1. 0
Films
Screens
The following slides describe the composition
and uses of intraoral and extraoral films and
intensifying screens.
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2. Intraoral Film
Intraoral film is used for (1) bitewing films
(named for the tab that sticks out from the side
of the film which resembles a wing and on
which the patient bites); this film shows the
crowns of both maxillary and mandibular teeth
on one film; (2) periapical films, which show
the entire length of the teeth in either the
maxillary or mandibular arch and (3) occlusal
films, which are usually exposed at
approximately right angles (perpendicular) to
the occlusal plane and show broad areas of the
teeth and bone.
3. Bitewing Film
The bitewing film is used to identify interproximal
caries (where the teeth contact each other; black
arrows) and the appearance of the alveolar bone
(red arrows). The white areas on the film are
amalgam restorations.
4. Periapical Film
Periapical means “around periapical pathology
the apex”. This film is
intended to show the area
around the root of the tooth.
Normally, the entire tooth is
seen, allowing the internal
resorption
identification of root
problems, interproximal
caries, and the condition of
the bone surrounding the
teeth. This film is also used
in endodontic treatment of a
caries
tooth.
5. Occlusal Film
The occlusal film is used
to identify the extent of
larger pathological
conditions, to locate an
object in the buccolingual
direction, to show the
developing dentition in Impacted maxillary canine
children and to image
patients with trismus
(inability to open the
mouth).
Anterior dentition - Child
6. Extraoral Film
Extraoral films used in Dentistry include the
Panoramic, Lateral oblique jaw film, Skull film,
Cepahalometric and TMJ (temporomandibular
joint). These will be discussed briefly in the
following slides.
7. The panoramic film is the most common extraoral
film used in dentistry. It does not provide the detail
that intraoral films do but it gives an overall view
of the entire dentition, both maxillary and
mandibular. It is very helpful for third molar
extractions
8. The lateral oblique jaw film can be used to image
the third molar region in adults and to show the
developing posterior dentition in children. It is
only used if a panoramic x-ray machine is not
available. The panoramic film is preferred.
9. Skull films, such as this
PA (postero-anterior)
view, are used to evaluate
trauma and
developmental problems.
This patient had external
fixation appliances
placed to help expand the
bone.
10. Ortho-surg. patient – jaw realignment Surgery patient- mandibular implant
Cephalometric films, such as the lateral cephs
above, are used to identify both the bone and the
soft tissue outline on the same film. This film is
used routinely by orthodontists in developing
treatment plans for their patients. It is also used
by oral surgeons for evaluating trauma and
conditions requiring surgical correction.
11. Transcranial film Tomogram
Temporomandibular joint (TMJ) films provide
information on the components of this joint,
including the head of the condyle, the glenoid
fossa and the articular eminence.
12. Film Composition
An x-ray film is composed of a plastic (polyester)
base covered on both sides with an emulsion;
this is called a double-emulsion film. The
emulsion contains silver halide crystals which
are surrounded by gelatin. The silver halide
crystals are affected by the x-rays and eventually
form the image during film processing. The
gelatin, similar to that used in desserts, is
porous, allowing processing chemicals to reach
the silver halide crystals, and is also clear,
allowing light to readily pass through when
viewing films.
(continued on next slide)
13. Film Composition (continued) 0
The emulsion (gray lines below) is attached to the
base with a very thin layer of adhesive (green lines
below). The base has a slight bluish tint which makes
viewing the films easier on the eye. The emulsion is
covered with a thin layer of gelatin, a “supercoat,”
which helps to protect the film (yellow lines below).
Double emulsion
blue-tinted base adhesive
(emusion on both sides)
supercoat emulsion with silver halide
crystals and gelatin
14. Silver Halide Crystals
There are two types of silver halide crystals. Tabular
(flat) crystals are used in F-speed (Insight) film and in T-
Mat and Ektavision film. The crystals are placed in the
emulsion so that the flat surface (top view below) is
parallel with the surface of the film. Globular (rounded)
crystals are used in D-speed (Ultraspeed) film; these
crystals are like small pebbles.
tabular globular
top view
side view
tabular
15. Film Types
There are two types of film used in Dentistry. The
first of these, Direct Exposure Film, is used
intraorally. It is exposed when x-rays come in
contact with it. The film is sealed in a light-tight
packet because visible light, a type of
electromagnetic radiation along with x-rays, will
also expose the film. There are two types of
direct exposure film: D-speed, also called
Ultraspeed, and F-speed, which is called Insight.
16. Film Types (continued)
The other type of film is Screen Film. Screen films
are used for extraoral radiographs. Screen film is
made to be especially sensitive to the effects of
light from an intensifying screen. When these
screens, on either side of the film in a cassette, are
exposed to x-rays, they emit light which in turn
exposes the film. (The x-rays contribute a very
small percentage of the actual exposure of the
film). Using the screen-film combination allows a
very large reduction in the amount of radiation
needed to expose the film (30-60 times less
radiation than that required by direct exposure
film).
17. Intensifying Screen Function
One of the properties of x-rays is that they cause
certain materials to fluoresce (emit light); the
phosphor crystals found in intensifying screens
are one of these materials. The light emission is
usually green or blue, depending on the type of
phosphor crystal used. The composition of the
films used with these screens is adjusted by the
manufacturer to be sensitive to either blue light or
green light. It is important to make sure that the
correct film is used with whichever type screen is
selected. (Blue-sensitive film with blue light-
emitting screen, etc.)
18. 0
Intensifying Screen Composition
(this side toward film)
The base of the screen (yellow line above) is made of
plastic and provides support. A reflecting layer
(silver line) reflects light emitted by the phosphor
back toward the film. The phosphor layer (green line)
contains the phosphor crystals that emit the light.
The surface of the phosphor layer is covered with a
protecting coat (white line) , which is a thin layer of
plastic that protects the phosphor layer from
damage when the screens are handled.
19. 0
Rare Earth Phosphor
The most common type of phosphors being used
are the rare earth phosphors, which emit blue or
green light depending on the type of rare earth
material being used. (Click to show interaction of
x-rays with phosphor crystals)
film
= phosphor crystal
20. Intensifying Screen Speed
0
The speed of the screen depends on crystal size and
the thickness of the phosphor layer (larger crystals
and thicker layer increase speed). Image quality
decreases as the screen speed increases. The three
speeds are:
• Fast (Rapid): requires the least exposure but the
images are less sharp
• Medium (Par): medium speed, medium sharpness
• Detail (Slow): produces the sharpest images but
requires the most exposure
21. Cassette
A cassette holds two
intensifying screens
(one on each side) in
tight contact with the
film. The cassette is
Rigid metal cassette either rigid (metal) or
soft (vinyl), depending
on the type of panoramic
machine.
The rigid cassette has
a layer of foam
padding under each
screen to assure tight
contact with the film.
Flexible vinyl cassette
(See next slide)
22. Cassette/Screens/Film
x-rays
cassette front
foam (rigid cassettes)
screen support
phosphor/coating
film
phosphor/coating
screen support
foam (rigid cassettes)
cassette back
23. 0
The surface of the
screens must be kept
very clean. Any debris
in the cassette
(between the screen
and film) will result in
a white spot on the
film (red arrow). The
other white spots
(green arrows)
represent tonsillar
calcifications.
24. 0
Screen Film (continued)
The two types of screen film used with rare earth
screens are T-Mat and Ektavision. These films are
available in three styles: G, which is used to
provide the best contrast; L, which has the widest
latitude (long-scale contrast) and is good for soft
tissue visualization and H, which is used to provide
an extra film for referral purposes (two films are
placed in the cassette at the same time).
The advantage of Ektavision film over T-Mat film is
that it has anti-crossover layers incorporated into
the film. This prevents light from one screen
affecting both emulsion layers; this produces a
sharper image on the film. (See following slides).
25. T-Mat (crossover) 0
Light produced by the phosphor crystal spreads out
as it goes toward the film and with T-Mat film it
affects the emulsion on both sides. Since it has
spread out more when it reaches the emulsion on
the opposite side of the film (crossover), the
sharpness (edge detail) of the image is decreased.
film
26. Ektavision (anti-crossover) 0
Ektavision film has a crossover control layer on each
side of the film base. These layers allow the light from a
phosphor crystal to reach the emulsion on the same
side as the crystal but prevent the light from reaching
the emulsion on the opposite side of the film. X-rays
easily pass through this anticrossover layer.
film
27. Film Sizes (Intraoral)
# 0: Used in children for both periapical (PA) and
bitewing (BW) films; used for small mouths.
# 1: Used for adult anterior periapicals with the
paralleling technique.
# 2: Used for adult posterior periapicals and
bitewings and for children with larger mouths; also
used in anterior region of adults for periapical
films
taken with bisecting-angle technique; may also be
used for occlusal films in children.
# 3: Used for extra-long bitewing films; one film
covers all teeth on one side of the mouth.
# 4: Used for occlusal films (primarily adults).
(See next slide for comparative sizes)
29. Film Sizes (Extraoral)
5” x 12” and 6” x 12”: Both of these films are used
in panoramic radiography. Some machines use 5”
x 12” and others use 6” x 12”.
8” x 10”: This size is used for cephalometric films,
skull films and tomograms (TMJ).
5” x 7”: This size is not often used. It may be used
for lateral oblique jaw films or for transcranial films
(used for TMJ views).
30. Film Speed 0
The speed of a film represents the amount of
radiation required to produce a radiograph of
acceptable density. (Density is the degree of
darkening of the film; the middle film below has
acceptable density. The one on the left is too light
and the one on the right is too dark). As the speed
of the film increases, the amount of radiation
needed to properly expose it decreases.
31. Intraoral Film Speed
D-speed (Ultraspeed): Once the most common
intraoral film speed used, it is now gradually being
replaced by F-speed film. Technically, this slower
film produces sharper images, improving the
diagnostic ability of the film. It has globular
crystals.
F-speed (Insight): this film has larger silver halide
crystals; they are flat tabular crystals. Because of
the larger size, less radiation is needed to expose
these crystals, resulting in a 60 % reduction in
patient exposure when compared to D-speed film.
32. Extraoral Film Speed
The speed of extraoral film is increased with an
increase in the size of the silver halide crystals.
In general, the faster the film, the less sharp the
radiographic image will be.
Extraoral film is always used with intensifying
screens. Like films, screens have different
speeds.
The overall speed of an extraoral film system
(film plus screen) is determined by the
combined speeds of the film and the screen.
33. Clinasept Barrier Packets 0
Clinasept barriers are sealed plastic covers that protect
intraoral film packets from saliva contamination. After
exposing the film, the barrier is opened at the notch
(see below) and dropped into a bag without touching
the film (see next slide).
front notch back
34. Removing the clinasept
barrier from the film
packet and dropping it
into the film bag. The
film packet must not be
touched with the gloves
that have been in the
patient’s mouth. This
helps to assure that the
film packet is not
contaminated when it is
taken to the darkroom
for processing.
35. Film Packet
The x-ray film packet is made of plastic or paper,
depending on film size. The cover protects the film
from light and moisture. The back side identifies the
type of film (by color), the number of films in the
packet (also by color), and the location of the
identifying dot used for film mounting.
dot
# of films
#2 #2 in packet
#1
plastic plastic
paper
D-speed F-speed
tab
(Ultraspeed) (Insight)
36. Contents of Film Packet 0
Black paper: surrounds film;
protects emulsion.
Film: one or two films;
raised dot in one corner
used for film orientation.
Lead foil: protects film from
backscatter (see next slide);
reduces patient exposure;
strengthens packet; pattern
on foil identifies when film is
placed backwards (back of
film faces teeth).
37. 0
Scatter (secondary) radiation is produced when the
primary x-rays from the x-ray tube interact with the
patient’s hard and soft tissues. Backscatter radiation
refers to those scattered x-rays that go “back”
toward the film.
Primary x-rays
Scatter (secondary) x-rays
38. 0
Film Storage
• Films should be stored at 50–70 degrees F.
Storage at high temperatures may result
in film fogging.
• Opened boxes of screen (extraoral) film need
to be kept in light-tight area (darkroom);
need to be cool.
• Use film before expiration date to avoid
film fogging.
• Do not store film in room where radiographs
are taken
39. 0
This concludes the section on Films and
Screens.
Additional self-study modules are available
at: http://dent.osu.edu/radiology/resources.htm
If you have any questions, you may e-mail
me at: jaynes.1@osu.edu
Robert M. Jaynes, DDS, MS
Director, Radiology Group
College of Dentistry
Ohio State University
