test 2 Flashcards
the dental x ray films serves as a recording medium or
image receptor
image receptor refers to
a picture or likeness of an object
the term receptor refers to something that responds to
stimulus
film base is a
thin flexible (blue tinted to enhance contrast and image quality) covered with photographic emulsion on both sides
adhesive holds
emulsion to film on both sides
emulsion is
is a gelatin with suspended silver halides salt crystals. When placed in water the gelatin swells exposing the silver salts to the developing sol’n. As the gel dries and shrinks, the smooth surface left becomes the radiograph.
During radiation exposure, the x-rays strike and ionize some, but not all, of the
silver halide crystals, resulting in the formation of a latent image (invisible image).
Radiation striking the film causes
ionization of the silver halide
true or false
The amount of radiation is dependent upon what it passes through first.
true
The silver halide salts in the gelatin is very sensitive to
xrays
. The more radiation these crystals absorb
the darker the image will be.
Processing fluids react with these crystals to
produce a visible image on the film
On dental film
90-99% of the salts are silver halide
-1-10% is silver iodide
A Protective Layer, or supercoating of gelatin protects
the emulsion layers
composition of DentalX-ray Film
Film base
Adhesive
Emulsion
Protective layer
What is a thin flexible (blue tinted to enhance contract and image quality covered with photogaphic emulsion on both sides
Film base
What holds emulsion to film on both sides
adhesive
Emulsion is
a gelatin with suspended silver halides salt crystals. When placed in water the gelatin swells exposing the silver salts to the developing sol’n. As the gel dries and shrinks, the smooth surface left becomes the radiograph
During radiation exposure, the x-rays
strike and ionize some, but not all, of the silver halide crystals, resulting in the formation of a latent image (invisible image).
Radiation striking the film causes
ionization of the silver halide. The amount of radiation is dependent upon what it passes through first.
The silver halide salts in the gelatin is
very sensitive to x-rays. The more radiation these crystals absorb the darker the image will be.
Processing fluids react with these crystals to
produce a visible image on the film
Silver halide crystals
On dental film
-90-99% of the salts are silver halide
-1-10% is silver iodide
A Protective Layer, or supercoating of gelatin protects the emulsion layers
Outer Film Packet
Mechanical barrier which is a plastic envelope-like package which protects the film from light, scratches, etc.
Identification dot is visible on the back of the packet- the flap side with color. This raised dot on the film denotes front and back or which side is up.
This dot is ALWAYS placed in the holder 1st
White side toward PID
Intraoral film packets showing the front or tube side (white, unprinted side of the film packet) (top) and the back side (color-coded side) of the film packet (bottom).
WHITE SOLID is top
COLOR CODED IS BOTTOM
layers of x ray film
Photograph of the back of an open film packet. (1) Moisture-resistant outer wrap. (2) Black paper. (3) Film. (4) Lead foil backing.
BLACK PAPER
The paper protects the protective layer over the emulsion on the film base.
Shields film base from light.
A processing error occurs when this black paper is loaded into the processor with the film
LEAD FOIL
Sheet of lead nearest the flap side of the packet therefore the back of the packet. Its purpose is to absorb backscatter radiation- that is deflected radiation back toward the film.
Note the embossed pattern on the end. This is called a herringbone pattern. This pattern along with a much lighter film appears when the operator puts the film in the holder backwards.
TYPES OF FILM
Intraoral
Extraoral
Duplicating
Types of Dental X-ray Film
intraoral
Film packet Packaging Speed groups Film size Types of projections
intraora film packet review
Intraoral-film packets containing 1 or 2 film, black paper, wrapping, lead, foil, outer wrapping
Each film has raised dot on the corner. The raised portion is the front of the film
Black paper helps keep light out
Lead foil helps absorb scatter radiation and prevents back-scatter to fog image. A herringbone pattern appears when film is placed backwards.
film speed
the faster the film, the less radiation is required
the larger the crysta
the faster the film but the grainier the sharpness
the thicker the emulsion
the faster the film
special radiosensitive dyes
incease film speed
FILM SPEED
A F D
A is the slowest and F is the fastest
Only D and F film is still available
FILM SIZES
Size 0- Pedo
Size 1- Pedo and adult anterior where palate is narrow
Size 2-standard PA
Size 3-Longer for BW’s
Size 4-Occlusal films 2 ¼ inches by 3 inches
T OR F
With the exception of the large occlusal film, all intraoral film sizes are available both with and without an attached bitetab for use in taking bitewing projections.
TRUE
bite wing views
BW- views of crowns of teeth and alveolar crests and caries
- views of maxilllary and mandibular teeth on the same film
- views to some extent the occlusion of molars
Periapical
PA—named for the apex of tooth
–views the entire tooth and the surrounding bone
occlusall radiograph
survey large areas especially the floor of the mouth
Extraoral film—screen
screen film-image is from intensifying fluorescent light instead of directly from x-rays
Packaging
Film size
5 x 7 lateral views of the TMJ, Jaw, etc
8 x 10 cephalometric profiles—orthodontist
5 x 12 or 6 x 12 panoramic film
intensifying screens
Transfers x-ray energy into visible light
- allows for much less radiation since intensified - smooth plastic almost looks like cardboard - coated with minute fluorescent crystals called phosphors - when exposed to x-rays phosphors fluoresce and emit blue or green light
in extraora film
Screen film must be placed between
intensifying screen inside of a cassette either rigid or flexibl
in extral oral film blue…
Blue sensitive film must be paired with blue light screens. This is a conventional tungstate screen where the phosphors emit blue light.
in extra oral film the newer rare earth screen
The newer rare earth screen phosphors emit green light and must also be paired with green sensitive film. The rare earth need even less radiation than the blue.
dupicaing film
Only one side is coated with emulsion and appears dull
non-emulsion side is shiny and appears darker (this side is away from the radiograph)
Dull side toward radiograph being copied
Does not use x-rays but light so film is light sensitive
Radiograph film is extremely sensitive to:
Radiation Light Heat and humidity Chemical fumes Physical pressure
film storage
Film should be stored in original packaging in a lead-lined or a fog film box
Keep away from “the line of fire” from the tubehead
Keep away from ligh
Keep in a cool dry place
The darkroom is hotter and has chemical fumes so should not be a storage area
Do not put heavy items on top to create pressure
Shelf life date is printed on the box
t
Radiolucent refers to the portion of the radiograph
black or dak
A diagnostic radiograph has both
black and white portions with many areas of gray.
Radiolucent-portion on the film that is dark or black—the x-rays pass through the tissues
with little or no resistance so the majority strike the film causing darkness
Radiopaque- the light or more white portions on a radiograph– fewer x-rays
can pass through dense structure or tissues so fewer x-ray actually strike the film
examples of radiolucent
soft tissue and air spaces
exampes of radioopaque
enamel
denitn
bone
Density-
the overall blackness of a radiograph. In other words, it must have enough color to be viewed when light is shined through it. Too dark is just as bad as too light.
Milliamperage, kilovoltage, and exposure time
are setting factors of density
also thickness makes a difference
Amt of light transmitted through a film
Less dense-
More dense-
Less dense- much light transmitted
More dense- less light transmitted
density is the blackness that results
Is the blackness that results from the darkening of crystals in the emulsion of the film caused by interaction with x-ray photons.
More photons = darker film
CONTRAST
can be defined as the difference between how black and white with many shades of gray. The more visible shades of gray, the longer the contrast scale and the better the radiograph. This is low contrast. More detail is distinquishable.
Low contrast or long-scale contrast result when
higher kvp is used
think of contrast like the
keys on a piano
The longer the piano keyboard, the more keys are available to play more notes and therefore more of a song than if you only used a few keys.
So we want L and L—low and long contrast
contrast can also be definied as the visibe
difference between densities on a radiograph which is dependent upon the object being filmed (subject) and the film
Subject contrast
a. there must be some difference
example: factory x-raying bolts
b.Increased kV produces lower contrast, more grays which is good
Decreased kV produces higher contrast which is bad
c. Scatter radiation
penetrometer tests demonstrate
radiographically that a longer contrast scale results from the use of 100 kilovolt exposures. Dental radiographs exposed at 100 kVp have long-scale contrast. Radiographs exposed at 65 kVp have short-scale contrast.
exposed at 60 kVp, has
high contrast
exposed at 90 has
low contrast
output consistency test is monitored by
using stepwedge which is a device with layered metal steps of varying thickness to determine film density and contrast. It may also be used to test the strength of the chemicals
stepwedge is place on a
#2 film and exposed. This is compared to a reference film. Reference film is film that is taken on a different day and is considered acceptable
sharpness is
The clarity of the outline of the structures are dependent upon:
a. Geometric factors b. Crystal size in the film emulsion-the larger the crystal the less sharp the image
penumbra
a shadowing around an object, a “halo effect” related to
- Focal spot size- smaller is better
- Long Target- object distance
- Short Object- film distances
- Paralellism-absolute must
- Perpendicular relationship of the central ray to the object and the film
the three subject contras or Radi. image
subject
kvp
scattered radiation
film contrast for rad image
film type
exposure
processing
geometric factos
focal spot size target fim distance object film distance motion screen thickness screen film contact
a small focal spot
and a large
increases sharpness
decreases
long target
short target
increase sharpness
decrease
short target film
long object film
decrease sharpness
increase
no movement
movement
sharp image
fuzzy image
thin screen
thick screen
increase sharp
decrease sharp
small crystals
large crystals
increase sharpness
decrease
geometric factors
A. Focal spot
a.Decreased focal spot increased sharpness
b.If patient or film moves—motion increases focal spot
B. Target Film Distance
a. anode distance to the film
b. PID are 8 or 16 inches
c. decreasing distance makes the beam more divergent
Geometric factors continued
C. Object Film Distance
a. distance of teeth to film
b. decreased distance increases sharpness and decreases magnification
D. Motion-decreases sharpness
E. Screen thickness (intensifying screens)
Are made of crystals that emit light when struck by x-rays. Light intensifies image
Use of screen decreases sharpness
Increasing thickness of screen decreases sharpness
F. Screen Film Contact
Crystal Size
The crystal size in the film emulsion is important in sharpness. We will cover indepth in Chapter 7, but in essence decreasing the crystal size increases sharpness.
Magnification
Mostly influenced by the target-object-distance (which is the length of the PID for our purposes) and the object-film distance
The longer the PID the less magnification but there is an increase in sharpness
distortion
Unequal magnification usually caused by the film not being parallel to the teeth thus the x-rays are not penetrating at a perpendicular angle
Varying exposure factors
mA=the amount of x-rays generated
Increasing the mA darkens the radiograph
Decreasing mA lightens the radiograph
Exposure time
Increasing time darkens the radiograph
Decreasing time lightens radiograph
This is a factor that you can and may change especially for children
increasing kv gives a
shorter wavelength and increases the energy thus increasing penetration.
This is the only factor that directly influences contrast
If mA is the amount of radiation and kV is the INTENSITY of radiation,
then if you increase kV you must decrease mA or decrease the exposure time to compensate
Rule: For every 15 kV increase,
divide the time in half (time/2). For every 15 kV decrease double you time (timex2).
target surface
target film
Target-surface-anode to skin (error, not pushing ring in next to face)
Target-film—-Anode to film
Increasing distance decreases magnification, increases sharpness and decreases penumbra
true or fase
4–5 Using a small focal spot on the target, a long target–film distance, and a short object–film distance will result in a sharp image.
true
Large focal spot on the target and long object
film distance results in more penumbra and therefore loss of image sharpness.
movement of tube head
Motion, even slight, of the tube head will effectively create a larger surface area of the focal spot, resulting in penumbra
The operator must take into account several distances to produce the ideal diagnostic quality image:
The distance between the x-ray source and the surface of the patient’s skin
The distance between the object to be x-rayed and the film
The distance between the x-ray source and the recording plane of the film
processings is
is bringing the latent or hidden (invisible) image on the film to a visible useful radiograph
Preserves the visible image so that a permanent record is created and does not disappear or deteriorates over time
reduction is when
the exposed halide portion through chemical processed is removed leaving the black metallic silver.
Selective Reduction removes
ALL unexposed silver halides leaving nothing.
Reduction is achieved
by the developing solution. Selective Reduction occurs in the fixer.
Developer + rinsing + fixer + rinsing + drying
The film is then placed in fixer solution. The fixer removes
the unexposed silver halides and creates the white or clear areas.
grays
Grays are differing amounts of radiation passing through.
clear film means
no radiation struck the film
steps in manual processing
Developing- solution reduces the silver halide to black metallic solution
Rinsing- purpose is to remove as much of the alkaline developer as possible (fixer lasts longer)
Fixing-removes unused silver halide
Washing- removes any chemicals that may be left
Drying- air or heated to dry film for handling
Automatic Film Processing Solutions
Developer
Fixer
Hardening agents
Replenisher
a fixer
Stops further film development—keeps image permanently
Removes undeveloped silver halide
Hardens emulsion
You will not need to know individual chemical names
Manual Film Processing
Equipment Maintenance Preparation Procedure Following the procedure
the idea floating ttempfor manual fim is
68 degrees five minutes
automati film processing
Faster, usually within 5 minutes
Better quality
Roller transport moves film through the developer, fixer, water and drying compartments in a timed environment
Does require a warm-up
Solutions are supersaturated and contain more hardener in the developer
AUTOMATIC FILM PROCESSING CONTINUED
Some units automatically replenish solutions and others are operator dependent
REQUIRE TIMELY CLEANING
Rollers must be cleaned or film gets stuck or film is streaked
If your rollers are appearing silver, not clean
Care must be taken when processing multiple films to not overlap
A cleaning film (large extraoral film) should be run through the processor
at the beginning of each day before use to clean the rollers. This is in addition to the rollers removal and washed with running water at proper intervals.
SAFELIGHT
A commercially available bracket-type lamp with safelight filter shielding the short wavelength, blue-green region of the visible light spectrum given off by the bulb. The light given off by this filter would appear dark red.
need to know
Because of heating chemicals, the processor is the cause of fires in dental offices
In the darkroom, everything needs to be put in the same place every time
duplicators
Usually contain built-in ultraviolet light and a timer.
Duplicating film comes in panorex size sheets with emulsion only on one side which looks dark. The non-emulsion side appears shiny. Put the dull side against the radiograph with shiny side up.
The machine is turned on. Light is emitted. All of this under darkroom conditions. Then the film is sent through the developer just like an x-ray film would be.
NEVER, NEVER, EVER RELEASE
original films
film duplications
Duplicate radiographs for the patient, for referral, for transfer, for consultations, for publication, etc.
Duplicate radiographs are copies of the original and maybe obtained through a 2 film pack or through use of a duplicator.
duplicators
Usually contain built-in ultraviolet light and a timer.
Duplicating film comes in panorex size sheets with emulsion only on one side which looks dark. The non-emulsion side appears shiny. Put the dull side against the radiograph with shiny side up.
The machine is turned on. Light is emitted. All of this under darkroom conditions. Then the film is sent through the developer just like an x-ray film would be.
Developing errors
Underdeveloped film-light image- weak solutions or too little time in solutions
Overdeveloped film-dark image-developer is too hot, rollers got hung up keeping film in solution too long or timer is messed up
Reticulation of emulsion-cracked appearance- too big a difference in temperature between developer and fixer
if the film appears green on one side and blurred on the other it means
two fils run through the processor together
A Herringbone pattern across one end of the film and a lighter image overall indicates
the film was placed in the holder backwards
Cone cut indicates the ring
was not placed on the XCP properly or the PID was not lined up with the ring properly
an artifact
artifact is anything that appears that does not add diagnostic quality
Static electricity caused
by incorrect handling of film
what do we want to see in BW
Open Contacts
Detection of Decay
bitewings
Bitewings (BW’s) or interproximal radiographs may be taken using film holders or paper bite tabs
The BW should show the crowns of both maxillary and mandibular teeth in the same radiograph with open contacts between the teeth
The teeth should be in occlusion
bite wings again
BW’s are usually 2 or 4 films but a complete set of 7-8 vertical BW’s may be taken for periodontally involved teeth The film is placed horizontally usually with standard film #3 film is longer and usually requires only 1 per side but it is more narrow and shows less crestal bone and does not open contacts as well due to curve of the arch
bw anguation
BW vertical angulation is approximately +10 degrees which corrects for the slight buccal inclination of the maxillary teeth otherwise is would be zero angulation
Failure to have proper inclination of the PID results in showing one arch more than the other which means missing crestal bone levels
angulation again
More than 10 degrees shows more maxillary teeth
Less than 10 degrees shows more mandibular teeth
So if a question asks if you are showing too much of one arch over the other, the error is in Vertical angulation
film holders vs bitetabs
Bitetabs are more versatile Attach to the white side of the film Does not have external aiming device Not as bulky in the mouth Film holders Have external aiming device Uncomfortable and bulky Biteblock is thicker so less alveolar bone is visible
compromised film placement
Most common reason for poor BW’s is poor film placement due to
Patient complaints of discomfort or gagging
Tori
Shallow palate
Patient inability or refusal to open wide enough
central lateral bitewing
Film Position Aligned with distal edges of the canines Vertical position Central Ray Perpendicular to film at +100 angulation
canine bitewing
Film Position Centered on mandibular canine, parallel to mean tangent Vertical position Central Ray Perpendicular to film at +100 angulation
premolar bitewing
Film Position
Must be positioned so that the resulting film shows both the maxillary and mandibular premolars and the distal contact areas of both canines.
Film is parallel to plane of mandibular premolars
Tube Head angulation
Horizontal: Central beam directed perpendicular to the film plane
Vertical: Central beam +100
What Is an Acceptable Premolar Bitewing?
Open contacts between:
Canines and first premolars
First and second premolars
Occlusal plane in the middle of the film
molar bitewing
Film Position
Must be positioned so that the resulting film shows both the maxillary and mandibular molars and the distal contact areas of the premolars.
Film is parallel to plane of mandibular molars
Tube Head angulation
Horizontal: Central beam directed perpendicular to the film plane
Vertical: Central beam +100
What Is an Acceptable Molar Bitewing?
Open contacts between:
Distal contact of the second premolar and first molar
First and second molars and the second and third molar (if present)
Occlusal plane in the middle of the film
NOTE
The contact between the upper first and second molars is often closed on the molar bitewing and open on the premolar bitewing!
errors
Tilted films
Patient does not maintain pressure when biting
Patient swallows
Tori, etc obstructs film placement
Top edge of film is slanted due to touching tooth or palate
Poor placement on YOUR part
Not enough teeth to properly bite
film mounting is
the placement of radiographs in a holder that has the films arranged in an anatomical order
The advantages of this is the ease of viewing and interpreting in the correct order. There is less chance of error of misidentifying the tooth or reversing left and right.
film mounts may be fabritated out of
celluloid, cardboard, or plastic.
There are numerous combinations of sizes and number of frames
2 methods of mounting
Labial mounting method
Views as if you are standing in front of the patient and looking at them.
If I am holding a set of full mouth radiographs, the side in my left hand is the patient’s right side and the side is my right hand is the patient’s left side.
Imagine standing in front of the patient and bending the mount around their face, the radiograph will match the teeth.
MOST COMMON
- Lingual Mounting
- Views as if you are standing behind the patient so what is in your right hand is the patient’s right side and the left is the left.
- Seldom used
interpretation may be defined as
reading the radiograph and explaining what is observed in terms the patient understands.
Interpretation is also defined as the recognition of radiographic errors such as overlapping contacts, elongation, foreshortening, movement, normal and some abnormal developmental anatomies.
diagnosis defined as
the determination of the nature and the identification of an abnormal condition or disease
Diagnosis is the ultimate responsibility of the dentist.
More eyes looking, more likely to see caries, etc.
full mouth
series can be as few as 14 films or as many as 20. Mostly it is 18 films
3 anterior maxillary
3 anterior mandibular
2 posterior in each of 4 quadrants for 8 all together
4 BW’s
the purpose of periapical examination
The purpose of the periapical examination is to view the entire tooth and surrounding bone.
Periapical (PA) shows the entire tooth and should show at least
least 2 mm past the apex of the surrounding bone- bisecting or paralleling techniques may be used
Occlusal radiographs show
larger areas especially the floor of the mouth—a modification of the bisecting technique is used
in paralleing technique the film is
placed parallel to the long axis of the tooth
Since the structures in the mouth prevent parallel placement against the tooth, the film has to be placed
further away from the tooth so the object-film distance is increased so target-film should be increased
points of entry on face
Anterior centrals- tip of the nose
Canine- ala of the nose
Premolars below the pupil of the eye
Molars- the outer canthus of the eye
angulation
Angulation is the angle of alignment between the tubehead and the PID
HORIZONTAL ANGULATION—determines if the x-rays pass through interproximally. Overlapping teeth on the radiograph is poor angulation or extremely crooked teeth
more angulation
VERTICAL ANGULATION– PID and the tubehead are parallel to the floor the angle is zero
When the PID is pointed upward that is a negative angulation and pointed downward is positive
more more angulation
Excessive vertical angulation foreshortens the picture; Too little angulation elongates.
With XCP-excessive-lose portion of the crown
Too little angulation-lose apex
usually
Usually the anterior has vertical film placement and posterior has horizontal film placement
BUT if better bone loss levels are desired vertical posterior may be taken
bisecting
that 2 triangles having equal angles and a common side are equal triangles
Paralleling states that a right angle technique should be used because of less chance of operator error and uses shadow casting rules
shadow casting rules
Use smallest focal spot possible
Object should be as far as practical from the source of radiation
Object and film should be as close as possible to each other
Object and film be parallel to each other
Radiation must strike the object and film at right angles
principles of bisecting
Very helpful in children and adults with shallow palates, tori, or edentulous
Page 139, Figure 12-2 shows bisector line
To bisect you must look at the angle formed by the long axis of the tooth and the film. Imagine a line between and this is the bisector line
Place the PID to right angles to the bisector line
normally for bitewings the film is placed
placed horizontally. The main purpose for BW’s is to diagnose interproximal caries but they are also very helpful for determining bone level.
premolar bite wing should
SHOW THE DISTAL OF THE CANINE AND OPEN ALL CONTACTS BUT ESPECIALLY THE PREMOLAR CONTACTS. IT SHOULD ALSO SHOW EQUAL AMOUNTS OF THE CROWN PROTIONS OF BOTH THE MAXILLLARY AND MANDIBULAR TEETH. +10 DEGREES FOR THE PID. THE MOST COMMON MISTAKE IS PLACING THE FILM AND POINTING THE PID AT ZERO DEGREES. +10 MEANS THE PID IS POINTED SLIGHTLY DOWNWARD NOT EVEN.
molar bitewing should
SHOW THE MOLAR CONTACTS OPEN
+10 DEGREES FOR THE PID
THE TEETH SHOULD BE TOGETHER ON THE BITEBLOCK OR BITETAB. WHEN THE TEETH ARE NOT TOGETHER, YOU WILL NOT HAVE THE BONE LEVEL IN THE PICTURE
quality assurance
REFERENCE FILM-A FILM PROCESSED UNDER IDEAL CIRCUMSTANCES. A FILM IS RUN EACH MORNING AND CHECKED AGAINST THE REFERENCE FILM TO CHECK THE PROCESSING CHEMISTRY
coint test
THE PURPOSE OF THE COIN TEST IS TO TEST THE DARKROOM LIGHT.
AFTER EXPOSING A #2 FILM AT THE LOWEST POSSIBLE SETTING ON THE COUNTERTOP, TAKE IT TO THE DARKROOM AND OPEN THE FILM AND PLACE ON A PAPER TOWEL. LAY A COIN ON THE FILM FOR TWO MINUTES IN THE DARKROOM WITH ONLY THE DARKROOM LIGHT ON. THEN PROCESS THE FILM NORMALLY.
film fog test
ANY TIME A NEW BOX OF FILM IS OPENED, A SAMPLE FILM SHOULD BE TAKEN TO TEST THE FILM FOR FOG BEFORE USING WITH A PATIENT.
beam alignment test
THE PURPOSE OF THIS ACTIVITY IS TO DETERMINE THE SIZE AND ALIGNMENT OF THE PRIMARY BEAM.
(PRETTY MUCH SET AND TESTED WHEN X-RAY MACHINE IS INSTALLED, NOW)
unit output test
THE PURPOSE IS TO EVALUATE THE DENTAL X-RAY UNIT FOR CONSISTENCY OF RADIATION OUTPUT.
THIS IS THE STEPWEDGE TEST
ma caibration testq
THE PURPOSE IS TO EVALUATE THE RADIATION OUTPUT AS CONTROLLED BY THE MILLIAMPERAGE SETTING. THIS IS ASSUMING THE MACHINE HAS A MILLIAMPERAGE SETTING AND IS NOT PRESET IN THE MACHINE
