to minimize patient exposure to radiation?
ALARA - as low as reasonably achievable
Which type of collimator is used more to reduce patient exposure
Rectangular
Who invented the x-ray tube?
William D Coolidge, 1913
