FILMS
&
ACCESSORIES
INTRODUCTION
X-ray film is a medium used to capture the image for
interpretation and storage
EVOLUTION OF FILMS
1895 - German dentist Otto Walkhoff – first dental radiograph
- glass photographic plates wrapped in black paper and
rubber.
1896 – C Edmund Kells – exposed first dental radiograph using a
living person
1913 – hand wrapped moisture proof packet containing two
films were introduced
1919 - first machine wrapped films – Regular film (Kodak)
became commercially available.
1924 – Radiatized film (Kodak)-emulsion placed on both
sides double speed & reduced exposure to 50%
1940 - improved radiatized (kodak)-ultra speed
1980 - Ekta speed film (Kodak)- reduced exposure 50%
2000 – Eastman Kodak introduced InSight, an F-speed intraoral
film
EVOLUTION OF FILM BASE
1920- cellulose nitrate base (highly inflammable and emitted poisonous
gases when burned)
1924- cellulose triacetate base – non inflammable, expensive, tendency
to break, subject to mold, wrinkled
1960 - film base of polyester [DACRON]- stronger-thinner films madenot tend to wrap.
CONVENTIONAL FILMS
Types of films
I) Based on use
- intra oral
- extra oral
- duplicating
- self developing
II) Based on mode of action
- direct exposure/non screen
- indirect exposure/screen
III) Based on speed
- slow speed
- fast speed
- high speed
III) Based on emulsion coating
- single coated
- double coated
IV) Based on packaging
- single film packet
- double film packet
V)Based on type of emulsion
- blue sensitive
- green sensitive
- orthochromatic
- panchromatic
- infra red
FILM COMPOSITION
Base - 0.18mm , polyester polyethlene terephthalate
transparent/ bluish tint
withstand heat, moisture & chemicals
support to emulsion
Adhesive layer – both side
attach emulsion to the base
Emulsion - 2 components
a) Silver halide – Ag B and Ag I
To increase photo sensitivity - traces of sulphur and gold
b) Vehicle – gelatinous and non gelatinous material
- to evenly disperse the silver halide
- absorbs the processing solutions allowing chemicals to
reach and react the silver halide grains
Protective overcoat - an additional layer of vehicle
- to protect film from damage – scratching, contamination
or roller pressure
FILM PACKAGING
Contents of an intra oral film packet
A)outer wrapper
B)protective black paper
C)the film
D)sheet of lead foil
Outer white paper or plastic wrap - resistant to moisture
Label side
Tube side
Thin lead foil with an embossed pattern – behind the film away from
the tube
shields film from secondary radiation/back scatter & reduces film fog
Reduces patient exposure – absorbing residual x-ray beam
Black paper wrapping – protective cover
Types of intra oral films
Periapical films - used to record crown, root
and surrounding bone
Bite wing films – used to record coronal
portions of maxillary and
mandibular teeth in one
image
Occlusal films – used to show larger areas of
maxilla or mandible. Film
is held in place by patient
biting lightly on it to support
it between occlusal surfaces
of the teeth
Based on size of films
35
57 x 76mm
Based on film speed
It is the amount of radiation and exposure time required to produce
a radiograph of standard density
- determined by
1. size of halide crystals.
2. thickness of emulsion.
3. presence of special radiosensitive dyes.
Alphabetical classification – identify film speed- A to F.
D-speed and E-speed used in dentistry.
Scanning electron micrographs of emulsion
comparing globular silver halide crystals of
Ultra-Speed film (A) and flat tabular silver
halide crystals of Insight film (B)
EXTRA ORAL FILMS
Films placed outside the mouth during exposure
eg:- panoramic projections, skull radiographs, lateral oblique
projections etc
Film packaging
- designed to be used outside the mouth so not enclosed in
moisture proof packets.
Sizes
- Panoramic - 6”x 12”or 5”x 12”
- Skull views – 8”x 10”
- lateral oblique – 5”x 7”
- CT and MRI – 14”x 17”
DUPLICATING FILMS
Used to make identical copies of intraoral & extra oral radiographs
Used in darkroom settings & not exposed to x-rays
Emulsion only on one side of film and this side contacts radiograph
to be duplicated and held tightly together
A light source or duplicator is activated with a set timer
Once exposed, film processed using manual or automatic
processing techniques.
SELF DEVELOPING FILMS
Films in a special sachets containing developer and fixer.
After exposure developer tab is pulled and spread over film
After 30sec fixer tab is pulled and similarly milked down to the film.
Used chemicals discarded and film rinsed with water for 10mts
Darkroom facilities not needed, time saving,
Expensive, poor image quality, flexible,
easily bent film packet, image deteriorate
with time, no lead foil, difficult to use
with holders
FILM STORAGE
Clean, cool, dry, light tight location
40 – 60 % humidity
70 º Fahrenheit
Away from chemical fumes
Safe from radiation exposure
Boxes placed on their edges
Expiration date clearly visible.
Film can be stored for about 45 days, use
the first-in first-out rule
ACCESSORIES
1) Film holders
2) Cassettes
3) Intensifying screens
4) Grids
FILM HOLDERS
RINN SNAP-A-RAY FILM HOLDER
Plastic film holder.
No film backing-film bend-distortion
RINN XCP INSTRUMENTS
Designed by Dr.William J Updegrave, Philadelphia
Instrument consists of 3 components
Anterior and posterior bite blocks: designed to retain film packet by
means of tension created by a semi-flexible plastic backing.
Indicator rod: made of stainless steel.
Used to align x-ray cone with the
film.
Locator ring: to align the cone
with the film to prevent cone cut
Sterilization - Rinse in running tap
water and remove saliva, steam
autoclaved, dry heat sterilization
ADVANTAGES OF FILM HOLDERS
Film placement parallel to long axis of tooth maintaining flat
planes.
Retain film position until properly exposed.
DISADVANTAGES OF FILM HOLDERS
Presence of bite block-resting on teeth-film not extend beyond
apical region-not able to examine apical tissues or structures
Mouth closing over the block-prevent from checking position of
film in mouth-by operator
Cause distortion of teeth- difficult to angulate tube in abnormal
conditions
CASSETTES
- Flat box used for transporting
a film
- holds the intensifying screen
and film in close contact with
each other
FUNCTIONS:
1. Prevent light exposure
2. maintains film in close contact with the screen during exposure
IDEAL REQUIREMENTS:
1. should not be heavy
2. should not damage easily & should be strong enough to
withstand daily rough handling.
3. design should help easy handling in diminished light setting of
dark room.
4. should have smooth outline and round corners
TYPES OF CASSETTES
Rigid cassettes
Book like container consisting of two aluminium
or bakelite leaves which open and close on
hinges.
Front cover lid– faces the tube head- constructed
of plastic or low density metal- less resistance to
passage of x-rays.
Black plate- heavy metal lined with
lead-absorb x-rays passing through
enclosed film-reduce scatter radiation.
FLEXIBLE CASSETTES:
Used for adaptation of
round surfaces. Panoramic
cassettes are flexible. To
load properly film must be
placed b/w the screens and
pushed to end of cassettes.
CURVED CASSETTES:
Used to achieve a parallel
relationship b/w the subject
and film in certain
anatomical regions with
curvature.
INTENSIFYING SCREENS
It is part of a cassette, positioned inside a cassette that hold it in
contact with x-ray film to maximize the sharpness of the image.
Used in pairs- one on each side of film.
Function – to make the film 10-60 times more sensitive to x- rays
than film alone
Reduces x-ray exposure to patient
Used in all kinds of extra-oral radiography
Intra oral radiography- not used- reduce
resolution of resulting image.
COMPOSITION
Base:
polyester plastic having
thickness 0.25mm
support materials comprising screen .
Reflecting layer:
white layer
of TiO2. reflects light emitted by
phosphor layer.
Phosphor layer: light sensitive
phosphor crystals suspended in plastic
material.
Protective layer: plastic coat of about
.8micrometre thick
Speed and resolution of a screen depends on –
i)
ii)
iii)
iv)
Phosphor type and conversion energy
Thickness of phosphor layer and coating weight
Presence of reflective layer
Presence of light absorbing dyes in phosphor binder or
protective coating
v) Phosphor grain size
GRIDS
Devices which reduce the amount of scattered radiation reaching
the film
Positioned b/w object & film
Consists of large no: of long parallel strips of radio opaque material
eg: lead interspersed with radiolucent with radiolucent interspace
material (plastic)
An IDEAL GRID should be capable of removing 80-90% of
scattered radiation– resultant image better contrast- improvement
called contrast improvement factor (k)
k = x-ray contrast with grid/ x-ray contrast without grid
ideal grid – k value- 1.5 to 3.5
GRID RATIO (r) =
thickness of lead strips (h)
width of radiolucent interspacer (d)
higher grid ratio- effective removal of scattered radiation from
beam
STATIONARY GRIDS:
1. LINEAR GRIDS:
strips of lead placed parallel to each other.
- some primary beam absorbed by lead in peripheral region.
2. FOCUSED GRID:
primary cut off prevented-- strips of lead are angled
progressively from center to the edge so that interspaces point at
the focal spot, thus their direction coincides with the direction of
the path of diverging photons
3. PSEUDO FOCUSED GRID: height of the strips is reduced
progressively from the center resulting in a reduced grid ratio
from the center to edge.
4. CROSSED GRID: two grids are placed on top of each other and at
right angles. It minimizes scattered radiation travelling in same line
as primary beam.
5. MOVING GRIDS: [POTTER BUCKY GRID]
- grid moved sideways across the film during exposure blurring
out of shadows of grid strips from the films.
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