FilmImage Characteristics

Processing

What is X-ray Film◦ Photographic film that has been adapted for

dental use◦ Photographic image – produced when exposed to

x-rays

Film Base – actual film◦ Flexible plastic◦ Withstands: Heat, moisture, chemical exposure◦ Transparent with blue tint: Emphasize contrast of image Enhance image quality

◦ Purpose of film base: provide support for the emulsion

Adhesive layer◦ Thin layer of adhesive material◦ Covers both sides of film base◦ Attaches the emulsion to the base – allows

emulsion to adhere

Film emulsion◦ Coating attached to both sides of film base◦ Gives film greater sensitivity to x-radiation –

shortens exposure time

Made of:◦ Gelatin

Used to suspend and evenly disperse silver halide crystals over the film base

It absorbs processing solutions and allows the chemicals to react with silver halide crystals

RHS – may ask what type of material is in emulsion – silver halide or silver bromide

Made of:◦Silver halide crystals Silver bromide and silver iodide Absorb radiation during x-ray exposure

and store energy from the radiation Small crystals require more radiation

(better resolution) Large crystals require less radiation

Protective layer◦Thin layer over emulsion to protect film during handling

Silver halide crystals absorb x-radiation during exposure and stores energy from radiation

Energy is stored at different levels based on density of objects exposed

Stored energy within silver halide crystals form a pattern & creates an invisible image within emulsion of exposed film – latent image

Denser object – more energy absorbed by object – lighter it appears on film◦ Film positioned behind amalgam restoration

receives almost no radiation◦ Amalgam is dense & absorbs x-ray energy◦ Silver halide crystals are not energized – fall off

film leaving area opaque◦ Appear white on film

Less dense objects appear darker on film◦ Correspond to airspace◦ Little or no density (tissue, sinus, carious tissue)◦ Film receives more radiation◦ Silver halide crystals are highly energized

Intraoral film◦ Placed INSIDE the mouth◦ Used to examine teeth & supporting structures◦ Film packet:

Soft vinyl Protects film from light and saliva

Intraoral film◦Labeled with: Type of film Film speed Film size Amount per packet (single or double) Expiration date

Intraoral film◦Black paper Shields from light

◦Lead foil – behind film “herringbone or tire track” effect – may

appear lighter Blocks radiation – helps with fogging Protects from some scatter radiation

Intraoral film:◦ Identification dot Small raised bump Raised bump on solid white side of film

– faces PID On one corner of film Placed in slot of bite block – makes dot

go – Toward the occlusal/incisal surface of

teeth

Periapical – PA◦ Entire tooth◦ 2 – 3 mm around end of root◦ PDL & Lamina Dura

Bitewing – BWX ◦ Examine interproximal – cavities – usually taken

once a year – maybe taken twice depending on Pt◦ Crowns – Max & Man occl. – bone & gum height

Occlusal - #4 film – usually on children

Film size◦ 0 – children, referred to as Pedo Film◦ 1 – anterior adult – pedo◦ 2 – Standard (most common)◦ 3 – posterior (BW, longer narrower than #2)◦ 4 - occlusal

Refers to the amount of radiation to produce a radiograph

A speed (slowest) to F speed (fastest) Only D speed film and E speed film are used

for intraoral radiography E speed requires one-half the exposure time

of D speed – has comparable image contrast & resolution (less radiation for patient)

F speed requires one-third the exposure time of E speed film

Placed outside mouth during exposure Used to examine large areas of skull or jaws More sensitive to light/radiation than

intraoral film Films are placed in a cassette with

intensifying screens Intensifying screens step up/accelerate

radiation – reducing amount to pt

Panoramic Film aka Pano aka Panorex◦ Shows wide view of Max & Man – teeth 15% larger◦ Radiation level for a pano equivalent approx 4

PA’s◦ Used for TMJ or wisdom teeth

Cephalometric Film aka Ceph◦ Shows bony & soft tissue areas of facial profile◦ Side profile – TMJ, spine, neck, skull, ◦ Used for ortho to measure growth

Makes identical copy of a film Used for insurance claims or transferring

patients

Ideal radiograph is neither too light or too dark

A diagnostic radiograph is:◦Clear – crisp, clear image, like analog TV

vs. HD TV◦Undistorted◦Low Contrast – many varying shades of

gray

To fully understand why things appear dark or light on film we need to examine the characteristics of the objects

RHS – KNOWING WHETHER YOU ARE DESCRIBING THE OBJECT

OR OBJECT AS IT APPEARS ON THE FILM IS CRUCIAL TO YOUR UNDERSTANDING QUESTIONS ON RHS EXAM

Objects that allow light to pass through easily◦ Windows / glass◦ Air

When related to dentistry and radiographic film it would be termed radiolucent

Dark allows more x-rays to pass through Portion of processed film that is dark or

black Silver Halide Crystals are energized Structure that lacks density & allows x-ray

to pass with little or no resistance Structures do not appear or if they do they

are quite dark, even black, ex.: air space, gingiva, mucosa, tongue, cheek

Objects that do not allow light to pass through them easily◦ Wall ◦ Rocks◦ Metals

When related to dentistry and radiographic film it would be termed Radiopaque

Portion of a processed film that is light or white

Silver Halide Crystals have NOT been energized

Structures are dense & absorb or resist the passage of the x-ray

The more dense or thick the structure the lighter it appears, ex.: enamel, bone, amalgam, restorative metals

Problems that can occur on film Deals with size & shape of the image (tooth)

as it appears on the film Includes three characteristics:

◦ Sharpness◦ Magnification◦ Distortion

Refers to the clarity of the image Detail, resolution, & definition How crisp and sharp a picture

◦Seen by the amount of silver halide crystals Small crystals but lots of them = better

resolution yet requires more radiation to the patient

Penumbra◦When image on the radiograph looks fuzzy or

blurry◦Caused by movement of patient or PID

Clarity is not as good in F speed films but are good enough to diagnose

FYI – sharpness is one factor that is usually outside the control of the DA

When image of the object appears larger than actual size

Very important in Endodontics Influencing factors include:

◦Target to film distance – Source of x-rays to film 16” PID = less image magnification 8” PID = more image magnification

Influencing factors include cont.:◦Object to film distance – tooth to film

Closer the film is to the tooth the less image enlargement there will be on the film

One area where bisecting the angle is better – will have more magnification w/paralleling technique

Shape & Size of object Any variation in the shape of an image on film

Caused by improper angulation of the PID or improper film alignment

Improper Horizontal Angulation◦Can result in “fat images”◦The angle of x-ray beam (left to right)◦Causes overlapping

Mesial of one tooth on the distal of another◦PID should be at a 90 degree angle to film

Improper Vertical angulation◦ Results in either (short) Foreshortening or (long)

Elongation◦ Foreshortening

Angulation is to steep Too positive Excessive vertical angulation Image produced is shorter than its actual

size

Elongation◦Angulation is to low◦Too negative◦ Insufficient vertical angulation◦Image produced is longer that it’s actual size

Stepwedge: Aluminum of varied thickness◦Used to check short and long scale

contrast◦Placed on top of film – Expose◦Absorbs varying amounts of x-rays◦Different densities & contrasts will appear

– Ch.10

Film Processing – converting a latent image (invisible) on the film into a visible image and preserving it permanently

Latent Image – Invisible pattern◦Silver halide crystals absorb x-ray◦Energy is stored & forms an invisible

image◦Pattern not seen until developed

Reduction: During processing a chemical reaction occurs and halide portion of exposed silver halide crystal are removed

Selective Reduction◦ Exposed or energized Silver Halide Crystals

become black metallic silver– stay on film (behind radiolucent structures)

◦ Unexposed or un-energized Silver Halide Crystals are removed from film – fall off film (behind radiopaque structures)

Developer – Black bottle, Black lid, Black label

First solution to touch dental radiograph

Temperate determines total time it takes to complete x-ray

Creates the dark or black areas Softens emulsion – so picture will appear

Hydroquinone◦Creates the black tones & sharp contrast◦Temperature sensitive◦Inactive below 60 degrees◦Very active above 80 degrees

Elon◦ Acts quickly to produce visible image

Preservatives◦Prevent solution from oxidizing in the -

Accelerators◦Activates solution◦Soften

Restrainer◦Potassium bromide◦Stops development of both exposed &

unexposed silver halide crystals

Red bottle, red lid, red label Removes the unexposed silver halide

crystals Silver stays in fixer making it TOXIC Creates the white or light areas on dental

radiograph Black metallic silver is not removed &

remains on film Films can be left in the fixer for an indefinite

time without any effect on film

Films cannot be left in developer or water

Approximately 2 minutes in fixer the film may be viewed in light

Ingredients include:◦Fixing agent – removes or clears all

unexposed & undeveloped silver halide crystals from emulsions

Cont. Ingredients include:◦Preservative – prevents chemical

deterioration of the fixing agent◦Hardening agent – harden & shrink the

gelatin in the film emulsion after it has been softened by accelerator in the developing solution.

◦Acidifier – stops the developing process

Develop Rinse Fixer Water Wash Drying

Developer◦ First step in film processing◦ Temp. of developer determines time◦ 68 degrees is optimum temp. for 4 ½ to 5 mins◦ Range 68 – 74 optimun – Check temp. daily◦ Below 60 – react slow & film appears light◦ Above 80 – react fast & film appears dark◦ Warmer solution – shorter time◦ Cooler solution – longer time

Rinse◦ To remove the developer from the film and stop

the development process◦ Usually about 30 seconds

Fixer ◦ Usually double the time to spend in Fixer◦ If 5 minutes in developer then 10 mins in fix

Water wash ◦ Always for 20 – 30 minutes◦ Removes all excess chemicals from emulsion

Drying◦ Hang films on film hanger to Dry

Special machine – works through rollers Developer – still the first solution to touch

film & optimum temp 80 degrees Fixer – second solution to touch film Rinse – rinses films Dryer – dries films quickly Replenisher pump – automatically

replenishes chemicals – maintain adequate freshness, strength & solution levels

Provides a completely dark environment where x-ray film can be handled and processed

Location & Size◦ Large enough for all equipment and a person◦ Should be at least 16-20 square ft (4x4,4x5)◦ Ventilation system

Temperature – approx. 70 degrees – if exceeds 90 film fogging may occur

Lighting◦ Should be completely dark – light tight◦ Any visible white light will be bad for film & cause

film fogging◦ Safelight

Red – orange spectrum Low intensity light (15 watt) or regular white bulb

w/light filter GBX2 best with extra-oral film Must be placed a minimum of 4 ft away from working

area

Film is adversely affected by:◦ Heat◦ Humidity ◦ Radiation

To prevent film fog:◦ Keep film in cool dry place◦ Temp ranges from 50 – 70 degrees◦ Shield from radiation sources◦ Watch expiration date