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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 Copyright t) 20ll-2011 - Denhl Decks

DENTAL DECKS RADIOLOGY 2011-2012

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DENTAL DECKSRADIOLOGYDigital RadWhich tlTe of digital image receptor is most common at tlris time?. CID (Charge InjectionDevice). CMOS/APS (Complementarv Metal Oxide Seniconductor/Atiive Pixel Sensor). CCD(Charge-Coupled Device)1Copyright t) 20ll-2011 - Denhl DecksA 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 m

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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

Copyright t) 20ll-2011 - Denhl Decks

A number ofcomponenls are required lbr direct digital image producrion. These components include an x-raysource, 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 ofx-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 5I2x 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 intraorllradiography, 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 of100 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 rctivearea for image acquisition.

The charge injection device or CID is another sensor technology used in dental digital radiograph). A CIDis a silicon-bascd solid-state imaging rcceptor much like the CCD. Structurally, howevcr, the CID differs fromthe 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 moni-tor within seconds.

. 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

Cop)right O 201 I -20 12 - Dmtal Decks

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 liomonc 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 collimationand thc highest speed lilm arc mcthods thal rcducc rudiation cxposurc. Chcmicals ar(} nccded to process the imageand 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 languagcis 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 humaneyc is ablc to detect approximatcly 32 gray lcvcls.

Dircct digital imaging has dislinct advantagcs ovcr lilnt in Icrms ofcxposurc rcduclion, climlnation ofprocessingchcmicals, 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, indirectdigital 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 tox-rays. an image appears on the computer screen. Software is then used to enhance andstore 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 phosphorsis 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 inevery 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 notinstantaneously be viewed on the monitor, but takes from 30 seconds to 5.5 ninutes de-

pending upon the system and certain variables.

RADIOLOGY Dig Rad

You have a patient who is extr€m€ly concerned about the radiationerposure 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 andis 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 andshortcst 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

5Cop)righr r.ar 20ll-l0ll - Dental Decks

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-speedfilm and about 50% shoter than those of F-sneed hlm. This translates into less radiationexposure 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 mouthofthe patient to capture the radiographic image. The sensor is used instead ofintraolal film. As in conventional radiography the x-ray beam is aimed to strikethe sensor An electronic charge is produced on the surface of the sensori thiselectronic 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-raysUo.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 bicanri:-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 dimensionaldirrortion ofa radiographic image is influenced by:'object-film alignment:10 minimize dimensionaldistortion the film and should be parallel to the longa\ is ofthc rooth. Foreshortening rcsultsfrom excessive verti{:al angulation when the x-ray bcarn is perlac: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 describes3r r-rav wrth many shades ofgray and few areas ofblack and white. High contra;t describcs an x_ray withman! black and white areas and ferv shades ofqray.

. Amalgam

. Enamel

. Dentin

. Bone

. Maxillary sinus space

. The patient

. The dentist

. The state

. None ofthe above

6Copright @ 201 I -20 12 - De.tal Deck

7Coplright O 201 I -2012 - Ddtal Decks

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 ofradiographs (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 fromliability.

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 leftside 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.wingx-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 eachpatient's needs

. None ofthe above

8Copyrighr 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.

9Copyright O 2011-l0l: - Denral Decfts

Decisions about the number, t)?e and frequency ofdental x-rays are determin€d by thedentist based on each patient's needs. Every patient has a different dental condition andthus the frequency of x-rays is different as well. There are guidelines published by theADA 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 ormore teeth or possible impacted teeth need more frequent radiographic examinationsthan patients without such problems. Remember: For a pediatric patient who is cariesfree (and asy-mptomatic). the first bite-wing radiographs should not be taken until thespaces between the posterior teeth have closed.

Note: Occult diseases (/br example, small carious lesions, .!-sts qnd tumors) are thosepresenting 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 signsor 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 olboneextending 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 oftenappears 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 pointto in the anterior region ofthe maxilla.

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

Copynglu a 2011'2012 ' Denral Decks

As the mouth is opened, the process moves forward, and therefore it comes into r iewmost 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 insome 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'cIfrenretdtio 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-7point 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-5point to in the mandibular molar region.

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

13

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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

5. The radlopaque structure + Inferior border ofmandible

NormalAnat

Identify each structure that the arrows 1-8point to in the maxillary molar region.

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

't4Coplrighr r.!' 201 l-l0l: - Denral Dccks

RADIOLOGY

Identify each structure that the arrows I -7poina to in the mandibular incisor region.

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

Copyriglrt O 20ll l0l: DenElDecks

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--4point 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 1-3point to in the msndibular premolar rsgion.

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

Copyrighr C 20ll-2012 - Dental Decks

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

3. Large radiolucent space -> Submandibular gland fossa

Identify each structure that th€ arrows 1-7point 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 1-6point to in the maxillary canine region.

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

CoplriShr lO 201 1,2012, Den6l Decks

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 1-6point to in the maxillary molar region.

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

20Copvrighl C 20ll ?01: Denr.l Dects

RADIOLOGY NormalAnat

Identify each structure that the arrows 1-3point 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 1-4point 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 1-8point to in the maxillary incisor region.

*Counesy Dr. Stuart C whrte. UCLA School ofDenristry.

23

Cotlright ilt 20ll-10l2 - Denral Decks

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-9point to in the maxillary incisor region,

"Counesy D' Sruan C. Whire. UCI-A School of Dcnrisrry24

Coplright r.!l20ll-20ll - Dental Dccks

RADIOLOGY NormalAnat

Identify each structure that the arrows 1-12point to in the maxillary canine region,

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

Copyri8hr !12011 :0ll - Dentel Decks

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

12. The opaque line -+ DEI

NormalAnat

Identify each structure that the arrows 1-8point 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 1-15point to in the partial panorex.

C. While, UCLA

CopyriShr i.] 20ll 2012 ' Denral Decks

.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

15. The oprquc msss -) Hyoid bone

RADIOLOGY NormalAnat

Identify each structure that th€ arrows 1-13point 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

29Copyrighr 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 developmentprocess to chemically reduce ths exposed, energized silver halide crvstats

to trlack metallic silver.

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

RADIOLOGY

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 scncraicsthe 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 fixerhardens 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) drythe film.

''.' Which ingredient of lixer solution fuDctions to remove ill unerposed andunderdweloped 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

Coplrighr O 20ll-2012 - Denral Dects

X-.ay fixing solrtion conlains thc following:. Thc fixing agent f. /e.7rirg ager, is madc upofsodium thiosulfate orammonium thiosulfate and is commonlycalled hwo. The purposc ofthc fixing agcnt is to remove or clear all unerposed and underd€veloped silverhalide 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 forthc 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 dryAutomatic 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

Fig #!

. Aft€r processing a film, you notice that is rppears too darkWhat 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 processingsolutions and *dter brthi a!'oid

Sudden t€mperature changebetween developer and water bath

- Exrmine film p.rckets for defects- Never unwrap films in the trcsence oflvhite lighr

- Check the filter and bulb wattage ofth€ safe light- Check rhc darkroorn fbr light leaks- Check rhe erpiration date offillnpackages

' 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 toohot

Lxample Appearance Problems Solutions

Developercut-off

Stmight u'hite border Underdeveloped portion offilm due to low level ofdeveloper

Check developer levcl bcforcprocessing: add solulion ifneeded

Fixetcu!-off

Straighi black border Unfixed portion offilm due tolow level offixer

Chcck fixer Ievel befbrc proc-essingl add solution ifneeded

Overlappedfilms

whitc or dark areas

appear on film whereoverlapped

Two films contacing each

other during processingSeparate films so thal no contactiakes placc during processing

Airbubbles whitc spots Air trapped on ihe filmsurface after being placed inthe processing solutions

cenlly agitale film racks aftcrplacing in processrng solutions

Fingemailal.ifact

Black crescentshaped lnarks

Film emulsion damaged bythe opemtoa's fingemail duringrough handling

cenlly handle films by the edScs

onlY

Fingerprintartifact

Black fingcr?rint Fi:m louched by ingers thatare contaminated with fluorideor developer

Wash and dry hands thoroughlybefore processing

Staticelectricjty

Thin. black, branching - occurs when film packet isopened quickly- Occurs when film pack isopened before the radiographertouches a conduciive object

- Open film packel slowiy

- Touch a conductive objectbefore unwrapping films

Scratchcdfilm

Soft emulsion removed fromthe film by a shalp objecr

Use care when handling filmsand film racks

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

I)enni$ron from !l\e\rer

. REM

.RAD

. Roentgen

.Qy

. Mature bone cells

. Muscle cells

. Nerve cells

. Epithelial cells

34Coplrighe20ll-2012 - Dentd Dect3

Coplright C 2011-2012 - Denral Decfts

The rad (radiotion absorbed dose) is a unit used to measure a quantity called absorbeddose. 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 ergsper gram of material. The unit rad can be used for any type of radiation, but it does notdescribe the biological effects ofthe different radiations.

The rem (roentgen equivalent man) is a unit used to derive a quantity called equivalentdose. 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 amountofabsorbed dose. Equivalent dose is often expressed in terms ofthousandths ofa rem, ormrem. 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 lorradiation protection purposes that accounts for the exposure effects of different types ofradiation. 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 toa 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. Appro\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 thatrs 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

Coplriglrt €i 201l-2012, Denial Decks

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 receivedand 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 inthe 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 withsmall amounts ofradiation absorbed repeatedly over a long period oftimc- Repeated low levcls ofradiarionerposure 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, Ifcxrracting afler radiolherupy, lhc use ofsystemic antibiolics is recommended. Sonc sludies suggesl hypeftaricoxygcn 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.- Pcnons younger than 20 ycars ofage are more al risk for solid tumors and leukcmias than adults

. 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

Coplrighr O 20ll-2012 - Dental tr€cks

The oral cavity is irradiated during the course oftreating radioscnsilivc oral malignant tumors. usually squa-mous cell carcinoma. Radiation therapy for malignant lesions in the oral cavity is usually indicated when the

lesion is radiosensitiv€, Ndvanced, or deeply invasiv€ and cannot be approached surgically. Fractionationofthe totalx-ray dose into multiple smalldoses provides greater tumor destruction than would be possible witha largc single dosc. Fractionation also allows incr€ased cellular r€pair of Dolmal tissues, \\+ich are believedro havc an iiheritantly grcatcr capacity for recov€ry than tumor cells. Another vahrc offractionation is that i1

increases the mean orygen tension in an inadiated rumor, rendering the turnor cells morc radiosensitive.

Radiation effect on oral tissu€s:. Oral mucous membranes: by the end of the sccond weck ofthempy the mucous mcmbrancs bcgin toshow areas ofrcdness and inflammation (zac.rrr'ti9. As therapy continues. lhe mucous membmne beginsto break down, u,ith the fomation ofa white to yellow pseudomembralne ldesquamated epithelial larcr).At the cnd oftherapy the mucositis is usually most severe, secondary infection by Candida albicans is acommon complication. After inadiation the mucosa bcgins to heal rapidli, and is usually complete byabout 2 months.. Taste buds: arc sensitive to radiation. Therapeutic doses cause extensive degeneration ofnormal histo-logic architccture oftaste buds. Patients often notice a loss oftastc acuity during the second o. third week

ofradiotherapy.. Salivary glands: during the first lew weeks ofthenpy thcre is usually marked and progtessive loss ofsali-\'ary secretion. fi€ extent ofreduced flow is dose-dependent. The mouth becomes dry freloslomldl and ten-der, and swallo$'ing is difliculr and painful. xcrostomia that has persisted belond a year is lcss Iikely toshow significant retum of function. Importrnt: Salivary changcs hav€ a profound influence on thc oralmicroflora and secondarily on the dentition, often leading to radiation caries.. Teeth: inadiation ofteeth with therapeutic doses during their development severely tetards their growth.

\ote: Aduh reeih are vcry resistant to the direct effects ofradiation exposure.. Radiation cariesi is a rampant lonn ofdentaldecay that may occur in patients who have received a course

ofradiotherapy. The carious lesions result lronl changes in the salivary glands and saliva, including reduced

tlo(. decreased pH. reduced buffering capacity, and increased viscosiLv.. Bone: lhc primary damagc to maturc bone rcsults from radiation-induced damagc to lhe fine vasculature,

\\ hrch is normally already sparse in a dense bone such as the mandible. Subsequent to irmdialion lhere may

be a replacement ofnormal marrow with f'atty narrow offibrous connective tissue. ln addition, the endos-

reum become atrophic, sho*,ing a lack ofosteoblastic and osteoclastic acti\.ity, an indication ofn€crosis.

The speed with which electrons travel from the filament ofthe cathode to the target oftheanode depends upon the potential difference between the two electrodes (kilovoltage).This, in turn, has a very important effect on the x-rays produced at the focal spot.

The kilovoltage has nothing to do with the number of electrons that compose the streamflowing from cathode to anode. The numb€r of electrons (vhich determines the quan-tity o-fx-rals producedl is controlled by the temperature of the tungsten filament (mil-liumperage setting). The hotter the filament, the more electrodes are enitted and availableto form the electron stream (the x-ra1,tube cut-rent).Inthe x-ray tube the number ofelec-trons flowing per second is measured in milliamperes. The intensity of x-rays producedat a particular kilovoltage depends on that number. Note: Setting the x-ray machine for aspecific milliamperage actually means adjusting the filament temperature to yield the cur-rent flow indicated. The milliamperage range for dental radiography is 7-15 mA.

l. In dental radiography, the quality ofthe x-ray beam is controlled by kVp.2. The kilovoltage range for most dental x-ray rnachines is 65-100 kV.3. Digital units use a range from 8-40 kvp.4. A higher kilovoltage produces x-rays with greater energy Ievels, shorterwavelengths and more penetrating ability.5.To increase film density, you should increase mA, kVp and time. Also, youshould decrease the source-object distance.

r Note*,'

. One-fourth as intense

. One-eighth as intense

. Four times as intense

. Eight times as intense

. Decreased density

. More latitude

. A shorter scale of contrast

. A longer scale ofcontrast

40Coplright O 201l-2012 - Dental Dects

41

Cop)aiglit O 20ll 2012, Denial Decks

The Inverse Square Law is stated as follows: The intensity ofan x-ray beam at a given pointis inversely proportional to the square ofthe distance from the source ofradiation.Important: Changing the distance between the x-ray tube and the patient thus has a markedeffect on beam intensity.

The intensity of an x-ray beam at a given point is dependent on the distance ofthe measur-

ing device from the focal spot. The reason for this decrease in intensity frtr,l, il rs ,nversely pro-portional) is that the x-ray beam spreads out as it moves from the source. The "spread out"beam is less intense.

For example, when the PID length is changed from 8 to l6 inches, the sourcelo-film distance

is doubled. According to the Inve6e Square Law, the resultant beam is one-fourth as in-tense. When the PID length is changed from l6 to 8 inches, the source-to-film distance is re-duced by one-half. According to the Inverse Square Law, the resultant beam is four times as

intense.

The following mathematical formula is used to calculate the Inverse Square Law:

original intensity = new distance2

new intensity original distance':

Remember: The intensity ofthe radiation is inversely proportional to the square ofthe dis-tance.

Important: The thickness of alumrrr,tm (approxinateb'2 mm) placed n the path ofthe x-raybeam that reduces the intensity by one-halfis termed the half-value layer. For example, if an

x-ral beam is said to have a half-value of4 mm, a thickness of4 mm of aluminum would be

necessary to decrease its intensity by one-half. Measuring the half-value layer determines thepenetrating quality of the beam. The higher the half-value layel the more penetrating the

beam.

One effect ofa change in kilovoltage is a changc in the penetrating power ofthe x-rays. Incrcasing kilo-voltage reduces subject cont ast (and the longer lhe scdle ofcontt?saJ; decreasing kilovoltagc incrcascs

subject contrast fard rhe shorter lhe scale of conlrasl. A second effect ofan increase in kilovoltage is

that not only are neu', morc pcnctrating x-rays produced, but morc ofthe less pcnctrating rays which were

also produced at the lower kilovoltage are omitted. Remember: Kilovoltagc controls the speed ofelec-trons.

Conclusion: kilovoltage influences the x-ray be.m and radiograph by:

. Altering contrast quality ([or patienls v,ilh thick jaws, iro"ase I ilovoltage)

. Detcrmining the quality ofthe x-rays produced

. Detcnninillg the velocity ofthe electrons to the anodc

Sharpness refers to thc capability ofthe x-ray film to reproduce the distinct outlines ofan objcct, or, in

othcr s ords. to how well the smallcst dctails ofan object are reproduced on a dental x-ray. A ccrtain lack

oi imagc sharpness is prescnt in every dental x-ray. The fuzzy. unclcar area that sunounds a radiographic

image is termcd the penumbra. Thc sha.pness ofa film is influenced by three factors:

. Focal spot siz€: the tungsten target ofthc anode senes as a focal spot; this small area convcrts bom-

barding electrons into x-ray photons. The focal spot concentrates the electrons and crcatcs an cnor_

mous amount ofheat. The size ofthe focal spot ranges from 0.6 mm: to 1.0 mm:and is determined

bt rhe manufacturer ofthe equipment. lmporlant: The smaller the focal spot area, the sharper the

inlage appears: the larger the focal spot arca, the greater the loss of imagc sharpness. Fitm composition: sharpness is relative to the size ofthe crystals found in the emulsion. The emul-

sion offastcr film contains larger crystals that produce less image sharpness, whcreas slowcr filmcontains smaller crystals that produce more image sharpness.. \Iovement: a loss of image sharpness occurs ifeither the film or the paticnt moves during x-ray cx-posute.

Note: Image sharpness can also be improved by increasing the distance between the focal spot and thc

object by using a long, open-cndcd cylinder and also by decreasing thc distance betwceil the object and

the film.

'kVp

.mA

. Exposure time

. Whether the film is a one-film packet or a two-film packel

t2Coptr'glt @ 2011,2012, Denial Decks

. Positive anode

. Negative anode

. Positive cathode

. Negative cathode

43Coplriglt O20ll-2012 - Dental Decks

Density rcfcrs lo thc ovcralldarkncss r/b/d(izer, ofa radiograph:. Dcnsit_v will increase as mA. kvp, or cxposurc limc is incressed. Dcnsity will decrease as mA, kVp. or cxposurc timc is decreased. Reducing lhc distancc bctwccn thc focal spot and thc film also increases thc dcnsit)

Note: Thc thicker thc objcct or thc grcatcr its dcnsity, thc morc thc x-ra] bcam is attcnuatcd and lhc lighter thc rc-sultant image will bc.

Thc blackening oflhe fi1rn Nflcr x-ray cxposurc is cxprcsscd in tcnns ofits optical densit!:

whcrc l0 is thc rnlcnsity ofincidcnt light /e,.a.,/.),r a vi4 rar./ and Ir is thc intcnsity ofthc lighl transmittcd through thc lilm.

In roulinc radiogr.phy thc uscful rangc ollilnr dcnsilics is approximatcly 0,j ften light) to 2 l|e^ dort.t. Bcyondthcsc cxtrcmcs thc imagc is usually too light or 1oo dark to bc diagnoslically uscful. Not€: ln a \\,cll-cxposcd andproccsscd radiograph. thc opticaldcnsit_v ofcnamcl is about 0.,1, dcntin is about L0, and soli lissuc 1s about 2.0.

Rcmcmber: Thc operator ofan x-my unil is in conirol ofthrcc factors:

L Kilo\oltage: thc quality or penetrating power ofthc x-ray bcam

2.}{illiamperrge: the quantity or numbcr of x-rays produccd*** lncrcasing nrillianrpcragc rcsults in an increase in thc numbcrofx-rays produced and an increase in lhc tcm-

ocralurc of thc filamcnt.3. Exposure time: thc lcngth of time x-rays are produccd and patient is cxposcd to lbcm. ljxposurc tnnc is mcas-

urcd in impulses bccausc x-rays arc crcalcd in a scrics ofbursts or pulscs rathcr than a continuous skcam. Oncinrpul\c occurs clcry 1160 ofa second; thcretbrc, 60 impulscs occur in I second.

L Radiographic speed is thc amounl ofradialion rcquircd 1o prodlcc a radiographic tilm ofslandarddcnsir,v. Thc fastcst dcntal film cuncntly availablc is F-spccd.

2.Thc film characlcristic thal js ihc rcvcrsc ofcontrast is film latitude. Thc highcr thc contrast. thcsmallcr thc laiitudc and the lowcr thc contrast, thc grcalcr Ihc latiludc. La{itudc is. thercforc, thc rangc

ofradlation intensitics that a film is capablc ofrccording.l. Radiographic not(le /o/-nrrre) is thc appcarancc ofuncvcn dcns;ty ofan cxposcd radiographic film..l Rrdiographic artifact$ arc dcfccts causcd by cnors in film handling or crrors in film proccssing. ormarks or scratchcs fiom rough handling.5. Sharpness is thc ability ofan x-ray lo dcfinc an cdgc prcciscly.

6. Rcsolulion. or rcsolving powcr, is thc ability ofan x-ray to rccord scparalc structurcs that a.c closclogcthcr.

Thc r-ral tubehead is a tighlly scalcd. hcavy mctal housing that conlains thc x-ray tubc thal produccs dcnlal x-ray!.Thc componen! pans ofthc tubchcad includc the following:

. Ntetal housing: is thc mctal body oflhc tubchcad lhat sunounds ihc x'ray tubc and transfonncrs and is iillcd \lithoil: it prolccts thc x ray tube and grounds thc hiSh-voltagc componcnts.Insulating oil: ;s thc oil tha! srmounds thc x-ray tubc and transformcrs insidc thc lubchcadi it prcvents ovcrhcatingby absorbing thc heat crcalcd by thc produclion ofx-rays

'Tubeherd seal: or thc aluminum or lcadcd glass covcring thc tubchcad that pcrmits lhc cxil ofx-rays lionl thctubchcadt it scals lhc oil rn lhc tubchcad and acts as a flltcr to Ihc x'ray bcam. X-ray tube: is thc hcart ofthc x-ray gcncrating systcm. Transformer: is thc dclicc that altcrs thc voltagc ofincoming clcctricilv. Aluminum di$ksl shccts of0.5-mn thick alurninum placcd in thc path ofthc x-ray bcaml they filtcr out non'pcnctrating, longcr wavclcngth x-mys. Lead collimator: is a lcad platc wilb a central holc that fits dirccily ovcr thc opcning ofdrc mcial housing whcrcthc x-rays cxit; ii rcstricts lhc sizc ofthe x-ray beam. Position-indic:rting device (PID)r is an opcn'cndcd. lcad-lincd cylindcr that cxtends from thc opcning ofthcmctal housing ofthc tubchcad; it aims and shapcs thc x-ray beam

Thc x-rar" tube is thc hcarl ofthc x-ray gcncrating systcm. It consists ofa lead-glass housing, a negative cathode,and a positive rnode. Electrons arc produccd in thc cathode and acceleratcd toward thc anodc; thc anode con\cr(s

lhc electrons into x-ravs.. l,eaded-glass housing: is a leaded-glass vacumm tubc that prevents x-rays liom cscaping in all dircclions. Oncccnlral arca ofthe ieadcd-glass tubc has a "window" that pcrmils lhc x-ray bcam lo cxit the lubc aDd directs lhex-ray bcan toward thc aluminum disks, collimator and PID.. Cathodc /r/ r€gdrtrt, r1e. rftr.L,/: consists ofa tungsten wire lilament in a cup-shapcd holdct nradc of molyb-denum. The purposc oflhc calhodc is to supply the electrons nccsssary to gcncralc x-rays. Thc clcclrons pro

duced in rhc nega(i!e cathodc arc accclcratcd loward thc posjlivc anodc. Thc cathode includcs thc ibllorling:. Tungsten filament: is a coilcd wirc madc oftungstcn. which produccs clcctrons \vhcn heatcd.llollbdenum cup: tbcuscs thc clcctrons into a narro$,bcam and dirccts thc bcam across thc tube lo*,ard drc

tungstcn targcl ofthe anode.

^node (ot poriti\,t ?l?(rod4r consisls ofa waftr-thin tungstcn platc cmbcddc'd in a solid coppcr cord. Thc pw'

pose oithe anode is to convert elcct.ons into x-ray photons. The anodc in€ludcs thc following

. Tungsten target: scrv€s as a focal spol and convcrts bombarding clectrons into x-ray photons

. Copper stem: funclions to dissipatc thc hcat away from thc tungstcn largct

D = log l0 (lo.l1)

Notc.

. Copper stem

. Filament

. Vacuum

. Molybdenum cup

44Coplrighr O 201 I -2012 - D€ntal Drcks

. A neutral atom without a nucleus

. An atom with equal numbers ofprotons and electrons

. A neutral atom that loses an electron and becomes a positive ion

. None ofthe above

45

Coplrighr @ 201 I -2012 - D€ntal D€cks

X'.a\s arc gencratcd whcn a srrcam ot clcctrons (\'hkh are prod ed hr rre /i/drrertl tra\cls from thc calhodc tolhc anodc ond is suddcnlr- stoppcd by its impact on thc tungslcn larscl. Thc filancnt locrlcd in rhe carhodc is nradc

oilungrrcn Nirc Thc smallarca on thc targcl that thc clcclrons strikc is callcd drc focal spot -il

is lhc source of \-

L Thc sizc of thc fbcal spol directly influences thc x-nty dcfinition: thc larger the focal spot. thc

\oles greai€r rhe loss nfdcfin:(ion and r\c greater lhe lo\r oI rhc .hartnc.. ol lhc imalc: Copper rs uscd Io hous!' thc anodc bccausc it is a good thcrmal conduclor. dissipating hcat tiom thc

tungstcn krgct and rcducing thc risk ofrnclring lhc largct-

ReFinrcd ti.m Haring. Joen Ia.-nuc.i and l-lura Ja.rn: DentalRxdioErdy Princlties rnd Tec|'.\ue\: lhinl Ldilron O 1000.$nh t.nnss.n ftonr Flsc\icr

Refrinted no'n Haring..roen lrnnuccr trnd Laura J.nsen Denhl Rtdrgrdphl: tnncrples ardTechniqoes: Ihid ldiron '! 1000.wirh pennr$io. from FheYler.

Matter is anything lhat occupics spacc and has mass; rlhcn mattcr is altcrcd, energy rcsulls. Thc indamcntal unilofmaller is thc atom. Thc atom consists oal\vo parls:

. A ccntral nucl€us: is composcd of protons and neutrons. Protons carry positiv€ clcctnc!l chargcs, !{hcrcas

ncutrons cary no clcctrical chargc and arc slightly hcavicr than lhc proton. Orbitin8 electrons: arc t;ny negatively chargcd particlcs ihal havc vcry little mass; rn clcctron wcrghs approx-

imatcly 1/1800 as much as a prolon orncutron. Elcctrons rravcl around thc nuclcus in $cl1-dcllncd paths known

as orbits or shells

An atom contaiis a maximum ofsevcn shclls, cach localcd at a spccific distanc€ lion1lhc nuclcus and rcprescrtrng

diflcrcnt cncrgy lcvcls. Thc shclls arc dcsignatcd wift lhe lclters K, L. N{, N, O, P and Q; thc K shell is locatcd clos'est ro rhe nucleus and has $c highestenergy level. Elccrrons arc maintaincd in thcir orbits by thc electrostalic forceJ

orallraction. bclwccn thc posilivc nuclcus and thc ncgativc clcctrons. This is known as ihc binding energy ofan clcc-

tron. Atoms arc capablc ofconibining wilh cach olhcr 1o lbrm molcculcs.

A neutrrf atom conlains an cqual numbcr of protons (posi!i,e Lharyes) ]nd electrons /neg.?/a'. .rr4i.'.!/. An atorn

with an incomplclcly Ullcd outcr shcll is clcctrically unbalanccd and aiicmpls 1o capturc an clcclton from an adjaccni

atom. An aton that gains or loscs an clcclron and bccomes electrically unbalarccd is known as an ion. Ionization js

thc producrion ofions. or thc proccss ofconvcning an elom inlo ions. Ionizalion dcals \\'ith electrons only and rcquircs

sufticicnt encrgy ro ovcrcomc thc electrostatic lbrcc that binds thc clcctron to the nuclcus.

Ionizing rad;ation is capable ofproducing ions and can bc classificd inlo two groups:

. Particulate radiationr arc iiny particlcs ofmattcr that posscss mdss and lra!cl in straight lincs and al high spccds.

Thcrc arc lbur typcs:. llfectrons: can bc class classificd as beta particle. lldst nnring ?l.cttotlj eniuetl lon the tt (k'tts ol rd-dioactir. otonts) ot c thode rays (strcams ol hi!:h-spe.l ek'( trcDs thut origindte in an .\ tut nh.). Alpha particles: arc cniltcd from thc nuclci ofheavy mctals and cxisl as t\\'o protons and nculrcns. $ith-out clcclrons. Protonsi arc accclcrated paniclcs. spccifically hydrogcn nuclci, with a nlass of I and a chargc of+l. Neutrons: are accclcratcd pariiclcs with a mass of I and no clectrical chargc

. Electromagnetic radiation: can bc dcfined as lhc propagation ofwarc-likc cncrg)" /r'rrorlr l,alltr./ through spacc

or mattct Illcctromagnctic radiations arc manmade, or occur nah.rrally;cxamflcs includc coirnic rr] \ camma ruyJ,

x-r!!-s, UV rays. visiblc light. infrarcd light, radar $avcs, nicro$avcs, and radio wavcs. Thc particle concept(Q d,1tun l2orr) .haructcrizcs clcctromagnctic mdiations as discrctc bundics ofcncrg-v called photons or quanta,

Thc wave concept characterizes cleckomagnctic radialion as lvavcs and focuses on thc propenies ofvelocit]'.$avclcnglh. and frcqucncy.

. The first statement is true; the second statement is false

. The first statement is falsej the second statement is true

. Both statements are true

. Both statements are false

a6Coptright ,O 20 I 1,20 | ? , Denial Decks

Which of the following occurs only at 70kVp or higher and accounts for a verysmall part ofthe x-rays produced in the dental x-rry machin€?

. Compton scatter

. Coherent scatter

. General (Bremsstahlung) radiation

. Characteristic radiation

47

CopFighr O 201 l'2012' Dental Decks

llcctricity is thc encrgy that is uscd (o make x-rays. Electrical encrgv consists ofa flow ofclcctrons through a con-ductor; this flo$'is known as thc clcctric currcn(. The clcctric currcnr is tcnned direct currcnt frcl whcn thc clcc-trons flo$,in one direction through lbc co duclor Thc lcnn alternating current /-,14) dcscnbes a currcnt ;n whichthc elcctrons flow in tl4o opposite dircctions. Rectitication is thc convcrsion otaltcmatiig currcnt lo dircct currentithc dcntal x-ray tubc acts as r self-rectificr ir that it changcs AC irto DC \r'hilc producing x'rays. This cnsrLrcs that

lhc current is alwa]s flor}ing in thc samc dircclion, morc spccilically, liom cathode to anode.

Amperagc is thc rncasurcncDl ofthc number ofelectrons nroving through a conductor Current is measu.cd in am-peres or milliamperes /rr,.1/. l'oltage is the meas rcment ofelectrical force thal causcs clcctrors lo movc fron a ncg-ativc pole to a posili\'e oDc. Voltagc is measured in volts or kilovolts /krr. Note: ID thc produclion ofx-rays. bofi thclmpcrage and volfagc can bc adjuslcd on thc contfil pancl (mA aditstDrctt dnd kI? adiusttrcrt s\\itthes).

A circuit is a palh of clcctrica I currcnt. Two electrical circuits arc uscd in lhc production ofx-rays:a lolrrvoltageor filamcnt circuil and a high-voltage circuit. Thc Iilament circuit uscs J to 5 volts. regulatcs thc llo\\, ofclcckicalcurrcnt to thc filament ofthc x-ray tubc, and is controllcd by thc milliampere settings. Thc high-r'oltage circuituscs 65.000-100.000 ! olts. providcs thc high voltagc rcquircd lo accclcratc clcctrons and to gencratc x-rays in thc x-ray tubc, and is conlrollcd by thc lilovoltage settings.

A transformer is a dcvjcc that is uscd to cithcr incrcasc or dccrcasc lhc vollagc in an clcctrical circuil. Transfbrncrsaltcr thc \oltagc ofthc incoming eleckical currcnt and then routc lhc cleckical cncfgy to thc x-ray tubc. In lhc pro-

duction ofdcntal x-ra)'s, thrce transfbrmers arc used to adjusl lhc clcctrical circuils:. Step-down transformcr: is uscd to dccrcasc thc vollagc fiom thc inconring I l0 or 220 line voltage to the 3 to

5 \ ohs rcauircd. Step-up transformer: is used to inc.casc the voltag€ from the I l0 or 220 linc roltagc lo thc 65,000 to 100.000

\0lts rcquired. Auto-transformer: scn,cs as a voltagc compcnsator that corrccis for miror flu!tuations in the currcnl

I Thc milliamperage f/r,.|.) or tube current swltch on thc control panel regulates thc tempcr.tura of\ot{* th€ filament and thus thc number ofelectrons emitted,

2.Tube current or mA controls thc numbcr ofphotons gclcratcd //,rlersitt ol the bru , but rot thcbeam cncrgy. Thc quantity of radiation produccd by an x ray tubc is dircctly proponional 1o lhc tubc cur-rcnt /rr.,1/ cxposurc timc.L Thc livp control sclccts voltage from diftcrenl levels on thc autotransformcr and applies it across Ihcprimary winding ofthc slcp-up transtbrmcr,+. In dcntal x rays, the qualit) ofthe r-ray beam is controllcd by kvp.5. Thc cflcct ofchanging timc is sinply 1l) control thc "quanlily" ofthe ex?osutc (the nunbcr ol pho-Iotts sencratel).

Not all x-ra)s produccd in thc x-ray lubc arc thc same; x-rays rlilltr in energy and wavclength Th€ cnergy and

lvrvclcnglh ofx-ravs varies bascd on how the clcctrons intcract wilh thc tu'rgstcn atonrs in lhe anodc. Thc kinctic cn

crgy of rhc clcctrcns is converted to x-ray pholons via onc oft$o mcchanisns:

. Gene.^l (Rrcnsstrfihnrg or braking radiation: a fomi ofradialion lhat occurs lrhcn speeding clcctrons are

slosed bccausc ofihcir intcraclions with thc nuclei oftarget alofis. Thc tcmr braking radiation, rcLrs to thc sud-

den stoppnrg or slowing ofhigh-speed eleclrons hitling the tarSet in thc anodc. Most x-rays arc produccd in lhis

nlanner; lpprorimately 707o ofthc x-ray cncrgy produced at thc anodc can be classificd as gcncral radiation. Charactcristic radiationr is produccd wien a high-spccd clcctron dislodgcs an inncr shell elcctron liom thc

tungslcn alonl and causcs ionization ofthat atom. This tlpc ofradiation accounts for a vert-' small part oi x rays

produced in thc dcntal x-ray nrachinc and occurs only at 70 kvp and abovc bccausc thc binding cncrgy oflhc Kshcll .lcctron is approxirnatcly 70 kcv

Priman radiation refcrs to lhc pcnctrating x-ray bcam that is produccd at lhe llrrgcl oflhc anode and cxjls thc lubc

hJld Tlij \,rr] beam is olicn rcfcrrcd to as thc primary bcam or useful beam.

Secondarr r!diation reicrs to x-radialion that is crc.rtcd whcn thc primary bcam inlcracls u'ith mattcr li tl tal rd',li ].t,rp/l.krutoitklud(skesolitissu(softheheud,thehotrcsolth"skull,adtheteeth).NoteiSccondaryislessf Jn.rratrng lhan primary radialion.

Coherent scaner is onc ofrhc intcracrions ofx-radialion rvith mattcr in which thc path ofan x-ray pholon is altcrcd

b\ 'ran

cr $ ith ou t a c h,lngc in cncrly. Cohcrcnt scattcr accounts for 8 o/" of t hc inicractions of mattcr with thc dcnia I

ComDton scatter is onc ofthe intcractions olx-radiation with matter in which thc x-ray photon is dcllcctcd from its

parh and loses cnergy. (lomplom scaitcr accounts ibr 6270 ofihc scaitcr that occurs in diagnostic radiography

Photoelectric absorption is onc ofthe intcractions ofx-radjation \\'ith mattcr, 3n x-ray photon intcracb with an or'brtrl .1cctron, and all of the cnerg! of the photon is absorbed by thc displaccd clcclron in thc form of kinctic en-

crg] Thrs accounts for 307o oflhc inlcractions ofmattelwith lhc dcntal x-ray bcam.

Dclennining the qurntily ofrudiation exposufc or dosc is tcrmcd "dosimetr).". Erposure: is a measurc ofradiation quantily, the capacily of thc radiation to ionizc uir Thc roentgcn /Rl is thc

tradilional unil ofradiation exposurc mcasurcd in arr. A bsorbed dose: is a m casurc o f enerey impartcd by any typc of ionizing radiatbn 1o a nass of any typc of matltcr Thc SI unit is thc gr"d-r, (Gy). thc tradilional unit is lhe /ad. Effective dosc: is uscd to cstimalc lhc risk in humars. Thc unil ofcfteclive dose is thc Str'r'l?,'/ (Sv). Radioactiritr: is thc decav ratc ofradioactivc matcriai. The unit is thc 8c(quercl(Bq)

All ofthe following rre components of inherent liltration EXCEPT one.Which one is the EXCEPIIOM

. oit

. Unleaded glass window

. A leaded cone

. Tubehead seal

48Copyright O 201 l-20 | 2 - Dental Decks

Rad Protection

Man has always been exposed to natural radiation arising from the earth aswell as from outside the €arth. The radiation we rec€ive from outer space is

called terrestrial radiation or terrestrial rays.

We afso receive exposure from man-made (artificial) radiation, such as x-rays,radiation used to diagnose diseases and for cancer therapy.

. The first statement is true; the second statement is lalse

. The first statement is false; the second statement is true

. Both statements are true

. Both statements are false

49Cop)rlghr C 20ll 20ll, Denral Decks

There are two types of filtration used in the dental x-ray tubehead:

. 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. The inherent fil-tration of the dental x-ray machine is equivalent to approximately 0.5 to 1.0 tnm ofaluminum.. Added filtration: refers to the placement of aluminum disks in the path ofthe x-raybeam between the collimator and the tubehead seal in the dental x-ray machine. The

purpose of the aluminum disks is to filter out the longer wavelength, low-energy x-rays from the x-ray beam. The low-energy, longer wavelength x-rays are harmful to thepatient and are not useful in diagnostic radiography.

The total filtration ofthe x-ray beam before it reaches the patient consists of the inher-ent filtration plus the added filtration. Important: Govemment regulations require totalfiltration to be equal to the equivalent of 1.5 mm of aluminum for up to 70 kVp and 2.5

mm of aluminum for higher voltages.

, . .. l. Longer wavefength x-rays (those produced ut lower kilovollages) are eas-

.:.r-olcq',' ily atrsorbed.'.:.ta,;tt... 2. Shorter wavelength x-rays (those produced at higher kilovoltages) pene-

trate objects more rcadlly (the!-Jbt"m the image on theJilm).3. Filtration of the x-ray beam results in a higher energy and a more penetr-

ating useful beam. Filtration reduces patient dose, decreases contrast and in-cr€as€s the density of film.

Remember: The x-ray beam is composed ofrays ofdifferent wavelengths and penetrat-

ing po*er (the tern used Jbr this is polychromatic) because the potential across the tube

changes constantly as the voltage varies.

*** The radiation wc rcceive liom outer space is called cosmic radiation or cosmic rays.

Sources of radiation exposure:. Naturaf r:rdiation /rackgrourul rarliation)t is by f'ar the largest contributor (8J%) to the radiafion expo-sufe ofpeople living in thc U.S. today. Background radiation, resulting fiom extemal and intemal sources,

vrelds an a\erage annual E ofabout 3 msv.

- Erternal: exposure in this category is due to cosmic and terrestrial (/iom lie rolll rtdiation or that orig-inaling in thc cnvironment. These sources contribute about l670 ofthe radiation exposure lo lhe popula-

tion.- Internal: sources ofintemal radiation include inhaled mdon fi6z,, and ingested radionuclides 111%/.

. ArtificiAl radiation lnan-made radiation)i Ihese may be categorized into tbree major groups -medicaldiagnosis and treatmcnr (11%, of rJhich dental x-ray examinations are rcspottsible for only 2,5% ofthk

alerage a ual t-ru! diagnosrt etporrle/, consumer and industnal products and sources d9'o/, and nuclearmedicine f4?ir. Artificial radiation yields an average annual E ofaboul0.60 mSv or l77o ofthe annual ra-

diation exposure !o the U.S. population.

Radiation protection standards dictate the maximum dose ofradiation that an individual can receive. Thc max-imum permissibl€ dose /MPD./ is defined by the N^tional Council on Radiation Protection and Measurements

fNCRP) as the maximum dose equivalent that a body is pelmifted to receive in a specific period oftime. TheMPD is the dose ofradiation that the body can endure with little or no injury Important: The yearly MPDfor a non-occupationally exposcd person is 0.1 rem/year (.0001 Sv/year). The yearly MPD for occupation-ally cxposcd pcrsons, or persons who work with radiation, is 5.0 rem/year (0.05 Sv,/year). The IUPD for an

occupationallv e!posed pregnant woman is the same as that for a nonoccupationally exposed pcrson, or 0.1

rem/year (.0001 Svlyear).

Exposure and dose in radiography: The goal ofradiatiorl protectjon procedures is to minimize the exposure

of ofllce perconnel and patients during the radiographic examination. The philosophy ofradiation protection

currently used in practice today is based on the principles ofALAR{ (As Low As Reasonabb' Ac hierah le ).

Note: The primary risk from dental radiogEphy is radiation-induced cancer. Although the risk involved withdental radiography is extremely small in comparison with other risks such as smoking or consumption of fattyfoods, no brsis exists to assume that it is zero.

. 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

50Cop)right O 201l-2012 - D€ntal Decks

. Discrimination

. Collimation

. Filtration

. Barrier placement

5tCoplriSht O 201l-2012 ' Dmtal Decls

.\ll ofthe lbllowing reduce the amount ofradiation to thc patient:

. Lead aprons and collars. Lcaded thyroid collars are recommendcd in individuals undcr 30 years ofage.lvlany statcs mandate lhe use ofa lead apron on all patients.. Increased flhmtion using an aluminum disk. Use E-speed film. F-spced fitm or digiral imaging for pcriapical and bite$ing radiographs. Lead diaphragms placcd within the cone ofan x-ray tubehcad. Collimating an x-ray beam: using a r€ctangular collimator siSnificandy reduces patlenl exposure. Using a long 116 ircl, PID is prclcrrcd because it produces less divcrgence oflhe x-ray beam. By doing

Ihis )ou are increasing the source-film distance and rcducing patient exposurc as \r'cll as inlproving imagc

. The use of rrre earth intensifying screens for all panoramic and cephrlomctric radiography

. Frlrn-holding devices are also eflective in reducing a patient's exposufe to x-radistion

. E\posure iactor seleciion also limits the amount ofx-radiation cxposure reccivcd by thc patient The den-

iilassisrant can control thc cxposure factorsby adjusdng thc kilovoltage peak, milliamperage. and dre time

ic:tings on thc control panel ofthc dcnlal x-ray machine. Note: On some machines the kvp peak and orA

:eirings are presct by the manufacturff and cannot be adjusted.

- \ .cI'irg of ?0 lo c0 k\ p lecn. nalicnls cxf'osure ro 3 mitrimum- Scr m'\ value to high€st possible value ifvariablc. Iligher mn sefiings produce a beam \\ ith morc crl-

ergt and increasc the intensity ofthe x-ray beam.

- \diust exposure time to achieve optimum densityImportant: nrA and exposure time are inversely relatcd. \lllen altering mA, the exposure time nustbc adiusred to maintain diagnoslic density ofa film.

Operator protectioni Radiation exposure to the opcralor can be reduced by standing at least six feet a\\'ay,_::.r:c a l.ed shield, or bolh when exposiDg €diographs. The operator should never remain in lhe room hold-_: :-:: \-.3\ packcl irl place tbr the palicnt. If a film must be held in place by someonc else (/br d clliki).

:::ac :h.' f,rr.nI and havc him or her hold rhe film. AII dental personnel should lvcar film badgcs thal moniior

:\.r.,r:. lloiages. \otei The opemtor must avoid the primary x-ray beam by positioning lhemselves at a 90

ro l-15 degree angle ro ihe beam.

\ote: R:sarding the taking and processing of dentr I radiographs, al$ays remcmber!o maintain prop€r in-fection controf /appl.l tniverssl prccauliohs) at all tim€s!:!

In the x-ray tubehead a collimator (leatl plate \4ith a hole in the middlel is uscd to restrict the size and

shape ofthe x-ray bea . A collimator may have either a round or rectangular opcniDE.

. A rectangular collimator resfficts the size ofthe x-ray beam to an area slightly iarger than a sizc 2

InrrdL,ral film anJ \rgnificantll rcduccs paticnl c\lo\urc. A circular collimator produces a cone-shaped beam that is ?.75 inchcs /7 czrl in diameler, consid-erabJy Iargcr than a size 2 intraoral film. Important: wtcn using a circular collimator. fcdcral regu-lations require that thc x-ray beam be collimated to a diameter of no more than 2.75 inches 17 cD,as it exits from the PID and rcaches thc skin ofthe patient.

The positioning-indicating device /P1Dl, or cone. is uscd to dircct thc x-ray beam. Therc are three basic

types ofPlDs:. Conical: appears as a closed. pointed plastic cone. Wlen x-rays exit from the pointed cone, they pen-

etmte the plastic and produce scatler radiation. To climinatc cone-produced scattct radiation. the

conrcal PID r\ no longer used in dcnliqlrv.. Open ended and lead-lined rectangular or round PIDs: arc uscd that do not producc scatter tadia-tion. Both rectangular and round PIDS are commonly available in n\,o lcngths:

. Short /8-i,r.r,

. Long (16-inch)*** Thc long PID is preferred because less divergence of the x-ray bcam occlrrs. Of the three

r-vpes of PlDs. the rectangular type is most effective in rcducing patient exposurc.

These devices do not reduce thc amount of radiation rcceivcd by thc exposed tissucs. but reduce thcradiation to surrounding tissues duc to x-ray bcam divcrgcncc.

Remember: The x-ray beam consists ofmany different $'avelengths. The short w.velength (high en-

er'gl, rays have great penetrating powcr; long wavelength flox,erergl, rays have low pcnctrating po\r'er

and do not rench ihe fiJm in reasonable quantitics since thcy are atlenuated by the soft tissues. Low en-

crgy rays add only to thc total amount ofradiation the patient receives. Aluminum discs are used to fil-ter out the useless long wave rays. increasing the overall quality ofthe beam.

. The film is bent

. The film is placed backwards in the mouth

. An improper vertical angulation is used

. An improper horizontal angulation is used

. Source-film distance

. Film-object distance

. Focal spot size

. Central ray direction

. Film parallelism

52

CoDright O20ll-2012 - Dental D€ck

Copright O 201l-2012 - D€nbl Deck

Figure #1. A rcversed film appcars

light lvith a hcrringbonc cfiect.

\ . .rlr thol(ri refnnred fionr Hlrlng- Joc.lannuccr and Laura J.nsen: DerialRadiography: Iri.ciples.nd Te.hniques:Ihrd F.dilion O :000.

IIf .ennjrion liom Elsevier

Five rules for accurate image formation when taking x-rays:

l. Use the smallest focal spot that is practical.Note: The size ofthe focal spot influences radiographic definition or sharpness. Theyare inversely proportional. The operator cannot control the size ofthe focal spot.

2. Use the longest source-film distance that is practical in the panicular situation.

i. Place the film as close as possible to the structure being radiographed.

J. Direct the central ray at as close to a right angle to the film as anatomical structuresll ill allorv.

5. As far as is practical. keep the film parallel to the structure being radiographed.

Figure #3. Thc bcnt tilm appcars distorted.

t_igure #2. The film dcmonstrates a doublc cxposure. Figure #4. Movcmcnt rcsulls in a blurred image.

RADIOLOGY Tech

A periapical of the left maxillary canine shows an elongated tooth whichdoes not capture the apex of the canine. \yhile taking the periapical

of the left maxillary canine, the operator had an:

. lncorrect horizontal angulation

. Incorrect vertical angulation

. Either ofthe above

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Copyrighr C 20ll l0ll Denlal Decks

RADIOLOGY Tech

The two radiographs below were taken with the buccal object rule inmind, In film #2, the x-ray tube was directed from a mesial angulation.What is the spacial position of the circular object in these radiographs?

. The object lies lingual to the first molar

. The object lies buccal to the first molar

. The object lies between the second premolar and the first molar

. The object lies directly apical to the first molar

Film #l 55 Film #2Copyright C:01l -1012 - Dental Decks

Vertical angulation is directing x-rays so that they pass vertically through the part being examined.This is accomplishcd by positioning thc tubchcad and direction ofthc ccntral ray in an up-and-down (vertical) planc. lmportant: Foreshortening (See fgurc #1) rcfcrs to a shortcncd imagcand elongation /Seefgzrc #2) refers to an elongated image. Both are produced by an incorrect ver-tical angulation. Excessive vertical angulation causes foreshortened images, while insullicientvcrtical angulation causcs clongatcd images.

Figure #1. If the verticalangulation is too stccp. thcimages a.c foreshoracned.

Figure #2. Ifthe venicalangulation is too flat. thcimagcs arc elongatcd.

Borh phoros rerrinred fromHlnng, Joen Iannucci andLaun J$sn: DenraL Radioela-phy: Principles and Tcchniqueslftnd Ednion. O 1000, rvilh

I)emission frcm Eh.vi.r

Horizontal angulation is maintaining the central ray at 0 degrees as the tube is n]oved around thehead. This is accomplished by positioning the tubehead and direction ofthe central ray in a side-to-side (horizotlt.il) plane. r-ote: The general rule for horizontal angulation is that the central rayshould be perpendicular to the mean antcropostcrior plane ofthe teeth being x-rayed.

Important: lncorect horizontal tube angulation causes overlapping (teeth images are superim-po,;ed on eaclt otlrcr).

Tle central ray is said to be at 0 degrees when the x-ray tube is adjusted so that the central ray isparallel to the floor Ifthe tubehead is directed at the floor, it is called positive angulation; ifit is

dirccted toward the cciling. it is called negative angulation.

The buccaf obj€ct rule falso called the tube shili technique) is used to determine an ob-ject's spatial position within the jaws. This technique utilizes two radiographs of an ob-ject exposed with slightly different tube angulations. It then compares the object's position

on the radiograph with respect to a r€ferenc€ point (e.g., /re root of a tooth,/.

lf the tube is shifted and directed from a more mesial direction, and the object inquestion appears to have moved mesially with respect to the reference point, then the ob-ject Iies lingual to that reference point. Conversely, ifthe tube is shifted mesially and the

object in question moves distally, it lies on the buccal aspect ofthe reference object.

Remember the acronym SLIQB -+ $ame-!ingual, Qpposite-guccal.

*** Ilthe object in question appears to move in the same direction as the x-ray tube, itis on the lingual aspect. lfit appears to move in the opposite direction as the x-ray tube,

it is on the buccal aspect.

Tech

After developing her bitewings, a d€ntist realizes that she has too muchoverlap t etween the contacts of adjacent teeth. This is an error caused by:

. Too much vertical angulation

. Too little vertical angulation

. lncorrect horizontal angulation

. Beam not aimed at center of fihrl

55

CoDtighr e 201l-2012 - Dental Decks

RADIOLOGY Tech

Which of the following positioning errors is the most likelycause ofthe reverse occlusal plane curve on the panorex below?

. Chin tilted too far upward

. Chin tilted too far downward

. Head tumed slightly

coplri8ht <) 20ll-201: Denral Dects

Some errors often made when taking dental radiographs:. Elongation (most common error): teeth appear too long

-may be caused by too lit-

tle vertical angulation, the film not parallel to tbe long axis ofthe teeth or the occlusal plane

not being parallel to the floor.. Foreshortening: teeth appear too short may be caused by too much vertical angul-

ation or poor chair position.. Cone cutting: portion of film will appear clear with a curved line

- the beam was

not aimed at the center ofthe film. See figure #l. Herringbone effect: zigzagged pattern appears on the film

- the film was placed

backwards in the mouth.. Poor film placement: the film was not placed lhr enough back or not forward enough

in the mouth. See figure #2. Overlapping: interproximal areas are overlapped, reduces diagnostic quality offilm

-due to incorrect horizontal angulation (the central x-ray was not directed perp-

penditular to the curvature of the qrch and through the conldclt. See

ligur€ #1.,\ cone'cur appears as. Figur€ #2. Improper filln place- Figure #3.lncorecr horizontalangula-

cLr\.d une\posed ldear) arca on } mcnt: no apices appear on ihis film tion results in orerlapped conlactareas

A (t r.e phoNi repnnled fron Hrrin-q, Jocn lannucci and Laura Janscn: Dcntal Rrdrograthy: Principles and Techniqu.s: Third Edrtion aa

:on. \rh |lemr$ion fro'n Else\ier

*** Mandibular structures look narrower and maxillary structures look wider (looks Iikeo "frotn").

Chin tilted too far downward:

L Occlusal plane shows an excessive upward curve (look like a "big smile").See figure trelow2. Severe interproximal overlapping, anterior teeth appear very distofied.

Tech

The periapical x-ray below appears distorted,What is the most likely cause of this?

. Overbent film

. Patient had glasses on

. Exposure to secondary radiation

. Cone cutting

. X-ray arm drifted

Tlnd Edition O ?000.

Copyflghr C 201I,2012 - Dental Decks

IOLOGY Tech

Which ofthe following is a major disadvantage of the paralleling technique?

. The image formed on the film will not have dimensional accuracy

. Due to the amount ofdistortion, periodontal bone height cannot be accurately diagnosed

. An increase in exposure time is necessary due to the use of a long cone

. An increase in exposure time is necessary due to the use ofa short cone

59

Coptrigh aC 20ll 201? Denral Deck.

Some other common errors made when taking dental radiographs cause:. Light films (undarexposetl /intage NOT dense e ough)'. ircorTect milliamperage floo/onf or exposure (too short)a incorrect focal film distance; cone too far from patient's f'ace,

film pJaced backu,ards. See figure #1. Dark fifms (overexposed / image too dense) , incorrect rnilliamperage (too h igh), expo-s\ve /too long), incorrect kVp (too higlt). See figure #2. Double exposure: hlm rvas used twice. Fogged {ilms: exposed to radiation other than primary beam. See figure #3. Artifacts:patient didn't remove eyeglasses, earrings, or rernovable prosthetic appliances.. Poor contrast: incorect kVp (too high). Blurred image: patient movement or drifting ofx-ray arm. Clear films: were not exDosed to rudiation

Figure #1. \n undcrcxposcdrilln anp.ars hght.

l-igure #2, An ovcrcxposcdfiln appean dark.

l'igure #3, A fbggcd film appcarsgray and lacks dctail and contrast

The paralleling technique is based on the concept ofparalielism. Other names for this tech-nique include XCP (extension tone paralleling te.hnique), rtght-aflgle technique, and long-cone technique. Note: This is the preftred technique for making intraorcl x-rays.

Basic Principles:. Film is placed parallel to the long axis ofthe tooth being x-rayed. Central x-ray is directed perpendicular to both the tilm and thc long axis ofthe tooth. A film holder lXCPl must be used to keep the film parallel to the Jong axis ofthe to()th. The object-film distance must be increased b keep the film parallel. This results inirnage magnification and loss ofdefinition. The source-film distance must also be increased to compensate for the image magnific-ation and to make sure that oniy the most parallel rays uill be aimed at thetooth and thefiln. Using a long cone (16 inclt tatEet-liln distonce) results in greater deflnition and less

imase masnification.

\'rlr.erhfr.rrepnnredlonHdnng.JoerlanrucciandLauraJans.n DentalRadrogi.phl: rniciplcs a.d Techn'que!: Thi.d Edrlron. C

: ,' * rh rennl\sl.n fon llscvier

ReFnred tilJn lllrine. Joe. lannucci.nd Lnura Jrn5c.: I)cnlal ltrdiogr!tht Pnncrpler and lechnquer: ThtrdFdnlon t 1000. \irh l]crni$ro.

Positions of thc lilm, tccth, and scntral ray of thc x-ray bcam in thcparalleling tcchnique. Thc film arrd long axis oflhc tooth arc |arallel.Tbc ccntral ray is pcrpcndicular 1() thc loorh and fi1nl. An incrcascdtargetfilm distance //6 ir.l.t is .equired.

. Image on x-ray film may be dimensionally distorted (amount may vary)

. lncreased exposure time

. Due to the use ofa short cone (which results in divetgent rays), the image is not a truereproduction of the object

. May not be able to judge the correct alveolar bone height

60

Coplrighr O20ll-2012 - Dental Decks

6tCopFSh O20ll-2012 - Dental Decks

*** The exposure time is actually decreased.

The bisecting technique (also knov'n as the short-cone technique) rs based on the geometric

principal known as the rule of isometry. The rule states that two triangles are equal iftheyhave two equal angles and share a common side.

The following best describes the bisecting t€chnique:. The dental x-ray film is placed along the lingual surface ofthe tooth. At the point where the film contacts the tooth, an angle is formed by the plane ofthe filmand the long axis ofthe tooth. The person taking the x-ray needs to visualize a plane that bis€cts this angle. This plane

is called the imaginary bisector -this

creates two equal angles and provides a commonside for the two imaginary equal tdangles.. The central ray is positioned perpendicular to the imaginary bisector

LOng axrsot looth

Cenkalray

lmaganarybisector

Central ray of theX{ay beam aimed tfiroughthe toolh apax

Length of imag€

tong axis of the toothBisecting line

Long axis of ihe film

Vertical angulation

Reprinr€d frotn H.ri.g. Joen Iannucci and Laura

Janscn: Dental RadiogrAphy: Princilles and Tech-

niques:Third Edition. O 2000. srlh pennnnon lrom

Figure #1. The theoreticalbasis ofthe bisected

angle technique. The angle between the longaxes ofthe tooth and film is biscctcd and x-raybeam aimed at right angles to this linc, throughthe apcx of the tooth. With this geometricalamangement, the length of thc tooth in themouth is equalto the length ofthc image ofthetooth on thc film, but as shown, thc pcriodon-tal bone levels will not bc represented accu-rately.

Both lrhoros r€prinred fton Haring, Joen llnnucci and LaunJansen: Dental R.diography: Pflncitles and Techniquesr ThndEdiiion.O 2000. wilh p.mssion fron Elsevier.

BA

Figure #2. Diagrams showing the magnification ofthe image that results from using (A) a shon cone

and a diverging x-ray beam and (B) a long cone and a near-parallel x-ray bcam.

RADIOLOGY X-rays

Posterior bitewing radiographs are the most useful x-ray projection fordetecting caries in the distal third of a canine and the interproximal and

occlusal surfaces of premolars and molars,

Periapical radiographs are used primarily for detecting changesin the periapical and interradicular bone.

. 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

62

Cop$i8hr lil 201 1,201 2, Denral Decls

RADIOLOGY X-rays

The occlusal film is the film ofchoice for the evaluation ofperiodontal disease.

The bisecting techniqu€ is th€ preferred periapical exposure method for thedemonstrrtion ofthe anatomic features of p€riodontal disease.

. The llrst 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 lalse

63

Cop)righr all 2011 l0l? Denral Decks

Radiography is uscful for the detcction ofdcntal carics because the carious proccss causcs tooth demin€ral-ization. The carious lesion (the demircrali:ed ared ofthe tooth that alloN.t greater passage ol Fqt is darkerthan the unaliected portion (more radiolucen, and may be detected on radiographs. Note: The most usefuladult bitcwing cxamination consists offour no. 2 size films for separate prcmolar and molar projections.

A number ofcolor changes may be seen *,ith dental caries. Occlusd surfaces may show dark stairling in rhefissures, pits. aud grooves, or may show ar obvious cavitation. Because ofthe superirnposition ofthe dense

buccal and lingual enamel cusps, early occlusal caries is diflicult to sec on a dental x-rayi consequentl)! oc-clusal caries is not seen on an x-ray until there is involvement of the DEJ. Important: The classic radi-ogmphic appearance ofocclusal caries extending into dentin is a bmad-based, radiolucent zone, often beneatha fissure, with little or no apparcnt changcs in thc cnamcl.

Caries that appear interproximally may be diflicult or impossible to detecr clinically.On a dental x-ray. inter-proximal caries is typically seen at or just below the contact point. As caries progresses inward through rhe

enamel oflhe looth. it assumes a tri{ngular configuration; the ap€)r ot' the lriangle is seen al the DEJ. Ascaries rcaches thc DEl, it spreads laterally and continues into dentin. Another triangular configuradon is

scen in denlin; this timc lhe base ofthe dangle is along the DEJ and thc apex is point€d loward the pulpchamber.

Because ofthe superimposition ofthe dersities ofnonnal tooth structure, buccal and lingual caries are diffi-cult to detect on a dental x-ray and ar€ best detected clinicall),. \\hen vie',\'ed on a dental x-ray, caries that in-volves the buccal or lingxal surface appears as a small, circular radiolucent ar€a with sharp, well-d€finedborders. As ihese lesions progress, they become elliptic or semilunar.

Clinicall,v. root surface cari€s is easily detected on exposed root surfaccs. The most common locations includerhe e\posed roots ofthe mandibular premolar and molar areas. On a dental x-my, mot surl_ace caries appears

as r cupped-out or crater-shaped radioluc€ncy j ust below the CEJ. Early lesions may be difficull to detect

on the dental x-ray.

orher radiosraphic appearances ofdental caries include: recunent caries, rvhich appears as a radiolucenc!adjacent to an existing restoration, and rampant caries, which affects numerous teeth.

Dcntal radiogmphs play an intcgral rolc in thc asscssmcnl ofpc.iodontal discasc. Dcntal radiographs must bc used

in conjunction $,ith a clinical cxaminadon. Thc periapical radiograph is lhc film of choice for thc cvaluation ofpcriodontal discasc. Thc paralleling technique is lbc prcfcrrcd pcriapical €xposure method for thc dcmonstralion

ofthc anatomic fcaturcs ofDcnodontal discasc.

Thc radiographic appcarance ofhealthy alveolrr bone can be dcscribcd as tbllo$si. l,amin! dura: in hcalth. dle lamina dura around thc roots oflhe (ccth appcars as a dense radiopaquc linc.

'Alveolar crest: the normal alvcolar crcst is located approximatcly 1.5 to 2.0 mm rpical to the Cf,J ofadjacentteeth. Thc sbrpe and dcnsily varies between thc antcrior and poslcrior rcgions ollhc mouth. In the snterior rc-gions, thc alvcolar crcst appears pointcd snd sharp and is normall) \'ery radiopNque' In the postcrior rcgions,

the alvcolar crest appears tlat, smooth, and parallel to a line betwcen adjacent CEJ's. Thc alvcolar crcst in thcpostcrior regions appcars slightly less rrdiopaquc than that in lhc anterior rcgions.

' Pcriodontal ligament space: rhc normal pcriodontal ligamcnl spacc appcars as a thin radiolucenl line bct\l ccn

thc root ofthc tooth and the lamina dum. In hcallh. it is continuous around thc root structurc and is 01 unifbrm thick-

lflportant: With pcriodontal discasc, the alvcolar crest is no longer locatcd L5 to 2.0 mm apical to thc CEJ and no

longer appcars radiopaquc. Instead, thc alvcolar crcsl appears indistinct, and bonc loss is sccr-

Patlern ofbone lossi. Horizontal bone loss: thc bonc loss occurs in a plane parallel to the CEJs ofadjaccnt tccth.Note: ln horizon-

tal bonc loss rhc crcst ofthc buccal and lingual cortical plates and the intervcning intcrdenlal bonc havc bccn rc-

. vertical (angular) ttone lo.si thc bonc loss do€s not occur in a planc parallcl to thc Cts's ofadjaccnt tcclh.

Note: wilh thcsc dcfccts thc crcst ofthc rcmaining bonc typically displays an oblique angulation to the Iinc ofthc ChJs in the arca ofthc involvcd tccth.

Classification of periodontal dise.se:. ADA Case Type I (gr'rgivr?r9r No bony changc sccn. ADA Case Type If fedrb' peiodontitis)i Mildbonc loss /./'.rld/ .rdrg?.tl is sccn. ADA Case Type II I f,, oderute periodontitis)t Modcratc bonc loss f/, ro JJ% /rrt is sccn. Thc patlcm ofboncloss may bc horizontal or vcnical and thc distnbution may bc localized or gcncralizcd. Furcation involvcmcntmay also oc sccn.. ADA case Type lV /ssverc peiodontitis). S.\erc bonc loss f-r3% or rrol", is sccn. Bonc loss is so cxlcnsivc that

thc rcmaining tccth show cxcessivc mobilily and dritling. Extcnsive horizontal and vcrtjcal dcfccts may bc prcs-

X-rays

A small town dentist gets a phone call late on Saturday night from a patient ofrecord. Th€ patient has been in a bar fight where he was punched just below the

right eye. The dentist suspects a zygomatic complex fracture. Which ofthefollowing projections is best for this examination?

. Waters projection

. Submentovertex projection

. Reverse Towne projection

. Lateral cephalometdc projection

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Coplright rC 20ll ?01: Denral Decks

RADIOLOGY X-rays

At the dental clinic, an emergency patient arrives complaining of swellingassociated with a carious upper left molar. The patient complains of"stuffiness'and feels more so when she bends ov€r to pick up stuff.

The dental clinic is equipped with conventional radiography. Which of thefollowing projections is best for the examination ofthe rnaxillary sinus?

. Lateral jarv projection

. Reverse Toivne projection

. Waters projection

. Submentovertex projection

For this projection the neck is maximally extended and the film cassette touches the topofthe head. The x-ray beam enters the head under the chin (near the mental tubercle ofthe mandible) and, exits at the vertex. This view is used in conjunction with other projec-tions, and allows direct visualization ofthe base ofthe skull. The zygomatic arches stand

out like rhe handles ofa jug on this view.

; Film! casse[e

Floor

Re[inred lion Haring. Joen lannucciand Laun.]anrcnr Denlal R.diogrdph]:Pnnciples and Techiiques: Tlird Ed,r,on q 2000.r'ith l]emisstun liom El

This is a posterior-anterior projection with the patient's face lying against the film and the

x-ray source behind the patent's head. Waters' projection is the most useful conventional

radiographic technique to image the maxillary sinuses. In this projection, the radiographic

densities ofnormal maxillary sinuses are the same on both sides and equal to those oftheorbits. Ifone ofthe sinuses is diseased, Waters projection will exhibit either a radiopaque

tllildl level, a sinus opacification, mucosal hyperplasia, a radiopaque growth or a loss ofconical borders of sinus. Other useful projections include periapical, panoramic, occlusal,

lateral head. and Caldwell. It is also one of the best films for radiographic diagnosis ofmid-facial fractures.

X-ray unrt

film

tl

Tip ol nose l'trom

Filmcasselle

Reprinled from Haling.J@n lannucci and LauraJansenrD.ntal Ra-

diognphyr Pn.ciples and Techniqu.s: Thnd Ednion. O 2000. $ithpemision fron Ehelier

On the way out ofyour dental chair, the patient gets up too fast,feels dizy, and falls chin lirst onto your tiled operatory floor.

Suspecting bilrteral subcondylar fractures, which of the followingproiections would best allow for this examination?

. Waters projection

. Transcranial projection

. Townes projection

. Submentovertex projection

CoplriShr O 201l,?012 , Dental Decks

. Evaluation of impacted teeth

. Evaluation oferuption pattems and growth and development

. Diagnosis ofearly carious lesions

. Detection ofdiseases, lesions, and conditions ofthe jaws

. Examination ofthe extent of large lesions

. Evaluation of trauma

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Coplriglu C 201 l-2012 - Dental D€cks

Uses of the prnorrmic radiograph include Nll of the followingEXCEPT oae.Which one is the TXCEPTIOIW

The patient lies on his back with the film under his head. The x-ray source is from thefront, but rotated 30 degrees from the Frankfort plane and is directed right at the condyles.

The Townes projection is often ofvalue in assessing the status ofthe condyles, condy-lar neck and rami because superimposition ofthe mastoid and zygoma over the condylarneck region in the straight postero-anterior projection often makes interpretation diffi-cult. The Townes projection eliminates this superimposition, thus giving good visualiza-tion of lhe condvlar area and rami.

Note: The "reverse Towne projection" is used to identifyfractures of the condylar neck and ramus area.

The following can be demonstrated on conventional TMJradiographs:

. Position ofthe condyles in the glenoid fossa

. The range of antero-posterior movement ofthecondyles

. Areas ofbone destruction on condylar heads

Repriiled fiom Harng. Joen lannuccr andI -anra Jrnsen, De.t.l RadiosEphy: Prnripksr.d Techniques: Ihird iid'r,on. O 1000. wrth

l]emission lion lllsc\ie.

*** The main drawback ofa panoramic radiograph is that thcre is a loss ofimage detail /il r't ,ard to didgno.te

earl! carious lesions). Bite-wing x-rays are requircd for the diagnosis ofcarious lesions

In prnoramic radiography, both ihe film and x-ray tubeh€ad are conneoed and rotale sim haneously around

the patient during exposure. The movcmcnt ofthc film and the tubehead produces an image through the process

kno$'n as tomography. Rotational centers allow the image layer to confomr to the elliptical shape of the

dental arches. The numbcr and location of the rotational centers influence the size and shape of thc focaltrough.

The focrl trough is a three-dimensional curved zone in nhich structures are clearly demonstrated on a

panoranric radiograph: the structures located within thc focal trough appear reasonably well delined,whcreasstructures outside ofthc focal trough appear blurred.

The paticn! must b€ positioned according to the manuf'acturer's rccommendalions for the positioning ofthespine @erjictlr straighr.teeth (anterior teeth positioned in theloul trough indicated l)) the groove in the bite

b/o.i), midsagittaf plane (petpendidtlar to the lloor). FrankJort pl^ne lpurdllelto the Jloor),lips (.[ased on

bite blo(k)and. aon+re lpositioned on the nol oflhe noulh). \oter Ale^d apron must be placed on the patient

and all radiodense objects must be r€mov€d from the head and neck region.

Other indications fot a panoramic radiogr:rph:. Treatment planning /e spec ia lb' ort hodontic cases). E\ aluation ofanomalies

' Edenrulous patients /ptior to construding.lull aentrres). Patients thal are unable to !olerate inlm-oral x-rays

Important:The panoramic radiograph is tl.pically used to supplement bite-wing and periapical films and is not

a substiturc for infraoml films. The panoramic radiograph should not be used !o evaluatc caries, periodontal dis-

ease. and periapical lesions. Note: Apanoramic radiograph gives less detail and definition than periapical ra-

diographs due io intensifying screens, movement ofthe x-ray nlbe and film and increased object-film distance.

Oiherdisadvantages of a panoramic radiograph:

. Image quality: not as sharp due to intensilying screens

. Distonion ofimage due to increased objecl-film distancc

. Focal trough limitations:objects ofinterest lhat are located outside the focal trough are not seen

. Eouiomcnt cost

RADIOLOGY X-rays

Identify each structure numbered in the partial panoramic radiograph below?

''Counes) Dr Sruan C. $}ne. UCLA School of Denlislry "

68

Cop\righi (l 20l l-201 1 - Denral Dects

RADIOLOGY X-rays

A phenomenon caused by a relatively lower x-ray absorption onthe mesial or distal aspect ofteeth, between the edge of the enamel

and the adjacent crest of the alveolar ridge is called:

. Apical burnout

. Cen ical bumout

. Coronal burnout

. Root bumout

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Cotlrighr ill201l-10l2 - Denral Decks

l. Th€ opaque mass J Inferior concha

2. The opaqu€ line -+ Medial wall ofmaxillary sinus

3.Theopaqueline ) Posterior wall of zygomatic process ofmaxilla4. The opaqu€ line -+ Posterior wall ofmaxillary sinus

5, The opeque mass J Zygomatic arch

6. The opaque line -+ Hard palatc/floor of nasal fossa7. The opaque line + Floorof ms,(illarysinus8, The line ofcontrast -r Dorsum oftongue9. Th€ opaque line of contrasl r Inferior border of pterygoid plares

10. The verticNl lin€ ofcontrast -+ Posterior wall ofnasopharynxll. The opaque mass -) Soft palate

12. The line ofcontrast --) Dorsum oftongue13. The opaqu€ msss -+ Calcified stylo-hyoid ligament14, The opaque mass --) Ear lobe

15. The fine of contrast J Inferior border ofopposite mandible /dkd ghost image ofcontralaleral nalrdible)

The panoramic radiograph is excellent for third molar pathology as well as to observe the TMJ, rhe sinuses,

and siafogaphy irftic, is a lechnique used in ra.liology in h,hich a salivaD'gla d is.lilned a,l'ter an opaque

st$stance is injected into lrs 1/l/.r. A sialolith which is located in Wharton's duct, however, can best be viewed

by using a cross-sectional occlusal x-ray.

lmporlant:lfall metallic or radiodense obj ects (e.g-, ef'eglasses, edrings, necklaces, hairpins, removable

partfulde tures, complete dentures, orthodonti. retainers, hearing aids, antl napkin chains) are not removed

before the exposure ofa panoramic film, a ghost image results lhat obscures diagnostic information.

A ghost imege is a radiopaque artifact seen on a panoramic film that is produced when a mdiodense object is

penetrat€d twice by the x-ray beam. A ghost image rescmbles its real counterpart and is found on the oppo_

site side ofthe film; it appears indistinct, lrrger, and higher than its actual counterpan.

\ote:vie\\ the panoramic x-ray as ifyou were looking at the patient, with structures on the patient's right side

positioned on your left. In this way, the image is presented to you in the sam€ orientation as ihat ofthe peri-

rprcal and bite-wing x-rays, making ioterpretation more comfortable.

Remember: Intensiling screens are routinely used in panoramic radiography because they significantly re-

duce thc amount ofradiation rcquired for properly exposing o radiograph. Also, several manufacturers have

developed direct digital acquisition panoramic machines. Tle receptor on such a machine is either an array

of charged-coupled devices /CCD, ora film-sized photostimulable storage phosphor plate (PSPJ ratberlhanfilm.

Because of the relative diminished x-ray absorption, these arcas appcar relatively radioluc€nt with ill-de-fined margins.

It is causcd by the normal configuration of the affected teeth (lre c?r,le ntoefiamel junction). which results indecreased x-ray absomtion in those areas.

Importanl: These radiolucencies should be anticipated \r'hen viewing x-rays ofalmost any tooth and shouldnot be mistaken for a ca ous lesion.

Borh phoios reprinted from uaring. Joen lannucci lnd Laur.Jans.ni Denral RrdioSr.phy: Pnnciples and Techniques: ThirdEdnion. O 20{0, *ith penntrs,on fron El*!M

Limitations of radiogruphs:

. Radiographs provide a two-dimensional view ofa three-dim€nsional situstion

. Radiographs will lend to show less severe bone deshuction than is actually present

. Radiographs do not demonstrate the soft tissue to hard tissue relationships and therefore provide no in-formation about the depth ofperiodontal pockets. The earliest finc?ien, mild destructive lesions in bone do not caus€ sumcient alterations in density tobe detectable

RADIOLOGY X-rays

dentify this view? What are its indications? How is the patient positioned?

70

Cop]_rigbr a:01l -l0ll - Dental Decls

RADIOLOGY X-rays

A pati€nt is coming into your office for the first time. You can see obviouscarious lesions on the facial surfaces of multiple teeth when she talks. Due toher high caries activity, you take a full mouth series. Of these radiographs,

which are the most useful in detecting interproximal caries?

. Periapical radiographs

. Bitewing radiographs

. Occlusal radiographs

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Cop),riglrt (l 20ll l0ll Derr.l Decks

The lateral cephalometric x-ray must be compared with "normal" lateral radiographs

from an accepted norm. Linear and angular measurements are obtained utilizing knownanatomical landmarks in the lateral head radiography ofthe patient. These measurements

are then compared with those considered within normal limits and in that way enable the

orthodontist to assess aberrations in the dentition and iaw structures which result in mal-occlusion.

Analysis ofcephalometric radiographs is not limited to the hard structures such as boneand teeth, but also includes measurements ofsoit tissue structures such as the nose, lips,and solt tissue chin.

Superimposition in longitudinal cephalometric studies is generally on a reference planeand a registration point. This will best demonstrate the growth of structures farthestfrom the plane and the point. The most stable area from which to evaluate craniofacialsrowth is the anterior cranial base because of its early cessation of growth.

Cephalometrics are useful in assessing tooth-to-tooth, bone-to-bone, and tooth-to-bone re-lationships. Serial cephalometric films can show the amount and direction of growth.\ote: The lateral cephalometric is commonly used by orthodontists in evaluation ofgro$ th and development.

*** Thcsc x-rays show thc crowns ofboth N{ax. and Mand- tecth; not root apiccs.

Thc primart rerson for taking bitcwing radiographs is to dctcct interproximal cari€s. Thcy arc also uscful in moniloring thc progression ofperiodontal disease. Thcsc films sho\,crcslal bonc lcvcls as rvcil as intcrproximal arcasoi both archcs. 1n ordcr for thc fi lm 1o bc of diagnoslic usc. lhe qual ity of thc fo llo\r'ing must bc cxccl Icnl: dimcnsionalaccurac\', opcn contacts. and oplimum contrast and clarity olthc imagc.

\\ hcn taking bitewing radiographs, the film must bc placcd in cithcr! horizontal or vertical position and thc ccn-Iral ra\ should bc direclcd slightly do*,nward through the contacts and includc thc crowns ofthe maxillary andnandibuhr lcelh and thc ah,colarcrcsts. ltrtical bitewirgs providc morc pcriodontal infonnation, such as bory dc1-rcrs 3nd furcalion involvcmcnt. A izzy or indistinct imagc ofcrcstal bone is oftcn associatcd wjth carly pcriodon-Inrs. T\ o bitcwrngs arc usually taken on a child, one on cach sidc. lfthc child has primary dcntition only, numbcr"0"ilm1iu5cd Ifrhc child has mixcd dcnlition. numbcr"l film is utilizcd. Oncc thc individualhas sccond molars. twolo i'our numbcr "l fillnsarcconvcntionallyutilizcd.Ifusingfourfilms,onclllmimagcsthcprcmolararca.rvhilcthcorhL'. ima,:cs thc molar arca. Somctimcs nvo. long. numbcr "3 ' lilms are Dtilizcd (o,rc lbr ekh si./c/ instead oftwonunrL,cr ^: iilms on cach sidc. This practicc is nol rccommcnded duc to thc curvaturc ofrhc arch making it difiicultro opcn allcontactson onc film.

I Thc vcrtical angulation for bitcwing radiograpbs should b€ bchvccn +8 and +10 dcgrces.

\ots!. 2. Adjust horizontal angulation to dircct thc ccntral ray loward thc ccnlcr oflhc film.3. Alv€olar bone resorption is best demonstratcd on bitoving x,rays.

r',..-: ,l \trtical bitewing x-rals will show morc dveolar bone than traditional horizonlal bitewings.5. The larg€st intraoral film size is # "4".6. Thc strndard fllm sizc is # "2".7. Occlusal rldiographs display a relatively large scgment ofthc dcntal arch. May includc thc palatcor floor oflhe mouth and a rcasonablc cxlcnl ofcontiguous lateral strxctures.lJ. Conccm about radialion protcction is most imponant for children bccausc oftheir greater sensitiv-ity to irradiation. Thc bcst way to rcducc unncccssary cxposure is lbr thc dentist to lakc thc minimalnumber offilms rcquired lbr each patient and to usc thyroid shields,9. No incidcnccs havc bcen report€d ofdamagc to a fbtus from dcntal x rays. Howcvcr, radiographiccxamjnation tbr tbc prcEnant paticnt should bc consistcnt with the patienas necds.I0. widcning oi lhc pcriodontal ligamcnt space at (he apex ofthc intcrradicular bony cresl oflhc furc,a(ion is strong evidence that thc pcriodonral diseasc proccss involvcs thc firrcarion.I 1. The most common route for furcation involvcment of thc maxillarv oermancnt first molar isfiom thc mesial sidc.

. The image produced is less distorted

. The processing solutions are absorbed more easily

. The film has less sensitivity to radiation

. The film requires less radiation exposure to make an image

72Coplriglt O 201 I -20 l2 - Denral Decks

. The flrst 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

73Cop)'right O 20ll-2012 - Dental Decks

The use oflntensifying screens nequlres more rrdiation to expos€ a screenlilm and results in more radiation exposure for the patient

The x-ray film used in dentistry has four basic components:

L Film base: is a flexible piece ofpolyestcr plastic that rneasurcs 0.2 mm thick and is constructed towithstand hcat, moisnrre, and chenrical exposure. Thc primary purposc ofthe film base is to providea stable support for the delicate emulsion; it also provides strength.2. Adhesive layer: is a thin layer ofadhesive material that covers both sides ofthc film base. It scncsto attach the emulsion to thc basc.

3. Film emulsion: is a coatirg aftached to both sides ofthe fllm base by rhc adhesive layer to Sivethe film greater sensitivity to x-radiation. It is a homogeneous mixfurc ofgelatin and silver halidecrystals.

. Gelatin: is Llsed to suspcnd and cvcnly dispcrsc millions ofmicroscopic silver halide cwstalsover the film base. During film proccssing. thc gclatin serves to absorb thc processing solutionsand allows the chcmicals to react with the silver halide crystals.. Halide crystals: is a chemical component rhat is sensitive to radiation arld light. Silver bromideand silver iodide are two rypes of silver halide crystals fbund in film cmulsion; the typical emul-sion is 80 to 9970 silver bromide and I to loyo silver iodide.

4. Protective layeri is a thin, transparent coating plaoed over the emulsion. It sencs to protect thccmulsion surface from manipulation as wellas mcchanicaland processing damagc.

Den!al x-ray film packets have four basic components:

l. Intraoral x-ray film: is a double-emulsion typc of film; doublc-cmulsion film is used instead ofsingle-emulsion lilm bccausc it requires less mdiation exposure to prodlice an imagc. Tlc film packct

may conlain one film or two films. In one comer ofthe intraoral film, a small raiscd bump kno&n as

the identification dot is found. The raised bun]p is used to detormine film orientation.L Paper film rvrapperi within the film packet is a black paper protectivc shcet that covers the filmand shiclds thc film from light.,l. Lead foil sheet: is a single piece oflead foil that is found within the film packct. It is positioncd

bchind the l'ilm to shield the film from back-scattered /.recor./dr-1, radiation that rcsults in film fog.,+. outer package $ rapping: is a soft virlyl or papet wrapper that hermctically seals the film packet.

prorcctr\e black paper. and lcad foil shcct.

*** The use ol'inlensilying scrccns requires less radiation to expose a scrcen filn and rcsults in less

radiation exposure fbr the patient.

An intensifying screen is a dcvicc that transfers x-ray energy into visible lighti the visible light. intum. cxposcs thc screen lilm. Tlrcsc scrcens intensify the cflcct ofx-rays on thc liln With the usc

of intcnsilying screens, less radiation is required to cxposc a screen film, and the paticnt is exposed

to less radiation. Note: A screen film is an cxtraoral Iiln that requircs the use ofa scrccn lbr ex-

posure.

ln ertraoral radiography, a screen film is sandwiched bctwccn two intensifying screens and se-

cured in a cassette. An intensifying screen is a smooth plastic shcct coated with rninutc fl'torcs-ccnt crystals knou,n as phosphors. Wben exposed to x-rays. the phosphors lluoresce and emit

visible light in thc blue or green spcctrum; the emitted light thcn exposes the fiLn. Conventional

calcium tungstate screens have phosphors that cmit bjue light. Thc newer rare earth screens

have phosphors /r.rrall.t, rare-eafih elenents lanthatum a Ll gu./o/iiittrt.) that emit grccn lightImportant: Thc rarc earth screens arc more ellicient and requirc lcss x-ray exposurc and are con-

sidcrcd l'astcr.

L Duplicating film is a special typc of photographic film used to makc an idcnlical

\ot€ copy ol'an intraoral or extraoral radiograph. lt is used in a darkroom and is not exposed

to x-radiation.2. Film is advcrsely affected by hcat, humidily, and radiation and nrust bc storcd away

l'rom sources of radiation in tcmperatures of 50 to 70"F and with a rclative humiditylcvel of30 to 509/o.

3. Dental film should always be used bcforc thc expiration datc on the label.

4. A grid is composcd of a scries of thin lead strips embcddcd in a matcrial 1e g , p/as

ti4 that pcrmils the passage ofthc x-ray beam. It l'unctions to prevent scatter radia-tion from rcaching the film during exposurc. This decreases film fbg and increases the

contrast of the radiographic image.