DANB Radiology Exam

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What is the base of dental film composed of?

blue tinted polyester acetate

What is the emulsion composed of?

gelatin and silver halide crystals

What determines the speed of dental films?

size of crystals, thickness of emulsion, radiosensitive dyes

What is the purpose of the lead foil?

absorb scatter radiation and prevent fogging

How does film speed correlate with definition and detail?

faster film = lower definition and detail

What speed films are most commonly used?

D, E, F

size film used for PA's on small children


size film used for BW on adults when only one film is taken on each side


size film used for anterior PA's for patients with narrow arches


size film used for PA's on adults


size film used for BW on adults


size film used for occlusals on adults


What is the purpose of the embossed dot

to distinguish b/w patient's right and left side

What is the latent image

invisible image (remains like this until film is processed)

What happens in the developer

reduces the exposed silver halide crystals to black metallic silver

What happens in the fixer

removes the unexposed silver halide crystals

how long does film stay in the developer

5 min

how long are films fixed

10 min (dbl the development time)

how long does the first rinse last

20 seconds

how long is the final rinse

20 min

what is the optimum processing temp.

68 degrees F

when can the films be exposed to white light

after 2-3 min of fixing if needed

what causes film fogging

-old or contaminated processing solutions
-exposure to chemical fumes
-faulty safelight
-scatter radiation

what would cause a film to be too light

-depleted developer solution
-excessive fixation (takes all crystals off)

what would cause a film to be too dark

-developer is too strong
-not enough fixation
-exposure to white light
-improper safelighting

What causes a HERRINGBONE effect

film placed backwards

what would happen to a film that is placed in the fixer prior to development

blank or clear
(takes all of the crystals off)

what is reticulation

cracking of the emulsion caused by excessive temp diff. b/w any darkroom solutions

how would a film appear if submerged totally in the developer but not in the fixer

top of film delineated by a straight line then dark

film submerged totally in fixer but not in developer

part that was fixed but not developed would be clear

what size bulb is used in safelight

7 1/2 or 15 watt

what type of safelight filter is acceptable

GBX - 2

how far from the work surface must the safelight be mounted

4 feet

diff. b/w direct and indirect exposure sensor?

direct - directly obtaining a digital image by exposing intraoral sensor to x-rays to provide an image that can be viewed on a computer

indirect - photostimuable phosphor plate sensor technology, obtaining a digital image in which an exposed phosphor plate is placed into a scanner and then converted into a digital image

what film is used to diagnose interproximal decay


what projection would you take for a patient complaining of pain in the lower left molar area

left molar PA

what is the purpose of a pano

image the entire dentition, surrounding alveolar bone, sinuses, and the TMJ, examine large area of face and jaws, locate impacted teeth, retain root tips, evaluate trauma, lesions, and diseases, and assess growth and development

what causes foreshortening

excessive vertical angulation

what causes elongation

insufficient vertical angulation

what causes overlapping

incorrect horrizontal angulation

what causes conecut

not centered on sensor

what causes clear film

no exposure, or fixer before developer

what causes missing crowns

excessive vertical angulation

what causes missing apices

insufficient vertical angulation

when mounting a film the dot is convex, on what side of the mouth would you find #32?

left side

how do you differentiate b/w max and mand molar when mounting

- max molars have 3 roots, mand have 2 roots

what size film is 7/8 x 1 3/8

No. 0

what size film is 15/16 x 1 9/16

No. 1

what size film is 1 1/4 x 1 5/8

No. 2

what size film is 1 1/16 x 2 1/8

No. 3

what size film is 2 1/4 x 3

No. 4

Explain PSP

-Photostimuable Phosphor Plate aka storage phosphor system
-indirect digital imaging
-captures analog data then processed in a laser scanning device
-light is then converted into electrical signal that the computer uses to create the digital image

how does exposure time differ b/w adults and children

cut exposure time by 1/3

what type of projection is used to visualize the crestol alveolar bone on a patient with moderate to severe bone loss

vertical BW

max. centrals anatomy

-nasal septum, ant. nasal spine, nasal fossa, median palatine suture, incisive foramen

max lat. canine anatomy

nasal fossa, max sinus

max premolar anatomy

max. sinus, zygoma

max molar anatomy

max sinus, zygoma, max tuberosity, coranoid process

mand central anatomy

genial tubercles, lingual foramen

mand lateral/canine anatomy


mand premolar anatomy

mental foramen, mental ridge, mand canal

mand molar anatomy

mand canal, external oblique ridge, beg. of ramus

what would cause increased magnification, decreased resolution and edge sharpness

increased focal spot size, decrease source-object distance, & increased object-film distance

according the principles of shadow casting, preferred object-film distance

as close as possible

according to principles of shadow casting, preferred source-object distance

as far as practical

according to principles of shadow casting, how should the film be placed in relation to the tooth?


according to principles of shadow casting, how should the central beam be directed

perpendicular to the tooth and film

what periapical technique offers the best diagnostic quality?

paralleling; meets more principles of shadow casting

what is penumbra

shadow around the tooth

how is vertical angulation established with the bisecting technique

beam is perpendicular to the imaginary line that bisects the angle formed by the long axis and the film

how is vertical angulation established with the paralleling technique

perpendicular to the film, parallel to the bite portion of the stabe

how does packet placement differ b/w bisecting and paralleling

-bisecting - packet is as close to tooth as possible, but not parallel

-parallel - packet is parallel to tooth, further away

what is the proper patient position for BW's?

ala-tragus line is parallel to the floor

proper patient positioning for bisecting

max arch ala-tragus parallel to floor
mand arch

proper patient positiong for paralleling

doesn't matter

what is the best method of reducing radiation to the patient

rectangular collimation and fast film speed

how far should the operator stand from the source of radiation

6 ft

what is the primary beam

original, undeflected, useful beam

what is done to the primary beam to make is useful

filtration and collimation

what is the purpose of collimation

reduce size and shape of beam

what is the collimator made out of


what is the purpose of filtration

absorb long wavelengths / soft radiation

what are filters made out of


what is inherent filtration

produced by internal barriers in tube head
(ex: glass and insulating oils)

what is added filtration

filters placed in PID after tubehead production

how much total filtration is required of x-ray machines that operate lower than 70 kVp

1.5 mm

total filtration required of x-ray machines that operate above 70 kVp

2.5 mm

what is the source-skin distance of x-ray machine that operates at 75 kVp

8-16 inches

what is the maximum size of the x-ray beam at the patients face

2.75 inches

desired thickness of lead apron

.25 mm

how should the frequency of radiographic exposures be determined

depends on the needs of the patient, established after intraoral exam

how often are BW taken on children with high risk

every 6 mths

how does the reproductive capacity of a cell correlate with radiosensitivity

rapidly producing cells are more sensitive to radiation

what 3 types of cells are most radiosensitive

WBC, RBC, immature reproductive cells

what 3 types of cells are most radioresistant

nerve, brain, muscle

what types of cells must be effected in order for mutation to occur

genetic cells

what are the 2 units used to measure exposure to radiation

Roentgen (R)

what 2 unites are used to measure absorption


what 2 unites are used to measure biologic effect and dose equivalent

Sv & Rem

what is the annual MPD for radiation workers

50 mSv or 5 REM

what is the annual MPD for pregnant dental assistant

5 mSv or .5 REM
1/10th dosage of gen. public

what are photons

quantum of energy

what part of the x-ray machine is responsible for providing the electrons


how are x-rays formed in the tubehead

-turn on machine
-adjust settings
-press exposure button
-filament heats up/thermoionic emmision
-electron cloud is formed
-electrons flow from cathode to anode
-electrons strike target
-energy is converted into x-rays and heat

what part of the x-ray machine helps remove heat

copper stem, radiator and air space

what is formed when high speed electrons strike the target

x-ray and heat

list the properties of x-rays

-travel in straight lines
-no mass/weight
-travel and speed of light
-no charge
-interact w/ matter causing ionization
-can penetrate opaque tissues and structures
-can effect photographic film emulsion
-can effect biologic tissue

what looking at a PANO what causes a big smile

chin down

how should x-ray film be stored

-original packaging
-area sheilded from radiation
-50-70 degrees F

what are occlusal radiographs used to diagnose

-locate retained roots
-locate unerrupted or impacted teeth
-evaluate for diseases and lesions
-locate foreign bodies
-reveal presence of salivary stones (sialothiths)
-aid in evaluating fractures
-size and shape of tori
-aid in examining patients with trismus (patient can only open mouth a few mm)
-evaluate borders of sinus
-examine cleft palates
-substitute for PA's for young children or patient who can't tolerate

how often should developing solutions be changed

every 4 weeks

how does exposure time for edentulous patients compare to dentulous patients

1/5 exposure time for edentulous

how does exposure time for children compare to that of an adult


what is scatter radiation

x-rays that have been deflected from an object and have changed paths

what is secondary radiation

x-rays that have gone thru an object and are now a newer weaker beam

what equation is used to calculate the accumulated MPD


what is the term to describe the overall blackness of a radiograph


what control factors effect the density of a radiograph

mA & time

what control factors effect contrast


if the kVp is increased from 75-90, what must be done to achieve a radiograph of comparible density

-decrease mA & time

if the source-object distance is cut from 16 to 8 , what must be changed to compensate

method should be compensated for bisecting or paralleling

You take a radiograph using 10 mA 30 impulses and 90 kVp, your dentist wants a radiograph with increased contrast and equal density. What settings would you use?

decrease kVp by 15 and double exposure time
10 mA 60 impules 75 kVp

which projection is used to view sinuses


what is the earliest sign of radiation exposure


which anatomical structures appear radiolucent

soft tissue, air space

which anatomical structures appear radiopaque

dentin, enamel, bone

what is the latent period

time b/w exposure and 1st clinically observable symptoms

who discovered x-rays


what are the short term effects of radiation exposure

erythema, vomitting, nausea, hemorrage, diarrhea, hair loss

what are the long term effects of radiation exposure

cancer, cateracts, embryologic defects, genetic mutations, low birth weight

what exposure is taken to determine jaw relationships in ortho treatment planning

lateral cephalometric

what is the purpose of taking radiographs of an edentulous patient

-detect pathological lesions
-establish position of mental foramen
-establish position of mand canal
-determine quality & quantity of alveolar bone present

what exposure would be useful in identifying salivary stones in the submandibular gland

mand occlusal

what device is used to check quality of processing chemicals

step-wedge or test film

what NC agency is resposible for monitoring dental x-ray equipment


what are common sources of background radiation

cosmic , naturally occuring radiation from earth, radiation for radioactive materials

how are indirect exposure films exposed

x-rays hit phosphor screen creating florescent light that exposes the film

3 film holding devices used for paralleling

dentsply rinn, XCP, XCP-DS, flow dental RAPD

3 film holding devices used for bisecting

dentsply rinn stabe, BAI, dental SUPA

what is the ADA approved method of mounting dental radiographs


what is the bremsstrahlung radiation

aka general radiation; stopping or slowing of the electrons of the cathode stream as they collide with the nuclei of the target atoms

what is characteristic radiation

a form of radiation originating from an atom following removal of an electron or excitation of an atom

what is the major diff. b/w particulate and electromagnetic radiation

-particulate radiation: made of protons, neutrons, electrons and alpha and beta particles; has mass

-electromagnetic radiation: made of photons; no mass

which radiographic technique records the most accurate image of crowns, roots, and supporting structures in a selected area?

periapical examination, paralleling technique

A patient complains of pain in the upper molar region. What radiographic exposure should be made?


What type of x-rays have greater penetrating power, long or short wavelength?


in the darkroom, you unwrap a film and place a coin on top of the film for several minutes. when you process the film, you notice a slight, well-defined white circle on the film. what does this mean?

failed safelight test, suggesting that the safelight conditions in the darkroom are fogging the film

what would cause a properly exposed film to appear dark?

-temp. too high
-time too long

-developer concentration too high
-inadequate fixation
-accidental exposure to light
-improper safelighting

what are automatic processors faster than manual processing?

b/c of its stability to produce a large volume of radiographs in a short amount of time

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