radio 13-14

digital rad

Which type of digital image receptor is most common at this time?

CID (charge injection device)

• CMOS/APS (complementary metal oxide semiconductor/active pixel sensor)

• CCD (charge-coupled device)

1copyright O 2013-2014- Dental Decks

RADIOLOGY

digital rad

Which of the following are advantages of direct digital radiography.

Select all that apply.

superior gray-scale resolution

' reduced patient exposure to x-radiation

•

increased speed of image viewing

'

lower equipment and film costs

• sensor size

• increased efficiency

• effective patient education tool

• enhancement of diagnostic image

RADIOLOGY

i

2

copyright © 2013-2014- Dental Decks

^>tA4S03lS

^

Digital imaging

• filmless imaging system

• method of capturing a radiographic image

with a sensor, breaking the image into electronic

pieces and presenting & storing the image using

a computer

Direct digital image production requires

• x-ray source

• digital intraoral sensor

• computer

• high-resolution monitor

• software & printer

Digital intraoral sensor

• small intraoral detector used to capture a

radiographic image

• when x-rays strike the sensor, an electronic

charge is produc ed on the surface of the

sensor, this electronic charge is digitized or

converted to digital form

• may be wired or wireless

• sensor transmits information to computer

Pixel or picture element

• discrete unit of information

• consists of a small electron well where the x-

ray or light energy is deposited upon exposure

(/digital image is composed ofpixejsh

• CCD (charge-coupled device)

(CCDTjHiarge-coupled device)

• most common digital image receptor

• in the intraoral sensor, a solid-state detector

that contains a silicon chip with an embedded

electronic circuit

• sensitive to light or x-rays

• 640 x 480 pixels in size

CMOS/APS (complementary metal oxide

semiconductor/active pixel sensor)

•Jatest development in direct digital sensor

tecnnSlogy

• externally identical to CCD

i • differs in the way pixel s are read

• • advantages include lower production cost of

* the chip, lower power requirement s & greater

'. durability

• • smaUef.acjtive

a r e a

f °

r image acquisition

VCIDjJfcharge injection device)

• another sensor technology

• silicon based solid-state imaging receptor

similar to CCD

• no computer is required to process the images

• system features CID x-ray sensor, cord and

plug that are inserted into a light source on a

camera platform

Advantages of digital imaging

• superior gray scale resolution

256 shades of gray used instead of the 16-25 shades

used with film

• reduced exposure to radiation

radiation exposure is 50% to 90% less than what is

used to expose E-speed film

• increased speed of image viewing

images can be viewed instantly which allows for

immediate intetpretation

• lower equipment and film cost

no need for purchase of film and related processing

supplies and equipment

• increased efficiency

allows dental professionals to be more productive;

image storage and communication are easier with

digital networking

• enhancement of diagnostic image

features such as colorization and zooming allow for

highlighting of conditions; the gray scale may be re-

YSBjed. (digital subtraction)

• effective patient education tool

the size of images displayed monitor are easier for

the patient to see; allows for chairside education and

interaction

8

' superior gray-scale resolution

' reduced patient exposure to x-radiation

> increased speed of image viewing

> lower equipment and film costs

' increased efficiency

' effective patient education tool

' enhancement of diagnostic image

Disadvantages of digital imaging

• sensor size

some sensors are thicker and less flexible than

film and may stimulate the gag reflex

• initial set up costs

significant initial cost for purchase of digital

equipment as well as maintenance and repairs

• resolution / image quality

conventional x-ray film has a resolution of 12

•n - 20 lp/mm (linepairs per millimeter); digital

Mmaging using a CCD has a resolution of 10

lp/mm; because human eye can only perceive 8

N> - 10 lp/mm — digital imaging performs at

least as well as traditional radiography

• infection control

some sensors cannot withstand heat steriliza

tion; barrier protection is required

• wear & tear

sensors are subject to damage, wear & tear and

have a limited lifespan

• legal issues

because digital images can be enhanced, there

may be legal implications

digital rad

A method of obtaining a digital image where the sensor captures the image

and immediately transfers it to a computer is termed:

indirect digital imaging

• direct digital imaging

• storage phosphor imaging

3

copyright O 2013-2014- Dental Decks

RADIOLOGY

digital rad

A patient is extremely concerned about radiation exposure. Which of the fol

lowing is best for limiting the amount of exposure he will receive during a ful l

mouth series?

• use of digital imaging

• use of E-speed films

• use of F-speed films

• substitute a panoramic image for the ful l mouth series

4copyright © 2013-2014- Dental Decks

RADIOLOGY

' direct digital imaging

Digital imaging• filmless imaging system• methods of obtaining a digital image:direct and indirect

Direct digital imaging• required components- x-ray machine- intraoral sensor- computer & monitor• utilizes a sensor with a fiberoptic cable that islinked to a computer• sensor is placed intraorally and exposed tox-radiation

• images are captured via a sensor(CCD, CMOS/APS or CID)

• the sensor transmits the image to a computermonitor• images appear on monitor within seconds ofexposure• software is used to enhance & store the image

Indirect digital imaging• scanning of traditional films• storage phosphor imaging

Scanning of traditional films• required components- CCD camera- computer & monitor

• existing films are scanned and digitized using aCCD camera

• CCD camera scans radiograph, converts theimage and displays it on monitor• is inferior to direct digital imaging• image is a "copy" not an "original"

^ S t e a g e ,

phosphor imaging ss P£{>

• required components.-phosphor- coated plate

- electronic processor/scanner- computer & monitor• a "wireless" digital imaging system

• a reusable imaging plate coated with phosphorsis used instead of a sensor with a fiberoptic cable• plates are similar to intraoral film in size, shape& thickness• image recorded on plate

• after exposure, plate is placed in electronicprocessor where a laser scans the plate; imageis transferred to the monitor within time framenf'jQ.s.gcciridr

1

to

5 minutes

• also referred to as photo-stimulable phosphorimaging or PSP imaging

• use of digital imaging

Digital imaging

• requires LESS radiation than conventional films because the sensor is more sensitive to

x-rays than dental film

• exposure time for digital imaging is approximately 5-0% less than what is required for F-

speed film

• intraoral, panoramic and other extraoral films may all be obtained digitally

Intraoral film

speed

• E-speed film is no longer available

• Only D-speed film and F-speed film are available for use with intraoral radiography

• F-speed film is recommended by the ADA

Q * ^ £ ^ £ S d j £ 2

u

j

r e s

6p%_qf the exposure time of D-speed

Other ways to limit exposure to x-radiation

• proper prescribing of dental radiographs based on individual needs of patient

• use of lead apron & thyroid collar

• use

of proper dental x-ray equipment

• use of rectangular position-indicating device (PID)

• use of beam

alignment devices

• use of proper technique

• proper sensor handing

• proper image retrieval

image char

A radiograph that exhibits areas of black and white is termed high contrast

and is said to have a short contrast scale; a radiograph the exhibits many

shades of gray is termed low contrast and is said to have a long contrast scale.

To limit image magnification, the longest target-receptor distance and short

est object-receptor distance are used. ^He

• both statements are true

• both statements are false

• the first statement is true, the second is false

• the first statement is false, the second is true

5

copyright 2013-2014- Dental Decks

RADIOLOGY

image char

Rank the following from LEAST radiopaque to MOST radiopaque.

amalgam

• bone

• dentin

> maxillary sinus

• enamel


RADIOLOGY


contrastthe difference in degrees of blackness (densi-

tjg£) between adjacent areas on a dental radi

ograph.• high contrast describes an image that ap

pears mostly black & white; shades of gray

are absent

• low contrast describes an image with

many shades of gray; few areas of black

and white

scales of contrast

the range of useful densities seen on a dental

radiograph.

short-scale contrast

describes a high contrast image

with densities of black & white

that results from using a .low

kilovoltage.^Mi l ium V ,

long-scale contrast

describes a low contrast image

with many shades of gray that

results from using a highkilo-

voltaee.

magnification

a radiographic image that appears larger than

the actual size of the object it represents; mag

nification is influenced by the target-receptor

distance and the object-receptor distance.

target-receptor distance -

• distance between the source of x-rays and

the image receptor ilm / W . * ^

• a longer PID

results in a longer target-recep

tor distance and helps to limit magnification

object-receptor distance

s

*f-

Q^

• distance between the tooth and the image

receptor

• the closer the receptor is to the tooth, the less

magnification is seen on the image

to limit magnification

• use a long target-receptor distance/I

target-

receptor distance

• use a short object-receptor distance/J, object

-receptor distance

bus cm

LOW CONTRAST •• LONG-SCALE CONTRAST

HV**t kvp

'image receptor=digital sensor or x-ray film

• s i n us — b o n e — d e n t i n — enamelfit

radiolucent structures

• lack density

• permit

the passage of x-radiation

• absorb very little x-radiation

more x-rays to the receptor*

• appear dark or black on an image

amalgam

radiopaque structures

• are dense

• resist the passage of x-radiation

• absorb the x-radiation

• allow few_xjay.s to reach the receptor

• appear light or white on an image

Examples of radiolucent structures/mate

rials — BLACK or DARK

• air space images

• soft tissue images

• canals

• foramens

• fossas

• sinuses

• sutures

• caries

• pulp cavities

• periodontal ligament space

• denture acrylic

• some composite restorations

Examples of radiopaque structures/mate

rials _ WHITE or LIGHT

• enamel

• dentin

•bone

• lamina dura

• septa

• tubercles

• tuberosities

• ridges

• processes

• amalgams, metal restorations

• implants

• gutta percha

LUCENT means TRANSPARENT and

suggests something that lacks density —

something that lacks density permits the pas

sage of x-rays & appears RADIOLUCENT

^ S

OPAQUE means NOT TRANSPARENT

and suggests something that is more dense

— something that is more dense resists

the

passage of the x-rays & appears RA

DIOPAQUE

*receptot=digital

sensor or x-ray film

misc.

Dental radiographs are the legal property of the:

patient

• dentist

• state

>

none of the above

7


RADIOLOGY

misc.

A dental hygienist in your practice has an adult recall patient without evi

dence of caries who states she needs bite-wing x-rays because it has been 6

months since her last dental images. The hygienist should tell the pat ient

that:

• yes, she is correct, it is time for new x-ray images

• bite-wings should be taken only once per year, not twice

• images should be taken based on patient need instead of a set time frame

• none of the above

scopyright © 2013-2014- Dental Decks

RADIOLOGY

Dental radiographs

• original radiographs are legally theproperty of the dentist even though thepatient or an insurance company may havepaid for them• the radiographs are the property of thedentist because they are indispensable to thedentist as part of the patient record• radiographs should be kept indefinitely

Patient access to radiographs• patients have a right to reasonable accessof their dental radiographs

• access includes copies of original radiographs (not originals) forwarded to thedentist who will be responsible for the patient's dental care

• dentist

Patients who refuse dental radiographs

• when a patient refuses to have dental radiographs, the dentist must decide whetherdiagnosis and treatment can take placewithout the recommended radiographs• no document can be signed by the patientthat releases the dentist from liability

Very important: the patient record, including radiographs, is legal documentation of apatient's condition.

Patient record must contain documentation of

• informed consent• number & type of radiographs exposed• rationale for taking radiographs• diagnostic information obtained from in

terpretation

• images should be taken based on patient need instead of a set time

Prescribing dental radiographs

• the dentist is responsible for prescribing the number, type and frequency of dental ra

diographs

• each patient's condition is different and therefore each patient must be evaluated for

radiographs on an individual basis

• a radiographic examination should never include a set number and type of images at

a set interval

• guidelines for prescribing dental radiographs are published by the American Dental

Association (ADA) in conjunction with the Food & Drug Administrations (FDA)

• visit www.ADA.org for current guidelines

• patients with caries, periodontal disease, tooth mobility, pain and impacted teeth need

more frequent radiographic examinations

Guidelines for radiographs in the recall patient

with clinical caries or risk of caries

• bite-wings at 6 - 12 month intervals

with no clinical caries or risk of caries

• bite wings at 24 - 36 month intervals

with periodontal disease

• clinical judgement for radiographs needed to evaluate periodontal disease; selected

bite-wings & periapicals

http://www.ada.org/

http://www.ada.org/

http://www.ada.org/

http://www.ada.org/

normal anat

Identify the structures indicated in the images below.

Image 1 Image 2

Reprinted from Haring, Joen Iannucci and Laura Jansen: Dental Radiography:

Principles and Techniques: Third Edition. © 2000, with permission from Elsevier.


RADIOLOGY

normal anat

The coronoid process often appears on what periapical image?

•maxillary incisor

• maxillary molar

• mandibular incisor

• mandibular molar

10copyright €> 20 13-2014- Dental Decks

RADIOLOGY

Res

Image 1- hamulus v

• a.k.a. hamular process

• small, hook-like projection of bone

• extends ..fmm the medial Pterygoid

jg|atejof^e

m

sjp;hjenoidjbone

• located posterior to the maxillary

tuberosity

• appears radiopaque

• on a maxillary molar periapical image,

appears as a hook-like radiopaque struc

ture

• varies in length, shape & density

• not always visible, depends on receptor

placement

hamulus

' maxillary tuberosity

*b

Image 2- maxillary tuberosity

• rounded prominence of bone that ex

tends distal to the third molar region


• on a maxillary molar periapical

image, appears as a rounded ra

diopaque bulge distal to the third

molar region

• varies in size, shape and density

• not always visible, depends on re

ceptor placement

maxillary molar

Coronoid process

• coronoid means "resembling the beak of a crow"

• large prominence of bone on anterior ramus of mandible

• is thin and triangular in shape

• serves as an attachment site for one of the muscles of mastication


• on a maxillary molar periapical image, appears as a beak-shaped radiopacity located

inferior to, or superimposed over, the maxillary tuberosity

• varies in shape and density

• not always visible, depends on receptor placement

Reprinted from Haring, Joen Iannucci and Laura Jansen Lind: Radiographic

Interpretation for the Dental Hygienist. © 1993, with permission from Elsevier.

normal anat

Identify the structures labeled 1 - 8 on the image below.

"Courtesy Dr. Stuart C. White, UCLA School of Dentistry." y\


RADIOLOGY

normal anat


"Courtesy Dr. Stuart C White, UCLA School of Dentistry." 1 2

copyright ©2013-2014-Dental Decks

RADIOLOGY

' answers 1-8 below

1. lateral wall of the incisive (nasopalatine) canal

radiopaque line

2. anterior wall of the maxillary sinus

radiopaque line

3. nasopalatine fossa

radiolucent space

4. floor of nasal fossa

radiopaque line

5. soft tissue outline of the nose

slightly radiopaque outline

6. lamina dura

radiopaque line

7. border of maxillary sinus

radiopaque line

"Courtesy Dr. Stuart C. White, UCLA

School of Dentistry."

8. periodontal ligament space

radiolucent line

• answers 1 -7 below

1. anterior nasal spine

radiopaque line

2..lateral wall of nasopalatine canal

radiopaque line

3. median palatal suture

radiolucent line


radiopaque line

5. incisive (nasoplatine) foramen

radiolucent structure

6. soft tissue outline of tip of nose

slightly ra^oplique'^uTrihe

7. alveolar crest

radiopaque line

"Courtesy Dr. Stuart C White, UCLASchool of Dentistry."

normal anat

Identify the structures labeled 1- 5 on the image below.

Courtesy Dr. Stuart C. White, UCLA School of Dentistry."

13

copyright©2013-2014-Dental Decks

RADIOLOGY

normal anat


"Courtesy Dr. Stuart C. White, UCLA School of Dentistry.'

14


RADIOLOGY

• answers 1-5 below

1. nutrient canal

radiopaque

lines

2. bony trabecular plate

radiopaque line

3. inferior border of mandibular canal

radiopaque line

4. submandibular gland fossa

radiolucent space

5. inferior border of mandible

radiopaque structure

1. anterior wall of maxillary sinus

radiopaque line



< answers 1 - 8 below

2. inferior nasal conchae A -

radiopaque mass


radiopaque line

4. inferior border of zygomatic process of maxilla

j - shaped radiopaque line C/*

5. posterior wall of zygomatic process of maxilla

radiopaque line

6.jnieiifljLboxd£t:.QLzygoma # ^

radiopaque line

7. floor of maxillary sinus

radiopaque line

8. mucosa over alveolar bone

slightly radiopaque structure



normal anat


"Courtesy Dr. Stuart C. White, UCLA School of Dentistry." .. _

copyright ©2013-2014- Dental Decks

RADIOLOGY

normal anat


"Courtesy Dr. Stuart C. White, UCLA School of Dentistry."

16


• answers 1 - 7 below

1. lingual cusp of 1st premolar

radiopaque area


radiolucent line

3. film holder

radiopaque area

4. genial tubercles

donut shaped radiopacity

5. lingual foramen

radiolucent circle

6. bony trabeculations

radiopaque lines

7. marrow space

radiolucent area





radiolucent line

2. mental foramen

ovoid radiolucency


radiolucent area

4. film clip mark

radiolucent artifact

"Courtesy Dr. Stuart C. White, UCLASchool of Dentistry."

normal anat



17


RADIOLOGY

normal anat


"Courtesy Dr. Stuart C. White, UCLA School of Dentistry." 1 8

copyright e 2013-2014- Dental Decks

RADIOLOGY 18


1. cement-enamel junction (CEJ)

radiopaque line

2. mental foramen

ovoid radiolucency


large radiolucent area



1 . inferior nasal conchae

radiopaque mass

• answers 1- 7 below

2. anterior wall of maxillary sinus

radiopaque line


radiopaque line

4. maxillary sinus

radiolucent space


radiopaque line

6.inferior border of the zygomaticTiV lll lll lWW II » IIIIMI ijitilllll mi I I . Nil,? ,

process of the maxillaradiopaque area




radiopaque band

normal anat


Courtesy Dr. Stuart C. White, UCLA School of Dentistry." 19


RADIOLOGY

normal anat



20copyright C 2013-2014- Dental Decks

RADIOLOGY



radiopaque line

2. lateral wall

in incisive canal )

radiopaque line

3 .

ala

of nose

radiopaque line

4. anterior wall

of maxillary sinus

radiopaque line

5. maxillary sinus

radiolucent space


radiopaque band "Courtesy Dr. Stuart C. White, UCLA


1. dentino-enamel junction (DEJ)

radiopaque line

' answers 1 - 6 below


radiolucent line

3. lamina dura

radiopaque line

4. periodontal ligament space of

palatal root

radiolucent line

5. film holder

radiopaque area

6. mucosa over alveolar bone

slightly radiopaque structure

"Courtesy Dr. Stuart C. White, UCLASchool of Dentistry."

normal anat



21

copyright ©2013-2014-Dental Decks

RADIOLOGY

normal anat


Courtesy Dr. Stuart C. White, UCLA School of Dentistry."


RADIOLOGY


1. mandibular tori

radiopaque masses

2. lingual foramen

radiolucent circle

3. genial tubercles

donut shaped radiopacity




1. alveolar crest of bone


2. lamina dura

radiopaque line


radiolucent line


radiopaque lines



normal ant


"Courtesy Dr. Stuart C. White, UCLA School of Dentistry." 2

3

= =

_ _ _ _ ^ _ _ ^ _ _ copyright ©2013-2014-Dental Decks

RADIOLOGY

normal anat



copyright ©2013-2014- Dental Decks

RADIOLOGY

1. marrow space

radiolucent space



radiolucent line

3. bony trabecular plate

radiopaque line

4. lamina dura

radiopaque line

5. pulp canal

radiolucent space

6. alveolar crest

radiopaque area

7. dentin

radiopaque area"Courtesy Dr. Stuart C. White, UCLA


8. enamel

radiopaque area

1. dentin

radiopaque area



radiopaque lines

3. marrow space

radiolucent area

4. pulp canal

radiolucent space


radiolucent line

6. lamina dura

radiopaque line

7. alveolar crest


8. enamel

radiopaque band



9. pulp chamber

radiolucent space

normal anat

Identify the structures labeled 1-12 on the image below.



RADIOLOGY

normal anat



6


RADIOLOGY



radiopaque lines

2. marrow space

radiolucent area

3. tooth #10

maxillary lateral incisor

4. lamina dura

radiopaque line

5. dentin

radiopaque area


radiolucent line

7. alveolar crest


8. pulp canal

radiolucent space

9. pulp chamber

radiolucent space

10. enamel

radiopaque band

ll«jraU£dJiJmdot

radiopaque circle

12. dentino-enameTjunction

radiopaque line




1. tooth #3

maxillary first molar

2. amalgam restoration

3. plastic bite block

faint opacity

4. film dot

rounajradiolucency

5. black letters - PLS

indicates Kodak Ektaspeed plus film

6. lamina dura

radiopaque line


radiolucent line



8. lamina dura

radiopaque line

normal anat

Identify the structures labeled 1 -15 on the image below.

"Courtesy Dr. StuartC. White, UCLA


RADIOLOGY

27


normal anat

Identify the structures labeled 1 -13 on the image below.

"Courtesy Dr. Smart

C. White, UCLASchool of Dentistry."

28


RADIOLOGY

answers 1-15 below

1. air in nasal fossa

raHTolucenTspace

2. nasal septum

radiopaque line

3-lateralwaU of nasal septum

medial wall of maxillary sinus

radiopaque lines

4. infraorbital rim

radiopaque line

5- wall of infraorbital canal

radiopaque line

6. pterveomaxillary fissure

radiolucent space

7. pterygoid spine of sphenoid

radiopaque line

8. zygomatic arch

radiopaque mass

9. posterior wall of maxillary sinus

radiopaque line

10 . posterior wall of the zygomatic

process of the maxilla

radiopaque line

11. ear lobe

radiopaque mass



12. inferior border of the mandibular canal

radiopaque line

13. anterior nasal spine

v-shaped radiopacity

14. inferior border of the mandible

radiopaque band

15. hyoid bone


• answers 1-1 3 below

1. tip of nose

radiopaque area

2. hard palate / floor of nasal fossa

radiopaque line

3. orbit

radiolucent area

4. hard palate / floor of nasal fossa

radiopaque line


radiopaque line

6. soft palate


7. air between soft palate & tongue

radiolucent space

8.._dorsum of the tongue

radiopaque line

9. ghost ima^eofop^>ositerartius

^TndTcateTrjy radiopaque dote

10 .

mental foramen

ovoid radiolucency

11. shadow of cervical spine

diffuse opacity




broad radiolucent area

13. articular eminence / articular tubercle

radiopaque prominence

processing

The pattern of stored energy on an exposed film is termed the latent image;

this image remains invisible unt il it undergoes processing.

The function of the developer solution is to chemically reduce the exposed,

energized silver halide crystals to black metallic silver.





29copyright©2013-2014-Dental Decks

RADIOLOGY

processing

Which ingredient in the fixer solution functions to remove all unexposed and

underdeveloped silver halide crystals from the emulsion?

• fixing agent

• acidifier

• hardening agent

• preservative



RADIOLOGY

both statements are true

Film processing

converts the latent image to a visible image and

preserves the image on film

Latent

image

• the film emulsion absorbs x:

rays during ex-jffgnni «r^ W e s the energy,within the silver

halide crystals

• the stored energy forms a pattern and creates

an invisible image

• the pattern of stored energy cannot be seen

and is referred to as the latent image; it re

mains invisible until chemical processing

Black areas of the visible image

• appear radiolucent f-;y

• created by deposits of black metallic silver

• structures that permit the passage of the

x-ray beam allow more x-rays to reach the

film & energize more silver halide crystals

• more energized silver halide crystals result

in more deposits of black metallic silver

White areas of the visible image

• appear radiopaque ^?Ci

• results from .unexposed silver halide crystals

• structures that resist the passage of the x-ray

beam restrict or limit amount of x-rays that

reach the film resulting in no energized silver

halide crystals and no deposits of black metal

lic silver

Film processing steps

1. development - developer solution removes

halide portion of exposed silver halide crystals;

this reduction of exposed crystals results in pre-

cipitated.Wackjnel^icjy]yer 6^FJsJheopti-

mal temperature for developer)

2. rinsing - water removes developer & stops

development process

3. fixing - fixer solution removes unexposed sil

ver

halide crystals

& hardens the

film

4. washing - water removesaTTexcess chemi

cals from the emulsion

5. drying

Developer composition

• developing agent contains 2 chemicals hy-

Cdroquinone

& cloijj

hydroquinone slpjvly

con

verts silver halide crystals & generates black

tones ;elon-quickly converts silver halide crys

tals & generates gray tones

• preservative is Sodium sulfite; prevents oxi

dation of developer agents

• accelerator is sodium carbonate; activates

the developer & softens emulsion^

^t^*-*******

««..«——"""-'^

• restrainer ts;potassium bromide; prevents

developer from deveToping

unexposed crystals

Fixer composition

• fixing agent (a.k.a. clearing agent or

hypo) is^xliu^Jhiojul&teorammonium

t h i o s u l f a t e ; removes or clears" all un-

exposed & underdeveloped silver halide

crystals from emulsion; clears the film so

that black image produced by the devel

oper can be seen

• preservative is,si»{Uumjmlfite (same as

in developer); prevents the deterioration of

the fixing agent

• hardening agent is potassium alum;

shrinks and hardens the gelatin in the

emulsion

• acidifier is acj^ j ic id j ) r sulfuric acid;

neutralizes the alkaline developer and

stops development process & provides

necessary acidic environment for fixer

Safelighting

• lighting that is required in darkroom for

safe illumination while processing x-ray

film

Q

J

^JJQdak^BXd

t

£S^hMM?r with a

15-watt bulb at least 4 feet away from

working surface

• fixing agent

Film processing steps

1.

development

2. rinsing

3. fixing

4. washing

5. drying

Manual film processing

• a.k.a. hand processing or tank processing

• method used to process films where all

steps are performed manually

• equipment needed includes processing

tanks with covers, thermometer, timer,

film hangers and stirring rod

• typical processing times include:

5 min utes in developer —> 30 second rinse

—> 10 minutes in fixer —• at l e a s t d Q a n m -

utgsjriwash

• as a rule, fixing time is twice as long as

developing time

Automatic film processing

• method used to process films using

where all steps of film processing are au

tomated

• automatic processor is required

• total processing time is 4-6 minutes

processing

Your assistant has processed three panoramic films today. She noticed the

films are progressively getting lighter and lighter. What should be done to

correct the problem?

• decrease the temperature of the developer

• increase the temperature of the fixer

• replenish the developer

• process the films a second time

• decrease the time in the developer

31copyright S> 2013-2014- Dental Decks

RADIOLOGY

processing

Your assistant has just processed a film that appears too dark. Identify each of

the potential causes of this problem.

• inadequate time in developer

• excessive time in developer

• developer solution too cool

• developer solution too hot

• depleted developer

• concentrated developer

RADIOLOGY

32copyright 6> 2013-2014- Dental Decks

' replenish the developer

Replenisher solutions

• a replenisher is a superconcentrated solu

tion that is added to the existing processing

solutions to compensate for the loss of vol

ume and strength that occurs due to oxida-

tion

• '

:

-

r

'

• both the developer and fixer must be re-

plenished daily to maintain adequate fresh-

ness

• replenishment main tains adequate con

centrations of chemicals which ensures uni

form processing

• failure to use replenishing solutions results

in non-diagnostic radiographs

Processing solutions

• include developer, fixer & replenisher

• must follow manufacturer directions for

storage, mixing & replenishing

• the developer and fixer must be changed at

the same time every 3-4 weeks or more often

with high volume of processing

• tanks must be scrubbed and cleaned when

changing solutions

Developer solution life is affected by

• cleanliness of tank

• size of films processed

• number of films processed

• temperature

• evaporation

Depleted developer

• is weakened, lacks concentration

• does not fully develop the latent image

• produces a non-diagnostic image with red

uced density and contrast

• results in underdeveloped films

• underdeveloped films appear light

Underdeveloped film

• appears light

• causes

- time/inadequate time in developer

- temperature/developer too cool

- concentration/depleted developer

• solutions

- t i m e / time in developer

- temperature/t temperature

- concentration/replenish developer

• excessive time in developer

• developer solution too hot

• concentrated developer

Time and Temperature: Problems and Solutions

Example

Underdevelopedfilm

Overdevelopedfilm

Reticulation of

emulsion

Appearance

Light

Dark

Cracked

Problems

- Inadequate development time

- Developer solution too cool

- Inaccurate timer or thermometer

- Depicted or contaminateddeveloper solution

- Excessive developing time

- Developer solution too hot- Inaccurate timer or thermometer- Concentrated developer solution

Sudden temperature changebetween developer and water bath

Solutions

- Check development time

- Check developer temperature

- Replace faulty timer or thermometer

- Replenish developer with freshsolutions as needed

- Check development time- Check developer temperature- Replace faulty timer or thermometer

- Replenish developer with freshsolutions as needed

Check temperature of processing

solutions and water bath; avoid

drastic temperature differences

Reprinted from Iannucci, Joen M. and Laura Jansen: Dental Radiography Principles and Techniques. Fourth Edition, d

from Elsevier Saunders

2012, with permission

processing

Black branching lines appear on a processed him. Which of the following is

the most likely cause?

• fixer cut-off

• developer cut-off

• fingernail damage

• static electricity

• air bubbles


RADIOLOGY

Dose equivalent is expressed in terms of:

• coulombs/kilogram (C/kg)

• gray

(Gy)

• sievert (Sv)

• quality factor (QF)

rad biology

RADIOLOGY

34


• static electricity

Film Handling: Problems and Solutions

Example

Developer

cut-off

Fixer

cut-off

Over

lapped

films

Air

bubbles

Fingernail

artifact

Finger

print

artifact

Static

,eh?ctricity

Scratched

film

Appearance

Straight white

border

Straight black

border

White or dark areas

appear on film where

overlapped

White spots

Black crescent-

shaped marks

Black fingerprint

Thin, black,

branching lines

White lines

Problems

Underdeveloped portion of

film due to low level of

developer

Unfixed portion of film due to

low level of fixer

Two films contacting each

other during processing

Air trapped on the film

surface after being placed in

the processing solutions

Film emulsion damaged by

the operator's fingernail during

rough handling

Film touched by fingers that

are contaminated with fluoride

or developer

- Occurs when film packet is

opened quickly

- Occurs when film pack i s

opened before the radiographer

touches a conductive object

Soft emulsion removed from

the film by a sharp object

Solutions

Check developer level before

processing; add solution if

needed

Check fixer level before pro

cessing; add solution if needed

Separate films so that no contact

takes place during processing

Gently agitate film racks after

placing in processing solutions

Gently handle films holding

them on the edges only

Wash and dry hands thoroughly

before processing

- Open film packet slowly

- Touch a conductive object

before unwrapping films

Use care when handling films

and film racks

Reprinted from lannucci, Joen M. and Laura Jansen: Denial Radiography Principles and Techniques. Fourth Edition. © 2012, with permissionfrom Elsevier Saunders

sievert (Sv)

Exposure measurement

• exposure refers to the measurement of ion

ization in air produced by x-rays

• roentgen (R)

is a way of measuring radia

tion exposure by determining the amount of

ionization that occurs in air

• R is limited to measurement in air

• there is no SI unit for exposure that is equiv

alent to the R

• exposure expressed in Coulombs per kilo

gram (C/kg)

Dose measurement

• dose refers to amount of energy absorbed

by a tissue

• rad is a unit of absorbed dose that is equal

to the deposition of 100

ergs/g of tissue

• the SI unit for rad is gray (Gy)

Dose equivalent

• rem is traditional unit of dose equivalent

used to compare the biologi&.£ffects_of dif

ferent Jypes

of radiation on a tissue or organ

• is the product of Gy x QF (quality factor)

specific for the radiation type

• for x-rays, QF=1

5Tumt

for rem is sievert (Sv)

Unit Definition Conversion

Traditional System (older system)

roentgen (R)

radiation

absorbed close

(rad)

1 rem = rads X QFroentgen

equivalent (in)

man (rem)

SI system (newer system)

lR = 87erg/g

1 rad = 100 erg

1R =

2.58X10 'C/kg

1 rad = 0.01 Gy

Coulombs

per kilogram

(C/kg)

gray (Gy)

sievert (Sv)

1 Gy = 0.01 J/kg

lSv = GyXQF | 1

1 rem = 0.01 Sv

1 C/kg = 3880 R

is*si«

rads

: Sv = 100 rerh>

rad biology

List the following cells from most RADIORESISTANT to most RADIOSENSITIVE.

muscle

small lymphocyte

skin

thyroid gland


RADIOLOGY

rad biology

After the bombings of Hiroshima, there were many persons exposed to radi

ation. Symptoms such as hair loss did not occur until days following the ex

posure. The time between exposure and onset of symptoms is termed:

latent period

• period of cell injury

• recovery period

• cumulative effects period


RADIOLOGY

muscle — thyroid gland — skin — small lymphocyte

• all ionizing radiations are harmful

to living tissues

• radiation produces chemical changes

that results in biologic damage in living

tissues

• not all cells respond to radiation in the

same manner

• cells respond to radiation based on mi

totic activity, differentiation and cell

metabolism

• cells that are dividing and immature

are most susceptible to radiation

• radiosensitive cells are susceptible to ra

diation exposure

• the most radiosensitive cell is the small

lymphjaq&e

• radioresistant cells are resistant to radi

ation exposure

• the most radioresistant cells are muscle

anrlnjejye

• radiation effects are classified as somatic

(occur in person irradiated) or genetic

(passed on to future generation)

Sensitivity Radiosensitive Radioresistant Cells Sensitivity

high

high

high

high

fairly high

fairly high

fairly high

small lymphocyte

bone marrow

reproductive cells

intestinal mucosa

skin

lens of eye

oral mucosa

muscle tissue

nerve tissue

mature bone/cartilage

salivary gland

thyroid gland

kidney

liver

low

low

fairly low

fairly low

fairly low

fairly low

fairly low

latent period

Mechanisms of radiation injury

• ionization & free radical formation are re

sponsible for cell injury

• free radical formation is the primary mecha

nism responsible for damage

Theories of radiation injury

• direct theory - cell damage results when ra

diation directly hits critical areas within the cell

& direct alteration of the cell occurs

• indirect theory - suggests that x-ray photons

are absorbed within the cell and cause the for

mation free radicals & toxins which result in cell

damage K- f*W+ wa - ^W , W * eeA i ,

Dose-response curve

• a dose-response curve is used to demonstrate

the response of tissues to the dose of radiation

received

• a threshold dose does not exist & response of

tissues is directly proportional to the dose

• injury from radiation depends on total dose,

.„dose ratej^anjount of tissue affected, cgjl sen

sitivity and age

Stochastic & nonstochastic effects

• stochastic effects occur as a direct function of

dose (cancer, genetic mutations)

• nonstochastic effects have a threshold and in

crease in severity with increased dose (hair loss,

decreased fertility)

Radiation injury sequence

• latent period - period of time between exposure

and onset of symptoms

• period of injury - follows latent period and may

result in cell death, change in cell function or ab

normal mitosis

• period of recovery - follows injury; depending on

a number of factors, cells can repair the damage

caused by radiation

Radiation effects

• short term effects occur when large amounts are

absorbed in a short period of time (not applicable

to dentistry)

• long term effects occur when small amounts are

absorbed over a long period of time; linked to in

duction of cancer, birth & genetic effects

• cumulative effects occur; radiation damage is ad

ditive and unrepaired damage accumulates in the tis

sues and leads to health problems (cancer, cataract

formation, birth defects)

Radiation effects on cells

• the cell nucleus is more sensitive to radiation than

cytoplasm; DNA is affected

• cell division is disrupted which may lead to dis

rupted cell function or cell death

• radiation causes cell death by damaging chromo

somes

rad biology

A patient with a large squamous cell carcinoma of the lateral border of the

tongue is scheduled for a radical neck dissection. Prophylactic extractions of

hopeless teeth must be done to prevent which of the following?

osteoradionecrosis

bisphosphonate osteoradionecrosis

• periodontal disease

• rampant caries

none of the above


RADIOLOGY

rad biology

The most common oral problems that occur following radiation and

chemotherapy include mucositis, infection, pain and bleeding.

The oral cavity is irradiated during the course of treating radiosensitive oral

malignancies, usually squamous cell carcinoma.



> the first statement is true, the second is false

«the first statement is false, the second is true

38


RADIOLOGY

Definition

• most serious possible complication facing the

oral cancer patient

• condition of non-vital bone in a site of radio

therapy; bone dies as a complication of radio

therapy

• is not

an infection

Cause

• radiation therapy destroys cancerous cells but

also destroys normal cells, damag ing small ar

teries and reducing circulation

• insufficient blood supply to the irradiated area

decreases the ability to heal, and any subse

quent infections to the jaw can pose a huge

risk

to the patient

• patients receiving high dQjt££_Qf,xadiation

£>40 Gv) to the jaw area are at risk

Histologic features- 3 H's

v* hypocellular bone

v^hypovascular tissue

v""hypoxic tissue & bone

Prevention

• extr act all hopeless teeth 3 weeks prior to ra

diotherapy

• if extracting after radiotherapy, use of systemic

antibiotics is warranted

• hyperbaric oxygen treatments before and

after radiotherapy may be helpful

• osteoradionecrosis

Clinical features

• may involve the maxilla or mandible

• more common in the mandible

• most frequently occurs when an insult to the bone

is sustained in the irradiated area, such as related

subsequent surgery, biopsy, tooth extractions or

denture irritations

• may also be precipitated by periodontal disease

or occur spontaneously

• symptoms may include pain, swelling, reduced

mobility, drainage, exposed bone in the involved

area and destruction of bone

• symptoms may occur months or years after the

radiotherapy

Management

• difficult to manage

• preventio n is key

• debridement of infected bone may be required

• advanced cases may require radical surgery

• patients must be followed closely by physicians

and dentist regularly


Radiation therapy of oral cavity

• used to treat radiosensitive oral malignant tu

mors, usually squamous cell

carcinoma

• indicated when the tumor is radiosensitive,

advanced, or, cannot be treated surgically be

cause it is deeply invasive

• fractionation

- total radiation dose is delivered in smaller

multiple doses

- provides greater tumor destruction than a sin

gle large dose

- allows for increased cellular r epai r of nor

mal tissues

- increases mean oxygen tension resulting

in

tumor cells that arc more radiosensitiveWMMIMM n

Radiation effects

on the teeth

• irradiation of developing teeth severely retards

growth

• adult teeth are radioresistant\3^<'

Radiation effects on bone

• irradiation of bone results in damage to the

fine vasculature

• normal marrow may be replaced with fatty

maiTOW

or fibrous connective tissue

• necrosis may occur and exhibits loss of os

teoblastic and osteoclastic activity

Radiation effects on oral tissues Ks

• occurs by end of 2

nd

weekpf

therapy *5»jf

• mucositis results; appears as areas of redness and

inflammation

• as therapy continues, the oral tissues break down

resulting in formation of white pseudomembranes

• oral condition worsens with continued therapy

and candidiasis often occurs

• following therapy, oral tissues heal within ap-

proximately 2 months ifogut 8

Radiation effects on taste buds /-'

• taste buds are radiosensitive

• radiation therapy damages taste buds

• a loss of taste may first occur during the 2

nd or

3

rd week of radiation therapy

Radiation effects on salivary glands

• radiation therapy damages salivary gland tissues

• there is a m ark ed & progressive loss of salivary

secretion; extent of reduced flow is dependent on

dose

• causes decreases in saliva, p H

& buffering ca

pacity

• causes increased viscosity

• dry moutn (xerostomia) results & makes the pa

tient susceptible to radiation caries - a rampant

form of caries

• xerostomia causes tenderness of oral tissues and

difficulty in swallowing

rad char

In the dental x-ray tube, the number of electrons flowing per second is meas

ured by:

• kilovoltage peak (kVp)

• milliamperage (mA)

• time (in seconds)

• all of the above

39


RADIOLOGY

rad char

When the PID length is changed from 8

to 16 , the target-receptor distance

is doubled. According to the Inverse Square Law, the resultant x-ray beam is:

• 1/4 as intense

• 1/8 as intense

• four times more intense

• eight times more intense


40

copyright e 2013-2014- Dental Decks

RADIOLOGY

W ~

TJu^-^ milliamperage (mA)

^rrv*4

^ V t i

x_

ra y beam intensity

time and distance

x-ray beam quality & kVp

• quality refers to the average energyor 7

intensity is the total energy contained in

penetra tin g power of the x-ray beam and the x-ray beam at a specific area at a given

is controlled by the kilovoltage peak (kVp) time

• kVp controls the speed & energy of the ~ Qrfntensity is affected by kVp, m A , exposure

electrons and determines the penet rating

power of the beam £>

• kVp range for dental radiography is s k ^

c^iookv^i Tt<y

x-ray beam quantity & mA ™ « - * .

• quantity refers to the number of x-rays J ^ ^ H , a*

1

produced and is controlled by the mil-' e

\^

l

%

liamperage (mA)

• mA

controls the amperage of the fila

ment current and the amount of electrons

that pass through the filament

• mA

controls the temperature

of the fil

ament

• as the mA increases, more electrons pass

through the filament and more x-rays are

produced

• J T I A range for dental radiography is

j ^ l 5 m A P

^ TiHmmiini iM urn

to remember, think alphabeti cal order ...

kVp= quali ty ( k & 1)

mA = quan tity ( m & n )

Adjustment

T

1

r

i

T

i

kVp

kVp

mA

mA

time

time

Film

appears

darker

lighter

darker

lighter

darker

lighter

to INCREASE film density & make it darker,

INCREASE:

• mA

•kVp

• time

to DECREASE film density & make it lighter,

DECREASE:

• mA

•kVp

• time

Inverse Square Law

• defined as:

the intensity of the radiation is inversely

proportional to the square of the distance

from the source of radiation

• inversely proportional means that as one

variable increases, the other decreases

• when

the target-receptor distance is in

creased, the intensity is decreased

original intensity . new intensity

new distance2 original distance

2

OS

V£

closer

Reprinted from lannucci, Jocn M. and Howerton,Laura Jansen: Dental Radiography Principles andTechniques. Fourth edition © 2012, with permissionfrom Elsevier Saunders.

• 1/4 as intense

Example:

If the PID

length is changed from 8" to 16", how

does this increase in target-receptor distance af

fect the intensity of the beam?

plug numbers into the mathematical for

mula:

x /82

4*

/

U

K

IW

solve for x

1 / x= 162 / 8

2

1 / x= 256 / 64

1 / x= 4 / 1

x= 1/4 answer

• doubling the distance results in a beam that

is % as intense

• the x-ray beam that exits an 8" PID is more

intense than one the exits a 16 " PID (see dia

gram)

The distance traveled by the x-ray beam affects

the intensity; distances to be considered include

the following:

• target-surface distance is the distance from

the source of radiation to the surface of the pa

tient's skin

• target-object distance is the distance from

the source of radiation to the tooth

• target-receptor distance is the distance from

the source of radiation to the receptor ffilm or

sensor)

rad char

A 6'5 muscular male with a large mandible requires a complete series of den

tal images. You plan to increase the kVp because of his size. Identify each of

the following that results with the increased kVp:

• a more penetrating beam

' a less penetrating beam

• a reduced subject contrast

• an increased subject contrast

• long scale contrast

• short scale contrast


RADIOLOGY

rad char

Identify each of the following that influence the density of an image:

•kVp

• mA

• exposure time

• use of a 2 film packet

42


RADIOLOGY

Increased kVp

• produces x-rays with increased energy

(speed) and shorter wavelength

• increases the penetrating power of the x-

ray beam

• is needed for larger patients with large

bones and significant amounts of soft tissue

• results in increased density (makes image

darker)

• results in reduced or low contrast which is

long-scale contrast

Contrast

• refers to how sharply dark and light areas

are separated or differentiated on an image

• the difference in degrees of blackness be

tween adjacent areas on a dental radiograph

• a more penetrating beam

• a reduced subject contrast

• long scale contrast

Long-scale contrast

• LONG scale =

JLOW contrast =

LOTS of gray

• a low contrast image exhibits many shades

of gray

• a low contrast image does not exhibit black

& white

Adjustment

T

(High)

4(Low)

kVp

kVp

Contrastscale

LONG

lots of gray

SHORT

black & white

Contrast

LOW

HIGH

Contrast & kVp

• adjustment of kVp affects contrast

• with low kVp (65-70), a high contrast

image results

• with high kVp (90), a low contrast image

results

Patient size & kVp

• large patients need increased kVp;

if not increased — image appears LIGHT

• small patients need decreased kVp;

if not decreased — image appears DARK

Density description

• a visual characteristic of a radiographic

image

• overall blackness or darkness of an image

• when a dental image viewed, the relative

transparency of areas depends on the distri

bution of black silver particles

• density is the degree of.silver blackening

• an image of correct density allows one to

view the black areas (air space images),

white areas (enamel, dentin, bone) and gray

areas (soft tissue)

Factors that influence density

• exposure factors

-kVp

- mA

- exposure time

• thickness of subject

adjustments in kVp, mA and exposure time

can be made to compensate for size variations

• an increase in any exposure factor , sepa

rately or combined, increases the density of

an image

\9

Adjustment

T

4

r

4.

T

4

tx

4

kVp

kVp

mA

mA

time

time

thickness

thickness

••

.

kVp

mA

exposure time

Densitv Film

t

4

t

4

T

4

4

T

appears

darker

lighter

darker

lighter

darker

lighter

lighter

darker

Size of patient

• thickness of subject also affects density;

with a large patient (thick bones, excess soft

tissue), fewer x-rays reach the receptor and

as a result, the image appears lighter

• with increased thickness, a decreased den

sity results

• with decreased thickness, an increased

density results

Note: the use of a 2-film packet does not affect

the density of the image

rad physics

Which of the following converts electrons into x-rays?

• positive anode

1 negative anode

' positive cathode

• negative cathode


RADIOLOGY

rad physics

Which of the following focuses the electrons into a narrow beam and directs

the beam across the tube toward the tungsten target of the anode?

• copper stem

• tungsten filament

• insulating oil

• molybdenum cup

• lead collimator

44


RADIOLOGY

•positive anode

X-ray tube• heart of the x-ray generating system

• critical to the production of x-rays

• glass vacuum tube from which all the air has

been removed

• component parts include leaded glass hous-

_ing, negative cathode & positive anode

Leaded-glass housing

• leaded-glass vacuum tube that prevents x-rays from escaping in all directions

• a "window" permits the x-ray beam to exitthe tube

Reprinted from Iannucci, Jocn M. and Howerton, Laura

Jansen: Dental Radiography Principles and Techniques.

Fourth edition © 2012 with permission from Elsevier-Saun-

ders.

to remember,think CATNAP...

cathode is negative

| Cathode/negative electrode

• supplies electrons necessary to generate x-rays

• consists of a tungsten wire filament in amolybdenum cup-shaped holder

• tungsten filament (coiled tungsten wire)

produces electrons when heated

• molybdenum cup focuses the electronsinto a narrow beam and directs the beamacross the tube toward the tungsten target ofthe anode

Anonode/positive electrode•odeisTnto x-• converts electronslivto x-ray photons

• consists of a wafer-thin tungsten plate em

bedded in a solid copper rod

• tungsten target serves as a focal spot and

converts bombarding electrons into x-ray

photons

• copper stem functions to dissipate the heat

away from the tungsten target

molybdenum cup

Production of x-rays

• tungsten filament is heated and electrons

are produced

• molybdenum cup focuses the electrons

into a narrow beam and directs the beam to

wards the tungsten target in the anode

• x-rays are generated when the beam is sud

denly stopped by the tungsten target

•4fafi.en£igy_of motion is converted to x-ray

energy (1%) and heat (99%)

• insulating oil that surrounds the x-ray tube

absorbs the heat

• x-rays that are produced are emitted in all

directions; leaded-glass housing of tube pre

vents the x-rays from escaping

• small number of x-rays exit the x-ray tube

through the unleaded glass window area

• x-rays travel through unleaded glass win

dow, through the tubehead seal and then the

aluminium disks

• the lead collimator restricts the size of the

beam and the x-ray beam travels down the

lead lined position -indicating device (PID)

and exits at the opening

Reprinted from Haring, Joen Iannucci and Laura lansen: Dental Radiogra

phy: Principles and Techniques: Third Edition. © 2000, with permission front

Elsevier.

Component functions

• tungsten filament of cathode produces

electrons when heated

• molybdenum cup of cathode focuses the

electrons into a narrow beam and directs

the beam towards the tungsten target in the

anode

• tungsten target in anode stops the elec

trons and converts the energy into x-rays &

heat

•(copper stenijjserves to dissipate the heat

that is createdwith the production of x-rays

|i_Metal

ji housing£ of x-ray1 tube-

1

J

a-lnsulating

: oil

K. . -

Lead Unleaded glasscollimator window of

x-ray tube

'osition

indicating

device

rad physics

Identify each of the following that are properties of x-rays:

• no weight

• travel at speed of sound

• have no charge

• cannot be deflected or scattered

• are invisible

• are absorbed by matter

• do not damage living cells

• do not cause fluorescence45


RADIOLOGY

rad physics

Rectification is the conversion of a direct current (DC) to an alternating cur

rent (AC).

The dental x-ray tube acts as self-rectifier in that in changes DC to AC while

producing x-rays.





46copyright ® 2013-2014- Dental Decks

RADIOLOGY

Properties of x-rays

• appearance

invisible and cannot be detected by

any of the senses

• mass

have no mass or weight

• charge

have no charge

• speed

travel at the speed of light

• wavelength

travel in waves and have short wave

lengths with a high frequency\V""

• path of travel

travel in straight lines and can be de

flected, or scattered

• focusing capability

cannot be focused to a point and al

ways diverge from a point

• no weight

• have no charge

• are invisible

• are absorbed by matter

• penetrating power

can penetrate liquids, solids, and gases;

the composition of the substance deter

mines whether x-rays penetrate or pass

through, or are absorbed

• absorption

absorbed by matter; the absorption de

pends on the atomic structure of mat

ter and the wavelength of the x-ray

• ionization capability

can interact with materials they pene

trate and cause ionization

• fluorescence capability

can cause certain substances to fluo

resce or emit radiation in longer wave

lengths (e.g., visible light and

ultraviolet light)

• effect on film

can produce an image on photographic

film

• effect on living tissues

cause biologic changes in living cells

• electricity is the energy used to make x-

rays; electrical energy consists of a flow of

electrons through a conductor; this flow is

known as the electrical current

• electrical current is termed direct current

(DC) when the electrons flow in one direc

tion through the conductor

• alternating current (AC) describes an elec

trical current in which the electrons flow in

two, opposite directions

• rectification is the conversion of AC to DC

• dental x-ray tube acts as a self-rectifier in

that it changes AC into DC while producing

x-rays; ensures that current is always flowing

in the same direction from cathode to anode

• amperage is the measurement of the num

ber of electrons moving through a conductor,^,

c7irrentls~measured in amperes (A) or mil-

liampcres (mA)

• voltage is the, measurement of electrical

force that causes electrons to move from a

negative pole to a positive one; measured in

volts (V) or kilovolts (kV)

• circuit is a path of electrical current; two

electrical circuits are used to produce x-rays:

a low-voltage/filament circuit and a high-

voltage circuit

* % .


• low voltage/filament circuit uses 3 to 5

volts, regulates the flow of electrical current

to the filament; controlled by mA settings

• high-voltage circuit uses 65,000 to 100,000

volts, provides the high voltage required to

accelerate; controlled by kVp settings

• transformer is a device that is used to either

increase or decrease the voltage in an electri

cal circuit; it alters the voltage of the incom

ing current and then routes the electrical

energy to the x-ray tube; three types of trans

formers are used to adjust the electrical cir

cuits (see below)

• step-down transformer is used to decrease

the voltage from the incoming 110- or 220-

line voltage to the 3 to 5 volts used by the fil

ament circuit

• high-voltage circuit uses both a step-up

transformer and autotransformer

• step-up transformer is used to increase the

voltage from the incoming 110- or 220-line

voltage to the 65,000 to 100,000 volts used

by the high-voltage circuit

• autotransformer serves as a voltage com

pensator that corrects for minor fluctuations

in the current

rad physics

Which of the following occurs only at 70 kVp or higher and accounts for a very

small part of the x-rays produced in the dental x-ray machine?

• compton

scatter

• coherent scatter

• characteristic radiation

• general (Bremsstrahlung) radiation

47copyright ©

2013-2014-

Dental Decks

RADIOLOGY

rad protection

Identify each component of inherent filtration:

• insulating oil

• unleaded glass window

• lead lined PID

• tubeheadseal

48


RADIOLOGY

> characteristic radiation

Types of x-rays

• not all x-rays produced in the x-ray tube are

the same; x-rays differ in energy and wave

length

• energy and wavelength varies based on how

the elections interact with the tungsten in the

anode

• kinetic energy_of electrons isconverted to

x-ray photons via general (braking or Brem-

sstrahlui'g) radiation or characteristic radiat-

ion

• genera l/braking radiation is produced

when speeding electrons slow down due to in

teractions with the nuclei of the tungsten tar

get atoms

- braking refers to the sudden stopping or

slowing of high-speed electrons when they

hit or come close to the tungsten target

- 70% of the x-ray energy produced is gen

eral radiation

• characteristic radiation is produced when

a high-speed electron dislodges an inner-shell

electron from the tungsten atom and causes

ionization " I

- the remaining electrons rearrange to fill the

vacancy resulting in a loss of energy & pro

duction of x-ray photon

- only a small % of x-rays produced; occurs

only at > 70 kVp

Definitions

• primary radiation is the penetrating x-ray

beam that is produced at the target of the

anode and exits the tubehead; a.k.a. primary

or useful beam

• secondary radiation is x-radiation that is

created when the primary beam interacts with

matter; ig less penetrating thanprimaryradia-

tion

• scatter radiation, a form of secondary rad

iation, is the result of an x-ray deflected from

its path by the interaction with matter; deflect

ed in all directions by the patient's tissues;

detrimental to tissues

• id Compton scatter] ionization takes place;

& \§ an x-ray photon collides with an n outer-shell

C *> > electron and gives up part of its energy to

'£ eject the electron from its orbit; x-ray photon

•*J*Hoses energy and continues in a different dir-

% ection (scatters) at a lower energy level; ac

counts forJ>2% of the scatter that occurs

• coherent or unmodified scatter occurs

when a low-energy x-ray photon interacts

with an outer-shell electron; no change in the

atom occurs; x-ray photon of scattered radiat

ion is produced; x-ray photon is scattered in

a different direction from that of the incident

photon; noJoss of energy and no ionization

occur; accounts for 8% of the interactions

insulating oil

< unleaded glass window

' tubehead seal

• inherent filtration takes place when the

primary beam passes through the glass

window of the x-ray tube, the insulating

oil, and the tubehead seal

• inherent filtration of the dental x-ray

machine is approximately 0.5 to 1.0 milli

meter (mm) of aluminum

• inherent filtration alone does not meet

the standards regulated by state and federal

laws; added filtration is required

OvtiioKjljtJ

. i

OMMUMHW <k<»

4r

^> -s tow e*<av*

Reprinted f rom Iannucci,

Joen

M. and Howerton, Laura Jansen: D e n ^ '

**^5l$

lal Radiography Principles and Techniques. Fourth edition © 2012 (/

willi

permission from Elsevier-Saunders.

Aluminum filter

~

r>K

- 1

Long and short

wavelengths

Shortwavelenotbs

Enlargement o detail

• added filtration refers to the placement

of aluminum discs in the path of the x-

ray beam between the collimator and the

tubehead seal

• aluminum discs can be added to the

tubehead in 0.5 mm increments

• purpose of the aluminum discs is to fil

ter out the longer-wavelength, low-en

ergy x-rays from the x-ray beam

• low-energy, longer wavelength x-rays

are harmful to the patient and are not

useful in diagnostic radiography

• filtration of the x-ray beam results in

a higher energy & more penetrating

useful beam

• state and federal laws regulate the re

quired thickness of total filtration = in

herent filtration + added filtration

• dental x-ray machines operating at ,<

70 kVp require a minimum total of 1.5

mm aluminum filtration

• dental x-ray machines operat ing at

> 70 kVp require a minimum total of 2.5

mm aluminum filtration

rad protection

Identify each of the following that is recommended for operator protection

during exposure.

•

stand 3 feet away from x-ray tubehead

• stand at a 45-75 degree angle to the beam

• wear a lead apron

•

stand behind a barrier

•

hold the

PID

• hold the film if the patient cannot stabilize it

49


RADIOLOGY

rad protection

Prior to x-ray exposure, the proper prescribing of radiographs and the use of

proper equipment can minimize the amount of radiation that a patient re

ceives.

Radiographs must be prescribed by the dentist based on the individual needs

of the patient.





50


RADIOLOGY

rad protection

Identify each of the following that is recommended for operator protection

during exposure.

• stand 3 feet away from x-ray tubehead

• stand at a 45-75 degree angle to the beam

• wear a lead apron

• stand behind a barrier

•holdthe PID

• hold the film if the patient cannot stabilize it


RADIOLOGY

rad protection

Prior to x-ray exposure, the proper prescribing of radiographs and the use of

proper equipment can minimize the amount of radiation that a patient re

ceives.

Radiographs must be prescribed by the dentist based on the individual needs

of the patient.






RADIOLOGY

Operator protection guidelines

• must use proper protection during exposure

to avoid the primary beam, scatter radiation

etc.

• must avoid the primary beam

• distance, position and shielding are all im

portant for protection

Distance recommendations

• must stand at least 6' away from the tube-head

• if distance is not possible, a protective bar

rier must be used

Primary beam

Y '

.••••.. ' -:.,.\:.-: ••:::•-::•• ' '

l W

'

Radiographer

135

Reprinted

from Iannucci, Joen

M. and Howerton, Laura Jansen:

Dental Radiography Principles and Techniques. Fourth edition

•D 2012 with permission from Elsevier-Saunders.

• stand behind a barrier

Position recommendations

• must stand perpendicular to the primary

beam, or, at a £0-135 degree angle to the

beam ' •

• never hold a film in place for a patient dur

ing exposure

• never hold the PID during exposure

Shielding recommendations

• whenever possible, stand behind a protec

tive barrier, such as a wall

Maximum permissible dose (MPD)

• MPD is the dose of radiation the body can

endure with little or no injury

• for non-occupationally exposed person limit

is 0.001 Sv/year

• for occupationally exposed person limit is

0.05 Sv/year

• for occupationally exposed pregnant person

— limit is 0.001 Sv/year

ALARA concept

•As Low As Reasonably Achievable concept

states that all exposure to radiation must be

kept to a minimum

• applies to patients & operators

Patient protection before exposure

• proper prescribing of dental radi

ographs

• use of proper equipment including

filtration, collimation and PID

• the rectangular PID (instead of

round) is most effective in reducing pa

tient exposure

• use of a long PID is more effective

than use of a short PID

Patient protection during exposure

• use of thyroid collar for intraoral

films and lead apron for all films

• use of digital imaging or use fastest

film

available (F-speed)

• use of beam alignment devices

• use of correct exposure factors (kVp,

mA & exposure time)

• use of proper technique


Patient protection after exposure

• proper sensor or film handling

• proper image retrieval or film pro

cessing

Guidelines for prescribing of dental

radiographs

• dentist is responsible for ordering im

ages & uses professional judgment to

make decisions concerning the num

ber, type and frequency of dental radi

ographs

• radiographic exam should never in

clude a predetermined number of

films

• radiographs should never be taken at

predetermined time intervals

• radiographs should be ordered based

on the individual needs of the patient

• guidelines for prescribing dental ra

diographs have been determined by

the ADA and FDA

rad protection

Which of the following is used to restrict the size and shape of the x-ray beam

and to reduce patient exposure?

• aluminum discs

• collimation

• inherent filtration

• total filtration

51copyright

€>

2013-2014- Dental Decks

RADIOLOGY 51

tech

If a processed film appears light with herringbone or tire track pattern on it,

which of the following is the likely cause?

• the film was bent during placement

• the film was reversed (placed backwards) during exposure

• the film was exposed twice

• the patient moved during exposure

52


RADIOLOGY

collimation

Collimation

• used to restrict the size and shape of

the x-ray beam & to reduce patient

exposure

• a collimator is a lead plate with hole

in the middle, is fitted over the open

ing of the machine housing where the

beam exits

• collimator may have a round or rec

tangular opening

• rectangular collimator restricts the

size of the beam to slightly larger than

a size 2 film and significantly re

stricts patient exposure

• circular collimator produces a cone

shaped beam & restricts the size of the

beam to 2.75" in diameter

• when using a circular collimator, fed

eral regulations re quire that the

beam be restricted to 2.75" as it exits

the PID and reaches the skin of the pa

tient

Position indicating device (PID)

• the PID or cone is an extension of the

x-ray tubehead used to direct the

beam

• types of PID include conical, round

and rectangular

• a conical PID is a closed plastic cone

that produces scatter radiation;no longer

used in dentistry

• a round PID is a tubular open ended

lead- lined extension; no PID scatter is

produced

• a rectangular PID is a rectangular

open ended lead-lined extension; is

most effective in reducing patient ex

posure; no PID scatter is produced

• both round and rectangular PIDs are

available in two lengths: short (8")

and long (16")

^ VtMJangPID

is preferred because less

V'uivergence of me*x-ray beam occurs

• the film was reversed (placed backwards) during exposure

A reversed

film is light &

exhibits a

herringbone

pattern.

A double exposure appears dark &

exhibits a double image.

A bent film appears stretched & distorted. With movement of the patient or PID, a blurred

image results.

Images reprinted from Iannucci , Joen M. and Howerton, Laura Jansen: Dental Radiography Principles and Techniques. Fourth edition © 2012

with permission from Elsevier-Saunders.

tech

Of the following factors that influence the geometric characteristics of an

image, which one is NOT able to be changed by the operator?

• target-receptor distance

• object-receptor distance

• film composition

• focal spot size

• object-receptor alignment

53copyright© 2013-2014- Dental Decks

RADIOLOGY

tech

A periapical image shows stretched and elongated maxillary central incisors.

Which of the following is the likely cause?

• vertical angulation is excessive/too steep

• vertical angulation is insufficient/too flat

• incorrect horizontal angulation

• any of the above

54


RADIOLOGY•-.

• focal spot size

Magnification

• enlargement of an image that results

from the divergent paths of x-ray beam

• some degree of magnification is pre s

ent in every image due to divergent paths

• influenced by target-receptor distance

and object-receptor distance

• target-receptor distance (or source to

receptor distance) is the distance be

tween the sou rce of x-rays & image re

ceptor

• PID determines target-receptor distance

• shorter PID results in more magnifi

cation; longer PID results in l e s s j n a g n i -

JBcatjori

• object-receptor distance is the dis

tance between the tooth & image recep

tor

• if there is decr eased dist ance between

the tooth & receptor, less magnification

occurs

• if there is increased distance between

the tooth & receptor, more magnification

occurs

Focal spot size

• tungsten target in anode is focal spot

• size ranges from0.6

-1.0 minj^nd

is de

termined by the manufacturer (cannot be

controlled by operator)

• the size of focal spot influences the

image sharpness

• the smaller the focal spot, the sharper

the image

In dental radiography, the most accurate

image:

• use the smallest focal spot size

• use the L ONG EST target-receptor dis

tance

• use the SHORTEST object-receptor

distance

• direct the central ray of the x-ray beam

perpendicular to the receptor and tooth

• keep the receptor parallel to the tooth

being imaged


Vertical angulation

• refers to the positioning of the PID in a

vertical, or up-and-down plane

• correct vertical angulation results in an

image that is the same

length as the tooth

• incorrect vertical angulation results in

ELONGATION or FORESHORTENING

• an elongated image appears long & results

from too flat vertical angulation

• a foreshortened image appears short & re

sults from too steep vertical angulation

• 0 degree vertical angulation = PID parallel

with floor

• positive vertical angulation = PID pointing

DOWN to floor/PID

above occlusal plane

• negative vertical angulation = PID point

ing UP to ceiling/PID

below occlusal plane

H

Vortical angulation

• refers to the positioning of the PID in a

horizontal or side-to-side plane

• when tire central ray is directed through the

interproximal contacts of the teeth, correct

horizontal angulation results and open con

tacts on seen the dental image

• incorrect horizontal angulation results in

overlapped contacts (contacts are superim

posed over each other)

ELONGATION resultswhen the vertical angulation is TOO FLAT;teeth look long &

stretched

FORESHORTENINGresults when the verticalangulation is TOOSTEEP; teeth look short

Both photos reprinted from Haring, Joen Iannucci and LauraJansen: Dental Radiography: Principles and Techniques: ThirdEdition. © 2000, with permission from Elsevier.

tech

Identify the cause of this panoramic image error seen below:

chin tipped too far upward

• chin tipped too far downward

' head tipped to one side


RADIOLOGY

Identify the cause of this distorted periapical film seen below:

tech

• film bending

• film creasing

• phalangioma

• double exposure

• movement

Reprinted from Haring,Joen Iannucci andLaura Jansen: DentalRadiography: Principles and Techniques:Third Edition. © 2000,with permission fromElsevier.

58


RADIOLOGY 58

• chin tipped too far downward

chin tipped too far downward \ /

(see image on reverse side)

• mandibular incisors appear blurred

• loss of detail in anterior apical region

• condyles may not be visible

• results in severe interproximal over

lapping

• occlusal plane has excessive upward

curve

• exaggerated smile line is seen

chin tipped too far forward A

(see image below) ' ^

• hard palate & floor of nasal cavity ap

pear superimposed over maxillary teeth

• maxillary incisors appear blurred

• maxillary incisors appear magnified

• occlusal plane

downward curve

• reverse smile line (frown) is seen

film bending

Film bending

• images appear stretched & distorted

• occurs due to curvature of hard palate

Film creasing

• crease appears as a thin black line

• represents where the emulsion of the film has

cracked

Phalangioma

• the bone of the patient's finger seen on the

image

• results when finger is in front of the receptor

instead of behind it (seen with use of bisecting

technique where patient holds the film— not

recommended)

Light film

• may result from und erexposure— too short

of exposure time, too low kVp or too low mA

Dark film

• may result from overexposure - too long of

exposure time, too high kVp or too high mA

Fogged film - s ^ -

• appears gray & lacks contrast

• occurs when film is exposed to radiation other

than primary beam (e.g., scatter)

• may result from improper safelighting or light

leaks in dark room

All three photos reprinted from Haring, Joen iannucci and Laura Jansen:

Dental Radiography: Principles and Techniques: Third Edition. © 2000,

with permission from Elsevier.

Black film

• exposed to light

Clear film

• film is unexposed

A light film results from

underexposure

a dark film results

from overexposure

a fogged film appears gray and

lacks contrast

tech

A periapical image shows overlapped contacts. This error is cause by:

• vertical angulation is excessive/too steep



• beam not centered over receptor

• poor receptor placement

RADIOLOGY


tech

Use the two images below to determine the spatial position of the round ob

ject. Following the exposure of image # 1 , the x-ray tubehead was moved and

the beam was directed from a mesial angulation in image #2. Given this in

formation, where is the round object located?

• lingual to the first molar

• buccal to the first molar

• in soft tissue

• in bone

<

c>

Film #1 Film #2


RADIOLOGY


Overlapped contacts

• if the central ray is not directed through

the interproximal contacts of the teeth, the

horizontal angulation is incorrect

• incorrect horizontal angulation results in

overlapped contacts seen on the image

Cone-cut

• if the beam is not centered over the recep

tor, a clear unexposed area or cone-cut is

seen on the image

• the PID or "cone" is said to "cut" the image

• a cone-cut may occur with the use of a rect

angular or round PID

• a conecut may occur with or without the

use of a beam alignment device

poor receptor placement

• a periapical image shows the entire tooth

and root, including the apical area and must

be placed to cover those areas

• incorrect periapical receptor placement

may result in absence of apical structures or

a tipped or tilted occlusal plane

• a bite-wing image shows the crowns of both

the maxillary and mandibular teeth, the inter

proximal areas and crestal bone

• incorrect bite-wing receptor placement

may result in absence of teeth or teeth surf-

faces on an image, tipped occlusal plane

Incorrect horizontal angulationresults in overlapped contacts.

If the beam is not centered over the receptor, a cone-cut results& a clear unexposedarea is seen.

Improper placement (if entireroot is not covered) will result inno apices appearing on the image.

Images reprinted from Haring, Joen Iannucci and Laura Jansen: Dental

Radiography: Principles and Techniques: Third Edition. © 2000, with

permission from Elsevier.

lingual to the first molar

Buccal object rule

• a.k.a. tube shift technique

• used to determine an object's spatial po-

sition/buccal-lingual relationship within

the jaws

• two images are obtained, each exposed

with a different angulation

• used to compare the object's position

with respect to a reference point (e.g., root

of a tooth)

Example

• if the PID is moved mesially and the ob

je ct in the second image appears to hav e

moved in the same direction, the object

lies to the lingual

• if the PID is moved mesial ly and the ob

je ct in the second image appea rs to have

moved in the opposite direction, the ob

je ct lies to the bu ccal

• use the acronym SLOB to remember the

buccal object rule

In image #1, notethe location of theobject in referenceto the mesial rootof the first molar.

In image #2, thePID was movedmesially; the ob

ject in referenceto the mesial rootof the first molarhas also movedmesially.

L - O - B RULE

Same = Lingual

extraoral

Identify the radiopaque areas labeled 1 & 2 on the image below.

Reprinted from Iannucci, Joen M. and Howerton, Laura Jansen: Dental Radiography Principles and

Techniques. Fourth edition © 2012 with permission from Elsevier-Saunders.

72copyright ©

2013-2014-

Dental Decks

RADIOLOGY

extraoral

Based on the image below, identify the approximate age of the patient.

Reprinted from Iannucci, Joen M. and Howerton, Laura Jansen: Dental Radiography Principles and Techniques.

Fourth edition © 2012 with permission from Elsevier-Saunders.

73

copyright o 2013-2014- Dental Decks

RADIOLOGY


Reprinted from Iannucci, joen M. and Howerton, Laura Jansen: Dental Radiography

Principles and Techniques. Fourth edition © 2012 with permission from Elsevier-Saunders.

1. Hoop earring

2. Ghost image of hoop earring

Ghost image

• defined as a radiopaque artifact on a

panoramic image that is produced when a

radiodense object is penetrated twice by the

x-ray beam

• occurs If all metallic or radiodense ob

jects (e.g., eyeglasses, earrings, necklaces,

hairpins, removable partial dentures, com

plete dentures, orthodontic retainers, hear

ing aids, napkin chains) are not removed

before exposure of panoramic receptor

•

obscures diagnostic information

Ghost image appearance

• resembles its real counterpart

• found on the opposite side of the image;

appears indistinct, larger, & highepthan

its actual counterpart

• a ghost image of a hoop earring appears

on the opposite side of the image as a ra-

diopacity that is larger & higher than the

real hoop earring; appears blurred in both

horizontal and vertical directions

• to avoid ghost images, instruct the pa

tient to remove all radiodense objects in the

head-and-neck region prior to exposure of

the panoramic receptor

' < 9 years old

Reprinted from Iannucci, Joen M. and Howerton, Laura Jansen: Dental Radiography Prin

ciples and Techniques. Fourth edition © 2012 with permission from Elsevier-Saunders.

The erupted permanent teeth are highlighted in gray in the charts below. Based on this in

formation, the panoramic film appears to represent a child of < 9 years old.

Permanent teeth

eruption charts

Maxillary

Central incisor

Lateral incisor

Canine

First premolar

Second premolar

First molar

Second

molar

Third molar

Age at eruption

7-8

8-9

11-12

10-12

10-12

6-7

12-13

17-21

Mandibular

Central incisor

Lateral incisor

Canine

First premolar

Second premolar

First molar

Second molar

Third molar

Age at eruption

6-7

7-8

9-10

10-12

11-12

6-7

11-13

17-21

tech

Identify each one of the followin g that is an advan tage of using the parallel

ing technique.

' receptor placement

i comfort

• accuracy

•simplicity

' duplication

59


RADIOLOGY

tech

Identify each one of the following that is a disadvantage of using the bisect

ing technique.

• decreased exposure time

• can be used without a beam alignment device

• distortion

• angulation problems


RADIOLOGY

Parelling technique

• based on concept of parallelism

• preferred technique for intraoral films

Basic principles

• receptor is placed parallel to the long axis

of the tooth being imaged

• central ray is directed perpendicular to

both the receptor & long axis of the tooth

• a beam alignment device must be used to

keep the receptor parallel to the tooth

• the object-receptor distance must be in

creased to keep the receptor and tooth paral

lel

• the target-receptor distance must be in

creased to make certain the most parallel rays

will be aimed at the tooth and receptor (16"

target-receptor distance)

Long axisol toolh

• accuracy

• simplicity

• duplication

Advantages

• accuracy - image is highly representative

of the actual tooth

• simplicity - simple & easy to learn and use

• duplication - easy to standardize and can be

accurately duplicated when serial images are

needed

Disadvantages

• receptor placement - it may be difficult for

operator to place the beam alignment device

in some patients

• discomfort - the beam alignment device

may cause discomfort

^to Positions of the receptor, tooth and central ray in the paral-

>ft ^% leling technique. The receptor & long axis of the tooth are par-**

<*•

allel. The central ray is perpendicular to the tooth and receptor.An increased target-receptor distance (16 ) is required.

Reprinted from Haring, Joen Iannucci and Laura Jansen: Dental Radiography:

Principles and Techniques: Third Edition. © 2000. with permission from El

sevier.

Bisecting technique

• based on rule of isometry

• technique used for periapicals

Basic principles

• receptor must cover area of interest

• receptor must be placed so 1/8" ex

tending beyond the occlusal or incisal

surfaces

• central ray is directed perpendicular

to the imaginary bisector

• central ray is directed through the

cont act a reas of the teeth

• x-ray beam must be centered over the

receptor so that the entire receptor is ex

posed

• distortion

• angulation problems

Advantages

• can be used withou t a bea m align ment

device and therefore may be more read

ily accepted by patients

• requires a shorter exposure time

Disadvantages

• image distortion (magnification) oc

curs when a short (8") PTD is used

• angulation problems may occur be

cause no beam alignment device is used

resulting in images that are elongated or

foreshortened

Length of image

The image on the receptor is equal to the length of the

tooth when the central ray is perpendicular to the "imag

inary bisector". A short (8 ") target-receptor distance is

required.

Reprinted from Haring, Joen Iannucci and Laura Jansen: Dental Radiography: Princi

ples and Techniques: Third Edition. © 2000, with permission from Elsevier.

radio 13-14

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