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Projection of central ray. Direct the central ray throughthe mesial contact of the canine without regard to thedistal contact.

Point of entry. The point of entry is nearly perpendicular to the ala of the nose, over theposition of the canine, and about 3 cm above the inferior border of the mandible.

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Image field. The radiograph of this area should show the distal half of the canine, thetwo premolars, and the first molar.

Film placement. Bring the no. 2 film into the mouthwith its plane nearly horizontal. Rotate the lead edge tothe floor of the mouth between the tongue and the teethwith the anterior border near the midline of the canine.Place the film away from the teeth to position it in thedeeper portion of the mouth. Placing the film toward themidline also provides more room for the anterior borderof the film in the curvature of the jaw as it sweeps ante-riorly. Prevent the anterior border from contacting thevery sensitive attached gingiva on the lingual surface ofthe mandible.

Projection of central ray. Position the film-holdinginstrument to project the central ray through the secondpremolar-molar area. The vertical angulation should besmall, nearly parallel with the occlusal plane, to keep thefilm as nearly parallel with the long axis of the teeth aspossible. Adjust the horizontal angulation and the place-ment of the film-holding device to direct the beamthrough the premolar contact points.

andPoint of entry. The point of entry of theabout 3 cm above the inferior border

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Image field. The radiograph of this region should include the distal half of the secondpremolar and the three mandibular permanent molars. In the case of an impacted thirdmolar or a pathologic condition distal to the third molar, a distal oblique molar projectionor even additional extraoral projections (panoramic or lateral ramus) may be required todemonstrate the area adequately. If the molar area is edentulous, place the film far enoughposterior to include the retromolar area in the examination.

Film placement. Place the no. 2 film in the mouth withits plane nearly horizontal. Rotate the inferior edge down-ward beneath the lateral border of the tongue, displac-ing it medially. The anterior edge of the film should be atabout the middle of the second premolar. Orient thelateral groove of the bite-block used with the Precisioninstrument parallel with the mean plane of the molars'buccal surfaces. In most cases the tongue forces the filmnear the alveolar process and molars, aligning it parallelwith the long axis of the teeth and the line of occlusion.

Projection of central ray. Proper placement of theholding instrument directs the central ray through thesecond molar. Adjust the horizontal angulation to projectthe beam through the contact areas. Because of the slightlingual inclination of the molars, the central ray mayhave some slight positive angulation (approximately 8

degrees).

Point of entry. Direct the point of entry of the central ray below the outer canthus of theeye about 3 cm above the inferior border of the mandible.

Projection of central ray. The position of the holdinginstrument projects the central ray from a more posterioraspect through the third molar area to the film.

Point of entry. Orient the point of entry about 3 cm above the antegonial notch on theinferior border of the mandible, in line with the anterior border of the ramus.

148 PART IV IMAGING PRINCIPLES AND TECHNIQUES

Alternatively, the anterior region is often covered byusing a no. 2 film behind the central incisors in themidline and one lingual to each canine. The film ispositioned behind the area of interest, with the apicalend against the mucosa on the lingual or palatalsurface. The occlusal or incisal edge is oriented againstthe teeth with an edge of the film extending just beyondthe teeth. If necessary for the patient's comfort, theanterior corner of the film can be softened by bendingit before it is placed against the mucosa. Care must betaken not to bend the film excessively because this mayresult (in considerable image distortion and pressuredefects in the emulsion that are apparent on theprocessed film.

directs the central ray perpendicular to the bisectingplane varies with the individual's anatomy. Severalmeasurements can be used as a general guide whenthe occlusal plane is oriented parallel with the floor(Box 8-2).

BITEWING EXAMINATIONS

Bitewing (also called interproximal) radiographs includethe crowns of the maxillary and mandibular teeth andthe alveolar crest on the same film. Bitewing filmsare particularly valuable for detecting interproximalcaries in the early stages of development before itbecomes clinically apparent. Because of the horizontalangle of the x-ray beam, these radiographs also mayreveal secondary caries below restorations that mayescape recognition in the periapical views. Bitewingprojections are also useful for evaluating the peri-odontal condition. They provide a good perspective ofthe alveolar bone crest, and changes in bone heightcan be assessed accurately through comparison withthe adjacent teeth. In addition, because of the angle ofprojection directly through the interproximal spaces,the bitewing film is especially effective and useful fordetecting calculus deposits in interproximal areas.(Because of its relatively low radiodensity, calculus isbetter visualized on radiographs made with reducedexposure.) The long axis of bitewing films usuallyare oriented horizontally but may be oriented

vertically.

Angulation of the Tube HeadHorizontal angulation. When a film-holding devicewith a beam-localizing ring is used, the instrument ispositioned horizontally so that when the tube is alignedwith the ring, the central ray is directed through thecontacts in the region being examined. If the film-holding device does not have a beam-localizing feature,the tube is pointed so as to direct the central raythrough the contacts. In this situation the radiationbeam is also centered on the film. This angulationusually is at right angles (in the horizontal projection)to the buccal or facial surfaces of the teeth in eachregIon.

Vertical angulation. In practice, the clinician's goal isto aim the central ray of the x-ray beam at right anglesto a plane bisecting the angle between the film andthe long axis of the tooth. This principle works wellwith flat, two-dimensional structures, but teeth thathave depth or are multirooted show evidence of dis-tortion. Excessive vertical angulation results in fore-shortening of the image, whereas insufficient verticalangulation results in image elongation; The angle that

Horizontal Bitewing FilmsTo obtain the desirable characteristics of the bitewingexamination described above, the beam is carefullyaligned between the teeth and parallel with the occlusalplane. As the film or film-holding instrument is placedin the mouth, the portion of the mandibular quadrantthat is being radiographed is in view. The position ofthe teeth in this segment of the mandibular quadrantis evaluated, and the beam is directed through the con-tacts. Some difference may exist in the curvature of themandibular and maxillary arches. However, when thex-ray beam is accurately directed through the mandibu-lar premolar contacts, overlapping is minimal or absentin the maxillary premolar segment. A few degrees of tol-erance are available in the horizontal angulation beforeoverlapping becomes critical. The contact between themaxillary first and second molars often is angled a fewdegrees more anteriorly than between the mandibularfirst and second molars. The aiming cylinder is posi-tioned about +10 degrees to project the beam parallelwith the occlusal plane (occlusal dentinoenamel junc-tion [DE]]). This minimizes overlapping of the oppos-ing cusps onto the occlusal surface and thus improves

PROJECTION

IncisorsCaninesPremolarsMolars

MAXILLA

+40 degrees+45 degrees+30 degrees+20 degrees

MANDIBLE

-15 degrees

-20 degrees

-10 degrees

-5 degrees

'wnen tne OCClusal plane IS orlentea parallel with the floor.NOTE: With a positive (+) angulation the aiming tube is pointed downward,and with a negative (-) angulation it is pointed upward.

,149INTRAORAL RADIOGRAPHIC EXAMINATIONSCHAPTER 8

FIG. 8-6 Film-holding device for bitewing radiographs.Note the external localizing ring, which is used to positionthe aiming tube of the x-ray machine to ensure that theentire film is in the x-ray beam.

FIG. 8-7 Bitewing loop, showing the tab that the patientbites on to support the film during exposure.

FIG.. 8-8 A set of vertical bitewings. Orienting the length ot the tllm vertically Increasesthe likelihood that even in patients with extensive alveolar bone loss, the residual alveolarcrests in the maxilla and the mandible will be recorded on the radiograph.

1 \VO postenor bIteWIng VIews, a premOlar and amolar, are recommended for each quadrant. However,for children 12 years old or younger, one bitewing film(no. 2 film) usually suffices. The premolar projectionshould include the distal half of the canines and thecrowns of the premolars. Because the mandibularcanines usually are more mesial than the maxillarycanines, the mandibular canine is used as the guide forplacement of the premolar bitewing film. The molarbitewing film is placed 1 or 2 mm beyond the most dis-tally erupted molar (maxillary or mandibular).

the probability of detecting early occlusa1leslons at the

DE].The XCP bitewing instrument has an external guide

ring for positioning the tube head. This reduces thepossibility of cone cutting the film (Fig. 8-6). To posi-tion the XCP instrument properly, the guide bar isplaced parallel with the direction of the beam thatopens the contacts of the dentition being examined.

A film fitted with a bitewing tab or loop may be usedinstead of a holding device (Fig. 8-7). The film is placedin a comfortable position lingual to the teeth to beexamined. The aiming cylinder is oriented in the pre-determined direction that passes the x-ray beamthrough the interproximal spaces. To help preventcone cutting, the central ray is directed toward thecenter of the bitewing tab, which protrudes to thebuccal side. The beam is angulated +7 to +10 degreesvertically to preclude overlap of the cusps onto theocclusal surface.

Vertical ISltewlng HlmsVertical bitewing films usually are used when the patienthas moderate to extensive alveolar bone loss. Orientingthe length of the film vertically increases the likelihoodthat the residual alveolar crests in the maxilla andthe mandible will be recorded on the radiograph(Fig. 8-8). The principles for positioning the film andorienting the x-ray beam are otherwise the same as forhorizontal bitewing projections.

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Image field. This projection should cover the distal portion of the mandibular canineanteriorly and show equally the crowns of the maxillary and mandibular premolar teeth.

Film placement. Place the film between the tongue andthe teeth, far enough from the lingual surface of the teethto prevent interference by the palate on closing and par-allel to the long axes of the teeth. The anterior border ofthe film should extend beyond the contact area betweenthe mandibular canine and first premolar. Hold the filmin place until the patient's mouth is completely closed.Holding the film while closing prevents it from being

displaced distally.

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Projection of central ray. Adjust the horizontal angula-tion of the cone to project the central ray to the centerof the film through the premolar contact areas. To com-pensate for the slight inclination of the film against thepalatal mucosa, the vertical angulation should be about+5 degrees. (In the drawing, the mandibular teeth are indashed lines.)

Point of entry. Identify the point of entry bythe central ray will enter the line of ~,,'. .r.~~ ~

premolar and first molar.the second

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Image field. This prOjection should Show tne distal SUrface or tne most posterior erupteamolar and equally the crowns of the maxillary and mandibular molars. Because the max-illary and mandibular molar contact areas may not be open from the same horizontal angu-lation, they may not be visible on one film. In this case it may be desirable to open themaxillary molar contacts because the mandibular molar contacts usually are open on the

periapical films.

Him placement. !'Iace tne film oetween tne tongue anate~th, as far lingual as practical to avoid contacting thesensitive attached gingiva. The distal margin of the filmshould extend 1 to 2 mm beyond the most posteriorerupted molar. When using the XCP, adjust the horizon-tal angulation by placing the guide bar parallel with thedirection of the central ray to open the contact areabetween the first and second molars.

Image field. This projection shows the palate, zygomaticprocesses of the maxilla, anteroinferior aspects of eachantrum, nasolacrimal canals, teeth from second molar tosecond molar, and nasal septum.Film placement. Seat the patient upright with the sagit-tal plane perpendicular to the floor and the occlusal planehorizontal. Place the film, with its long dimension per-pendicular to the sagittal plane, crosswise in the mouth.Gently push the film in backward until it contacts theanterior border of the mandibular rami. The patientstabilizes the film by gently closing the mouth.Projection of central ray. Direct the central ray at a ver-tical angulation of +65 degrees and a horizontal angula-tion of 0 degrees, to the bridge of the nose just belowthe nasion, toward the middle of the film.

Point of entry. Generally, the central ray enters the patient's face through the bridge of

the nose.

Image field. This projection shows a quadrant of thealveolar ridge of the maxilla, inferolateral aspect of theantrum, tuberosity, and teeth from the lateral incisor tothe contralateral third molar. In addition, the zygomaticprocess of the maxilla superimposes over the roots of themolar teeth.Film placement. Place the film with its long axis parallelwith the sagittal plane and on the side of interest, withthe tube side toward the side of the maxilla in question.Push the film posteriorly until it touches the ramus. Posi-tion the lateral border parallel with the buccal surfaces ofthe posterior teeth, extending laterally approximately1 cm past the buccal cusps. Ask the patient to close gentlyto hold the film in position.Projection of central ray. Orient the central ray with avertical angulation of +60 degrees, to a point 2 cm belowthe lateral canthus of the eye, directed toward the centerof the film.

Point of entry. The central ray enters at a point approximately 2 cm below the lateralcanthus of the eye.

Image field. This projection includes the anterior portionof the mandible, dentition from canine to canine, andinferior cortical border of the mandible.Film placement. Seat the patient tilted back so that theocclusal plane is 45 degrees above horizontal. Place thefilm in the mouth with the long axis perpendicular tothe sagittal plane and push it posteriorly until it touchesthe rami. Center the film with the pebbled side (tube side)down and ask the patient to bite lightly to hold the filmin position.Projection of central ray. Orient the central ray with-10 degrees angulation through the point of the chintoward the middle of the film; this gives the ray -55degrees of angulation to the plane of the film.

through the tipPoint of entry. The point of entryof the chin.

Image field. This projection covers the soft tissue of halfthe floor of the mouth, the buccal and lingual corticalplates of half of the mandible, and the teeth from thelateral incisor to the contralateral third molar. When thisview is used to provide an image of the floor of themouth, the exposure time should be reduced to one halfthat used to provide an image of the mandible.Film placement. Seat the patient in a semireclining posi-tion with the head tilted back so that the ala-tragus lineis almost perpendicular to the floor. Place the film in themouth with its long axis initially parallel with the sagittalplane and with the pebbled side down toward themandible. Place the film as far posterior as possible, thenshift the long axis buccally (right or left) so that the lateralborder of the film is parallel with the buccal surfaces ofthe posterior teeth and extends laterally approximately1 cm.Projection of central ray. Direct the central ray perpen-dicular to the center of the film through a point beneaththe chin, approximately 3 cm posterior to the point of thechin and 3 cm lateral to the midline.

Point of entry. The point of entry of the central ray is beneath the chin, approximately3 cm posterior to the chin and approximately 3 cm lateral to the midline.

required for the individual patient. These judgmentsare based on a careful clinical examination and con-sideration of the patient's age, medical history, growthconsiderations, and general oral health, as well aswhether caries is present and the time elapsed sinceprevious examinations. Prudence suggests makingbitewing examinations for caries assessment at periodicintervals after the patient's contacts have closed. Thefrequency should be determined partly by the patient'scaries rate. A periapical survey often is recommendedfor children early in the mixed dentition stage. Specialattention should be paid to procedures that reduceexposure (see Chapter 3) including use of fast film,proper processing, beam-limiting devices, and leadedaprons and thyroid shields.

Radiography in a child can be an interesting andchallenging experience. Although the principles ofperiapical radiography for children are the same asfor adults, in practice children present special consider-ations because of their small anatomic structures andpossible behavioral problems. The smaller size of thearches and dentition requires the use of smaller peri-apical film. The relatively shallow palate and floor of themouth may require further modification of film place-ment. Special radiographic examinations using occlusalfilm for extraoral projections have been su~~ested.

An occlusal radiograph displays a relatively largesegment of a dental arch. It may include the palate orfloor of the mouth and a reasonable extent of the con-tiguous lateral structures. Occlusal radiographs,also areuseful when patients are unable to open wide enoughfor periapical radiographs or for other reasons cannotaccept periapical radiography. Because occlusal radi-ographs are exposed at a steep angulation, they may beused with conventional periapical radiographs to deter-mine the location of objects in all three dimensions.Typically, the occlusal radiograph is especially useful inthe following cases:.To precisely locate roots and supernumerary, unerup-

ted, and impacted teeth (this technique is especiallyuseful for impacted canines and third molars)

.To localize foreign bodies in the jaws and stones inthe ducts of sublingual and submandibular glands

.To demonstrate and evaluate the integrity of the ante-rior, medial, and lateral outlines of the maxillary sinus

.To aid in the examination of patients with trismus,who can open their mouths only a few millimeters;this condition precludes intraoral radiography, whichmay be impossible or at least extremely painful forthe patient

.To obtain information about the location, nature,extent, and displacement of fractures of themandible and maxilla

.To determine the medial and lateral extent of disease(e.g., cysts, osteomyelitis, malignancies) and to detectdisease in the palate or floor of the mouthTo make an occlusal radiograph, a relatively large

film (7.7 X 5.8cm [3 x 2.3 inches]) is inserted betweenthe occlusal surfaces of the teeth. As its name implies,the film lies in the plane of occlusion. The "tube" side ofthis film is positioned toward the jaw to be examined, andthe x-ray beam is directed through the jaw to the film.Because of its size, the film allows examination of rela-tively large portions of the jaw. Standardized projectionsare used, which stipulate a desired relationship betweenthe central ray, film, and region being examined.However, the clinician should feel free to modify theserelationships to meet a specific clinical requirement.

PATIENT MANAGEMENT

Children often are apprehensive about the radi-ographic examination, much as they are about manyother types of dental procedures. The radiographicexamination usually is the first manipulative procedureperformed on a young patient. If this examination isnonthreatening and comfortable, subsequent dentalexperiences usually are accepted with little or no appre-hension. This apprehension is best allayed by familiar-izing children with the procedure, which is done byexplaining it in a manner they can comprehend. Itoften is wise to describe the x-ray machine as a cameraused to take pictures of teeth. The child can becomemore comfortable with the film and x-ray machine bytouching them before the examination. The operatorshould carryon a conversation with children to distractthem and gain their confidence. It may be advanta-geous for the child to watch an older brother or sisterbeing radiographed or to have the parent or dentalassistant serve as a model. For children who experiencea gagging sensation, the clinician can have thembreathe through their nose, curl their toes, make a fist,or follow other such devices to distract their attentionfrom the radiographic procedure. However, if the pro-cedure is postponed until the next appointment, thegag reflex may not be encountered or often is much

of ChildrenConcern about radiation protection is most importantfor children because of their greater sensitivity to irra-diation. The best way to reduce unnecessary exposureis for the dentist to make the minimal number of films

161INTRAORAL RADIOGRAPHIC EXAMINATIONSCHAPTER 8

easier for the patient to control. It is especially impor-tant to explain to the patient that the procedure will bemuch easier the next time-plant the positive thought.

Maxillary anterior occlusal projection. Place a no. 2film in the mouth with its long axis perpendicular tothe sagittal plane and the pebbled surface toward themaxillary teeth. Center the film on the midline with theanterior border extending just beyond the incisal edgesof the anterior teeth. Direct the central ray at a verticalangUlation of +60 degrees through the tip of the nosetoward the center of the film.

EXAMINATION COVERAGE

When a complete radiographic survey is necessary, itshould show the periapical region of all teeth, the prox-imal surfaces of all posterior teeth, and the crypts of thedeveloping permanent teeth. The number of projec-tions required depends on the chilq's size. Also, anexposure appropriate to the child's size should be used.For example, a 50% reduction in the rnA used for theusual young adult gives the proper density for patientsunder 10 years of age. Exposure is reduced about 25%for those between 10 and 15 years of age.

Mandibular anterior occlusal projection. Seat the childwith the head tipped back so that the occlusal plane isabout 25 degrees above the plane of the floor. Place ano. 2 film with the long axis perpendicular to the sagit-tal plane and the pebbled surface toward the mandibu-lar teeth. Orient the central ray at -30 degrees verticalangulation and through the tip of the chin toward thefilm.

Primary Dentition (3 to 6 Years)A combination of projections can be used to provideadequate coverage for the pedodontic patient. Thisexamination may consist of two anterior occlusal films,two posterior bitewing films, and up to four posteriorperiapical films as indicated (Fig. 8-9). For the maxil-lary and interproximal projections, the child is seatedupright with the sagittal plane perpendicular to andthe occlusal plane parallel with the floor (horizontalplane). For mandibular projections, except theocclusal, the child is seated upright with the sagittalplane perpendicular. The tragus corner of the mouthline is oriented parallel to the floor. Some find that apanoramic film, rather th~n the four periapical films, ismore informative and results in less exposur~ to thechild (see Chapter 3).

Bitewing projection. Use a no. 0 film with a paper loopfilm holder. Place the film in the child's mouth as inthe adult premolar bitewing projection. The imagefield should include the distal half of the canine andthe deciduous molars. Use a positive vertical angulationof +5 to +10 degrees. Orient the horizontal angle todirect the beam through the interproximal spaces.

Deciduous maxillary molar periapical projection. Use ano. 0 film in a modified XCP or BAI bite-block, eitherwith or without the aiming ring and indicator bar. Posi-tion the film in the midline of the palate with the ante-rior border extending to the maxillary primary canine.The image field of this projection should include thedistal half of the primary canine and both primary molars.

FIG. 8-9 Radiographic examination ot primary dentition consists ot two anterior occlusalviews, four posterior periapical views, and two bitewing views.

Deciduous' mandibular molar projection. Position ano. 0 film in a modified XCP or BAI bite-block, with orwithout the aiming ring and indicator bar, between theposterior teeth and tongue. The exposed radiographshould show the distal half of the mandibular primarycanine and the primary molar teeth.

Posterior bitewing projection. Expose bitewing projec-tions in the premolar region with no. 1 or no. 2 film aspreviously described, using either bitewing tabs or theRinn bitewing instrument. Expose four bitewing pro-jections when the second permanent molars have

erupted.

Mixed Dentition (7 to 12 Years)A complete examination of the mixed dentition, if indi-cated, consists of two incisor periapical films, fourcanine periapical films, four p9sterior periapical films,and two or four posterior bitewing films (Fig. 8-10). Forthe maxillary and interproximal projections, seat thechild upright with the sagittal plane perpendicularand the occlusal plane parallel to the floor. For themandibular projections, seat the child upright with thesagittal plane perpendicular and the ala-tragus line par-allel to the floor. Use the Precision Pedodontic or XCPinstruments for larger children. The BAI bite-blocksmay be more comfortable for smaller individuals.

The radiographic procedures that have been describedin this chapter are for the "well" patient. These proce-dures may need to be modified for patients who haveunusual difficulties. Specific modifications depend onthe patient's physical and emotional characteristics. Aswith any dental procedure, however, the dental assistantbegins the examination by showing appreciation of thepatient's condition and sympathy for any problems thatmight occur for either of them. If the assistant is kindbut firm, the patient's confidence increases, whichhelps the patient relax and cooperate. Following are afew conditions and circumstances that may be encoun-tered, with some recommendations and suggestionsthat may help the clinician achieve an adequate radi-ographic examination.

Maxillary anterior periapical projection. Center a no.1 film on the embrasure between the central incisors inthe mouth behind the maxillary central and lateral inci-sors. Center the film on the midline.

Mandibular anterior periapical projection. Position a no.1 film behind the mandibular central and lateral incisors.

INFECTION

Infection in the orofacial structures may result inedema and lead to trismus of some of the muscles ofmastication. As a result, intraoral radiography may bepainful to the patient and difficult for both the patientand radiologist. Under such circumstances extraoral orocclusal techniques may offer the only possibility of anexamination. The choice of a specific extraoral projec-

Canine periapical projection. Position a no. 1 filmbehind each of the canines.

Deciduous and permanent molar periapical projection.Position a no. 1 or no. 2 film (if the child is largeenough) with the anterior edge behind the canine.

FIG. 8-10 Radiographic examination ot mixed dentition consists of two incisor views,four canine views, four posterior views, and two bitewing views.

,CHAPTER 8 16.5IN I KAUKAL KAUIU~KAI'HIL tJ\AMINAIIUN:'

lion depends on the condItion and the areas to beexamined. Although the resulting radiograph may notbe ideal in many respects, it usually provides moreuseful information than the diagnostician would havewithout it. In the case of edema in an area to be exam-ined, increase exposure time to compensate for thetissue swelling.

TRAUMA

A patient who has suffered trauma may have a dental orfacial fracture. Dental fractures are best appreciatedusing periapical or occlusal radiographs. Special caremust be taken when making these views because of thecondition of the patient. Skeletal fractures are usuallybest seen with panoramic or other extraoral views, or aCT examination. In some cases patients with fractures ofthe facial skeleton may be bedridden because of involve-ment of other injuries. Consequently, an extraoral radi-ographic examination with the patient in the supineposition is necessary. However, the circumstances neednot compromise the techniques, and satisfactory intra-oral radiographs can be produced if the proper relativepositions of the tube, patient, and film are observed.

MENTALLY DI5ABLED PAT I EN I ~

Patients with mental disabilities may cause some diffi-culty for the radiologist who is attempting an examina-tion. The difficulty usually is the result of the patient'slack of coordination or in4bility to comprehend what isexpected. However, by performing the radiographicexamination speedily, unpredictable moves by thepatient can be minimized. In some cases sedation maybe required.

t'HY~ILALLY UI~AtSLtU t'AlltN I ~

Patients with physical disabilities (e.g., loss of vision, lossof hearing, loss of the use of any or all extremities, con-genital defects such as cleft palate) may require specialhandling during a radiographic examination. Thesepatients usually are cooperative and eager to assist.They may be accustomed to so much discomfort andinconvenience that their tolerance level is high, andthey are not challenged by the relatively slight irritationrepresented by the x-ray procedures. Generally, intrao-ral and extraoral radiographic examinations may beperformed for these patients if a good rapport betweenthe patient and radiology technician is established andmaintained. Members of the patient's family often arevery helpful in assisting the patient into and out of theexamination chair and in film positioning and holding,inasmuch as they usually are familiar with the patient'scondition and accustomed to coping with it.

GAG REFLEX

Occasionally, patients who need a radiographic exami-nation manifest a gag reflex at the slightest provocation.These patients usually are very apprehensive and fright-ened by unknown procedures; others simply seem tohave very sensitive tissue that precipitates a gag reflexwhen stimulated. This sensitivity is manifested when thefilm is placed in the oral cavity. To overcome this dis-ability, the radiologist should make an effort to relaxand reassure the patient. The radiologist can describeand explain the procedures. Often gagging can be con-trolled if the operator bolsters the patient's confidenceby demonstrating technical competence and showingauthority tempered with compassion. The gag reflexoften is worse when a patient is tired; therefore it isadvisable to perform the examination in the morning,when the individual is well rested, especially in the caseof children.

Stimulating the posterior dorsum of the tongue orthe soft palate usually initiates the gag reflex. Conse-quently, during the placement of the film, the tongueshould be very relaxed and positioned well to the floorof the mouth. This can be accomplished by asking thepatient to swallow deeply just before opening themouth for placement of the film. (The dentist shouldnever mention the ton~e, nor ask patients to relax thetongue; this usually makes them more conscious of itand precipitates involuntary movements.) The film iscarried into the mouth parallel to the occlusal plane.When the desired area is reached, the film is rotatedwith a decisive motiQn, bringing it into contact with thepalate or the floor of the mouth. Sliding it along thepalate or tongue is likely to stimulate the gag reflex.Also, the dentist must keep in mind that the longer thefilm stays in the mouth, the greater the possibility thatthe patient will start to gag. The patient should beadvised to breathe rapidly through the nose becausemouth breathing usually aggravates this condition.

Any little exercise that can be devised that does notinterfere with the x-ray examination but shifts thepatient's attention from the film and the mouth is likelyto relieve the gag reaction. Asking patients to hold theirbreath often can create such a distraction or to keep afoot or arm suspended during film placement andexposure. In extreme cases, topical anesthetic agents inmouthwashes or spray can be administered to producetemporary numbness of the tongue and palate toreduce gagging. However, in our experience this pro-cedure gives limited results. The most effectiveapproach is to reduce apprehension, minimize tissueirritation, and encourage rapid breathing through thenose. If all measures fail, an extraoral examination maybe the only means, short of administering general anes-thesia, to examine the patient radiographically.

RADIOGRAPHIC TECHNIQUESFOR ENDODONTICS

Radiographs are essential to the practice of endodon-tics. Not only are they indispensable for determiningthe diagnosis and prognosis of pulp treatment, they alsoare the most reliable method of managing endodontictreatment. The presence of a rubber dam, rubber damclamp, and root canal instruments may complicate anintraoral periapical examination by impairing pro-perfilm positioning and aiming cylinder angulation.Despite these obstacles, certain requirements must beobserved:1. The tooth being treated must be centered in the

image.2. The film must be positioned as far from the tooth

and apex as the region permits to ensure that theapex of the tooth and some periapical bone areapparent on the radiograph.

proper position by rotating the hemostat and film intoa position as near parallel as possible to the long axisof the tooth to be radiographed.

The aiming cylinder is aligned so as to direct thecentral ray perpendicular to the center of the film. Theplane of the end of the aiming cylinder should be par-allel with the hemostat handle. Mter the film is posi-tioned, the patient's hand is guided, with instructions,to hold and stabilize the hemostat against the teeth inthe same arch during exposure. As an alternative, thehemostat can be inserted through a bite-block ontowhich the patient can bite, providing stabilization of theinstrument and film.

Often a single radiograph of a multirooted toothmade at the normal vertical and horizontal projectiondoes not display all the roots. In these cases, when it isprudent to separate the roots on multirooted teeth, asecond projection may be made. The horizontal angu-lation is altered 20 degrees mesially to the hemostathandle for the maxillary premolars, 20 degrees mesiallyor distally for the maxillary molars, or 20 degrees dis-tally for an oblique projection of the mandibular molarroots.

If a sinus tract is encountered, its course is trackedby threading a no. 40 gutta-percha cone through thetract before the radiograph is made. It also is possibleto localize and determine the depth of periodontaldefects with this gutta-percha tracking technique.

A final radiograph of the treated tooth is made todemonstrate the quality of the root canal filling and thecondition of the periapical tissues after removal of theclamp and rubber dam.

Projection TechniqueFor maxillary projections, the patient is seated so thatthe sagittal plane is perpendicular and the occlusalplane is parallel to the floor. For mandibular projec-tions, the patient is seated upright with the sagittalplane perpendicular and the tragus corner of themouth line parallel to the floor. A hemostat is used asa film holder because it occupies minimal space and iseasy for the operator and patient to manage (see Fig.8-3, E); specially designed instruments for endodonticuse also may be used (Fig. 8-11).

A no. 2 periapical film is used for all projections. Foranterior projections, the film is grasped along the edgeof the short dimension of the film. For posterior pro-jections, the long side of the film is engaged. The filmin the hemostat is inserted into the mouth with the filmparallel to the occlusal plane. The film is placed in the

PREGNANCY

Although a fetus is sensitive to ionizing radiation, theamount of exposure received by an embryo or fetu&during dental radiography is extremely low. No inci-dences have been reported of damage to a fetus fromdental radiography. Regardless, prudence suggests thatsuch radiographic examinations be kept to a minimumconsistent with the mother's dental needs. As with anypatient, radiographic examination is limited duringpregnancy to cases with a specific diagnostic indication.With the low patient dose afforded by use of optimalradiation safety techniques (see Chapter 3), an intrao-ral or extraoral examination can be performed when-ever a reasonable diagnostic requirement exists.

EDENTULOUS PATIENTS

Radiographic examination of edentulous patients isimportant, whether the area of interest is one tooth oran entire arch. These areas may contain roots, residual

FIG. 8-11 Endoray film holder used for endodontic radi-

ographs. (Courtesy Dentsply Rinn, Elgin, III.)

CHAPTER 8 165INTRAORAL RADIOGRAPHIC EXAMINATIONS

infection, impact~d teeth, cysts, or other pathologicentities that may adversely affect the usefulness of pros-thetic appliances or the patient's health. Mter a deter-mination has been made that these entities are notpresent, repeated examinations to detect them are notwarranted. Edentulous patients typically represent,anolder age group, and their potential for developingmalignant tumors is higher. However, the low proba-bility of developing a malignancy does not constitute acontinuing indication for periodic radiographic exam-ination in the absence of other clinical signs or symp-toms. Mter a determination has been made that thejaws

are free of disease, periodic radiographs are notwarranted in the absence of symptoms.

lous ridge. This examination consists of seven projec-tions in each jaw (adult no. 2 film) as follows:

Central incisors (midline)Lateral-caninePremolarMolar

1 projection2 projections2 projections2 projections

BIBLIOGRAPHY

Radiographic Techniques for EdentulousPatientsIf available, a panoramic examination of the edentulousjaws is most convenient. If abnormalities of the alveolarridges are identified, the higher resolution of periapi-cal film is used to make intraoral projections to sup-plement the panoramic examination.

In a completely or partly edentulous patient, a film-holding device is used for intraoral radiography of thealveolar ridges. Placement of the film-holding instru-ment may be complicated by its tipping into the voidsnormally occupied by the crowns of the missing teeth.To manage this difficulty, cotton rolls are placedbetween the ridge and the film holder, supporting theholder in a horizontal position. An orthodontic elasticto hold cotton rolls to the bite-block on the film holderoften is useful when several such projections must beexposed. With elastics, it is simple to maneuver thecotton rolls into the areas that require support. Thepatient may steady the film-holding instrument with ahand or an opposing denture.

If panoramic equipment is not available, an exami-nation consisting of 14 intraoral films provides an excel-lent survey. The exposure required for an edentulousridge is approximately 25% less than that for a dentu-

Adriaens PA, De Boever], Vande Velde F: Comparison ofintra-oral long-cone paralleling radiographic surveys andorthoparitomographs with special reference to the boneheight,] Oral Rehabi19:355-65, 1982.

Biggerstaff RH, Phillips ]R: A quantitative comparison of par-alleling long-cone and bisection-of-angle periapical radiog-raphy, OralSurg Oral Med Oral Patho162:673-7, 1976.

Dubrez B,]acot-Descombes S, Cimasoni G: Reliability of a par-alleling instrument for dental radiographs, Oral Surg OralMed Oral Pathol Oral Radiol Endod 80:358-64, 1995.

Forsberg], Halse A: Radiographic simulation of a periapicallesion comparing the paralleling and the bisecting-angletechniques, Int Endod] 27:133-8, 1994.

Graf ]M, Mounir A, Payot P, Cimasoni G: A simple parallelinginstrument for superimposing radiographs of the molarregions, Oral Surg Oral Med Oral Pathol 66:502-6, 1988.

Medwedeff FM, Elcan PD: A precision technique to minimizeradiation, Dent Surv 43:45, 1967.

Scandrett FR et al: Radiographic examination of the edentu-lous patient. 1. Review of the literature and preliminaryreport comparing three methods, Oral Surg 35:266, 1973.

Schulze RK, d'Hoedt B: A method to calculate angular dis-parities between object and receptor in "paralleling tech-nique," Dentomaxillofac Radiol 31:32-8, 2002.

Updegrave \\1: Right angle (paralleling) dental radiographywith the conventional short (8 inch) tube, Gen Dent29:220-4, 1981.

Weclew TV: Comparing the paralleling extension cone tech-nique and the bisecting angle technique,] Acad Gen Dent22:18-20, 1974.

Weissman DD, Longhurst GE: Clinical evaluation of a rectan-gular field collimating device for periapical radiography,]ADA 82:580,1971.

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