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    IntroductionRadiography involves the use of x-radiation and thus is potentially dangerous if mishandled. Foryour own sake, and that of the staff, patient, and public, it is essential that you gain adequateknowledge of radiographic techniques and radiation health and safety, prior to performing clinicalprocedures.This course is intended to provide current, vital information on film and tube head placement, to

    serve as a guide to acquire new skills or refine current skills, and allow you to test yourself as youprogress through the pages.When you complete a continuing education course on the Dental ResourceNet, a form will comeup that requests your name, address, etc. If you are a member of the AGD, make sure to fill outthe field that asks for your AGD membership number (if you are not an AGD member, leaveblank). When you hit submit, a copy of the "proof of completion" is e-mailed directly to the AGDand P&G. For your records, make sure to print a copy of the "proof of completion" certificate.

    OverviewRadiography involves the use of x-radiation and thus is potentially dangerous if mishandled. Foryour own sake, and that of the staff, patient, and public, it is essential that you gain adequateknowledge of radiographic techniques and radiation health and safety, prior to performing clinical

    procedures.This course is intended to provide current, vital information on film and tube head placement, toserve as a guide to acquire new skills or refine current skills, and allow you to test yourself as youprogress through the pages

    Learning ObjectivesUpon the completion of this course, the dental professional will be able to:

    Understand the basic principles and concepts of intraoral procedures.

    Demonstrate the paralleling technique of intraoral radiology.

    Explain the bisecting angle technique of intraoral radiology.

    Identify proper techniques for bitewing radiography.

    Describe intraoral occlusal techniques.

    Course Contents

    Introduction

    Intraoral Procedures

    Paralleling Technique

    Paralleling Technique Methodology

    The Bisecting Angle Technique

    Bisecting Angle Methodology

    Bitewing Radiography Intraoral Occlusal Radiography

    Digital Radiology

    Summary

    Glossary

    Course Test

    About the Authors

    IntroductionRadiography involves the use of x-radiation and thus is potentially dangerous if mishandled. Foryour own sake, and that of the staff, patient, and public, it is essential that you gain adequateknowledge of radiographic techniques and radiation health and safety, prior to performing clinicalprocedures.

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    This course is intended to provide current, vital information on film and tube head placement, toserve as a guide to acquire new skills or refine current skills, and allow you to test yourself as youprogress through the pages.

    Intraoral Procedures

    IntroductionThe intraoral radiograph, when correlated with the case history and clinical examination, is one ofthe most important diagnostic aids available to the dental practitioner. When examined underproper conditions, diagnostic-quality intraoral radiographs reveal evidence of disease that cannototherwise be found. They also play a major role in forensic identification.Two of the fundamental rules of radiography are that 1) the central beam should pass through thearea to be examined, and 2) the x-ray film should be placed in position so as to record the imagewith the least amount of image distortion. Each of three types of intraoral radiologic examinationscommonly used in dental practiceperiapical, bitewing (interproximal), and occlusal examinationsdepend on the operators adherence to these two rules even though specific techniques,processes, and indications differ widely among them.Another aspect that these three examinations have in common pertains to the film packet. Thefilm packet has two sides, a tube side and a tongue side. The tube side may be plain or textured.When placed intraorally, the tube side always faces the radiation source, the tube head. Thetongue side may be colored and has a flange to open the packet and remove the film. Whenplaced intraorally, the tongue side always faces the patients tongue, except in the case of themandibular occlusal examination.Because of patient anatomic variations such as narrow arches, missing teeth, or the presence oftori, and limitations of the patients ability to open sufficiently (caused by age or other factors), ormaintain the film placement, a clinical examination must precede the taking of films. After theclinical examination, the operator can determine the number and size of films to expose, thetechnique modifications necessary, and the type of film retention devices to be employed.Advancements are continually being made in the development and manufacturing of the actual filmpacket. These advancements have helped to decrease radiation exposure. Whenever possiblethe "fastest" film speed should be used.Periapical RadiographsThe purpose of the intraoral periapical examination is to obtain a view of the entire tooth and its

    surrounding structures, as in Figure 1. Two exposure techniques may be employed for periapicalradiography: the paralleling technique and the bisecting angle technique. The parallelingtechnique is the preferred method. This technique provides less image distortion and reducesexcess radiation to the patient. The paralleling technique should always be attempted before othertechniques. The bisecting technique can be employed for patients unable to accommodate thepositioning of the paralleling technique. Candidates may include those with low palatal vaults andchildren. Disadvantages to the bisecting technique include image distortion and excess radiationdue to increased angulations involving the eye and thyroid glands. Regardless of the technique,however, the rules of radiography referred to earlier must be followed.

    Figure 1

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    Intraoral ProceduresBitewing RadiographsBitewing examinations were introduced by Raper in 1925. The greatest value of bitewingradiographs is the detection of interproximal caries in the early stages of development, before it isclinically apparent. The arrows in Figure 2 indicate areas of interproximal caries. Bitewingprojections also reveal the size of the pulp chamber and the relative extent to which proximal

    caries have penetrated.Bitewings also provide a useful adjunct to evaluating periodontal conditions, offer a good view ofthe septal alveolar crest, and, in addition, permit changes in bone height to be accurately assessedby comparison with adjacent teeth. Bitewings do not show the apices of the teeth and cannot beused to diagnose in this area.

    Figure 2Occlusal RadiographsOcclusal radiography is a supplementary radiographic examination designed to provide a moreextensive view of the maxilla and mandible (Figure 3).

    Figure 3The occlusal radiograph is very useful in determining the buccolingual extension of pathologicconditions, and provides additional information as to the extent and displacement of fractures ofthe mandible and maxilla. Occlusals also aid in localizing unerupted teeth, retained roots, foreignbodies, and calculi in the submandibular and sublingual salivary glands and ducts. It should benoted that when imaging soft tissues exposure time needs to be appropriately reduced.

    Dentulous Adult SurveyThe number of films needed for a full mouth series varies greatly. Some practitioners may prefer10 films, while others may prefer 18, 20 or more exposures.The selection of film sizes used in a full mouth series also varies. A full survey can consist ofnarrow anterior film (size #1); standard adult film (size #2); #2 bitewing film or long bitewing film(size #3), (Figure 4) and may include anterior bitewings. It is generally recommended to use 20films --- four bitewings and 16 periapicals. Eight anterior #1 films will allow for ease of filmplacement on patients with narrow palates. However, in some cases six anterior periapicals willcover the area needed.

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    By using #3 film only one film is used on both the right and left sides and opening both thepremolar and molar contacts on one film is very difficult. (Figure 5) With the use of #2 films forbitewings, the operator uses a total of four films. Each film is assigned either premolars or molars.(Figure 6) Use of the #2 films instead of #3 films for bitewings is not only more comfortable for thepatient but is easier for the operator to open the contacts.

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    Figure 5

    Figure 6

    Intraoral ProceduresEdentulous Adult SurveyBy definition, an edentulous patient is one without the natural dentition, and a partially edentulouspatient is one who retains some, but not all of the natural dentition. Merely because a patientsclinical exam reveals an edentulous state does not disqualify him or her from diagnosticradiographic examination. In fact, it is commonly accepted that certain areas of the patients jawsmay contain tooth roots or impacted teeth. Residual infection, tumors, cysts, or related pathologymay also be found, which, while not visible to the clinician, would hinder the effectiveness andcomfort of an appliance such as a denture and could potentially cause life threatening conditions tothe patient. In addition to the hidden pathology mentioned above, edentulous surveys reveal theposition of the foramina and the type of bone present.In the case of the partially edentulous patient, placement of the film holding device may be

    complicated by its tendency to tip or slip into the voids which would normally be occupied by thecrowns of the missing teeth. This can usually be overcome by placing cotton rolls between thepatients alveolar ridge and the film holder, thereby supporting the film holding device in position.A 14 or 16 film intraoral periapical survey will usually examine the tooth bearing region in mostedentulous patients (Figure 7). Bitewings are not needed because there are no interproximalareas to be examined.

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    Figure 7The use of film holders allow the paralleling technique to be used with edentulous patients. Theoperator may be able to reduce radiation exposure in the edentulous patient by 25% by using theparalleling technique. The film can be held in biteblocks to which cotton rolls have been taped. Toprevent patient discomfort on biting due to missing teeth and resultant over-closing of the arches,the cotton rolls can be attached to the upper and lower surfaces of the biteblocks. Opposing arch

    denture or partial denture appliances can be left in place to make contact with the biteblock.The radiographic film should be positioned with approximately one-third of the films verticaldimension protruding beyond the alveolar ridge; that is, the radiographic image should occupy two-thirds of the film. The horizontal angulation of the central beam is perpendicular to the film in thehorizontal plane. If bisecting, the vertical angulation of the central beam is much increased for anedentulous patient with minimal ridges. The film placement may be similar to that of an occlusalfilm, and this flat film placement is the principal cause of dimensional distortion. To determinevertical angulation it is necessary to estimate the long axis of the ridge instead of the tooth.

    Intraoral ProceduresMixed Dentition SurveyThe full mouth survey for pediatric patients may vary, depending on the patients age, eruption

    pattern, behavior, and the size of the childs mouth. In the six to nine-year-old group, a 12 filmsurvey, using #1 narrow film is recommended, and would include:

    Maxillary:o Central incisors

    o Right and left lateral incisors and canines

    o Right and left primary/permanent molars

    Mandibular:o Central incisors

    o Right and left lateral incisors and canines

    o Right and left primary/permanent molars

    Bitewings:

    o Right and left primary/permanent molars

    An adult-sized periapical film is used in the posterior region if the childs first permanent molar isfully developed. The size of the tooth requires the use of a large periapical film to capture thecomplete image.Pre-School Child SurveySince pre-school children have smaller mouths, reduced size pediatric films (film size #0) are usedto examine the posterior teeth, and adult films are used for anterior examinations in children whohave only primary (deciduous or "baby") teeth. For this group, an eight film survey isrecommended.

    Maxillary:o Central incisors

    o Right and left primary molars Mandibular:

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    o Central incisors

    o Right and left primary molars

    Bitewings:o Right and left primary molars

    The paralleling technique should be used whenever possible. This technique delivers the lowest

    dose of radiation possible. The bisecting angle technique is a viable alternative for pediatricradiography because the apices of the permanent molar teeth tend to lie above the palate andbelow the floor of the mouth in the undeveloped mandible. These positions prevent the image ofthe apices of the teeth from being projected into the oral cavity when the x-ray beam isperpendicular to the long axis of the teeth as it is when using the paralleling technique.

    Quiz

    1. What should be done before any radiographic examination?2. What are the fundamental rules of radiography?3. What is the purpose of the intraoral periapical examination?4. What are the two primary techniques used in periapical radiography?

    5. What is the primary purpose of bitewing radiographs?6. What else can be accurately assessed with bitewings?7. List five indications for taking occlusal radiographs.8. What sizes of periapical films are commonly used in a dentulous adult survey?9. Why should a radiographic examination be performed for a clinically edentulouspatient?10. How should film be positioned relative to the alveolar ridge?

    Answers

    1. A good clinical examination should be carried out before every radiographicexamination.2. The central beam should pass through the area to be examined and the x-ray film

    should be placed in position to record the image with the least amount of distortion.3. To obtain a view of the entire tooth and surrounding structures.4. Paralleling and bisecting angle technique.5. The detection of caries in the early stages of development.6. The detection of periodontal disease in the early stages.7. Detection of pathological lesions; fractures of the mandible and maxilla; foreignbodies; salivary calculi; localizing unerupted teeth.8. Number 1, 2 and 3 film.9. It is commonly accepted that certain areas in the jaws may contain roots, impactedteeth, residual infections, tumors, cysts, etc.10. The film should be placed with approximately one-third of the vertical dimensionprotruding beyond the alveolar ridge.

    Paralleling Technique

    Basic PrinciplesThe paralleling technique of intraoral radiography was developed by Gordon M. Fitzgerald, and isso named because the object (tooth), receptor (film packet), and end of the position indicatingdevice (PID) are all kept on parallel planes. Its basis lies in the principle that image sharpness isprimarily affected by focal-film distance (distance from the focal spot within the tube head and thefilm), object-film distance, motion, and the effective size of the focal spot of the x-ray tube.Successfully using the paralleling technique depends largely on maintaining certain essentialconditions as illustrated in Figure 8. These are: 1) the film packet should be flat; 2) the film packetmust be positioned parallel to the long axis of the teeth; and 3) the central ray of the x-ray beammust be kept perpendicular to the teeth and film.

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    Figure 8To achieve parallelism between the film and tooth (i.e., to avoid bending or angling the film) theremust be space between the object and film. However, remember that as the object-to-film

    distance increases, the image magnification or distortion also increases. To compensate,manufacturers are recessing the target (focal spot) into the back of the tube head. Depending onthe machine's age, and placement of the focal spot within the tube head, you may encounter long,medium, or short cones/PIDs. The goal is to have the focal spot at least 12" or 30 cm from the filmto reduce image distortion.The anatomic configuration of the oral cavity determines the distance needed between film andobject and varies among individuals. However, even under difficult conditions, a diagnostic qualityradiograph can be obtained provided that the film packet is not more than 20 degrees out ofparallel with the tooth, and that the face of the PID/cone is exactly parallel to the film packet toproduce a central beam which is perpendicular to the long axis of the tooth and the film packet.The major advantage of the paralleling technique, when done correctly, is that the image formedon the film will have both linear and dimensional accuracy. The major disadvantages are thedifficulty in placing the film packet and the relative discomfort the patient must endure as a result ofthe film holding devices used to maintain parallelism. The latter is particularly acute in patients

    with small mouths and in children. In certain circumstances the film and holder may be slightlytipped toward the palate to accommodate oral space and patient comfort. Too much palataltipping will throw off all parallel planes.

    Paralleling TechniqueBeam AngulationThe position of the x-ray tube head is usually adjusted in two directions: vertically and horizontally.The vertical plane is adjusted by moving the tube head up and down. The horizontal plane isadjusted by moving the tube head from side to side. By convention, deflecting the head so that itpoints downward is described as positive vertical angulation or + vertical. Correspondingly, anupward deflection is referred to as negative vertical angulation or - vertical (Figure 9). The degreeof vertical angulation is usually described in terms of plus or minus degrees as measured by a dial

    on the side of the tube head.

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    Figure 9When applying the paralleling technique, the vertical angulation is ALWAYS dictated tomaintaining the parallel plane. There is no set degree number to follow. As stated earlier underbasic principles, the object (tooth), receptor (film packet), and end of the position indicating device(PID) are all kept on parallel planes. If the vertical angulation is excessive the image will appearforeshortened. Insufficient vertical angulation procedures an elongated image.The beams horizontal direction determines the degree of overlap among the tooth images at theinterproximal spaces. If the beam is not perpendicular to the specific interproximal space(s) as itapproaches several relatively aligned objects, the objects overlap and the space(s) between themclose. Imagine a flashlight beam approaching a picket fence perpendicularly at a 90-degreeangle. The spaces between the pickets will remain open in the shadow image unless the beamangle varies from perpendicular or 90 degrees. The degree of overlapping of the image willincrease or decrease as the beam angle increases or decreases from the perpendicular.Film Holding DevicesThe paralleling technique requires the use of film holding devices to maintain the relatively precisepositioning needed. A great variety of film holders are commercially availablesimple, complex,light, heavy, reusable, disposable, autoclavable, and non-autoclavable. A few of the morecommon include XCP (extension cone paralleling) with localizing rings, Snap-a-ray, Precision

    rectangular paralleling device, Uni-Bite, and Stabe biteblock (Figure 10 and 11). Having severaloptions available will provide the operator different opportunities for enhanced patient comfort. It isnot uncommon to employ more than one option during the same radiographic survey.

    Figure 10

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    Figure 11The dental radiographer should be able to assess which holder best conforms to the technical anddiagnostic requirements of the job, the needs of the patient, and infection control protocols withinthe office.

    (Table 1: Paralleling - Exposure Guide and Film Placement - Helpful hints when utilizingStabe or Snap-a-ray film holders)

    Paralleling - Exposure Guide and Film PlacementHelpful hints when utilizing Stabe or Snap-a-ray film holders

    BITEWINGS Teeth to include C.R. Entry Point Vertical. Angulation

    R Molar BWX #1, 2, 3, 30, 31, 32 & D. of 4 & 29 contact of #2 & #3+ 10 (down angle ofPID)

    R Premolar BWX #4, 5, 28, 29 & D. of 6 and 27 contact of #4 & #5 + 10 (down)

    L Premolar BWXD. of #11 and 22, and #12, 13, 20,21

    contact of #12 & #13 + 10 (down)

    L Molar BWXD. of #13 and 20, 14, 15, 16, 17,18, 19

    contact of #14 & 15 + 10 (down)

    * * * * *

    ginary plane can be visualized on the face to offer approximate C.R. placement. For Maxillary exposures, imagine the plane to extend between thhe nose and the tragus of the ear (a.k.a. the ala-tragus line.) For Mandibular exposures, imagine this plane to extend between the commissure ofand the tragus of the ear (a.k.a. the commissure-tragus line.) Once this plane is established, the following entry points will be a guide for C.R.ent. Approximate vertical angulations are only guides and must be checked for paralleling before exposure as each persons anatomy is different.

    PERIAPICALS Teeth to includeApprox. C.R. Entry

    PointApprox. Vert. Ang.

    UR Molars #1, 2, half of #3outer canthus of theeye

    +20 - +30 (down)

    UR Premolars M. of #3, 4, 5, and half of #6 pupil of the eye +30 - + 40 (down)

    UR Canine center #6 c.r. at D. of 6 ala of the nose +45 - + 55 (down)

    Max. Incisors center #7, 8, 9, 10 (I.U. method) tip of the nose +40 - +50 (down)

    UL Canine center #11 c.r. at D. of 11 ala of the nose +45 - + 55 (down)

    UL Premolars half of #11, and 12, 13, M. of 14 pupil of the eye +30 - + 40 (down)

    UL Molars half of #14, and 15, 16outer canthus of the

    eye

    +20 - +30 (down)

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    LL Molars #17, 18, and half of 19outer canthus of theeye

    - 5 0 (up angle ofPID)

    LL Premolars M. of #19, and 20, 21, and half of 22 pupil of the eye -10 - -15 (up)

    LL Canine center #22 c.r. at D. of 22 ala of the nose -20 - -30 (up)

    Mand. Incisors center #23, 24, 25, 26 (I.U. method) cup the chin -15 - -25 (up)

    LR Canine center #27 c.r. at D. 27 ala of the nose -20 - -30 (up)

    LR Premolarshalf of #27, and 28, 29 and M. of#30

    pupil of the eye -10 - -15 (up)

    LR Molars half of #30, and 31, 32outer canthus of theeye

    - 5 0 (up)

    Willie Leeuw, CDA, BS - Indiana University Purdue University Fort Wayne , Department of Dental Assisting

    Quiz

    1. What is the basic principle of the paralleling technique?2. What is the major advantage of the paralleling technique?3. What are the major disadvantages?4. What must be done to achieve parallelism between the tooth and film?5. List several devices available to position the film properly when using theparalleling technique.

    Answers

    1. The film packet must be positioned parallel to the long axis of the teeth and the x-raybeam must be kept perpendicular to the teeth and film.2. Linear and dimensional accuracy.3. Difficulty in placement of the film packet, relative discomfort to the patient caused byfilm holding devices.4. The film must be placed away from the tooth.5. XCP with localizing rings, Snap-a-ray, Precision rectangular devices, Uni-Bite, and

    Stabe biteblock.

    Paralleling Technique MethodologyWhen taking a full mouth survey, a definite order of exposure should be preplanned and thenfollowed. Since patients tolerate anterior films better, they should be done first. Starting with themaxillary central incisors and proceeding distally, first along one side, then the other, isrecommended. The radiographic parameters or exposure factors should also be determined priorto placing films in the patients mouth.Patient PositioningWhen positioning a patient, there are two imaginary planes that must be considered. The occlusalplane runs horizontally, dividing the patients head into upper and lower portions. It can bevisualized by imagining the patient holding a ruler between his or her teeth. A midsagittal plane

    divides a mass (the patients head or body) on a vertical dimension into equal right and leftportions.When using the paralleling technique to examine the maxillary region, the patient is positioned sothat the occlusal plane of the maxilla is parallel to the floor and the sagittal plane of the patientshead is perpendicular to the floor.When paralleling the mandibular region, the patients position must be modified slightly so thatwhen the mouth is open, the mandible is parallel to the floor and the sagittal plane isperpendicular. This could mean that the patient must be tilted back in the chair.Before any radiographs are exposed, the patient must be protected with a lead apron and thyroidcollar. The apron must be properly placed to avoid interference with the radiographic exposure.(Figure 12)

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    Figure 12

    Paralleling Technique MethodologyFull Mouth Exposure with the Use of XCP DeviceProcedure for the Maxillary Central/Lateral Incisors

    1. Assemble the anterior film holder and insert the film packet vertically on theanterior biteblock. Use a #1 film.2. Center the film on the central/lateral incisors (Figure 13). Position the film in thepalate as posteriorly as possible so that the entire tooth length will appear on the film, withapproximately a one-eighth inch border of the film extending below the incisal edge of thecentrals. Position the biteblock on the incisal edges of the teeth to be radiographed(Figure 14). Proper positioning in this step will place the central ray of the x-ray beam atthe interproximal contact desired.

    Figure 13 Figure 14

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    3. A cotton roll may be inserted between the mandibular teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition.4. Slide the aiming ring down the indicator rod to the skin surface, align the x-raytube close to the aiming ring, and center (Figure 15).5. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

    Figure 15

    Paralleling Technique MethodologyFull Mouth Exposure with the Use of XCP DeviceProcedure for the Maxillary Canines

    1. Assemble the anterior film holder and insert the film packet vertically on theanterior biteblock. Use a #1 film.2. Center the film on the canine and first premolar (Figure 16). Position the film inthe palate as posteriorly as possible so that the entire tooth length will appear on the filmwith approximately a one-eighth inch border below the incisal edge of the canine. Positionthe biteblock on the incisal edges of the teeth to be radiographed (Figure 17). Properpositioning in this step will place the central ray of the x-ray beam at the interproximalcontact desired.

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    Figure 16 Figure 17

    3.

    4. A cotton roll may be inserted between the mandibular teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition.5. Slide the aiming ring down the indicator rod to the skin surface, align the x-raytube close to the aiming ring, and center (Figure 18).6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

    Figure 18Procedure for the Maxillary Premolars

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    1. Assemble the posterior film holder and insert the film packet horizontally in theposterior biteblock. Use a #2 film.2. Center the film on the premolars so that it is parallel to the long axis of the teeth(Figure 19). Position the film in the palate so that the entire tooth length will appear on thefilm with approximately a one-eighth inch border below the cuspal ridge. Align the anterioredge of the film packet with the canine so that the image captured on the anterior borderof the film will include the distal third of the canine. Position the biteblock on the occlusalsurfaces of the teeth to be radiographed (Figure 20). Proper positioning in this step willplace the central ray of the x-ray beam at the interproximal contact desired.

    Figure 19 Figure 20

    3.4. A cotton roll may be inserted between the mandibular teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition. (The occlusal border of the film tends to slip lingually.)5. Slide the aiming ring down the indicator rod to the skin surface, align the x-raytube close to the aiming ring, and center (Figure 21).6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

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    Figure 21

    Paralleling Technique MethodologyFull Mouth Exposure with the Use of XCP DeviceProcedure for the Maxillary Molar Region

    1. Assemble the posterior film holder and insert the film packet horizontally in theposterior biteblock. Use a #2 film.2. Center the film on the molars so that it is parallel to the long axis of the teeth(Figure 22). Position the film in the palate so that the entire tooth length will appear on thefilm with approximately a one-eighth inch border below the cuspal ridge. Align the anteriorborder of the film packet with the second premolar so that the image captured on theanterior edge of the film will be the distal third of the second premolar. Position thebiteblock on the occlusal surfaces of the teeth to be radiographed (Figure 23). Proper

    positioning in this step will place the central ray of the x-ray beam at the interproximalcontact desired.

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    Figure 22 Figure 23

    3.4. A cotton roll may be inserted between the mandibular teeth and the biteblock for

    patient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition.5. Slide the aiming ring down the indicator rod to the skin surface, align the x-raytube close to the aiming ring, and center (Figure 24).6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

    Figure 24

    Procedure for the Mandibular Central/Lateral Incisors

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    1. Assemble the anterior film holder and insert the film packet vertically on theanterior biteblock. Use a #1 film.2. Center the film on the mandibular central and lateral incisors (Figure 25). It maybe necessary to displace the tongue distally and depress the film onto the floor of themouth so that the entire tooth length will show with approximately a one-eighth inchborder above the incisal edges. The film must be as posterior as the anatomy allows andthe biteblock should be positioned on the edges of the incisors to be radiographed (Figure26). Proper positioning in this step will place the central ray of the x-ray beam at theinterproximal contact desired.

    Figure 25 Figure 26

    3.4. A cotton roll may be inserted between the maxillary teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition. The film should be straightened as the patient closes and the floor of the mouthrelaxes.

    5. Slide the aiming ring down the indicator rod to the skin surface, align the x-raytube close to the aiming ring, and center (Figure 27).6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

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    Figure 27

    Paralleling Technique MethodologyFull Mouth Exposure with the Use of XCP DeviceProcedure for the Mandibular Canines

    1. Assemble the anterior film holder and insert the film packet vertically on theanterior biteblock. Use a #1 film.2. Center the film on the mandibular canine (Figure 28). It may be necessary todisplace the tongue distally and depress the film onto the floor of the mouth so that theentire tooth length will show with approximately a one-eighth inch border above the cuspaledge. The film must be as posterior as the anatomy allows and the biteblock should bepositioned on the edges of the teeth to be radiographed (Figure 29). Proper positioning in

    this step will place the central ray of the x-ray beam at the interproximal contact desired.

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    Figure 28 Figure 29

    3.

    4. A cotton roll may be inserted between the maxillary teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition. The film should be straightened as the patient closes and the floor of the mouthrelaxes.5. Slide the aiming ring down the indicator rod to the skin surface, align the x-raytube close to the aiming ring, and center (Figure 30).6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

    Figure 30Procedure for the Mandibular Premolars

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    1. Assemble the posterior film holder and insert the film packet horizontally on theposterior biteblock. Use a #2 film.2. Center the film on the premolars so that it is parallel to the long axis of the teeth(Figure 31). The object-to-film distance in both the mandibular premolar and molarregions is minimal since the oral anatomy only allows the film to be positioned very closeto the teeth and still remain parallel. Align the anterior border of the film packet with thecanine so that the image captured on the anterior edge of the film will be the distal third ofthe canine. Position the biteblock on the occlusal surfaces of the teeth to be radiographed(Figure 32). Proper positioning in this step will place the central ray of the x-ray beam atthe interproximal contact desired.

    Figure 31 Figure 32

    3.4. A cotton roll may be inserted between the maxillary teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition. The film should be straightened as the patient closes and the floor of the mouthrelaxes.

    5. Slide the aiming ring down the indicator rod to the skin surface, align the x-raytube close to the aiming ring, and center (Figure 33).6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

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    Figure 33

    Paralleling Technique MethodologyFull Mouth Exposure with the Use of XCP DeviceProcedure for the Mandibular Molars

    1. Assemble the posterior film holder and insert the film packet horizontally on theposterior biteblock. Use a #2 film.2. Center the film on the molars so that it is parallel to the long axis of the teeth(Figure 34). Depress the film onto the floor of the mouth so the entire length of the teethwill appear with approximately a one-eighth inch border above the occlusal surface. Placethe film horizontally and position it lingually to the molars so that the long axis of the film isparallel to the long axis of the tooth. Align the anterior border of the film packet with thesecond premolar so that the image captured on the anterior edge of the film will be the

    distal third of the second premolar. Position the biteblock on the occlusal surfaces of themandibular teeth (Figure 35). Proper positioning in this step will place the central ray ofthe x-ray beam at the interproximal contact desired.

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    Figure 34 Figure 35

    3.

    4. A cotton roll may be inserted between the maxillary teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition. The film should be straightened as the patient closes and the floor of the mouthrelaxes.5. Slide the aiming ring down the indicator rod to the skin surface, align the x-raytube close to the aiming ring, and center (Figure 36).6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

    Figure 36Quiz

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    1. What is the recommended patient positioning for examining the maxillary regionusing the paralleling technique?2. What is the recommended patient positioning for examining the mandibularregion using the paralleling technique?

    Answers

    1. The occlusal plane of the maxilla is parallel to the floor and the sagittal plane of thepatients head is perpendicular to the floor.2. When the mouth is open, the mandibular occlusal plane is parallel to the floor and thesagittal plane of the patients head is perpendicular to the floor.

    The Bisecting Angle TechniqueBasic PrinciplesThe bisecting-the-angle or bisecting angle technique is based on the principle of aiming the centralray of the x-ray beam at right angles to an imaginary line which bisects the angle formed by thelongitudinal axis of the tooth and the plane of the film packet. While it is not necessary to go into along dissertation on plane geometry to understand this concept, a quick review will help make thetechnique more clear. To bisect is to divide a line or angle into two equal portions. A bisector is aplane or line that divides a line or angle into two equal portions. Figure 37 shows an equilateraltriangle, with legs AB=BC=CA, and the angles ABC=60 degrees, CAB=60 degrees and BCA=60degrees.

    Figure 37We see in Figure 37 the following:

    1. The dotted line BD bisects the triangle, dividing it exactly in half. Thus, two equaltriangles are formed from the original. Legs AB and BC were unchanged and thus are stillequal.2. The original line CA was divided in half by D, and thus the lines AD and CD areequal.3. We know that the angle at point B was 60 degrees, and since it was bisected(divided equally), it now is 30 degrees at the intersections of AD and BD.

    4. We also know that bisecting the angle did not affect the angle at the old point Awhich was 60 degrees, and still is.

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    5. The angle at the bisecting point DC must be 90 degrees because the sum of allthe angles in any triangle is 180 degrees, and thus 180-(60+30)=90.6. Cyzynskis Rule of Isometry states that two triangles are equal when they shareone complete side, and have two equal angles. We can see that triangles ADB and BDCshare the common side BD.7. We know further that the angles ADB and BDC are equal because D was definedas a bisector of the old angle ABC.8. Lastly, we know that the angles CAB and BCA were unchanged by bisecting andare still equal. Therefore, under Cyzynskis Theorem, we can prove the triangles ABDand CBD are equal.

    In dental radiography, the theorem is applied in the following manner. The film is positionedresting on the palate or on the floor of the mouth as close to the lingual tooth surfaces as possible.The plane of the film and the long (vertical) axis of the teeth to be radiographed form an angle withthe apex at the point where the film packet contacts the teeth. The apex in Figure 38 is located atthe point labeled B.In Figure 38, the long axis through the tooth forms one leg of a triangle (AB), the plane of the filmpacket another leg, (BC), both of which intersect at the apex, point B. A line representing thecentral x-ray beam will form the third leg of the triangle, AC. If an imaginary line bisected this axis-packet-ray triangle, the bisector, DB, would form the common side of two equal triangles as

    defined by Cyzynskis Theorem.

    Figure 38Since the sides formed by the tooths long axis and the film packet are equal, the image cast ontothe radiographic film would be the same length as the tooth or teeth casting that image. This linearequality is the basis for diagnostic quality bisecting angle radiographs.

    The Bisecting Angle TechniqueAnatomical ConsiderationsThe bisecting angle technique is of value when the paralleling technique cannot be utilized. Thismay include patients with small mouths and those with low palatal vaults. Because of the

    increased exposure to radiation in this technique, it should only be employed as necessary.Beam AngulationThe bisecting technique calls for varying beam angulations, depending on the region to beexamined.Horizontal angulation: The horizontal angulation of the tube head should be adjusted for eachprojection to position the central ray through the contacts in the region to be examined. Thisangulation will usually be at right angles to the buccal surfaces of the teeth to be radiographed.Vertical angulation: In practice, the operator should position the central ray of the x-ray beam sothat it is perpendicular to the imaginary line bisecting the angle formed between the tooth long axisand the film. This principle works well with flat, two-dimensional structures, but teeth that havedepth or are multirooted will produce distorted images. If the vertical angulation is excessive theimage will appear foreshortened. Insufficient vertical angulation produces an elongated image.The optimum angle will vary from patient to patient, but the chart below serves as a general

    guideline for beam angulation.Projection Maxilla Mandible

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    Incisors +40 degrees -15 degrees

    Canine +45 degrees -20 degrees

    Premolar +30 degrees -10 degrees

    Molar +20 degrees 2-5 degrees

    Film Holding DevicesSupporting the film pack with the patients forefinger is not recommended. This method hasseveral drawbacks. In addition to exposing the patients digit to additional radiation, the patientmay exert excessive force, thus bending the film and distorting the radiograph. The film may slipwithout the operators knowledge, and produce a radiograph outside the proper image field.Therefore, intraoral support is best accomplished using instruments that restrain the film and helpalign the beam properly.

    Quiz

    1. On what principle is the bisecting angle technique based?2. How did this principle originate?

    Answers

    1. The bisecting angle technique is based on the principle of aiming the central ray of thex-ray beam at right angles to an imaginary plane bisecting the angle formed by the longitudinalaxis of the tooth and the plane of the film packet.2. The principle originated from Cyzynskis Rule of Isometry (Cyzynskis Theorem) whichstates that two triangles are equal when they share one complete side and have two equalangles.

    Bisecting Angle MethodologyPatient PositioningMaxillary region: For bisecting angle radiographs of the maxilla, the patient should be positioned

    so that the maxillary occlusal plane is parallel to the floor and the sagittal plane of the patientshead is perpendicular to the floor.Mandibular region: For bisecting angle radiographs of the mandible, the patient should bepositioned so that the mandibular occlusal plane is parallel to the floor and the sagittal plane of thepatients head is perpendicular to the floor.Before any radiographs are exposed, the patient must be protected with a lead apron and thyroidcollar. The apron must be properly placed to avoid interference with the radiographic exposure.Full Mouth ExposureProcedure for the Maxillary Central/Lateral Incisors

    1. Assemble the anterior film holder and insert the film packet vertically on thebiteblock. Use a #1 film.2. Center the film on the central/lateral incisors as close as possible to the lingualsurfaces of the teeth with approximately a one-eighth inch border of the film extendingbelow the incisal edge of the centrals (Figure 39). Position the biteblock on the incisaledges of the teeth to be radiographed (Figure 40).

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    Figure 39 Figure 40

    3.4. A cotton roll may be inserted between the mandibular teeth and the biteblock for

    patient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition.5. Align the central ray perpendicular to the bisector vertically and at the desiredinterproximal contact to be viewed. Horizontally, the central ray should bisect thecentral/lateral (Figure 41). For maxillary exposures the tube head will be pointed down forpositive (+) angulation.6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

    Figure 41

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    Bisecting Angle MethodologyFull Mouth ExposureProcedure for the Maxillary Canines

    1. Assemble the anterior film holder and insert the film packet vertically on the

    biteblock. Use a #1 film.2. Center the film on the canine as close as possible to the lingual surfaces of theteeth with approximately a one-eighth inch border of the film extending below the incisaledge of the centrals (Figure 42). Position the biteblock on the incisal edges of the teeth tobe radiographed (Figure 43).

    Figure 42 Figure 43

    3.4. A cotton roll may be inserted between the mandibular teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition.

    5. Align the central ray perpendicular to the bisector vertically and at the desiredinterproximal contact to be viewed. Horizontally, the central ray should bisect the canine(Figure 44). For maxillary exposures the tube head will be pointed down for positive (+)angulation.6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

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    Figure 44Procedure for the Maxillary Premolars

    1. Assemble the posterior film holder and insert the film packet horizontally on thebiteblock. Use a #2 film.2. Center the film on the premolars as close as possible to the lingual surfaces ofthe teeth (Figure 45). Position the film in the palate so that the entire tooth length willappear on the film with approximately a one-eighth inch border below the cuspal ridge.Align the anterior border of the film packet with the canine so that the image captured onthe anterior edge of the film will be the distal third of the canine. Position the biteblock onthe occlusal surface of the teeth being radiographed (Figure 46).

    Figure 45 Figure 46

    3.

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    4. A cotton roll may be inserted between the mandibular teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition. (Watch the occlusal border of the film packet; it tends to slip down anteriorly.)5. Align the central ray perpendicular to the bisector vertically and at the desiredinterproximal contact to be viewed. Horizontally, the central ray should pass between thecontact of the first and second premolar (Figure 47). For maxillary exposures the tubehead will be pointed down for positive (+) angulation.6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

    Figure 47

    Bisecting Angle Methodology

    Full Mouth ExposureProcedure for the Maxillary Molars

    1. Assemble the posterior film holder and insert the film packet horizontally on thebiteblock. Use a #2 film.2. Center the film on the molars as close as possible to the lingual surfaces of theteeth (Figure 48). Position the film in the palate so that the entire tooth length will appearon the film with approximately a one-eighth inch border below the cuspal ridge. Align theanterior border of the film packet with the second premolar so that the image captured onthe anterior edge of the film is the distal third of the second premolar. Position thebiteblock on the occlusal surface of the teeth being radiographed (Figure 49).

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    Figure 48 Figure 49

    3.

    4. A cotton roll may be inserted between the mandibular teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition.5. Align the central ray perpendicular to the bisector vertically and at the desiredinterproximal contact to be viewed. Horizontally, the central ray should pass between thecontact of the first and second molar (Figure 50). For maxillary exposures the tube headwill be pointed down for positive (+) angulation.6. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

    Figure 50Procedure for the Mandibular Central/Lateral Incisors

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    1. Assemble the anterior film holder and insert the film packet vertically on thebiteblock. Use a #1 film.2. Center the film on the central/lateral incisors as close as possible to the lingualsurfaces of the teeth with approximately a one-eighth inch border of the film extendingabove the incisal edge of the centrals. Position the biteblock on the incisal edges of theteeth to be radiographed (Figure 51).

    Figure 51

    3. A cotton roll may be inserted between the maxillary incisors and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition. The film should be straightened as the patient closes and the floor of the mouthrelaxes.4. Align the central ray perpendicular to the bisector vertically and at the desiredinterproximal contact to be viewed. Horizontally, the central ray should pass between the

    central/lateral incisors (Figure 52). For mandibular exposures the tube head will bepointed up for negative (-) angulation.5. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

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    Figure 52

    Bisecting Angle MethodologyFull Mouth ExposureProcedure for the Mandibular Canines

    1. Assemble the anterior film holder and insert the film packet vertically on thebiteblock. Use a #1 film.2. Center the film on the canine as close as possible to the lingual surfaces of theteeth with approximately a one-eighth inch border of the film extending above the incisaledge of the canine. Position the biteblock on the incisal edges of the teeth to beradiographed (Figure 53).

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    Figure 53

    3. A cotton roll may be inserted between the maxillary teeth and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition. The film should be straightened as the patient closes and the floor of the mouthrelaxes.4. Align the central ray perpendicular to the bisector vertically and at the desiredinterproximal contact to be viewed. Horizontally, the central ray should bisect the canine(Figure 54). For mandibular exposures the tube head will be pointed up for negative (-)angulation.5. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

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    Figure 54Procedure for the Mandibular Premolars

    1. Assemble the posterior film holder and insert the film packet horizontally on thebiteblock. Use a #2 film.2. Center the film on the premolars as close as possible to the lingual surfaces ofthe teeth. Align the anterior border of the film packet with the canine so that the imagecaptured on the anterior edge of the film will be the distal third of the canine. Position thebiteblock on the occlusal surface of the teeth to be radiographed (Figure 55).

    Figure 55

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    3. A cotton roll may be inserted between the maxillary premolars and the biteblockfor patient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition. The film should be straightened as the patient closes and the floor of the mouthrelaxes.4. Align the central ray perpendicular to the bisector vertically and at the desiredinterproximal contact to be viewed. Horizontally, the central ray should pass between thefirst and second premolars (Figure 56). For mandibular exposures the tube head will bepointed up for negative (-) angulation.5. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

    Figure 56

    Bisecting Angle MethodologyFull Mouth ExposureProcedure for the Mandibular Molars

    1. Assemble the posterior film holder and insert the film packet horizontally on thebiteblock. Use a #2 film.2. Center the film on the molars as close as possible to the lingual surfaces of theteeth. Align the anterior border of the film packet with the second premolar so that theimage captured on the anterior edge of the film will be the distal third of the secondpremolar. Position the biteblock on the occlusal surface of the teeth to be radiographed(Figure 57).

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    Figure 57

    3. A cotton roll may be inserted between the maxillary molars and the biteblock forpatient comfort. Ask the patient to slowly, but firmly, bite onto the block to maintain filmposition. The film should be straightened as the patient closes and the floor of the mouthrelaxes.4. Align the central ray perpendicular to the bisector vertically and at the desiredinterproximal contact to be viewed. Horizontally, the central ray should pass between thecontact of the first and second molar (Figure 58). For mandibular exposures the tube headwill be pointed up for negative (-) angulation.5. Follow the film and equipment manufacturers recommendation concerningexposure factors. Make the exposure.

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    Figure 58

    Bitewing RadiographyBitewing radiographs are of particular value in detecting interproximal caries in the early stages ofdevelopment, before it is clinically apparent. For this reason it is critical that horizontal angulationbe accurately projected following the direction of the interproximal contacts and no overlappingcontacts be present on the film. Bitewing films are also useful in evaluation of the alveolar crestsfor detection of early periodontal disease.Basic PrinciplesBitewing radiographs are parallel films because the film is positioned parallel to the long axis of theteeth and the beam is perpendicular to the film as in Figure 59. A bitewing tab is utilized tostabilize the film as the patient bites together (Figure 60).

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    Figure 59 Figure 60

    Beam Angulation and Film Holding Devices

    Bitewing radiographs are usually exposed with an indicated vertical angulation of +10 degrees(tube head points down for positive (+) angulation). This, angulation provides an acceptablecompromise for the differences between the long axis inclinations of the maxillary and mandibularteeth. Horizontal angulation is aligned with the direction of the contact, and the central ray isdirected between the contact of the teeth to be radiographed. Horizontal angulation is achievedwhen the central ray of the x-ray beam is directed specifically between the contacts of the teeth tobe radiographed.The interproximal examination may be done using special #3 bitewing film but is preferablyachieved by using #2 films fitted with a tab. There are also film holding devices available thatsupport the film as well as provide an external reference for positioning the tube head. The patientstabilizes the film by gently biting together on the manufactured tab or on the instrument.Tube head position is illustrated in Figure 61, and a sample set of bitewing radiographs isillustrated in Figure 62.Before any radiographs are exposed, the patient must be protected with a lead apron and thyroid

    collar. The apron must be properly placed to avoid interference with the radiographic exposure.

    Figure 61

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    Figure 62

    Quiz

    1. What is the main purpose for taking bitewing radiographs?2. Why are bitewings exposed with a vertical angulation of +10 degrees?

    Answers

    1. To detect interproximal caries.2. To compromise for the differences in the long axis angulations of the maxillary andmandibular teeth.

    Intraoral Occlusal RadiographyMaxillary Topographical OcclusalThis projection (Figure 63) shows the palate (roof of the mouth), zygomatic process of the maxilla(a projection from the maxilla), antero-inferior aspects of each antrum (in this case, the maxillarysinuses), nasolacrimal canals (tear ducts), teeth from the left second molars to the central incisors,and the nasal septum (cartilage dividing the nose).

    Figure 63Uses: To view the maxilla for anterior alveolar fractures, cysts, supernumerary teeth andimpacted canines, and to view pathology at the apices of the incisors. It is not used to diagnoseperidontal conditions.

    Patient positioning: The patient is seated with the sagittal plane perpendicular to the floor andthe occlusal plane parallel to the floor. Before any radiographs are exposed, the patient must be

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    protected with a lead apron and thyroid collar. The apron must be properly placed to avoidinterference with the radiographic exposure.Film placement: With the tube side of the film (size #4) toward the maxilla, the film is placedcrosswise in the mouth, like a sandwich. It is gently pushed backwards until it contacts the anteriorborder of the mandibular ramus. The patient bites down gently to maintain position.Exposure factors: Follow the recommendations of the film and equipment manufacturer.Direction of the central ray: The central ray is directed at the center of the film with a verticalangulation of +65 degrees and a horizontal angulation of 0 degrees. In this case, the central raywill pass through the bridge of the nose, as in Figure 64.

    Figure 64Mandibular Topographical OcclusalUses: To view the anterior portion of the mandible for fractures, cysts, root tip and periapicalpathology. It provides a very good view of the symphysis region of the mandible. (Figure 65)

    Figure 65Patient positioning: The patient is seated with the head tilting slightly backward, so that theocclusal plane (ala-tragus line) is 45 degrees above the horizontal plane. Before any radiographs

    are exposed, the patient must be protected with a lead apron and thyroid collar. The apron mustbe properly placed to avoid interference with the radiographic exposure.

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    Film placement: With the tube side of the film (size #4) toward the mandible, the film is placedcrosswise in the mouth, like a sandwich. It is gently pushed backwards until it contacts the anteriorborder of the mandibular ramus. The patient bites down gently to maintain position.Exposure factors: Follow the recommendations of the film and equipment manufacturer.Direction of the central ray: The central ray is directed between the apices of the mandibularcentral incisors and the tube is angled at -55 degrees relative to the film plane, as in Figure 66.

    Figure 66

    Intraoral Occlusal RadiographyMaxillary Vertex OcclusalUses: To view the buccopalatal relationships of unerupted teeth in the dental arch. (Figure 67)

    Figure 67Patient positioning: The patient is seated with the sagittal plane perpendicular to the floor andthe occlusal plane parallel to the floor. Before any radiographs are exposed, the patient must beprotected with a lead apron and thyroid collar. The apron must be properly placed to avoidinterference with the radiographic exposure.Film placement: The film (size #4) is placed in the same manner as the Maxillary TopographicalOcclusal.Exposure factors: Follow the recommendations of the film and equipment manufacturer.Direction of the central ray: The central ray is directed through the top of the skull (hence thename vertex occlusal). Since the beam must penetrate a considerable amount of bone and soft

    tissue, the exposure time must be increased. The central ray is perpendicular to the film plane andis directed to the center of the film as in Figure 68.

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    Figure 68Mandibular Cross-Sectional OcclusalUses: To view the entire mandible for fractures, foreign bodies, root tips, salivary calculi, tori, etc.(Figure 69)

    Figure 69Patient positioning: The patients head may be in any comfortable position that allows thecentral ray to be directed perpendicular to the plane of the film packet. Before any radiographs areexposed, the patient must be protected with a lead apron and thyroid collar. The apron must be

    properly placed to avoid interference with the radiographic exposure.Film placement: The film (size #4) is placed in the same manner as the MandibularTopographical Occlusal.Exposure factors: Follow the recommendations of the film and equipment manufacturer.Direction of the central ray: The central ray is perpendicular to the film plane and is directed tothe center of the film as in Figure 70.

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    Figure 70

    Intraoral Occlusal RadiographyPosterior Oblique Maxillary OcclusalUses: To view the maxillary posterior region and provide a topographical view of the maxillarysinus. The projection may be used in place of periapical films in patients who have a tendency togag and for examining periapical pathology and root tips. (Figure 71)

    Figure 71Patient positioning: The patient is seated with the occlusal plane parallel to the floor and thesagittal plane perpendicular to the floor. Before any radiographs are exposed, the patient must beprotected with a lead apron and thyroid collar. The apron must be properly placed to avoidinterference with the radiographic exposure.Film placement: The film (size #4) plane should be parallel to the floor, and the packet should bepushed posteriorly as far as possible. The lateral border of the film should be positioned parallel tothe buccal surfaces of the posterior teeth and extend laterally approximately one-half inch past thebuccal cusps on the side of interest. The patient should bite down gently to maintain film position.Exposure factors: Follow the recommendations of the film and equipment manufacturer.Direction of the central ray: The tube is directed at right angles to the curve of the arch, andstrikes the center of the film packet as in Figure 72.

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    Figure 72Posterior Oblique Mandibular OcclusalUses: The projection is used to view the posterior teeth of the mandible to locate cysts, fractures,supernumerary teeth, and periapical pathology. It can be used in place of posterior periapicalfilms. (Figure 73)

    Figure 73Patient positioning: The patient is seated with the occlusal plane parallel to the floor and the

    sagittal plane perpendicular to the floor. Before any radiographs are exposed, the patient must beprotected with a lead apron and thyroid collar. The apron must be properly placed to avoidinterference with the radiographic exposure.Film placement: The film (size #4) plane should be parallel to the floor, and the packet should bepushed posteriorly as far as possible. The lateral border of the film should be positioned parallel tothe buccal surfaces of the posterior teeth and extend laterally approximately one-half inch past thebuccal cusps on the side of interest. The patient should bite down gently to maintain film position.Exposure factors: Follow the recommendations of the film and equipment manufacturer.Direction of the central ray: The tube is directed at the apex of the mandibular second premolar,and the central ray should strike the center of the film packet. The vertical angulation is -50degrees as in Figure 74.

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    Figure 74

    Intraoral Occlusal RadiographyModified Oblique Posterior Mandibular OcclusalUses: This projection is especially useful to detect calculi in the submandibular gland. Calculi areoften difficult to detect on conventional radiographs due to superimposition of the mandibular bone.(Figure 75)

    Figure 75Patient positioning and film placement: With the tube side of the film (size #4) toward themandible the film is placed in the patients mouth crosswise like a sandwich. The film plane shouldbe parallel to the floor, and the packet should be pushed posteriorly as far as possible. The lateralborder of the film should be positioned parallel to the buccal surfaces of the posterior teeth andextend laterally approximately one-half inch past the buccal cusps on the side of interest. Thepatients head is then rotated to the side and lifted up. Before any radiographs are exposed, thepatient must be protected with a lead apron and thyroid collar. The apron must be properly placedto avoid interference with the radiographic exposure.Exposure factors: Follow the recommendations of the film and equipment manufacturer.Direction of the central ray: The tube is positioned under and behind the mandible and the

    central ray is directed onto the center of the film so that it passes inside the ascending ramus sothat the submandibular gland will be between the tube and the film as in Figure 76.

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    Figure 76

    Digital RadiologyDigital imaging was introduced into dentistry in 1987. Digital sensors are used instead of x-ray film.Sensors can be wired or wireless depending on the system used. (Figures 77 and 78) Sensorsand tube head placement are the same for digital imaging as film and tube head placement is fortraditional radiology. Most standard radiographic machines can be converted to acquire digitalimages. Digital imaging still uses ionizing radiation, and therefore, before any radiographs areexposed, the patient must be protected with a lead apron and thyroid collar. The apron must beproperly placed to avoid interference with the radiographic exposure.The sensors are slightly thicker than a regular film. Modified film holders must be utilized in the

    placement of the sensors. These modified holders can be purchased from any major dental supplycompany. The sensors can be reused several times. Proper use of intraoral barrier and OSHAtechniques must be observed.The advantages of digital radiology are decreased exposure time to the patient, elimination ofdarkroom processing time and exposure to processing chemicals, immediate viewing, and abilityto easily and cost effectively transmit directly to third party facilities or affiliating dental offices.Additional computerized advantages include the ability to enhance the image for viewing. Once animage is in the computer, brightness and contrast and image reversal can be enhanced for optimalviewing of tissue and bone levels. The radiograph can be rotated and magnified to enhancedetails. An additional feature shows embossed images creating a stacked effect of the oral tissues.The main disadvantages are substantial start up costs including machinery and operatorycomputer technology, and compatibility with other software program and RAM capacity.Considerations must also be noted that although your office may utilize digital radiography, otherfacilities may not and the transfer of images between them could be more difficult.

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    Figure 77 Figure 78

    SummaryProper film and tube head placement are a critical component of the total radiographic procedure.Periapical, bitewing, and occlusal surveys are critical components of diagnosis and treatment ofdental patients. Because of the exposure to ionizing radiation, proper techniques must beemployed to reduce radiation exposure to the patient through the use of lead aprons, high speedfilm, and proper technique; thus decreasing additional film retakes. As technology advances indental radiology operators must maintain current knowledge and adapt their abilities for the best

    treatment of the patient.

    GlossaryAlveolar Crest highest part of the alveolar boneAlveolar Ridge part of the bone that contains the tooth socketsAnterior in frontApices plural for apex or tip of rootBisector a straight line that bisects an angleBuccal towards the cheekCalculi plural of calculus; a hard rough deposit on the tooth surfaceDigit finger or toeDistal tooth surface away from the midlineEdentulous without teethForamina plural for foramen; an openingHorizontal line extending from side to sideImpacted trapped below the surface as in an impacted third molarIncisal Edge biting surface of front teethInterproximal between the teethIntraoral inside the oral cavityLingually towards the tongueMandible lower jawMandibular Ramus portion of the mandible that extends back and upMaxilla upper jawMesial tooth surface towards the midline

    Occlusal biting surface of back teethPalatal pertaining to the roof of the mouthParallel extending in the same direction and same distance apart

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    Periapical surrounding the apex or tip of the toothPeriodontal surrounding the toothPeriodontal disease disease of the gums and supporting areas of the teethPerpendicular intersecting at a right anglePosteriorly behindSagittal Plane vertical plane dividing the bodySupernumerary teeth extra teethTori hard bony projectionsVertical line extending from top to bottom (up and down)