RADIOLOGY

Which of the following occurs only at 70kVp or higher and accounts for a very small part of the x-rays produced in the dental x-ray machine? Compton scatter Coherent scatter General (Bremsstahlung) radiation Characteristic radiation

Characteristic radiation 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 . Gene.^l (Rrcnsstrfihnrg pholons via onc oft$o mcchanisns: (the 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 sudden 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 . Charactcristic radiationr is produced at thc anodc can be classificd as 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 K shcll .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 ].t,rp/l.krutoitklud(skesolitissu(softheheud,thehotrcsolth"skull,adtheteeth).NoteiSccondaryisless f Jn.rratrng lhan primary radialion. Coherent scaner is onc ofrhc intcracrions ofx-radialion rvith mattcr in which thc path b\ 'ran cr $ ith ou t a c h,lngc in cncrly. Cohcrcnt scattcr accounts for 8 o/" nunbcr ol pho- gcncral radiation li tl tal rd' ofan x-ray pholon is altcrcd 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 matl tcr 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?,'/ . Radioactiritr: is thc decav ratc ofradioactivc matcriai. The unit is thc 8c(quercl(Bq)

Which of the following positioning errors is the most likely cause ofthe reverse occlusal plane Chin tilted too far upward Chin tilted too far downward Head tumed slightly

Chin tilted too far upward Mandibular structures look narrower and maxillary structures look wider o "frotn"). Chin tilted too far downward: L Occlusal plane shows an excessive upward curve See figure trelow (look like a "big smile"). 2. Severe interproximal overlapping, anterior teeth appear very distofied.

A straight white border appears on the x-ray film. What is the most likely cause of this? Fixer cut-off Developer cut-off Overlapped films Static electricity

Developer cut-off

All of the following are radioresistant cells except Mature bone cells Muscle cells Nerve cells Epithelial cells

Epithelial cells 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, l hcorics ofradialim injury: . Thc direct theort: suggcsts lhal ccll damagc rcsuhs whcn ionizirg radialion directll hits crilical arcas. or tar- !.rs. q Jlhin $c ccll. Dircct altcration ofbiologic molccrlcs (i.c., (u bohrlrat$, 14il!, prct?int, DN 1/ occuts. Ap pro\rrnalcl) one-third ofdrc biologic cffccls ofx-ray cxposurc rcsult from dircct cllccts. . Th. indircct theort suggcsts that x-ray photons is is l|rc pritnd^' 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 radicalforDaiion 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 Biological cfTects ofradiation can bc classificd as: . i/drndgel of(issucs to thc dosc arr?ornr.) Stochastic cftcctsi occur as a direct function of dosri lhc probabilirr" ofradiation rc- ofoccurrcncc incrcascs \\'iih incrcasing ibnrrbcd dose: howeve., lhc sclcrity ofcliccls does not dcpcnd on thc magnitudc ofthc ahsorbcd dose. Exam- rlc\ ofsrochastic cficcls includc cancer . r.€.. trrro,-./ induction and genetic m|Itations (i.?., DNA tld"ng.') \ on sroc h a stic cffects /.le ter ti i\ ti( L'[e. ts)t arc somatic cficcts tha! havc a th reshold and i n creasc in scvcrily $ith increasing absorbcd dosc.Eranrplcs of nonslochaslic eilccts includc erylhcma. oral changes. loss of hair, cararact ibnnation, and dccrcascd fcriility. Importanl When comparcd silh slochastic eflects. nonstochastic cl- fi-cts require Iarger radiaiion doscs to seriously impair hcalth. \ot .rll cclls rcspond 1r) r:rdidlion in thc samc manncr In general, thc gre.tcr thc rate or potential for mitosis and thr morc immsture rhc cclls and tissues are, thc greatcr the sensitiritl or susccplibility to radiation. Cclls that arc radiosensitire includc blood cclls. immaturc rcproductivc cclls, epithelial cclls, and iroung bonc cclls. Thc ccll that rs most scositive to radiation is ths small lymphocyrc. Radioresistant cclls includc cclls ofbonc. musclc and ncrvc. Rsdiosensitive organs composcd ofradioscnsitive cells includc lymphoid tissucs. bone marro$,, tcstcs. and inlcstincs.

The number of electrons flowing per second is measured by kvp mA Time (sec) All of the above

mA

All of the following are components of inherent filtration EXCEPT one. Oil Unleaded glass window A leaded cone Tubehead seal

A leaded cone 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 of aluminum. . Added filtration: refers to the placement of aluminum disks in the path ofthe x-ray beam 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 the patient 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 total filtration 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 .:.r-olcq',' ily atrsorbed. (those produced ut lower kilovollages) are eas- '.:.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.

A tall heavy male comes in, and you conclude that his lower jaw is flared. You intend to expose radiographs at a higher kVp than for your average sized patient. Increasing the kilovoltage causes the resultant xray to have Decreased density More latitude A shorter scale of contrast A longer scale ofcontrast

A longer scale of contrast One effect ofa change in kilovoltage is a changc in the voltage reduces subject cont ast subject contrast fard penetrating power ofthe x-rays. Incrcasing kilo- (and the longer lhe scdle ofcontt?saJ; decreasing kilovoltagc incrcascs 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 ofelectrons. Conclusion: kilovoltage influences the x-ray be.m and radiograph by: . . . Altering contrast quality ([or patienls v,ilh thick jaws, Detcrmining the quality ofthe x-rays produced Detcnninillg the velocity ofthe electrons to the anodc iro"ase I ilovoltage) 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 bombarding 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 emulsion offastcr film contains larger crystals that produce less image sharpness, whcreas slowcr film contains 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.

Which of the following describes ionization? 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

A neutral atom that loses an electron and becomes a positive ion Matter is anything lhat occupics spacc and has mass; rlhcn mattcr is altcrcd, energy rcsulls. Thc indamcntal unil ofmaller is thc atom. Thc atom consists oal\vo parls: . A ccntral nucl€us: is composcd of protons and neutrons. Protons carry ncutrons cary no clcctrical chargc and arc slightly hcavicr than lhc proton . positiv€ clcctnc!l chargcs, !{hcrcas Orbitin8 electrons: arc t;ny negatively chargcd particlcs ihal havc vcry little mass; rn clcctron wcrghs approx- imatcly 1/1800 as much as a as orbits or shells prolon orncutron. Elcctrons rravcl around thc nuclcus in $cl1-dcllncd paths known 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 clcctron. 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'. with an incomplclcly Ullcd outcr shcll is clcctrically unbalanccd and aiicmpls 1o capturc an clcclton from an adjaccni js thc producrion ofions. or thc atom. An aton that gains or loscs an clcclron and bccomes electrically unbalarccd is known as an ion. Ionization proccss .rr4i.'.!/. An atorn 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 Thcrc arc lbur typcs: . llfectrons: can bc class classificd as beta dioactir. otonts) ot c thode rays ofmattcr that posscss mdss and lra!cl in straight lincs and al high spccds. (strcams particle. lldst nnring ?l.cttotlj eniuetl lon 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] \ x-r!!-s, UV rays. visiblc light. infrarcd light, radar $avcs, nicro$avcs, and radio wavcs. Thc (Q d,1tun l2orr) .haructcrizcs clcctromagnctic mdiations as discrctc bundics ofcncrg-v called quanta, Thc wave concept characterizes cleckomagnctic radialion as lvavcs and focuses on thc $avclcnglh. and frcqucncy.

Which of the 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 of a short cone

An increase in exposure time is necessary due to the use of a long cone 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 in irnage magnification and loss ofdefinition . * rh rennl\sl.n fon llscvier The source-film distance must also be increased to compensate for the image magnification and to make sure that oniy the most parallel rays uill be aimed at thetooth and the filn. Using a long cone (16 inclt tatEet-liln distonce) results in greater deflnition and less imase masnification.

name the two xray projection techniques used in dental radiography:

Bisecting technique Paralleling technique

A patient is coming into your office for the first time. You can see obvious carious lesions on the facial surfaces of multiple teeth when she talks. Due to her 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

Bitewing radiographs . *** Thc Thcsc x-rays show thc crowns ofboth N{ax. and Mand- tecth; not root apiccs. primart rerson for taking bitcwing radiographs is to dctcct interproximal cari€s. Thcy arc also uscful in mon iloring thc progression ofperiodontal disease. Thcsc films sho\,crcslal bonc lcvcls as rvcil as intcrproximal arcas oi 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: dimcnsional accurac\', 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 and nandibuhr lcelh and thc ah,colarcrcsts. ltrtical bitewirgs providc morc pcriodontal infonnation, such as bory dc 1-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. two lo i'our numbcr "l fillnsarcconvcntionallyutilizcd.Ifusingfourfilms,onclllmimagcsthcprcmolararca.rvhilcthc orhL'. ima,:cs thc molar arca. Somctimcs nvo. long. numbcr "3 ' lilms are Dtilizcd nunrL,cr ^: iilms on cach sidc. This practicc ro opcn allcontactson onc film. \ots!. r',..-: ,l (o,rc lbr ekh si./c/ instead oftwo is nol rccommcnded duc to thc curvaturc ofrhc arch making it difiicult I Thc vcrtical angulation for bitcwing radiograpbs should b€ bchvccn 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. +8 and +10 dcgrces. \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 palatc or floor oflhe mouth and a rcasonablc cxlcnl ofcontiguous lateral strxctures. is most imponant for children bccausc oftheir greater sensitivity to irradiation. Thc bcst way to rcducc unncccssary cxposure is lbr thc dentist to lakc thc minimal lJ. Conccm about radialion protcction number 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, radiographic cxamjnation tbr tbc prcEnant paticnt should bc consistcnt with the patienas necds. I0. widcning oi lhc pcriodontal ligamcnt space at a(ion is strong evidence that thc pcriodonral (he apex ofthc intcrradicular bony cresl oflhc furc, diseasc proccss involvcs thc firrcarion. I 1. The most common route for furcation involvcment of thc maxillarv oermancnt first molar is fiom thc mesial sidc.

The occlusal film is the film ofchoice for the evaluation ofperiodontal disease. The bisecting technique is the preferred periapical exposure method for the demonstration ofthe anatomic features of periodontal disease. 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

Both statements are false Dcntal radiogmphs play an intcgral rolc in thc asscssmcnl ofpc.iodontal discasc. Dcntal radiographs must bc used in conjunction $,ith a clinical cxaminadon. Thc pcriodontal discasc. Thc paralleling technique is lbc ofthc anatomic fcaturcs ofDcnodontal discasc. periapical radiograph is lhc film of choice for thc cvaluation of prcfcrrcd pcriapical €xposure method for thc dcmonstralion Thc radiographic appcarance ofhealthy alveolrr bone can be dcscribcd as tbllo$si . l,amin! dura: in hcalth. dle lamina dura around thc roots oflhe 'Alveolar (ccth appcars as a dense radiopaquc linc. crest: the normal alvcolar crcst is located approximatcly 1.5 to 2.0 mm rpical to the Cf,J ofadjacent poslcrior rcgions ollhc mouth. In the snterior rcgions, teeth. Thc sbrpe and dcnsily varies between thc antcrior and thc alvcolar crcst appears pointcd snd sharp and is normall) \'ery radiopNque' In the the alvcolar crest appears tlat, smooth, and parallel to a line betwcen adjacent CEJ's. Thc alvcolar crcst in thc postcrior ' 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 tal bonc loss rhc crcst ofthc buccal and lingual cortical . postcrior rcgions, plane parallel to the CEJs ofadjaccnt tccth.Note: ln horizon- 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 of thc ChJs in the arca ofthc involvcd tccth.

The most common oral problems occuring after radiation and chemotherapy are mucositis, infection, pain and bleeding The oral cavity is irradiated during the course of treating radiosensitive oral malignant tumors, usually SSC 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

Both statements are true

Prior to xray exposure the proper prescribing of dentl radaiographs and the use of proper equipment can mimimize the amount of radaiation the patient receives. Radiographs must be prescribed by the dentist based on the individual needs of the patient 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

Both statements are true \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 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 ergt and increasc the intensity ofthe x-ray beam. - \diust exposure time to achieve optimum density patient The den- produce a beam \\ ith morc crl- Important: nrA and exposure time are inversely relatcd. \lllen altering mA, the exposure time nust bc 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 ro l-15 degree angle ro ihe beam. primary x-ray beam by positioning lhemselves at a 90 \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!:!

Rectification is the conversion of AC to DC The dental xray tube acts as a self rectifier in that it changes AC into DC while producing xrays 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

Both statements are true llcctricity is thc encrgy that is uscd (o make x-rays. Electrical encrgv consists ofa flow ofclcctrons through a conductor; 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 which thc elcctrons flow in tl4o opposite dircctions. Rectitication is thc convcrsion otaltcmatiig currcnt lo dircct currenti thc 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- l'oltage is the meas rcment ofelectrical force thal causcs clcctrors lo movc fron a ncgativc peres or milliamperes /rr,.1/. produclion ofx-rays. bofi thc lmpcrage and volfagc can bc adjuslcd on thc contfil pancl pole to a posili\'e oDc. Voltagc is measured in volts or kilovolts /krr. Note: ID thc (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 lolrrvoltage or filamcnt circuil and a high-voltage circuit. Thc Iilament circuit uscs J to 5 volts. regulatcs thc llo\\, ofclcckical currcnt to thc filament ofthc x-ray tubc, and is controllcd by thc milliampere settings. Thc high-r'oltage circuit uscs 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. Transfbrncrs altcr thc \oltagc ofthc incoming eleckical currcnt and then routc lhc cleckical cncfgy to thc x-ray tubc. In lhc production 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 \ot{* I Thc milliamperage f/r,.|.) or tube current swltch on thc control panel regulates thc tempcr.tura of th€ filament and thus thc number ofelectrons emitted, 2.Tube current or mA controls thc numbcr ofphotons gclcratcd //,rlersitt ol the bru , but rot thc by an x ray tubc is dircctly proponional 1o lhc tubc currcnt /rr.,1/ cxposurc timc. beam cncrgy. Thc quantity of radiation produccd L Thc livp control sclccts voltage from diftcrenl levels on thc autotransformcr and applies it across Ihc primary 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 Iotts sencratel).

Posterior bitewing radiographs are the most useful x-ray projection for detecting 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 changes in 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

Both statements are true 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 darker than the unaliected portion (more radiolucen, and may be detected on radiographs. Note: The most useful adult 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 rhe fissures, 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)! occlusal 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 beneath a 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. interproximal 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. As caries 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 pulp chamber. 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 involves the buccal or lingxal surface appears as a small, circular radiolucent ar€a with sharp, well-d€fined borders. 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 include rhe e\posed roots ofthe mandibular premolar and molar areas. On a dental x-my, mot surl_ace caries appears ust below the CEJ. Early lesions may be difficull to detect on the dental x-ray. as r cupped-out or crater-shaped radioluc€ncy j 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.

A radiograph that exhibits areas of black and white is termed high contrast and is said to have a short contrast scalei a radiograph that exhibits many shad€s of gray is termed low contrast and is said to hiye a long contrast scale. To limit image rnagnification, th€ longest target-film distance and shortcst object-Iilm distance are used. The first statement is true; the second statement is false The first statement is false; the second statement is true Both statements are true Both statements are false

Both statements are true The intase magnification on a dental x_ray is influenced ' TarqeFfifm dist^nce (a!ro La\etl sorrLel,-/irm bv the: distdn.e) is thc distance bctween the source or-r-rays Uo.al ,. \pot on the tungsten target) and the film lr is dercrmincd by the length ofrhe posirion_indicating :c rtl:o i:-r.h ttlletl ptD). When a longer pID is used, more parallei ra1,s ir; rhc middle ofrhe x-ray bicanr :he object rather than thc diverging x_rays from the pcriphcry ::i :ir{eafilm distance result in less image magnillcetion. j.i.: ' l: more image magnification. object-film distanc€: is the distance berween_the olthe beam. As a resuft, a tonger ond a shortcr pID and target-tilo distance object bcing rrdiographed /r7€ r.ro1[/ and rhc x-ray :i T Thc closer rhe proximiry ofrhe toorh 10 rhc film. fie less ima-ge enligcml;t thcre _;tt bc on the film. \ decrease In objecl_frrn' distance rcsurts in a decrease in magnitication, an_d an increase in objec!firm dis_ :.::r:c:esulti ln an increas€ in imagc magnification. \ djstorted image does not have the same size and shape as the object being radiographed. A dimensional dirrortion ofa radiographic image is influenced by: 'object-film alignment:10 minimize dimensionaldistortion a\ is ofthc rooth. Foreshortening rcsultsfrom the film and should be parallel to the long excessive verti{:al angulation when the x-ray bcarn is perl ac:rdtcular to rhe film but not thc toorh. Elongation resolrs \rhen the x-ray bearn is oricnred at righl an_ gles to the tooth but not to thc film. ' \-rai besm: to minimiTe dimensional disro(ion, the x-ray beam musr be directed perpendicurar :oo:h and rhe film. scales ofcontrast: is rhe range :he appearance ' ofan x-ray: ot'usefur densitics secn on a dentar radiograph.Tu,o rcrms arc us€d ro dcscribe short-scal€ contrast: is an x-ray that shows only tno densities. areds olblack and white. short_scale :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 rrast results from the usc ofa higher kilovotage range. contrsst is thc difrercnce in degrccs 3r r-rav wrth many shades ofbrackncss bct*een adiacsnt areas on an x-ray. Low contrast describes ofgray and few areas ofblack and white. High contra;t describcs an x_ray with man! black and white areas and ferv shades ofqray.

The pattern of stored energy on an exposed film is termed the latent image; this image remains invisible until it undergoes processing A chemical solution known as the developer is used in the development process to chemically reduce ths exposed, energized silver halide crystals to black metallic silver. 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

Both statements are true The purpose oflilm processing is trlofoldi . . To conven thc latent (invisible) imagc on the film into a visible imagc (re.ferred to as ghost image) -der'eloping To presene the visiblc image so that it is pemanent and docs not disappear tiom the dental x-ray fi\ing process \\-hen a bcam ofphotons exposes an x-ray film, it chemically changes thc photosensitivc siher halide crystals in the film emulsion lldtent image). Important: Exposed arcas will becomc radiolucent, s hereas nonexposed areas will become radiopaque. \-rat.' developing solution contains the following: .,\ developing agent, such as hydroquinone, which is a chemical compound that is capablc ofchang- ing the exposed silvcr halide crystals to black mctallic silvcr. At the same time, it produces no appre- ciablc cffcct on thc unexposed silver halidc crystals in the emulsion. Gives detail to the x-ray image. Note: Elon, also kno\r'n as metal, acts quickly to produce a visible radiographic inage. It scncraics the many shadcs of gray. . An lntioxidant preserrativ€, for example. sodium sulfite, prevents the developer solution from ox- idizing in the presencc ofair. . An accelerator an alkalt (sodium carbonate) activates thc dcveloping agents and maintains the alkalinity ofthe developer at the correct value. It softens geiatin ofcmulsion. . A restrainer, such as potassium bromide, is added to dcvclopcrs to conffol the action ofthe dev- eloping agent so that it does not develop the uncxposcd silvcr halide crystals to prodrtce fog. Noter Thc optimal iemperature for thc dcvcloper solution is 68oF. Importanti The function ofdeveloping solution is to remove the ha)idc portion ofthc enposed, energized silver halide crystals to black rnctallic silver, this is refened to as reduction. The developer solu- tion softcns the film emulsion during this proccss. The function offixing solution is lo stop developmcnt and remove remaining unenergized, unexposed silvcr halide crystals ftom the film emulsion. The fixer hardens thc film emulsion during thc proccss. Film processing involves the following 5 steps:( I (rinsing ) proccss immerse film in developer (2) rinse film in water bath dilutes lhe de*loper slott,ing the development process br removing lhe alkali accelerllor, vnting neutralizution ofthe acidfxer) (3) immerse film in fixcr (4) q'ash the film.

Which type of digital image receptor is most common at this time? CID (Charge Injection Device) CMOS/APS (Complementarv Metal Oxide Seniconductor/Atiive Pixel Sensor) CCD (Charge-Coupled Device)

CCD (Charge-Coupled Device) . . A number ofcomponenls are required lbr direct digital image producrion. These components include an x-ray source, an elecffonic s€nsor, a digitil interface card, a computer with an analog-to-digilal con\efter lADC). a screen monitor, sofhvarc, and a KB intemal memory cquipped printer Tlpically, systcms are PC based *ith a 486 or higher proccssor, 640 .|.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 semiconductor active pixel sensot (CMOS-APS). The CCD is thc most common device used today.The CCD is a solid-state detcctor composed ofan anay of x-ray or light sensitive pixels on a pure silicon chip. A pixel or picture element consisN of a small electron well into which thc x-ray or light energy is deposited upon exposure. The individual CCD pixel size is ap- proxirnately 40I wilh thc latest versious in the 20F range. Thc rows ofpixels are rrranged in a matrix of 5I2 x 512 pixels. Charge coupling is a process whereby the numbcr ofclcctrons deposited in cach ferred from one well 1{) thc next in a sequential manner to r rcad-out amplifier filr imagc display on the monitor. There are tuo typcs ofdigital sensor array designs: area and lin€ar. Ar€r arrays are used tbr intraorll radiography, while linear arrays are used in extraor|l imsging. Area arrays are available iD sizes compara- blc to size 0, size l, and size 2 film. but the sensors are rigid and thickcr than radiographic film and have a smaller sensitive area for image capture. The sensor communicates with the computcr through all electrical cable. The complementary metal oxide s€miconductor active pix€l sensor is the latest development in direct digiral sensor technology. Externally. CMOS sertsors appcar idcntical to CCD dctectors but lhey use fa'ryo.t-.4PS/ an aclive pixel technology and are l€ss expensive to manufacturc. Thc APS technology rsduces by a factor of 100 the system power required to process the image conpared with the CCD. In addition. rhe APS system eliminates the nccd for charge transf'er and may improvc the reliabilify and lifespan ofthe sensor. In sum- mary, CMOS sensors have scvcral advantages including design integration, low power requrremenls. mimu_ facturabiliry, and low cost. Horvever, CMOS scnsors have more fired pattern noise and a smaller rctive area for image acquisition. The charge injection device or CID is another sensor technology used in dental digital radiograph). A CID is a silicon-bascd solid-state imaging rcceptor much like the CCD. Structurally, howevcr, the CID differs from the CCD. No computer is required to process lhe images. This system features a CID x-ray sensor. cord, and plug that are insc(cd into the light source on a camera platform; digital images are seen on the system moni- tor within seconds.

Of the following factors affecting magnification which does the operator NOT hve control over? Source-film distance Film-object distance Focal spot size Central ray direction Film parallelism

Focal spot size 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. They are 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 structures ll ill allorv. Figure #3. Thc bcnt tilm appcars distorted. t_igure #2. The film dcmonstrates a doublc cxposure. Figure #4. Movcmcnt rcsulls in a blurred image. 5. As far as is practical. keep the film parallel to the structure being radiographed.

A phenomenon caused by a relatively lower x-ray absorption on the mesial or distal aspect ofteeth, between the edge of the enamel and the adjacent crest of the alveolar ridge is called: . Apical burnout Cervical bumout Coronal burnout Root bumout

Cervical bumout 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 decreased x-ray absomtion in those areas. (lre c?r,le ntoefiamel junction). which results in Importanl: These radiolucencies should be anticipated \r'hen viewing x-rays ofalmost any tooth and should not be mistaken for a ca ous lesion. 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 information about the depth ofperiodontal pockets . The earliest finc?ien, mild destructive lesions in bone do not caus€ sumcient alterations in density to be detectable

All of the following are advantages of direct digital rdiography except one: 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 . . .

Sensor size Digital or electronic imaging has bccn availablc lbr morc lhan a dccadc. lt is cslinatcd that l0-207o ofdcntal practitioncrs usc digital imaging tcchnology in thcir dcntal ovcr thc ncxt fivc to tcn ycars practicc. It is anticipatcd thcsc numbers will steadily increasc as dcntistry continucs to movc from film bascd to digital inraging. Film-based imaging consists ofx-ray inieraction with clcctrons in thc lilm cmulsion. production ofa lalcnl inragc, and chcnrical proccssing that transfoffns thc latcnt imagc into a visible onc. As such, radiographic fi1m providcs a mcdium for rccording. displayiDg, and sloring diaeirrosiic infbrmation. Film- bascd inragcs arc dcscribcd as analog images. Analog imagcs arc charactcrizcd by continuous shadcs ofgray liom onc arca to the next betwccn thc cxtrcmcs ofblack and \lhitc. Each shadc ofgray has an optical dcltrsity rclatcd to lhe amount oflight that can pass through thc imagc ai a spccific silc. Film displays higher resolution than digilal rcccpfors wilh a rcsolving powcr ofabout l6lplmm (lnrcs puirs/nil/td"/"r'l. However, tilm is a rclativcly in- eflicicnt radiation deiector ard, thus, rcquircs rclatively high radiation cxposurc.Thc usc oircctangular collimation and thc highest speed lilm arc mcthods thal rcducc rudiation cxposurc. Chcmicals ar(} nccded to process the image and arc olicn drc sourcc of crrors and rctakcs. Thc finalresult is a fixcd nnagc that is dillicult lo manipulalc oncc cap- Digital imaging is thc rcsult of x-ray intcrrction *ith clectrons in clectronic sensor pirels fpi./ru e ?l?nents), cotrvcrsion 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 and thcy form words eight or morc bits in lcngth c^llcd bytes. Thc total nunrbcr ofpossible bylcs for 8-bit languagc is 28 = 256. Thc analog-tc.digital converter translbrms analog data into numcrical dala bascd on thc binary num- bcr systcm. Thc vohagc of thc output signal is nrcasurcd and assigncd a numbcr trom 0 fbld.t/ cording to thc intcnsity ofthc voltagc. Thcsc numcrical assignmcnts translatc into 256 shades of gra!. Thc human eyc is ablc to detect approximatcly 32 gray lcvcls. Dircct digital imaging has dislinct advantagcs ovcr lilnt in Icrms ofcxposurc rcduclion, climlnation ofprocessing chcmicals, inslanr or rcal timc imagc production (bi to 255 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

(?) is used to restrict the size and shape of the xray beam and to reduce patient exposure Discrimination Collimation Filtration Barrier placement

Collimation \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 regulations require that thc x-ray beam be collimated to a diameter of no more than 2.75 inches 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 tadiation. 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 thc radiation to surrounding tissues duc to x-ray bcam divcrgcncc. Remember: The x-ray beam consists ofmany different $'avelengths. The short w.velength 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- er'gl, rays have great penetrating powcr; long wavelength flox,erergl, 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.

Uses of the panoramic radiograph include all of the following EXCEPT one.Which one is the exception? Evaluation of impacted teeth Evaluation oferuption pattems and growth and development Diagnosis ofearly carious lesions Detection ofdiseases, lesions, and conditions ofthe Examination ofthe extent of large lesions Evaluation of trauma

Diagnosis ofearly carious 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 focal trough. 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,whcreas structures outside ofthc focal trough appear blurred. The paticn! must b€ positioned according to the manuf'acturer's rccommendalions for the positioning ofthe spine @erjictlr straighr.teeth (anterior b/o.i), midsagittaf plane (petpendidtlar to the teeth positioned in theloul trough indicated l)) the lloor). FrankJort pl^ne lpurdllelto the on bite blo(k)and. aon+re lpositioned on the nol oflhe noulh). \oter Ale^d apron must be 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\ aluation ofanomalies /e spec ia lb' ort hodontic cases) 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, periapical lesions. Note: Apanoramic radiograph gives less detail and definition than periapical radiographs due io intensifying screens, movement ofthe x-ray nlbe and film and increased object-film distance. ease. and 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

You have a patient who is extr€m€ly concerned about the radiation erposure he will receive when he gets intraoral pictures taken. You let him know that if he wants the least exposure then you will use: Digital radiography E-speed films F-speed films Panoramic instead of a full mouth series

Digital radiography One ofthe positive features ofdigital radiography is that it requires less radiation than con- ventional radiography, because the sensor is more sensitive to x-rays than dental frlm. Ex- posure times for digital radiography are from 507o to 80%o shorter than those lor E-speed film and about 50% shoter than those of F-sneed hlm. This translates into less radiation exposure for the patient. ; - .. L All direct and PSP digital radiography systems use a conventional dental x- liotce:' ray unit. The literature emphasizes that the x-ray unit must have the ability to ;;;ra:,,t: reduce exposure times to 0.01 seconds to reduce the likelihood of oversaturat- ing the sensor. 2. In digital radiography, a sensoq or small detector is placed inside the mouth ofthe patient to capture the radiographic image. The sensor is used instead of intraolal film. As in conventional radiography the x-ray beam is aimed to strike the sensor An electronic charge is produced on the surface of the sensori this electronic signal is digitized, or converted into "digital" fom.r. 3. Digital radiography systems are not limited to intraoral images; panoramic and cephalometric images rray also be obtained.

A method of obtaining digital image where the sensor captures the image and immedietly ctransfers it to a computer is Indirect digital imaging Direct digital imaging Storage phosphor imaging

Direct digital imaging Three methods of obtaining a digital image currently exist: direct digital imaging, indirect digital imaging, and storage phosphor imaging. . To produce a direct digital x-ray image, three components are necessary: an x-ray machine, an intraonl sensor, and a computer monitor The images are captured using a solid-state de- a complementary metal oxide semiconductor/active pixel sensor tector or sensor such as a charge-coupled device {CCDJ, (CMOS / AP.S/. or a charge injection device then transmits the image to a computer monitor Within seconds of exposing the sensor to x-rays. an image appears on the computer screen. Software is then used to enhance and store the image. . The essential components ofan indirect digital imaging system include a CCD camera and computer. In this method, an existing x-my film is "digitized" using a CCD camera. The CCD camera scans the image, digitizcs or converts the image, and then displays it on the computer momtor . A third method ofobtaining a digital image is storage phosphor imaging, a wireless dig- ital radiography system. In this system, a reusable imaging plate coated with phosphors is used instead of a sensor with a fiber optic cable. The plates are described as "wireless" because they are not connected via cable or wire to the computer. The plates are similar in every way to conventional intraorul film, including size, thickness, rigidity and placement. These plates store the energy from incoming x-rays, and are then placed in a scanning de- vice. The scanner stimulates the stored x-ray infonnation by subjecting the plate to a laser light. When the light strikes the phosphor material, energy is released as a light signal in an electronic waveform and is converted to a digital image by the computer. The image can not instantaneously be viewed on the monitor, but takes from 30 seconds to 5.5 ninutes de- pending upon the system and certain variables.

After the bombings of hiroshima, there were many patients who were in the radiation zone. Although they were exposed, symptoms such as hair loss didnt occur until days later. This period of time between rdiation exposure and the onset of symptoms is called the Latent period Period of cell injury Recovery period Cumulative effects

Latent period

After processing a film, you notice that is rppears too dark. What is the most likely caused of this problem? Inadequate development time Developer solution too cool Depleted developer solution Excessive developing time

Excessive developing time

Which ingredient of fixer solution functions to remove all underexposed and underdeveloped silver halide crystals from the film emulsion? Fixing agent Acidifier Hardening agent Preservative

Fixing agent X-.ay fixing solrtion conlains thc following: . Thc fixing agent f. /e.7rirg ager, is madc upofsodium thiosulfate orammonium thiosulfate and is commonly called hwo. The purposc ofthc fixing agcnt is to remove or clear all unerposed and underd€veloped silver halide crystrls liom thc film emulsion. Thc chcmical "clcars" thc film so that thc black silver rmagc the dcvclopcr bccomcs distinctly pcrccptiblc. whcn the film is impropcrly cicarcd, the rcmaining unexposed sil- vcr halide crystals darkcn upon exposure to light and obscure ahe imagc. . An antioxidant preservative, thc samc prcservativc uscd in thc dcvclopcr solution. sodium sulfite, is also uscd in the fixer solution. lt prevcnts thc chcmical dctcrioration ofthc fixing aSent- . An acidifier such as acetic acid or sulfuric acid is uscd to ncufalizc thc alkaline dcvclopcr Any unncutralizcd alkali may cause the uncxposcd crltals to continue to dcvclop in thc fixcr It also produccs thc neccssary acidic cn- vironmcnt required by lhc fixing agcnt. . Thc hardener agcnt used is potassium alum, lt shrinks and hardcns thc gclatin in lhc film cmulsio affcr it has been softcned by the accclcmtor in thc developing lolution. It shoflcns drying timc and protccts the cmulsion fionr l'ollowing lixation, a walcr bath is used to wash the tilm.This stcp is ncccssary to thoroughly rcmovc all cxccss chcmicAls (i.e., thnsufaE ions atd sil\,er thiosurli?re.rnpldi€r, from thc cmulsio . Thc final step in rhc film proccssing is the drying ofthc films. Iiilms nay be air-dricd at room Ienpcraturc in a dus! lrec area or placcd in a hcated drying cabinct. Ntanual processing is a simplc mcthod uscd to dcvclop, rinsc, fix, and wash dcntal x_ray films lhc csscntial piecc ofcquipmcnt rcquircd for manual proccssing is a proccssing lank, which is containcr dividcd into compartmcnts for thc dcvclopcr solution, walcr bath. and fixcr solution. Notel Thc optimum tcmpcraturc lbr ihc devclopc. is bct$ccn 68'F and ?0'F, tnical timc in developer is 5 minutcs. nnsc lor 30 seconds, placc in fixcr solution for l0 minutcs and wash for at lcast l0 minulcs and dry Automatic processing is anothcr simplc way to proccss dental x-ray fillll. Thc essential piccc ofcquipmcnt required for automatic processing is thc automatic processor, which automalcs all film proccssing steps .- . 1. Fixing timc is always at lcast twice as long as thc dcvcloping limc. j\ote* ''&r! per gallon of solution per dr]. 2. wirh both automalic and manual processing,8 oz. offrcsh dcvclopcr and fixcr should bc added 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.

A periapical of the left maxillary canine shows an elongated tooth which does not capture the apex of the canine while taking the periapical of the left maxillary canine, the operator had an: lncorrect horizontal angulation Incorrect vertical angulation Either ofthe above

Incorrect vertical angulation 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-anddown (vertical) and elongation planc. lmportant: Foreshortening (See /Seefgzrc fgurc #2) refers to an elongated image. Both are #1) rcfcrs to a shortcncd imagc produced by an incorrect ver- tical angulation. Excessive vertical angulation causes foreshortened images, while insullicient vcrtical angulation causcs clongatcd images. Horizontal angulation is maintaining the central ray at 0 degrees as the tube is n]oved around the head. 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 ray should be perpendicular to the mean antcropostcrior plane ofthe teeth being x-rayed. Important: lncorect horizontal tube angulation causes overlapping po,;ed on eaclt otlrcr). (teeth images are superim- Tle central ray is said to be at 0 degrees when the x-ray tube is adjusted so that the central ray is parallel 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.

A patient has a large SCC of lateral border of the tongue which is going to require radical neck dissection. Prophylactic extractions will be done in order to prevent which of the following? Osteoradionecrosis Bisphosphonate related Osteonecrosis of the jaw Rampant periodontal disease None of the above

Osteoradionecrosis Thc clinical complications that occur in bone following inadiation relate to lhe marked reduction in vascularity possibilily that inf'eclion and nccrosis ofbone will resuh in a nonhealing \lound if the orrl mucous rtembrancs aQlredd] and the consequcnt d.crcased capacity oflhc bonc to resist infection. Therc is a strong r|rddidli.r,l breaks do\,'n. This may occur spontaneously or fbllowing a loolh extraclion or denture sore and is kno\\ n as osteorrdionecrosis, Osteoradionecrosis is morc common in the mandible than in thc maxilla. becausc oflhe richer vascular supplv to the nra\illa and lhc fact that lhe nandible is morc frequently inadialcd. Thc mosl conlmon faclors precipitating osleoradionecrosis arc pre- and pos!ilradialion extractions lnd periodonta] disease. Note: Damage to lhe blood lessels /d-f.)ppor_erl /o nen,es, ius(le, eL., predisposes a patient 1o thc developmen! of osteoradionecrosis Histopathologically, ihe I Hs ofORN arc hypocellu)ar bone. hypovascular tis\ue, and h),poxic tissue and bone To prerent osleoradionccrosis: extract all hopelcss tceth three weeks prior to bcadineck radiation trcattncnl, If cxrracting afler radiolherupy, lhc use ofsystemic antibiolics is recommended. Sonc sludies suggesl hypeftaric oxygcn rrealmcnls bcfore and afler lrcaimcnt to reduce the risk ofosleoradionecrosis flrr:r 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 periapical x-ray below appears distorted, What is the most likely cause of this? Exposure to secondary radiation Cone cutting X-ray arm drifted Overbent film Patient had glasses on

Overbent film 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 s\ve /too long), incorrect kVp (too . Double exposure: hlm rvas used twice . higlt). See figure #2 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 radiation

Which of the following focuses electrons into a narrow beam and directs the beam across the tube towards the tungsten target of the anode? Copper stem Filament Vacuum Molybdenum cup

Molybdenum cup X'.a\s arc gencratcd whcn a srrcam ot clcctrons (\'hkh are prod ed hr rre /i/drrertl tra\cls from thc calhodc to lhc 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 \oles -il L Thc sizc of thc fbcal spol directly influences thc x-nty dcfinition: thc larger the focal spot. thc greai€r rhe loss nfdcfin:(ion and r\c greater lhe lo\r oI rhc : Copper rs uscd Io hous!' thc anodc bccausc it is a tungstcn krgct and rcducing thc risk ofrnclring lhc largct

When the PID length is changed from 8 to 16 inches the source to film distance is doubled. According to the inverse square law the resulatant beam is One-fourth as intense One-eighth as intense Four times as intense Eight times as intense

One-fourth as intense The Inverse Square Law is stated as follows: The intensity ofan x-ray beam at a given point is 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 marked effect on beam intensity. The intensity of an x-ray beam at a given point is dependent on the distance ofthe measuring device from the focal spot. The reason for this decrease in intensity il rs ,nversely proportional) is that the x-ray beam spreads out as it moves from the source. The beam is less intense. frtr,l, 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 reduced 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 "spread (approxinateb'2 mm) placed n the path ofthe x-ray beam 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 the penetrating quality of the beam. The higher the half-value layel the more penetrating the beam.

Which of the following converts electrons to xrays? Positive anode Negative anode Positive cathode Negative cathode

Positive anode Thc x-ray tubehead is a tighlly scalcd. hcavy mctal housing that conlains thc x-ray tubc thal produccs dcnlal x-ray!. ofthc tubchcad includc the following: . Thc componen! pans Ntetal housing: is thc mctal body oflhc tubchcad lhat sunounds ihc x'ray tubc and transfonncrs and is iillcd \lith oil: 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 by absorbing thc heat crcalcd by thc 'Tubeherd produclion seal: or thc aluminum or lcadcd glass ofx-rays covcring thc tubchcad that pcrmits lhc cxil ofx-rays lionl thc tubchcadt 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$ksl shccts of0.5-mn thick alurninum placcd in thc path ofthc x-ray bcaml they filtcr out non' pcnctrating, longcr wavclcngth x-mys . Lead collimator: is a lcad platc wilb a central holc that fits dirccily ovcr thc opcning ofdrc mcial housing whcrc thc x-rays cxit; ii rcstricts lhc sizc ofthe x-ray beam . Position-indic:rting device (PID)r is an opcn'cndcd. lcad-lincd cylindcr that cxtends from thc opcning ofthc mctal housing ofthc tubchcad; it aims and shapcs thc x-ray beam Thc x-rar" tube is thc hcarl ofthc x-ray gcncrating systcm. It consists ofa lead-glass housing, a negative cathode, and a positive rnode. Electrons arc produccd in thc cathode and acceleratcd toward thc anodc; thc anode con\cr(s lhc electrons into x-ravs. . l,eaded-glass housing: is a leaded-glass vacumm tubc that prevents x-rays liom cscaping in all dircclions. Onc ccnlral arca ofthe ieadcd-glass tubc has a that pcrmils lhc x-ray bcam lo cxit the lubc aDd directs lhe x-ray bcan toward thc aluminum disks, collimator and PID. "window" . Cathodc /r/ r€gdrtrt, r1e. rftr.L,/: consists ofa tungsten wire lilament in a cup-shapcd holdct nradc of molyb- denum. The purposc oflhc calhodc is to supply the electrons nccsssary to gcncralc duced in rhc nega(i!e cathodc arc accclcratcd loward thc . . ovcrhcating x-rays. Thc clcclrons pro posjlivc anodc. Thc cathode includcs thc ibllorling: Tungsten filament: is a coilcd wirc madc oftungstcn. which produccs .llollbdenum clcctrons \vhcn heatcd cup: tbcuscs thc clcctrons into a narro$,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 . Copper stem: funclions to dissipatc thc hcat away from thc tungstcn largct

Equivalent dose is expressed as REM RAD Roentgen Qy

REM The rad (radiotion absorbed dose) is a unit used to measure a quantity called absorbed dose. This relates to the amount ofenergy actually absorbed in some material, and is used for any type ofradiation and any material. One rad is defined as the absorption of 100 ergs per gram of material. The unit rad can be used for any type of radiation, but it does not describe the biological effects ofthe different radiations. The rem (roentgen equivalent man) is a unit used to derive a quantity called equivalent dose. This relates the absorbed dose in human tissue to the effective biological damage ofthe radiation. Not all radiation has the same biological effect, even for the same amount ofabsorbed dose. Equivalent dose is often expressed in terms ofthousandths ofa rem, or mrem. To detenrine equivalent dose (rent),yon multiply absorbed dose ity factor (QF) that is unique to the type ofincident radiation. The QF (rad) by a qual- is a t'actor used lor radiation protection purposes that accounts for the exposure effects of different types of radiation. For x-rays QF : 1. The roentgen is a unit used to measure a quantity called exposure. This can only be used to describe an amount of gamma and x-rays, and only in air Exposure is a measure ofradiation quantity, the capacity ofthe radiation to ionize air. Equivalent dose is used to compare the biologic efl'ects ofdifferent types ofradiation to a tissue or organ. Effectiye dose is used to estimate the risk in humans. Gra\ /Gr, : 100 rad. js a unit lor measuring absorbed dose; the Sl unit equivalent to the rad: I gray

Ashley has taken 3 panoramic xrays today. During the day as she developed each film, she noticed the films getting lighter and lighter. What needs to be done so this problem gets corrected Decrease the temperature of the developing solution Increase the temperature of the developing solution Replenish the developing solution Increase the mA setting Increase the kvp setting

Replenish the developing solution As thc dcvcloping solution g€ts weaker, the films will get lighter. Both the devcloping and fixing solutions should be replenished on a daily basis Remember: with both automatic and manual 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 factors 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 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, #?or {ixer cut-offfs/rdight hlack border, Seetigure #3). 4. Light spots on film may result from contact with thc fixer beforc processing #1). 5. Developer spots appear dark or black (See Jigure #5).

A small town dentist gets a phone call late on Saturday night from a patient of record. The patient has been in a bar fight where he was punched just right eye. The dentist suspects a zygomatic complex fracture. Which ofthe following projections is best for this examination? Waters projection Submentovertex projection Reverse Towne projection Lateral cephalometric projection

Submentovertex projection For this projection the neck is maximally extended and the film cassette touches the top ofthe head. The x-ray beam enters the head under the chin (near the mental tubercle of the 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.

A herringbone or diamond effect will appear on the processed film when The film is bent The film is placed backwards in the mouth An improper vertical angulation is used An improper horizontal angulation is used

The film is placed backwards in the mouth

One advantage of a film with an emulsion coating on both sides (double emulsion film) is that: 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

The film requires less radiation exposure to make an image 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 to withstand hcat, moisnrre, and chenrical exposure. Thc primary purposc ofthe film base is to provide a 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 scncs to attach the emulsion to thc basc. 3. Film emulsion: is a coatirg aftached to both sides ofthe fllm base by rhc adhesive layer to Sive the film greater sensitivity to x-radiation. It is a homogeneous mixfurc ofgelatin and silver halide crystals. . Gelatin: is Llsed to suspcnd and cvcnly dispcrsc millions ofmicroscopic silver halide cwstals over the film base. During film proccssing. thc gclatin serves to absorb thc processing solutions and allows the chcmicals to react with the silver halide crystals. . Halide crystals: is a chemical component rhat is sensitive to radiation arld light. Silver bromide and silver iodide are two rypes of silver halide crystals fbund in film cmulsion; the typical emulsion 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 thc cmulsion 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 of single-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 film and 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.

Man has always been exposed to natural radiation arising from the earth as well as from outside the earth. The radiation we receive from outer space is called terrestrial radiation or terrestrial rays. We also 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 false The first statement is false; the second statement is true Both statements are true Both statements are false

The first statement is false; the second statement is true *** 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 population. - 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 diagnosis and treatmcnr (11%, of rJhich dental x-ray examinations are rcspottsible alerage a ual t-ru! diagnosrt etporrle/, consumer and industnal products and sources d9'o/, for and nuclear medicine 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 maximum permissibl€ dose /MPD./ fNCRP) -medical only 2,5% ofthk is defined by the N^tional Council on Radiation Protection and Measurements as the maximum dose equivalent that a body is pelmifted to receive in a specific period oftime. The MPD is the dose ofradiation that the body can endure with little or no injury Important: The yearly MPD for 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 patients during the radiographic examination. The philosophy ofradiation protection currently used in practice today is based on the principles ofALAR{ of ofllce perconnel and (As Low As Reasonabb' Ac hierah le ). Note: The primary risk from dental radiogEphy is radiation-induced cancer. Although the risk involved with dental radiography is extremely small in comparison with other risks such as smoking or consumption of fatty foods, no brsis exists to assume that it is zero.

Intensyfying screens transform xray energy into visible light which in turn exposes the screen film The use oflntensifying screens nequlres more rrdiation to expos€ a screen lilm and results in more radiation exposure for the patient 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

The flrst statement is true; the second statement is false *** 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. in tum. 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 exposure. 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 light Important: 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 humidity lcvel 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 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.

The two radiographs below were taken with the buccal object rule in mind, 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

The object lies lingual to the first molar The buccaf obj€ct rule ject's ject falso called the tube shili technique) is used to determine an ob- spatial position within the jaws. This technique utilizes two radiographs of an ob- 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 in question 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, it is on the lingual aspect. lfit appears to move in the opposite direction as the x-ray tube, it is on the buccal aspect.

On the way out ofyour dental chair, the patient gets up too fast, feels dizy, and falls chin first onto your tiled operatory floor. Suspecting bilrteral subcondylar fractures, which of the following proiections would best allow for this examination? Waters projection Transcranial projection Townes projection Submentovertex projection

Townes projection The patient lies on his back with the film under his head. The x-ray source is from the front, 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 condylar neck region in the straight postero-anterior projection often makes interpretation diffi- cult. The Townes projection eliminates this superimposition, thus giving good visualization of lhe condvlar area and rami. Towne projection" is used to identify fractures of the condylar neck and ramus area. Note: The "reverse The following can be demonstrated on conventional TMJ radiographs: . . . *** Position ofthe condyles in the glenoid fossa The range of antero-posterior movement ofthe condyles Areas ofbone destruction on condylar heads

At the dental clinic, an emergency patient arrives complaining of swelling associated with a carious upper left molar. The patient complains of "stuffiness'and feels more so when she bends over to pick up stuff. The dental clinic is equipped with conventional radiography. Which of the following projections is best for the examination ofthe rnaxillary sinus? Lateral jaw projection Reverse Towne projection Waters projection Submentovertex projection

Waters projection 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 ofthe orbits. 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 of conical 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 of mid-facial fractures.

The density of a radiograph is influenced by all of the following except one kVp mA Exposure time Whether the film is a one-film packet or a two-film packet

Whether the film is a one-film packet or a two-film packet 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 rcsultant 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 of D = log l0 (lo.l1) thc 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. Bcyond thcsc cxtrcmcs thc imagc is usually too light or 1oo dark to bc diagnoslically uscful. Not€: ln a \\,cll-cxposcd and proccsscd 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 tcmocralurc 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 inrpul\c occurs clcry 1160 ofa second; thcretbrc, 60 impulscs occur in I second. Notc. pulscs rathcr than a continuous skcam. Onc L Radiographic speed is thc amounl ofradialion rcquircd 1o prodlcc a radiographic tilm ofslandard dcnsir,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. thc smallcr 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. marks 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 closc logcthcr.

After developing her bitewings, a dentist realizes that she has too much overlap between 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 film

lncorrect horizontal angulation 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 not aimed at the center ofthe film. See figure #l . Herringbone effect: zigzagged pattern appears on the film backwards in the mouth. . - - the beam was the film was placed 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 of film -due to incorrect horizontal angulation penditular to the curvature of the qrch (the central x-ray was not directed perp- and through the conldclt.

Which of the folllowing is Not a disadvaanatage of the bisecting technique? 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 true reproduction of the object May not be able to judge the correct alveolar bone height

lncreased exposure time *** 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 ifthey have 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 film and 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 side for the two imaginary equal tdangles. . creates two equal angles and provides a common The central ray is positioned perpendicular to the imaginary bisector