Rad Theory W4

Chapters 9, 10, 11, 22

Image

refers to a picture of an object (tooth)

Receptor

receives image when irradiated

Components of Dental X-ray Film

1. Film Base

2. Adhesive layer

3. Film emulsion

4. Protective layer

Film base

flexible piece of polyester plastic (0.2 mm in thickness)

What component provides support for the emulsion

Film base

Adhesive layer

attaches the emulsion to the base

Film emulsion

attached to both sides of the film base by the adhesive layer

Film emulsion consists of

gelatin and silver halide crystals

Silver Halide Crystals

absorb radiation during x-ray exposure and store energy from the radiation

Emulsion

80-99% silver bromide crystals & 1-10% silver iodide

Protective layer

thin, transparent coating placed over the emulsion

protects emulsions from damage and manipulation

Latent Image

invisible image (invisible until film is processed)

Types of Dental X-ray Film

1. Intraoral

2. Extraoral

3. Duplicating

Intraoral film

placed inside the oral cavity during x-ray exposure

Types of Intraoral x-rays

perapical, bitewing, occlusal

Types of extraoral x-rays

panoramic, cephalometric

Periapical films

peri = around tooth apex = end of tooth

Horizontal bitewings are useful for?

diagnosing interproximal caries and bone level

The ______ the crystals, the faster the film speed

larger

Which film is the fastes?

F film is fastest (the larger crystals and an increased amount of silver bromide)

Does a fast speed film require more or less radiation?

Less

Faster film creates images that are

less sharp due to LARGE crystal size

FAST-LESS-LARGE

Slower film created images that are

more sharp due to SMALL crystal size

SLOW-MORE-SMALL

The tube side of an intraoral film packet must always face which way?

The teeth and the x-ray tubehead

The label side of the intraoral film packet must face which way?

the patient’s tongue (white in sight)

Screen films

placed between 2 special intensifying screens in a cassette

sensitive to fluorescent light rather than direct exposure to x-radiation

Cassette

holds extraoral film and intensifying screens

Panoramic Film

shows all teeth in the mouth

Cephalimetric Radiograph

used for oral surgery and ortho

shows the side profile and spine

Duplicating machines

like a photocopier for x-rays

(used for insurance companies)

Film should be stored in

a cool dry, place

away from radiation

What are the basic steps for manual processing?

1. Developement

2. Rinsing

3. Fixation

4. Washing

5. Drying

Development

emulsion is soften; silver halide crystals reduced to black causing dark or black images on a radiograph

Rinsing

film is rinsede to remove developer solution and STOP the developing proces

Fixation

removed unexposed silver halide crystals, creating white/clear areas on a radiograph; emulsion is hardened

Washing

remaining chemical solutions are removed in water bath

grey areas =

latent image produced by exposure

What are the 2 chemical solutions necessary for film processing?

developer and fixer

Developer composition

1. developing agent

2. preservative

3. accelerator

4. restrainer

Developing agent

1. Hydroquinone

   producing black tones and contrast in the image

   temp sensitive

2. Elon/Metol

   produces many shades of grey

   not temp sensitive

Preservative

extends the life of developer

accelorator

activates developing agent (alkaline environment)

Restrainer

prevents fogging

Fixer composition

1. fixing/clearing agent

2. preservative

3. hardening agent

4. acidifier

FIxing/clearing agent

removes all unexposed, underdeveloped silver halide crystals from the emulsion

ex. sodium thiosulfate

Preservative

Prevents deterioration of the fixing agent

ex. sodium sulfite

Hardening agent

-hardens and shrinks the gelatin in the emulsion

Acidifier

neutralizes the alkaline developer; provides necessary acidic environment required by the fixing agent

Darkroom

must be sealed off from any light leakage

Light film

underdeveloped film = low density

caused from insufficient developing time, low developer temps, contaminated dev solutions, inaccurate timer and thermometer

Dark film

overdeveloped film = image very dark

caused from excessive developing time, high developing temps

Reticulation

Film appears cracked

caused from a sudden change between dev and water bath temp

Developer spots

dark spots on film

caused from developer solution coming into contact with film before processing

Always ensure a clean working area

Fixer spots

white spots on film

caused from fixer solution coming into contact with the film before processing

Always ensure a clean working area

Yellow-brown stain

film appears yellowish-brown

caused from exhausted processing solutions, insufficient fixing/rinsing

Developer cut off

a straight white border appears on the film

caused from insufficient developer solution

Fixer cut-off

a straight black border appears on the film

caused by insufficient fixer

Overlapped film

2 films come into contact with each other during processing

Air bubbles

white spots caused by air is trapped on film after placed in processing solutions

(gently agitate film rack after placing in processing solutions)

Fingernail artifact

black, crecent shaped marks on filim

caused by rough handling of films

use finger pads and only handle the edges

Fingerprint artifact

a black fingerprint on film

Caused from touching the film with contaminated fingers of developer or fluoride

work in a clean area

Static electricity

film has thin black branching lines

caused by opening a film packet too quicklly prior to touching another object(carpeted area)

Scratched Film

white lines appear on flim

caused when film emulsions is removed form the base by a film clip or hanger

Light leak

exposed area appears black

caused from white light exposure or defective film packets

Fogged Film

film appears grey, lacks detal and definition

Film mounting

provides a systematic approach for viewing and evaluating radiographs

cardboard, plastic or vinyl

may be opaque or clea; opaque is preffered

What is the importantance of sequence?

efficiency and accuracy

FFP

faulty film placement

fix: move film accordingly

BB

Teeth not on bite block

fix: bite

FDP

faulty dot placement

1/8” IOES

+/- 1/8” inadequate occlusal edge space

OPNP

Occlusal plane not parallel to edge of film

HA

Horizontal angulation (closed contacts)

fix: center ray to go through the contacts

CC

Cone cut

fix: center PID over film

AC

Apex cut off

fix: move PID up, chair through window (XCP rinn)

RD

radiographic density

fix: set x-ray machine at 8 impulses, hold button long enough

FD

film damaged

fix: grab new film

VA

vertical angulation

(too much or too litlle angulation > foreshortening or elongation)

fix: correct angulation

FR

Film reversed

(lookes like tire tracks)

fix: put film in correct way

PP

Processing pitfall

fix: fill solutions properly, keep area clean

unexposed film

film appears clear

fix: expose film

Film appears black

film accidentally exposed to white light

Overexposed film

film appears dark

too much exposure time, kVp, or mA

Underexposed film

film appears light

insufficient exposure time, kVP, or mA

Phalangioama

finger appearing on film

patient holding film

Double exposure

film exposed twice

Penumbra

blurred images on film ‘

movement of client

Ghost image

metallic objects not removed before a panoramic film

Lead apron artifact

lead apron too high up and shows on film

Curve of spee

natural curvature of the teeth

Reverse smile line

clients chin is tipped up

not biting down properly

Curve too steep

chin too low

teeth anterior to the focal trough

client’s teeth are positioned too far forward on the bite block or anterior to the focal trough

anterior teeh appear narrow and out of focus