Radiology

RADIOLOGY

Digital

Rad

Which

tlTe

of

digital

image

receptor

is

most common

at tlris time?

.

_CID

(Charge

Injection

Device)

.

_CMOS/APS

(Complementarv

Metal

Oxide

Seniconductor/Atiive

Pixel

Sensor)

.

CCD

(Charge-Coupled

Device)

1

A number ofcomponenls are required lbr direct digital image producrion. These components include an x-ray

source, an elecffonic s€nsor, a digitil interface card, a computer with an analog-to-digilal con\efter lADC). a

screen monitor, sofhvarc, and a printer Tlpically, systcms are PC based

*ith

a 486 or higher proccssor, 640

KB intemal memory cquipped .|.t'ith an SVCA graphics card, and a high-resolution monitor /1024 X 768

pi*

e/j.). Direci digital senso$ are eilher a charge-cotlplcd device /Ca'D) or complemenlary metal oxide semicon-ductor active pixel sensot (CMOS-APS).

The CCD is thc most common device used today.The CCD is a solid-state detcctor composed ofan anay

of

x-ray or light sensitive pixels on a pure silicon chip. A pixel or picture element consisN of a small electron

well into which thc x-ray or light energy is deposited upon exposure. The individual CCD pixel size is

ap-proxirnately 40I wilh thc latest versious in the 20F range. Thc rows ofpixels are rrranged in a matrix of 5I2 x 512 pixels. Charge coupling is a process whereby the numbcr ofclcctrons deposited in cach pixel are

trans-ferred from one well 1{) thc next in a sequential manner to r rcad-out amplifier filr imagc display on the mon-itor. There are tuo typcs ofdigital sensor array designs: area and lin€ar. Ar€r arrays are used tbr

intraorll

radiography, while linear arrays are used in extraor|l imsging. Area arrays are available iD sizes

compara-blc to size 0, size

l,

and size 2 film. but the sensors are rigid and thickcr than radiographic film and have a

smaller sensitive area for image capture. The sensor communicates with the computcr through all electrical

cable.

The complementary metal oxide s€miconductor active pix€l _{sensor fa'ryo.t-.4PS/} is the latest development in direct digiral sensor technology. Externally. CMOS sertsors appcar idcntical to CCD dctectors but lhey use an aclive pixel technology and are l€ss expensive to manufacturc. Thc APS technology rsduces by a factor of

100 the system power required to process the image conpared with the CCD. In addition. rhe APS system

eliminates the nccd for charge transf'er and may improvc the reliabilify and lifespan ofthe sensor. In

sum-mary, CMOS sensors have scvcral advantages including design integration, low power requrremenls. mimu_

facturabiliry, and low cost. Horvever, CMOS scnsors have more fired pattern noise and a smaller rctive

area for image acquisition.

The charge injection device or CID is another sensor technology used in dental digital radiograph). A CID

is a silicon-bascd solid-state imaging rcceptor much like the CCD. Structurally, howevcr, the CID differs from

the CCD. No computer is required to process lhe images. This system features a CID x-ray sensor. cord, and

plug that are insc(cd into the light source on a camera platform; digital images are seen on the system

.

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

ofdiagnostic

image

Cop).dght O 201 I -20 l2 - Dental Decls

.

Indirect

digital

imaging

.

_Direct

_digital

_imaging

.

_Storage phosphor

imaging

Digital or electronic imaging has bccn availablc lbr morc lhan a dccadc. lt is cslinatcd that l0-207o ofdcntal prac-titioncrs usc digital imaging tcchnology in thcir dcntal practicc. It is anticipatcd thcsc numbers will steadily increasc

ovcr thc ncxt fivc to tcn ycars as dcntistry continucs to movc from film bascd to digital inraging. Film-based imag-ing consists ofx-ray inieraction with clcctrons in thc lilm cmulsion. production ofa lalcnl inragc, and chcnrical pro-ccssing that transfoffns thc latcnt imagc into a visible onc.

As such, radiographic fi1m providcs a mcdium for rccording. displayiDg, and sloring diaeirrosiic infbrmation. Film-bascd inragcs arc dcscribcd as analog images. Analog imagcs arc charactcrizcd by continuous shadcs ofgray liom

onc arca to the next betwccn thc cxtrcmcs ofblack and \lhitc. Each shadc ofgray has an optical dcltrsity klarknet,

rclatcd to lhe amount oflight that can pass through thc imagc ai a spccific silc. Film displays higher resolution than digilal rcccpfors wilh a rcsolving powcr ofabout l6lplmm (lnrcs puirs/nil/td"/"r'l. However, tilm is a rclativcly in-eflicicnt radiation deiector ard, thus, rcquircs rclatively high radiation cxposurc.Thc usc oircctangular collimation and thc highest speed lilm arc mcthods thal rcducc rudiation cxposurc. Chcmicals ar(} nccded to process the image

and arc olicn drc sourcc of crrors and rctakcs. Thc finalresult is a fixcd nnagc that is dillicult lo manipulalc oncc

cap-Digital imaging is thc rcsult of x-ray intcrrction

*ith

clectrons in clectronic sensor pirels fpi./ru e ?l?nents), cotr-vcrsion ofanalog data to digital data, computcr proccssing, and display ofihc visiblc imagc on a computcr scrccn. Data acquircd by thc scnsor is communicatcd to the conputcr in analog tbmr. Computcrs opcraic on thc binary

num-ber systcm in which hvo digits /0 dr./ // arc uscd to rcprcscnt data. Thcsc two charactcrs arc callcd bits (bi ar) digit), and thcy form words eight or morc bits in lcngth c^llcd bytes. Thc total nunrbcr ofpossible bylcs for 8-bit languagc

is 28 = 256. Thc analog-tc.digital converter translbrms analog data into numcrical dala bascd on thc binary

num-bcr systcm. Thc vohagc of thc output signal is nrcasurcd and assigncd a numbcr trom 0 _fbld.t/ to 255 (\'hit?)

ac-cording to thc intcnsity ofthc voltagc. Thcsc numcrical assignmcnts translatc into 256 shades of gra!. Thc human eyc is ablc to detect approximatcly 32 gray lcvcls.

Dircct digital imaging has dislinct advantagcs ovcr lilnt in Icrms ofcxposurc rcduclion, climlnation ofprocessing

chcmicals, inslanr or rcal timc imagc production and display. imagc cnhanccmcnt, paticnt educatjon utility, and

con-\ cnicnt sloragc. Thc actual amount ofcxposurc rcduction is dcpcndent on a numbcr offactors including film spccd.

s.nsor arca. collimation. and relakcs. Thc primary disadvantages includc drc rigidily and thickncss ofthc sensor, dccr.as.d rcsolution. highcr inilial systcm cost, unknown scnsor lifcspan. and pcrfccl scm iconduc tor chargc Iransfir. \ote: Infection controlprcscnts anolhcr chal lcngc forclinicians using dircct digitalimaging. CCD scnsors cannol bc

:t.ri1i/cd. Carc nccds to bc tak.n to propcrly prcparc, covcr, and cnsurc thc barrier is nol damagcd during paticnt

im-aging proccdurcs. Dircct saliva contact with thc rcccptor and clcctrical cablc must bc avoidcd to p.cvcnt

crossconta-Three methods

of

obtaining a

digital

image

currently

exist:

direct digital

imaging, indirect

digital

imaging, and storage phosphor imaging.

. _{To produce a}

_direct

_{digital x-ray image, three components} are necessary: an x-ray machine,

an

intraonl

sensor, and a computer

monitor

The images are captured using a solid-state

de-tector or sensor such as a charge-coupled device {CCDJ, a complementary metal oxide

semi-conductor/active

pixel

sensor (CMOS / AP.S/. or a charge injection device

_/C/Dl.

The sensor

then transmits the image to a computer

monitor Within

seconds

of

exposing the sensor to

x-rays. an image appears on the computer screen. Software is then used

to

enhance and store the image.

.

_{The essential components}

_{ofan indirect}

digital imaging system include a CCD camera and

computer.

In

this method, an existing

x-my

film

is

"digitized"

using a

CCD

camera. The

CCD camera scans the image, digitizcs or converts the image, and then displays

it

on the

computer

momtor

. A third method

ofobtaining

a digital image is storage

phosphor

imaging, a wireless dig-ital radiography system. In this system, a reusable

imaging plate

coated

with

phosphors

is used instead of a sensor

with

a

fiber optic

cable. The plates are described as "wireless"

because they are not connected via cable or

wire

to the computer. The plates are

similar

in

every way to conventional intraorul

film,

including size, thickness,

rigidity

and placement.

These plates store the energy from incoming x-rays, and are then placed

in

a scanning

de-vice. The scanner stimulates the stored x-ray

infonnation

by subjecting the plate to a laser

light. When the

light

strikes the phosphor material, energy is released as a

light

signal in an

electronic waveform and is converted to a digital image by the computer. The image can not

instantaneously be viewed on the monitor, but takes

from

30 seconds

to

5.5

ninutes

RADIOLOGY

_{Dig Rad}

You have

a

patient

who

is

extr€m€ly concerned about the

radiation

erposure

he

will

receive when

he gets

intraoral pictures

taken. You

let

him know that

if

he

wants the

least

exposure then you

will

use:

. Digital

radiography

.

_E-speed

_films

.

_F-speed

_films

.

Panoramic instead

ofa

full

mouth

series

Copyflglu a<i 2011,2011 - Dental Decks

RADIOLOGY

Image

Char

A

radiograph that exhibits

areas

of

black

and

white

is

termed high contrast

and

is

said

to

have a

short contrast

scalei

a

radiograph that exhibits many

shad€s

of

gray

is

termed low contrast

and

is

said

to

hiye

a

long

contrast

scale. To

limit

image

rnagnification,

th€ longest

target-film

distance and

shortcst object-Iilm

distance are

used.

.

The

first

statement is true; the second statement is false

.

_The

_first

_{statement is false; the second statement is true}

.

_Both

_{statements are} true

.

_Both

_{statements are} false

5

One

ofthe

positive features

ofdigital

radiography is that it requires less radiation than

con-ventional

radiography, because the sensor is more sensitive to x-rays than dental

frlm.

Ex-posure times for

digital

radiography are

from

507o to 80%o

shorter

than those

lor

E-speed

film

and about 50%

shoter

than those

of

F-sneed

hlm.

This translates

into

less

radiation

exposure

for

the patient.

- ..

L

All

direct

and PSP

digital

radiography

systems use a

conventional

dental

x-;

liotce:'

ray

unit. The literature

emphasizes that the

x-ray

unit

must have the

ability

to

;;;ra:,,t:

reduce exposure times to 0.01 seconds to reduce the

likelihood

of

oversaturat-ing

the sensor.

2.

In digital

radiography, a sensoq or

small

detector is placed inside the

mouth

ofthe

patient

to

capture the

radiographic

image. The sensor is used instead

of

intraolal

film.

As in conventional radiography the

x-ray

beam is aimed to strike the sensor An

electronic

charge is produced

on

the surface

of

the sensori

this

electronic

signal is

digitized,

or converted

into

"digital"

fom.r.

3.

Digital

radiography

systems are

not

limited

to intraoral

images; panoramic and cephalometric images

rray

also be obtained.

\lagnificationretirstoarar1iographicimagcthatappearsr",g"'@

ir::j

The intase magnification on a dental x_ray is influenced bv the:

'

TarqeFfifm dist^nce _{(a!ro La\etl sorrLel,-/irm distdn.e) is thc distance bctween the}

source or-r-rays Uo.al \pot on the tungsten target) and the film lr is dercrmincd by the length ofrhe posirion_indicating dc_ ,.

_:c

_rtl:o

_ttlletl

ptD). _{When a longer} pID _{is used, more parallei}

ra1,s

ir;

rhc middle ofrhe x-ray bicanr

i:-r.h :he object rather than thc diverging x_rays from the pcriphcry _{olthe beam. As} a resuft, a tonger

plI)

::i

:ir{eafilm distance result in less image magnillcetion. ond a shortcr pID and target-tilo distance re_

j.i.:

_l:

_{more image magnification.}

'

object-film distanc€: is the distance berween_the _{object bcing rrdiographed /r7€ r.ro1[/ and rhc x-ray}

:i

_\

T

Thc closer rhe proximiry ofrhe toorh 10 rhc film. fie less ima-ge

enligcml;t

thcre _;tt bc on the film.

decrease In _{objecl_frrn' distance rcsurts in a decrease in magnitication,}

an_d an increase in objec!firm dis_

:.::r:c:esulti ln an increas€ in imagc magnification.

\

djstorted image does not have the same size and shape as the object being radiographed. A dimensional dirrortion ofa radiographic image is influenced by:

'object-film

alignment:10 minimize dimensionaldistortion the film and should be parallel to the long

a\ is ofthc rooth. _{Foreshortening rcsultsfrom excessive verti{:al angulation}

when the x-ray bcarn is perl

ac:rdtcular to rhe film but not thc toorh. Elongation resolrs \rhen the x-ray bearn is oricnred at righl an_

gles to the tooth but not to thc film.

'

\-rai

besm: to minimiTe dimensional disro(ion, the x-ray beam musr be directed perpendicurar _!o rhe :oo:h and rhe film.

scales ofcontrast: is rhe range ot'usefur densitics secn on a dentar radiograph.Tu,o rcrms arc us€d ro dcscribe

:he appearance ofan x-ray:

' short-scal€ contrast: is an x-ray that shows only tno densities. areds olblack and white. short_scale con_

:rast results lionl the usc ofa lor{,er kilovoltage range.

.

_{Long-scrle contrast: is an x-ray that shows many}

densities, or nany shades ot gray. Long_scale con_

rrast results from the usc ofa higher kilovotage range.

contrsst is thc difrercnce in degrccs ofbrackncss bct*een adiacsnt areas on an x-ray. Low contrast describes

3r r-rav wrth many shades ofgray and few areas ofblack and white. High contra;t describcs an x_ray with man! black and white areas and ferv shades ofqray.

.

_Amalgam

.

_Enamel

.

_Dentin

.

_Bone

. Maxillary

sinus space

.

The

patient

.

_The

dentist

.

_The

_state

.

_None

_ofthe

above

6

Copright @ 201 I -20 12 - De.tal Deck

7

Radiopaque

structures/materials:

.

Less

radiation

penetrates the structure and reaches the

film

.

Radiopaque structures appear

white

on the processed

film

.

Dense materials such as

metals. enamel.

dentin.

and bone

Radiolucent

structures/materials:

.

_Allow

_radiation

_{to pass through, absorbing}

_very

_little

.

_More

_radiation

penetrates the structure and reaches the

film

.

_Radiolucent

structures appear

gray to black

on processed

filfir

.

Less dense materials,

including soft tissue and

air

space

Note:

Radiographs show shading

from black to white

fr?os/

radiolucent to

most

ra-diopoque).

Example: Least to most radiopaque:

periodontal ligament

space,

dentin,

enamel.

ZOE.

amalsam.

**+

_{Dental radiographs should be}

_{kept indefinitel"v.}

The

dental

record

must

include

documentation

of informed

consent and the exposure

of

radiographs (e.g.,

the

number

and

type of

_{.filn.s, the rationale./or}

exposure

and

the interpreto

tiotl).

Legally,

dental radiographs are the

property of

the d€ntist.

Patients do,

however,

have a

right to

reasonable access

to

the

dental radiographs,

which

includes

having

a copy

ofthe

radiographs

forwarded

to another dentist.

Note:

Patients may refuse

dental x-rays,

howeveq the dentist must decide whether an

ac-curate diagnosis can be

provided

and whether treatment can

providec.

Remember: No

document

can be signed

by

the

patient that

releases

the dentist

from

liability.

Important:

Based on the

orientation

ofthe

embossed d,ot

(i(lenti/ication

dot),

there are

two

methods

ofmounting

radiographs:

labial mounting

fi, ilh

the raised

or

convex side oJ the dot;facing the

vieu'erl

and

lingual

m o.|[]'ting

(with

the depressed

or

concave

tide

oJ the

dot

_Jacing

the vielr,er/. The

labial mounting

method is

recommended

by the

American

Dental Association. Note:

With

the

labial mounting

method, the radiographs are

viewed

as

ifthe

viewer

is

looking directly

at the patient; that is,

with

the

right

quadrants in the

left

side

of

the

film

mount

and those

ofthe left

quadrants

in

the

risht

side

ofthe film

mount.

Your dental hygienht

has a

patient

who

states

that

she needs

bite.wing

x-rays

because

it

has been

six months

since

the

last nlms

were

taken.

Your hygienist

should respond

in which manner listed

below?

.

_Agree

_with

_{the patient}

.

Tell

the patient that

bite-wing

x-rays should be taken once a year

.

_Tell

_the

_{patient that dental x-rays}

_{are taken}

_{only when}

_needed

_as

judged

by

each

patient's

needs

.

None

ofthe

above

8

Copyrighr O 2011,2012 , Denral Decks

Identify

the

structure

below

that

the arnows are

pointing to:

Reprirted fronHaring. Joenlannucc' andLauraJansen: Dentrl Rrdiography: Principles and Techniqles:Thnd Edilion. O:000, wirh permission fron Elsevier.

9

Decisions about the number,

t)?e

and frequency

ofdental

x-rays

are

determin€d

by

the

dentist

based on each

patient's

needs.

Every

patient has a

different

dental

condition

and thus

the frequency

of

x-rays is different

as

well.

There are

guidelines published by

the

ADA

that aid a dentist

in prescribing

the number, type and frequency

of

dental x-rays.

Note:

Patients

who

have tooth decay,

periodontal

disease, tooth

mobility,

pain

in

one

or

more

teeth

or possible impacted

teeth

need

more frequent

radiographic

examinations than patients

without

such problems.

Remember:

For

a

pediatric patient

who

is caries

free (and

asy-mptomatic). the

first bite-wing

radiographs should not be taken

until

the

spaces

between the

posterior

teeth have

closed.

Note: Occult

diseases

(/br

example,

small carious

lesions, .!-sts

qnd tumors)

are those presenting

no

clinical

signs

or

symptoms,

Because

occult

disease

in

the

perioral

tissues

is so rare (except

_Jbr

caries),

a

radiographic examination

of

the

jaws

should

not

be un-dertaken

solely to look

for

it

in

an

individual with

teeth when there are no

clinical

signs

or

symptoms.

However,

every

x-ray

taken should be evaluated

for

these lesions.

Remember:

Caries is an

exception to the

above

rule

because

ofits

much higher preva-lence as comnared to

occult

cvsts

or

tumors.

The

hamulus lalso

known as the hamular proc'ess.) is a srnall

hook-like

projection

olbone

extending from

the medial

pterygoid

plate

ofthe

sphenoid bone. The hamulus is located

posterior

to the

maxillary

tuberosity

region.

On the radiograph its image is seen in

proximity

to the

posterior

surface

ofthe

tuberosity

ofthe

maxilla.

It

varies

greatly in

length,

width

and shape

from

patient to patient.

It

usu-ally

exhibits

a bulbous

point,

but sometimes the

point

is tapered.

The

maxillary

tuberosity appears as a radiopaque bulge distal to the

third

molar region

Reprinred from Haring, Joen Iannucciand LauraJansen: DentalRadrography:Prin' ciples and Techniques: Ttird Edilion. o 2000. *ith pemission from Ekevi€r

RADIOLOGY

NormalAnat

The image

ofthe

coronoid

process

_of

the

mandible often

appears

in periapicrl

x-rrys

o{:

.

The

incisor region

ofthe

mandible

.

The

molar region of

the

mandible

.

_{The incisor region}

_{ofthe maxilla}

.

The

molar region

of

the

maxilla

10

Coplaight ie 20ll-201: - DeDtal Decks

NormalAnat

Identify

eech

structure

that

the

arrows 1-8 point

to in

the

anterior region

ofthe

maxilla.

''Cornesy Dr Sluan C. $'l'ne, UCLA SchooloiDenrisfy.' 11

As

the

mouth is

opened, the process moves

forward,

and

therefore

it

comes

into

r

iew

most often

when the mouth is opened to its

fullest

extent at the time the exposure is made.

It

is evidenced by a

tapered

or triangular radiopacity,

which

may be seen below,

or

in

some instances, superirrposed on the

molar

teeth and

maxilla.

The coronoid process appears as a triangular-shaped radiopacit_v.

Repnnred liom H.nDg. Joen Iannuccilnd L.ura Jansen Lind: Rldiograph'c Ifrenretdtio ior tlle Dent.l l lr-gienr \r. 10 199.1- sitir permissioi frcn El!e!rer

l.

The opaqu€

lin€

-+

Lateral

wall

ofnasopalatine

canal (inci.sive

canal)

2.

The opaque

line

-)

Anterior wall

of

maxillary

sinus

3.

'Ihe radiolucent structure

_-)

Nasopalatine lossa 4.

The opaque

line

_-)

Floor

ofnasal

fossa

5.

The opaque

structur€

-+

Soft tissue

tip

ofnose

6.

The opaque

line

-)

Lamrna dura

7.

The opaque

line

-+

Border

ofrnaxillary

sinus 8.

The radiolucent

line

-+

Periodontal ligament

space

NormalAnat

Identify

each

structure

that

the

rrrows

l-7

point to in

th€

anterior region

ofthe

''Counesy Dr. Stuan C. Whi1e. UCLA School of Denrisrry "

12

CopyriShr lil20ll'?01: ' DenEl Decks

Identify

each

structure

that

the

.rrows

l-5

point

to

in

the

mandibular molar region.

"Coudesy Dr. Stuan C. wlrire, UCLA School of Denrirry. ' 13

1.

The

opaque

structur€

+

Anterior

nasal spine

2.

The opaque

line

-t

Lateral

wall

ofnasopalatine

canal 3.

The

radiolucent

lin€

-+

Intermaxillary

suture

4.

The opaque

llne

+

Floor ofnasal

fossa

5.

The radlolucent

structure

+

Incisive/l.,lasopalatine

foramen

6.

The

rediopaque

line

-+

Soft tissue

tip ofnose

7.

The

oprque

structure

-t

Alveolar

crest

1.

The radiopaque linss

+

Nutrient

canal

2.

The opaque

line

-t

Bony

trabecular plate

3.

Th€

oprque

line

+

Inferior

border

ofrnandibular

canal d.

The

radiolucent

space

+

Submandibular gland fossa

NormalAnat

Identify

each

structure that

the

arrows

1-8

point to in

the

maxillary molar

region.

"Counesy Dr Stuart C. Whire. UCLA School ofDenrisrrv ' 't4

Coplrighr r.!' ₂₀₁

_l-l0l:

_{- Denral Dccks}

RADIOLOGY

Identify

each

structure

that

the

arrows

I

_-7

poina

to in

the

mandibular incisor

region.

"Counesy Dr Sruan C. Whne. UCI-A School ofDcntistry. ' 15

1.

The opaque

line

+

Anterior wall ofmaxillary

sinus 2.

The opaque mass

+

Inferior

concha

3.

The opaque

lin€

+

Floor

ofnasal

fossa

4.

The

opaque

line

+

Inferior

border

ofzygomatic

process

ofmaxilla

5.

The opaque

line

+

Posterior

wall ofzygomatic

process

ofmaxilla

6.

The opaque

line

+

Inferior

border

of

zygoma (zygomatic

arch)

7.

The opaque

line

+

Floor

ofmaxillary

sinus

8.

The

opaque

structure

+

Mucosa over

maxillary

alveolar ridge

1.

The opaque

structure

+

Lingual

cusp

of

lst

premolar

2.

The

radiolucent

line

-+

Periodontal ligament

space

3.

The

opaque mass

+

Film

holder

4.

The opaque mass

-+

Genial

tubercles 5.

The radlolucent

circle

+

Lingual

foramen

6.

The opaqneline

_-)

Bony

trabecular

plate

7.

The

radlolucent

sprce

-t

Marrow

space

Identify

each

structure

that

the

arrows

1--4

point

to

in

the

mandibular premolar region.

"Courtesy Dr Snran C. wltite. UCLA School of Denlistry"

16

Copy ighr C 2011,2012 - Dental Decks

Identify

each

structure

that

the

rrrows

1-3

point

to

in

the

msndibular premolar rsgion.

''Counesy Dr Stuan C. Write, UCLA School of Dentisrry "

l.

The radiolucent

line

-+

Periodontal lisament

sDace 2.

The radiolucent

space

-)

Mental

foramen

3.

Large radiolucent

space

-+

Submandibular gland fossa 4.

Dark

dot

-+

Film clin

mark

1.

The opaque

line

-)

Cemento-enameljunction

2.

The radiolucent

space

-+

Mental foramen

Identify

each

structure

that

th€

arrows

1-7

point to in

the

maxillary premolar region,

''Coudesy Dr Stuan C. \lhne, UCI-A School of Denrisln."

18

Copyrig|t aa 20ll-l0l: - Denral Decks

}IOLOGY

Identify

each

structure that

the

arrows

1-6

point to in

the

maxillary

canine

region.

''Counesy Dr Stuart C. White, UCLA School of Denrisrry. ' 19

1.

The opaque

mrss

-+

Inferior

concha

2.

The opaque

line

_-)

Anterior wall ofmaxillary

sinus

3.The opaqueline

+

Floor

ofnasal

fossa

4.

The radlolucent

space

+

Maxillary

sinus 5,

The opaque

line

-+

Floor

ofmaxillary

sinus

6.

The opaque

structure

+

Inferior

border

ofzygomatic

process

ofthe

maxilla

7.

The opaque

llne

+

Lingual

cusp

offirst

premolar

1.

The opaque

line

-+

Floor

ofnasal

fossa

2.

The opaque

line

_-)

Lateral

wall

in

nasopalatine canal 3.

The opaque

line

+

Ala ofnose

4,

The

oprque

line

-)

Anterior wall ofmaxillary

sinus

5.

The radiolucent

space

-t

Maxillary

sinus 6,

The

oprque

line

+

Lingual

cusp

of lst

premolar

RADIOLOGY

NormalAnat

Identify

each

structure that

the

arrows

1-6

point to in

the

maxillary molar

region.

''Counesl Dr Stuan C. Whire, UCLA SchoolofDenrsln. 20

Copvrighl C 20ll ?01: Denr.l Dects

RADIOLOGY

NormalAnat

Identify

each

structure

that

the

arrows 1-3

point to in

the

mandibular incisor

region.

''Coudes) Dr Sruan C. w]rne, UCLA S.hool of Dentinry " Copyrighr rr 20ll-l0l: - Denlal Dccks

1.

The opaque

line

-+

DEJ

2.

The

lucent

line

-+

Periodontal ligament

space

3.

The opaque

line

-+

Lamina

dura

4,

The

lucent

line

_->

Periodontal ligament

space

ofpalatal

root

5.

The opaque

spot

-+

Film

holder

6.

The opaque region

-+

Mucosa over

maxillary

ridge

l.

The radiopaque

masses -->

Mandibular

tori

2.

The radiolucent

circl€

-+

Lingual

foramen 3.

The

radiopaque

mass

-+

Genial

tubercles

RADIOLOGY

NormalAnat

Identify

each

structure that

the

arrows 1-4

point

to

in

the

mandibular incisor/canine region.

''Councsy Dr Sruart C. Wh're. UCI-A SchooIoIDcntistry.'

Copyrighr ill 20ll l012 DenralDectr

RADIOLOGY

NormalAnat

Identify

each

structure

that

the

arrows

1-8

point to in

the

maxillary incisor region.

*Counesy

Dr. Stuart C whrte. UCLA School ofDenristry. 23

l.

The radiopaque structure

+

Alveolar

cr€st 2.

The

radiopaque

line

+

Lamina dura

3.

The

radlolucent

line

+

Periodontal ligament

space

4.

The

radiopaque

line

+

Bony

trabecular plate

l.

The radlolucent

spsce

-t

Marrow

space

2.

The radiolucent

line

+

Periodontal ligament

space

3.

The

radiopaque

llne

+

Bony t'abecular plate

4.

The

rrdiopoque

line

_-l

Lamina dura

5.

The

lucent

line

-+

Pulp canal

6.

The opaque

structure

-+

Alveolar

crest 7.

The opaque

structure

-)

Dentin (root)

8.

The opaque

structure

+

Enamel

ofsrown

RADIOLOGY

NormalAnat

ldentify

each

structure that

the

arrows

l-9

point to in

the

maxillary incisor

region,

"Counesy D' Sruan C. Whire. UCI-A School of Dcnrisrry

24

Coplright r.!l20ll-20ll - Dental Dccks

RADIOLOGY

NormalAnat

Identify

each

structure

that

the

arrows 1-12

point

to

in

the

maxillary

canine

region,

''Counesy Dr Stuan C. Whre. UCLA School ofDentistry.-25

1.

The

opaque

materiol

+

Dentin

2.

The rsdiolucent

line

+

Bony

tabecular

plate

3.

The radlolucent

space

-t

Bony marrow

spac€ 4.

The lucent structure

+

Pulp canal

5.

The lucent

line

-+

Periodontal ligament

space 6.

The

opeque

line

+

Lamina dum

7.

The

oplque structure

-+

Alveolar

crest 8.

The

oprque structure

-)

Enanel

9.

The

lucent structure

+

Pulp

chamber

l.

The opaque

line

+

Trabecular

plate

2.

The

lucent sprce

-t

Marrow

space

3.

Tooth numb€r?

+

l0

4.

The opaque

line

+

Larnina duxa 5.

The opaque

materhl

-+

Dentin

6.

The

radiolucent

llne

+

Periodontal ligament

space 7.

The opaque

structure

+

Alveolar

crest

8.

The radiolucent structure

+

Pulp canal

9.

The radiolucent

structure

+

Pulp chamber

10.

The opaque

mtterid

+

Enamel

11.

The oprque

clrcle

+

Premolar buccal cusp over raised

film dot

NormalAnat

Identify

each

structure

that

the

arrows 1-8

point

to

in

th€

maxillary premolar region.

''Courtesv Dr Stuan C. Whire. UCLA School o i Dent istry."

CoDrighr

al:0ll

?012 Denral Decks

NormalAnat

Identify

each

structur€ that

the

arrows 1-15

point to in

the

partial panorex.

C. While, UCLA

.1,

Tooth number?

-+

3

2.lYhat

material

is

this?

-+

Silver

amalgam 3.

Whrt

ls

thls

oprcity?

+

Plastic

bite

block

4.

The

black

dot

+

Film dot

5.

The

black

marks

+

PLS for Kodak

Ektaspeed

plus

film

6.

The opaque

line

+

Lamina

dura

7.

The

lucent

line

+

Periodontal ligament

space

8.

The opaque

llne

+

Lamina dura

1.

The lucent sprce

-)

Air

in

nasal fossa 2.

The opaque

line

+

Nasal septum

3.

The opaque

line

+

Lateral

wall ofnasal

foss4 medial

wall ofmaxillary

sinus 4.

The opaque

line

+

Infrao6ital rim

5.

The opaque

line

+

Border

ofinfraorbital

canal 6.

The

radiolucent

space

+

Pterygomaxillary fissure

7.

The opaque

line

+

Pterygoid

spine

ofsphenoid

bone 8.

The opaque mass

+

Zygomatic

arch

9.

The

oprque

line

+

Posterior

wall of

maxllla

(maxillary

sinus)

10.

The

oprque

line

+

Posterior

wall of

zygomatic

process

of

maxilla

11.

The

opaque mass

+

Ear

lobe

12.

The

oprque

llne

+

Inferior

border

ofmandibular

canal

13.

The opaque

rnsss

+

Anterior

nasal spine

14.

The opaque

line

+

lnferior

border

ofmandible

RADIOLOGY

_NormalAnat

Identify

each

structure that

th€

arrows 1-13

point to in

the

partial

panorex.

.

The

first

statement is true; the second statement is false

.

The

first

statement is false; the second statement is true

.

_Both

_{statements are true}

.

Both

_{statements are thlse}

29

Copyrighr C

20tl,t0l:

Dcnrit Dccks

C. while. UCLA

The

pattern of

stored energy on an

exposed

film

is

t€rmed

tbe

latent

image;

this

image remains

_{invisible until}

_it

_{undergoes processing}

A chemical

solution known

as

_{the developer is}

used

in

the development

process

to

chemically

reduce

ths

exposed,

energized

silver halide

crvstats

to trlack

metallic

silver.

C.t\ric rr _{' -'nll} l0 I Dcnr,l DeLrr

1.

The

opacity

_->

Tipof

nose

2.

The

opaque

line

-+

Hard palate/floor

ofnasal

fossa

3.

The lucent area

-+

Orbit

4.

The opaque

line

5.

The opaque

line

Hard

palate/floor

ofnasal

fossa

Floor

of

n.raxillary sinus

6.

The opaque

structure

-+

Soft palate

7.

The radiolucent

space

-+

Air

between the soft palate and the dorsum

of

tongue 8.

The opaque

line

-+

Dorsum

oftongue

9.

The opaque

line (dots)

-+

Shadow

of

opposite

mandible

(re.ferred to as ghost image)

10.

The

lucent

oval

-+

Mental

foramen

11.

The

diffuse

opacity

-+

Shadow

ofcervical

spine

12.

The

broad lucency

-+

Submandibular gland fossa 13.

The

opacity

-+

Articular

tubercle

The purpose

oflilm

processing is trlofoldi

. To conven thc latent (invisible) imagc on the film into a visible imagc

-der'eloping

proccss . _To presene the visiblc image so that it is pemanent and docs not disappear tiom the dental x-ray

fi\ing

process

\\-hen a bcam ofphotons exposes an x-ray film, it chemically changes thc photosensitivc siher halide crystals in the

film

emulsion lldtent image).

Important:

Exposed arcas

will

becomc radiolucent, s hereas nonexposed areas

will

become radiopaque.

\-rat.'

developing solution contains the following:

.,\

developing agent, such as hydroquinone, which is a chemical compound that is capablc ofchang-ing the exposed silvcr halide crystals to black mctallic silvcr. At the same time, it produces no

appre-ciablc cffcct on thc unexposed silver halidc crystals in the emulsion. Gives detail to the x-ray image. Note: Elon, also kno\r'n as metal, acts quickly to produce a visible radiographic inage. It scncraics

the many shadcs of gray.

. _{An lntioxidant preserrativ€,} for example. sodium sulfite, prevents the developer solution from ox-idizing in the presencc ofair.

. _An

_accelerator

_{an alkalt (sodium}

_carbonate)

activates thc dcveloping agents and maintains the

alkalinity ofthe developer at the correct value. It softens geiatin ofcmulsion.

. A restrainer, such as potassium bromide, is added to dcvclopcrs to conffol the action ofthe

dev-eloping agent so that it does not develop the uncxposcd silvcr halide crystals to prodrtce fog.

Noter Thc optimal iemperature for thc dcvcloper solution is 68oF.

Importanti The function ofdeveloping solution is to remove the ha)idc portion ofthc enposed, ener-gized silver halide crystals to black rnctallic silver, this is refened to as reduction. The developer solu-tion softcns the film emulsion during this proccss. The function offixing solution is lo stop developmcnt

and remove remaining unenergized, unexposed silvcr halide crystals ftom the film emulsion. The fixer

hardens thc film emulsion during thc proccss.

Film processing involves the following 5 steps:( I ) immerse film in developer (2) rinse film in water bath

(rinsing dilutes lhe

de*loper

slott,ing the development process _{br removing lhe alkali accelerllor,}

Pre-vnting

neutralizution ofthe acidfxer) (3) immerse film in fixcr (4) q'ash film in watcr bath and (5) dry

''.'

Which ingredient of lixer solution

fuDctions

to

remove

ill

unerposed and

underdweloped silver

halide

crystals from

the

trlm

emulsion?

L-'

. Fixing

agent .

_Acidifier

.

_{Hardening agent}

.

_Preservative 30

Coplright O 20ll-2012 Dental Deck5

.

_Decrease the temperature

ofthe

developing solution

.

_Increase the temperature

ofthe

developing solution

.

Replenish the

developing solution

.

Increase the

mA

setting

.

_Increase the

kvp

setting

31

X-.ay fixing solrtion conlains thc following:

. Thc fixing agent f. /e.7rirg ager, is madc upofsodium thiosulfate orammonium thiosulfate and is commonly

called hwo. The purposc ofthc fixing agcnt is to remove or clear all unerposed and underd€veloped silver halide crystrls liom thc film emulsion. Thc chcmical "clcars" thc film so that thc black silver rmagc produccd by

the dcvclopcr bccomcs distinctly pcrccptiblc. whcn the film is impropcrly cicarcd, the rcmaining unexposed

sil-vcr halide crystals darkcn upon exposure to light and obscure ahe imagc.

. _An antioxidant preservative, thc samc prcservativc uscd in thc dcvclopcr solution. sodium sulfite, is also uscd in the fixer solution. lt prevcnts thc chcmical dctcrioration ofthc fixing

aSent-. _An acidifier such as acetic acid or sulfuric acid is uscd to ncufalizc thc alkaline dcvclopcr Any unncutralizcd alkali may cause the uncxposcd crltals to continue to dcvclop in thc fixcr It also produccs thc neccssary acidic

cn-vironmcnt required by lhc fixing agcnt.

. _{Thc hardener agcnt used is potassium alum, lt shrinks} and hardcns thc gclatin in lhc film cmulsio affcr it has been softcned by the accclcmtor in thc developing lolution. It shoflcns drying timc and protccts the cmulsion fionr

l'ollowing lixation, a walcr bath is used to wash the tilm.This stcp is ncccssary to thoroughly rcmovc all cxccss

chcmicAls (i.e., thnsufaE ions atd sil\,er thiosurli?re.rnpldi€r, from thc cmulsio .

Thc final step in rhc film proccssing is the drying ofthc films. Iiilms nay be air-dricd at room Ienpcraturc in a dus! lrec area or placcd in a hcated drying cabinct.

Ntanual processing is a simplc mcthod uscd to dcvclop, rinsc, fix, and wash dcntal x_ray films lhc csscntial piecc

ofcquipmcnt rcquircd for manual proccssing is a proccssing lank, which is containcr dividcd into compartmcnts for

thc dcvclopcr solution, walcr bath. and fixcr solution. Notel Thc optimum tcmpcraturc lbr ihc devclopc. is bct$ccn 68'F and ?0'F, tnical timc in developer is 5 minutcs. nnsc lor 30 seconds, placc in fixcr solution for l0 minutcs and

wash for at lcast l0 minulcs and dry

Automatic processing is anothcr simplc way to proccss dental x-ray fillll. Thc essential piccc ofcquipmcnt required for automatic processing is thc automatic processor, which automalcs all film proccssing steps

.-

.

1. Fixing timc is always at lcast twice as long as thc dcvcloping limc.

j\ote*

2. wirh both automalic and manual processing,8 oz. offrcsh dcvclopcr and fixcr should bc added per gallon of solution per dr].

''&r!

_{L tf}

u ariea radiograph werc proccsscd a sccond rime, thcrc would bc no cbangc in contmst or dcnsity. ,1. Safelighting providcs illumination in thc darkroom lo carry out proccssing activities safely without

cxposing or damaging the film. Thc GBX-2 safelight filter by Kodak with a l5-watl bulb at lcast 4 fcct

from thc workinq surfacc is rccommendcd.

As thc dcvcloping solution g€ts weaker, the films

will

get lighter. Both the devcloping and fixing solu-tions should be replenished on a daily basis Remember: with both automatic and manual processing 8 oz'

of fresh dcvclopcr and fixcr should be tdded per gallon of solution per da].These solutions also need to be

changed on a regular basis, and the tanks need to be scrubbcd and cleancd as well. The following fac-tors affcct the life ofa developing solutionl the clcanliness ofthe tanks, the sizc ofthe films processed, the number of films processcd, and the tempcrarure ofthe solution

l.

Yellowish-brown film

will

result from insufficient tlxing or rinsing (See _Jigute

#l).

2. Fogged film may also result from improper film storage or outdated films.

3. Low

solutio

levels

will

appear as: developcr cut-off fJll?lg, I vhile boftler SeeJigure

#?or {ixer cut-offfs/rdight hlack border, Seetigure #3).

4. Light spots on film may result from contact with thc fixer beforc processing

(Seefgrre

#1).

5. Developer spots appear dark or black (See _Jigure #5).

AI prctures .eprinFd from Hanng. Joen Iannucci and Laura Jdsen Lrnd: Rad iogrnphic Inrerprerltion for lhe Dotal Hygienisl. O 1993. $itb pemission iom Elsevier

.

Aft€r

processing

a

film,

you notice

that

is

rppears

too

dark

What

is the most

likely

caused

of this problem?

.

_{Inadequate development}

_time

.

_{Developer solution}

too

cool

.

_{Depleted developer}

_solution

.

_Excessive

_{developing time}

Copright O 201l-2012 DenlalDecks

.

_Fixer

_cut-off

.

_Developer

_cut-off

.

_Overlapped

_films

.

Static

electricity

Coprigh O 201 I -20 12 ' Dental Decks

A

straight white border

appears on the

x-ray film.

What

is

the most

likely

cause

of

this?

- Inadequate delelopmmt time - Developer solution too cool - lnaccurate trmer or thermometer - Depleted developer solution

- Check development nme - Check developcr tcmperxrure

- Replace t_aul9" timcr or lhermometer

- Replenish developcr vith fiesh

Chcck dcvclopment tjme

- Check developer temperaturc - Replace faulty timcr or thcnnometer

' Replcnish dcveloper with fresh

- Excessive developing time - Developer solution too hot

- lnaccurate tim€r or lhermometer

- concenEated developer solution

Check tempcrature of processing solutions and *dter brthi a!'oid

Sudden t€mperature change between developer and water bath

- Exrmine film p.rckets for defects

- Never unwrap films in the _trcsence of

lvhite lighr

- Check the filter and bulb wattage of

th€ safe light

- Check rhc darkroorn fbr light leaks - Check rhe erpiration date offilln packages

' Srorc films in a cod. dry. proiected arc! - Aroid contaminated solurions by

cover-ing tanks alier each usc - Check temperature ofdeveloper Gray: lack ofdetail - Improper safe lighting

'Light leaks in dark'room - outdated fitms - Improper film storage " Contaminated solutions - Developer solulion too hot

Lxample Appearance Problems Solutions

Developer

cut-off

Stmight u'hite border Underdeveloped portion of

film due to low level of developer

Check developer levcl bcforc

processing: add solulion

if

needed

Fixet

cu!-off

Straighi black border Unfixed portion offilm due to

low level offixer

Chcck fixer Ievel befbrc

proc-essingl add solution ifneeded

Overlapped

films

whitc or dark areas

appear on film where overlapped

Two films contacing each

other during processing

Separate films so thal no contact iakes placc during processing

Airbubbles whitc spots Air trapped on ihe film

surface after being placed in

the processing solutions

cenlly agitale film racks aftcr placing in processrng solutions

Fingemail

al.ifact

Black crescent

shaped lnarks

Film emulsion damaged by

the opemtoa's fingemail during

rough handling

cenlly handle films by the edScs

onlY

Fingerprint artifact

Black fingcr?rint Fi:m louched by ingers that

are contaminated with fluoride

or developer

Wash and dry hands thoroughly

before processing

Static

electricjty

Thin. black, branching - occurs when film packet is opened quickly

- Occurs when film pack is opened before the radiographer touches a conduciive object

- Open film packel slowiy

- Touch a conductive object

before unwrapping films

Scratchcd

film

Soft emulsion removed from

the film by a shalp objecr

Use care when handling films

and film racks

RqJr.rerl li.r Hrnng..loen tannu.ci and Lluri Jahen: Denlal RadDgrlphy: Pnnciples and Te.hnlques Thrd Ediri.n !' 1000. *nh

. REM

.RAD

.

Roentgen

.Qy

.

Mature

bone

cells

.

_{Muscle cells}

.

_Nerve

_cells

.

_{Epithelial cells}

34

Coplrighe20ll-2012 - Dentd Dect3

The

rad

(radiotion

absorbed dose) is a

unit

used to measure a

quantity

called

absorbed

dose. This relates to the amount

ofenergy actually

absorbed

in

some material, and is used

for any type

ofradiation

and any material. One rad is defined as the absorption

of

100 ergs

per gram

of

material. The unit

rad can be used

for

any

type

of

radiation, but

it

does not describe the

biological

effects

ofthe

different

radiations.

The rem

(roentgen equivalent

man)

is a

unit

used to

derive

a

quantity

called

equivalent

dose.

This

relates the absorbed dose

in

human tissue

to

the

effective

biological

damage

ofthe

radiation.

Not all

radiation has the same

biological

effect, even

for

the same amount

ofabsorbed

dose.

Equivalent

dose is often expressed

in

terms

ofthousandths

ofa

rem,

or

mrem. To

detenrine

equivalent

dose

(rent),yon multiply

absorbed dose

(rad) by

a

qual-ity

factor (QF)

that is unique to the type

ofincident

radiation.

The

_QF

is a t'actor used

lor

radiation protection

purposes that accounts

for

the exposure effects

of

different

types

of

radiation.

For

x-rays

QF

:

1.

The

roentgen

is a

unit

used to measure a

quantity

called exposure. This can

only

be used

to describe an amount

of

gamma and x-rays, and

only in

air

Exposure

is a measure

ofradiation

quantity, the capacity

ofthe

radiation to ionize

air.

Equivalent

dose is used to compare the

biologic

efl'ects

ofdifferent

types

ofradiation

to

a tissue or organ.

Effectiye

dose is used to estimate the

risk

in

humans.

Gra\

/Gr,

js a

unit lor

measuring absorbed dose; the

Sl unit

equivalent to the

rad:

I

gray

:

100 rad.

All ioniting radiation is h:rrmful and produccs chemical changes th.rt rcsults in biologic damsge in liviDg tissuc.

T\o spccific mcchanisms olradiation injury are possiblc: ionization and frec radical formation /1, is is l|rc pritnd^'

l

hcorics ofradialim injury:

. Thc direct theort: suggcsts lhal ccll damagc rcsuhs whcn ionizirg radialion directll hits crilical arcas. or

tar-!.rs. q Jlhin $c ccll. Dircct altcration ofbiologic molccrlcs (i.c., (u bohrlrat$, 14il!, prct?int, DN 1/ occuts. Ap pro\rrnalcl) one-third ofdrc biologic cffccls ofx-ray cxposurc rcsult from dircct cllccts.

. Th. indircct theort suggcsts that x-ray photons arc absorbed wilhin thc ccll and causc lhc lbnnation oi loxins.

\

hich in tum d.rnagc rhc ccll For cxamplc. \'hcn x-ray pholons arc absorbcd by watcr within a ccll. free radi-calforDaiion rcsul1s. Thc iicc radicals combinc to form loxins /s.g,

l/r(r.

which causc ccllular dysfunction and rro'lrg1. danl3sc. Aboul two{hirds of radiation-induced biological damagc rcsults fiom indircct ctlccls.

lmponant: I)amag. lo thc DNA molecul€ is lhc primafv ncchanism fbr radiation induccd cel1 dcirth. nutation, and

\ dos€ response curve is uscd to dcmonslratc thc rcsponsc i/drndgel of(issucs to thc dosc arr?ornr.) ofradiation

rc-Biological cfTects ofradiation can bc classificd as:

. _Stochastic cftcctsi occur as a direct function of dosri lhc probabilirr" ofoccurrcncc incrcascs \\'iih incrcasing

ibnrrbcd dose: howeve., lhc sclcrity ofcliccls does not dcpcnd on thc magnitudc ofthc ahsorbcd dose.

Exam-rlc\ ofsrochastic cficcls includc cancer r.€.. trrro,-./ induction and genetic m|Itations (i.?., DNA tld"ng.')

.

_\

on sroc h a stic cffects /.le ter

ti

i\ ti( L'[e. ts)t arc somatic cficcts tha! havc a th reshold and i n creasc in scvcrily $ith increasing absorbcd dosc.Eranrplcs of nonslochaslic eilccts includc erylhcma. oral changes. loss of hair,

cararact ibnnation, and dccrcascd fcriility. Importanl When comparcd silh slochastic eflects. nonstochastic

cl-fi-cts require Iarger radiaiion doscs to seriously impair hcalth.

\ot

.rll cclls rcspond 1r) r:rdidlion in thc samc manncr In general, thc gre.tcr thc rate or potential for mitosis and thr morc immsture rhc cclls and tissues are, thc greatcr the sensitiritl or susccplibility to radiation. Cclls that arc radiosensitire includc blood cclls. immaturc rcproductivc cclls, epithelial cclls, and _{iroung bonc cclls. Thc} ccll that

rs most scositive to radiation is ths small lymphocyrc. Radioresistant cclls includc cclls ofbonc. musclc and ncrvc. Rsdiosensitive organs composcd ofradioscnsitive cells includc lymphoid tissucs. bone marro$,, tcstcs. and inlcstincs. Examplcs of rad iorcsista n t tissues includc thc salivary glands. kidncy and liver

.

_{Latent period}

.

Period

ofcell

injury

.

Recovery

period

.

_Cumulative

_effects

.

_{Osteoradionecrosis}

.

Bisphosphinate related Osteonecrosis

ofthe jaw

.

Rampant

periodontal

disease

.

None

ofthe

above

36

Cop)ri8hr O 201 1,2012 - Dental Decks

37

Chemical reactions /e.g., ioni:dtkr1. .lree rudi(al fornalion) lhal lollo."\, the absorption of radiation occur

rap-idly at thc molecular level. I lonever. varying amounts of time are required fbr these changcs to alter cells and

cellular functions. As a result, the obsenable effects ofradiation are not visible immediately aftq cxposurc. Instead, following exposurc, a lat€nt period occurs. The latent period is the pcriod of time between radiation

exposure and the ons€t ofsymptoms. It may be short or lonc, depending on the tohl dose olradiation received

and the amount of time it look to receive the dosc.

Thc period ofcell injury fbllo$ s the latent period. Cellular injury may result in cell death. changes in ccll

tunc-tion or abnormal mitosis

ofcells-The r€covery p€riod is the last event in the sequcnce ofradialion injury Some cells rccover fioni the

radia-tion ir1jury, especially ifthe radiation is "low level."

Note: The eflects ofradiation exposure are additive and rhc damagc that rcmains unrepaired accumulatcs in

the tissues. The cumulative effects ofrepealed radialion exposure can lead to various serious health problems le.g., carcinogenesis, r|hi.h leuds to r\trious caxilonar, genetit nutatiotis whi.h cdure hirth defets.

difler-ent kinds of lculienia and utdrads).

Radiation effects can be classified as cithcr:

. _Shorl-term effects: ellecls ofradiation that appear within minutcs. days, or \r'eeksl associated with largc amounts ofradialion absorbed ir1 a short period oltime. These effects are not applicable !o dentistry.

.

Long-1€rm effects: effects of radiation that appear aftcr years, decades, or generations; associated with

small amounts ofradiation absorbed repeatedly over a long period oftimc- Repeated low levcls ofradiarion

erposure are linked to thc induction ofcancer, birth abnormalities, and genctic defects.

Radiation elTects on rells:

. _{The cell nucleus is morc sensitive to} radiation than the cytoplasm. Damage !o the nucleus allccts thc chro'

mosomes con{aining

D\A

and resuhs in disnlplion ofcell division, \l'hich in tum may lead !o disruprion

ot

cell lirnction or cell death.

. lllitotic delay occurs afier irrldiation ofa population ofdividing cells.

. Radialion causcs cell death by damaging chromosomcs! preventing successful mitosis and also by

appo-sit.s /proNromnted cell de.tth).

. _{Cell recovery involvljs} enzymatic repair of sirgle-strardcd brcaks of DNA.

Thc clinical complications that occur in bone following inadiation relate to lhe marked reduction in vascularity

and the consequcnt d.crcased capacity oflhc bonc to resist infection. Therc is a strong possibilily that inf'eclion and nccrosis ofbone will resuh in a nonhealing \lound if the orrl mucous rtembrancs aQlredd] tomprotniscd b)

r|rddidli.r,l breaks do\,'n. This may occur spontaneously or fbllowing a loolh extraclion or denture sore and is kno\\ n as osteorrdionecrosis,

Osteoradionecrosis is morc common in the mandible than in thc maxilla. becausc oflhe richer vascular supplv to the nra\illa and lhc fact that lhe nandible is morc frequently inadialcd. Thc mosl conlmon faclors precipitating

osleoradionecrosis arc pre- and pos!ilradialion extractions lnd periodonta] disease. Note: Damage to lhe blood lessels /d-f.)ppor_erl /o nen,es, ius(le, eL., predisposes a patient 1o thc developmen! of osteoradionecrosis

Histopathologically, ihe

I

Hs ofORN arc hypocellu)ar bone. hypovascular tis\ue, and h),poxic tissue and bone To prerent osleoradionccrosis: extract all hopelcss tceth three weeks prior to bcadineck radiation trcattncnl,

If

cxrracting afler radiolherupy, lhc use ofsystemic antibiolics is recommended. Sonc sludies suggesl hypeftaric

oxygcn rrealmcnls bcfore and afler lrcaimcnt to reduce the risk ofosleoradionecrosis flrr:r

r

soncrhd

(ontn'

Eflccls ofl'hole t ody irradiation:

. When the whole body is exposed to low or moderate doses of radialion. thcre are ch.rracleristic changes

kolled the aute rddiation slndtomc)

th

develop, which are quitc different irom thal secn when a relatively small volume oftissue is exposed.

. Embryos and fetuses are considerably more radiosensitive than adults bccause mosl embryonic cclls are

rel-atively undifferenliatcd and rapidly mitotic. Prenatal irradiation may lead to dcadr or lo spccific devclop menlal abnonnalilies depcnding on the stage of developmcnl at the tine of irradialion.

\otc:

No effccts on en'lbryos or fetuses have been shown from low doses used in denlal rldiography.

Late somatic effects:

. Somatic eflects are those seen in the irradiated individual. The most important are radialion-induccd cancers.

. Carcinogenesis:

- Radiation-induccd cancers are not distinguishable from cancers produccd by odrer causcs.

- Thc incidence ofleLlkcrnia bther thdn CLL) rises following cxposure ofthe bonc marrow lo radialion - Radiation induced solid canccrs, including in lhe thyroid. brain, and salivary glands. generally appeer 10

or more yean aftcr exposure and elevdled risk remai.s for lifetime.

.

The

first

statement is true; the second statement is false

.

The

first

statement is false; the second statement is true

. Both

statements are true

.

_Both

_{statements are false}

38

Coplrighi o 201l'2012 Dental Decks

. kvp

.mA

.

_Tirne

(sec)

.

_All

_of

_{the above}

39