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23220 Principles of Radiographic InterpretationEDUCATIONAL OBJECTIVESUpon completing this chapter, the student will be able to:1. Dene the key terms listed at the beginning of the chapter.2. Understand the steps to be taken in interpreting radiographs and their importance in establishing a diagnosis, as well as discuss how the patient’s signs and symptoms relate to the radiographic diagnosis.3. List the questions that the dental professional should ask and be able to answer prior to the radiographic procedure, as well as list the questions that the dental professional should ask after the preliminary radiographic examination is performed.KEY TERMSbenign lesionbilateral lesiondiagnosisdenitive diagnosisdierential diagnosisinterpretationmalignant growthunilateral lesionvitality testingprovides the signs or symptoms on which to build a diagno-sis. Other signs or symptoms that may be part of a diagnosis are gathered by using the patient’s chief complaint, dental and medical history, clinical examination, vitality testing, advanced imaging, biopsy, and laboratory tests. e steps that are to be taken in formulating a denitive diagnosis are: (1) identication of an area or structure that is questionable, (2) interpretation of what has been identied (dierential diagnosis), and (3) diagnosis based on the interpretation (denitive diagnosis). Because the role of supportive dental professionals is included in steps 1 and 2, they need to develop interpretive skills to identify all normal anatomic structures, both tooth and bone, and artifacts that may be visible on intraoral, panoramic, and other extraoral radiographs. e dental professional also must be able to dierentiate deviations in radiographic form and density from normal structures.To produce adequate diagnostic lms, the dental pro-fessional must know what relevant information is being sought from the radiograph. is base of knowledge makes exposing the radiographs a more challenging, interesting, and rewarding process. If dental professionals know how periapical pathologic conditions appear radiographically, they also will understand the necessity of seeing the entire periapical area of the tooth in question to make a proper diagnosis. For example, if dental professionals know how Introductione inclusion of the following ve chapters on interpreta-tion in this text is not meant to imply that it is the dental professional’s role to make the nal radiographic diagnosis but rather to stress that interpretation is only one step in preparing a diagnosis on a patient. is step should be shared by all of the dental clinicians. At present, the nal diagnostic role legally rests with the dentist, but certainly help and input from other members of the dental team should be encouraged. e purpose of Chapters 19 through 24 is to give dental professionals some basic understanding of radiographic interpretation, to stimulate interest, and to demonstrate the importance of producing an adequate diagnostic radiograph.is chapter discusses the main dierences between interpreting radiographs and ultimately formulating a denitive diagnosis. e diagnostic questions that the dental professional should ask in devising a dierential diagnosis are included in this chapter as well.Dierential Diagnosise dictionary denes interpretation as “an explanation” and diagnosis as “the art or act of identifying a disease from its signs and symptoms.” e interpretation of radiographs 233CHAPTER 20 Principles of Radiographic Interpretationdicult—and, in some cases, how impossible—it is to interpret caries on radiographs with horizontal overlapping of the teeth, they will be motivated to prevent or correct this error in technique to produce adequate diagnostic images.Diagnostic Questionsere are certain radiographic questions that diagnosticians should ask themselves and be able to answer to help make a proper dierential diagnosis. Further analysis of the dif-ferential diagnosis will lead to the denitive diagnosis. e list that follows contains questions to gather recommended clinical and radiographic information with which diagnosti-cians should be familiar.Preliminary Questions• Whatisthepatient’schiefcomplaint?Often,thisgivesimportant information that helps focus the diagnosis.• Whatweretheclinicalndingsthatpromptedthedentalprofessionaltorequesttheradiographs?• What radiographic projections are available, and whatadditional images should be ordered? e dental pro-fessional should start with the basic intraoral images, andthenprogressifnecessarytoanocclusalprojection,extraoral radiograph, panoramic view (Fig. 20.1), and nally a cone beam computed tomography (CBCT) scan or, in some cases, a magnetic resonance image (MRI).• Have periapical and bitewing radiographs been takenrecently?Previousimagesmaygiveahistoryoftreatment(e.g., signs of pulp capping bring periapical pathologic process to the forefront of the diagnostic possibilities; Fig. 20.2).Questions That Follow the Preliminary Radiographic Examination• Isaboneorsofttissuepathologysuspected?• What does the vitality test reveal? About 70% of allpathologicconditionsseeninthejawsaretheresultofnonvital teeth and their sequela.• Figure 20.1 Panoramic radiograph with third molar impaction. • Figure 20.2 Pulp capping. • Figure 20.3 Radiopaque (RO) lesion. • Isthelesionradiolucent(RL),radiopaque(RO),ormixed (bothRLandROcomponents;Figs.20.3to20.5)?• Couldthesuspected“lesion”beananatomiclandmark(Fig. 20.6)? Landmarks are located in specic areasthroughout the oral cavity and are well within normal limits.• Whereis the lesionlocated? Is itin themandible, themaxilla,orelsewhere?Certainlesionsareseen moreinone jaw than the other or can usually occur in onelocation(e.g.,anasopalatinecyst;Fig.20.7).• Isthelesionaunilateral or bilateral lesion(Fig.20.8)?Most (but not all) bilateral ndings are normal anatomic landmarks.HELPFUL HINTWhen distinguishing between whether a radiographic nding is an anatomic landmark or a suspicious lesion, it is important to know the radiographic appearance (radiopaque [RO] or radiolucent [RL]) of the anatomic landmarks and their respective locations. 234 CHAPTER 20 Principles of Radiographic Interpretation• Figure 20.5 Radiolucent (RL) lesion. • Figure 20.6 Normal anatomy. • Figure 20.7 Nasopalatine cyst. • Figure 20.8 Bilateral lesion. • Figure 20.4 Mixed lesion. 235CHAPTER 20 Principles of Radiographic Interpretation• What isthe sizeand shape of the lesion(expressed inmillimeters)?• Are the borders of the lesionwell dened (Fig.20.9)?Well-dened lesions are the signs of a benign lesion, whereas poorly dened borders suggest a malignant growth.• Isthelesionunilocularormultilocular(Fig.20.10)?• How has the lesion aected the teeth in the area?Has there been root resorption or root displacement (Fig.20.11)?• Canthelesionbeseeninthethreeplanes?Ifnot,thenfurther imaging is needed.• Can all the borders of the lesion be visualized (Fig.20.12)?Ifnot,thenfurtherimagingisnecessary.• If previous images of the lesion are available, what isthe rate of growth of the lesion? Certain lesions (e.g.,• Figure 20.9 Lesion with distinct borders. • Figure 20.10 Multilocular lesion. • Figure 20.11 Root resorption. • Figure 20.12 All the borders of the lesion are not seen. malignancies) have rapid growth, whereas cysts and benign lesions grow slowly.• Haveallimpactedteethandedentulousareasbeenvisu-alized?Justbecausetheareaisedentulousdoesnotmeanthat radiographs are unnecessary. An occult pathologic process may be present.Chapter Summary• edentalprofessionalis responsibleforexposingandinterpreting radiographs. e interpretation will ulti-mately lead to the formulation of a denitive diagnosis and treatment plan for the patient.• e three steps that are taken in forming a diagnosisare: (1) identication of an area or structure of concern, (2) radiographic interpretation of what has been identied (dierential diagnosis), and (3) a diagnosis 236 CHAPTER 20 Principles of Radiographic Interpretation• Dentalprofessionalsshouldbecapableofansweringtheproper diagnostic questions needed to formulate the appropriate diagnosis for their patients.based on the radiographic interpretation (denitive diagnosis).• elesionsthatareobservedontheradiographicimagesmust be described and documented in terms of their appearance(RO,RL,ormixed),size,andlocation.Chapter Review QuestionsMatchingMatch the term in Column A with the appropriate descrip-tion in Column B.Column A Column B1. Unilocular lesion2. Radiopaque lesion3. Bilateral lesion4. Radiolucent lesion5. Mixed lesion6. Multilocular lesion7. Unilateral lesion8. Vitality test a. Appears “light” on a radiograph b. A test used to decide if a tooth is vital or nonvital c. Occurs on one side of the oral cavity d. Appears light and dark on a radiograph e. Has one chamber f. Occurs on both sides of the oral cavity g. Has more than one chamber h. Appears dark on a radiographCritical Thinking ExerciseA new patient presents with pain and swelling in the area of tooth #12. e dentist requests that a periapical radiograph of tooth #12 be taken. e image reveals part of a radiolu-cency at the apex of tooth #12. Upon clinical examination, the dental professional notices exudate coming from the swellingonthebuccalsurfaceoftooth#12.Listthestepsthat should be taken in formulating a dierential diagnosis of the area of concern. Be sure to include the answers to the following diagnostic questions in your description. a. Whatisthepatient’schiefcomplaint? b. Whatwerethe clinical ndings thatpromptedthedentalprofessionaltorequesttheradiographs? c. What radiographic projections are available, andwhatadditionalimagesshouldbeordered? d. Have periapical and bitewing radiographs beentakenrecently? e. Isaboneorsofttissuepathologysuspected? f. Whatdoesthevitalitytestreveal? g. IsthelesionRL,RO,ormixed? h. Couldthesuspectedlesionbeananatomiclandmark? i. Whereisthelesionlocated? j. Isthelesionaunilateralorbilaterallesion? k. Whatisthesizeandshapeofthelesion? l. Arethebordersofthelesionwelldened? m. Isthelesionunilocularormultilocular? n. Howhasthelesionaectedtheteethinthearea? o. Canthelesionbeseeninthreeplanes? p. Canallthebordersofthelesionbevisualized?BibliographyIannucciJM,HowertonLJ:Dental radiography: Principles and tech-niques,ed5,StLouis,MO,2016,ElsevierSaunders.WhiteSC,PharoahMJ:Oral radiology: Principles and interpretation, ed7,StLouis,MO,2013,Mosby.