18 Image Types & Interpretation Practice Questions & Answers

1. 1. A dentist has completed a clinical examination of an adult recall patient whose posterior contacts are tight and cannot be checked with an explorer, and wants to evaluate the proximal surfaces of the posterior teeth. Which image type is indicated for this clinical question?

   • A.Posterior bitewings, which record the crowns of both arches and the interproximal surfaces✓ Answer
   • B.Posterior periapicals, which record each tooth from the crown through the apex and beyond
   • C.A panoramic image, which records both arches and the adjacent structures in one survey view
   • D.A maxillary occlusal image, which records a large area of one arch on a single large receptor

   The bitewing places the crowns of both arches and the contact areas on one image with the beam directed through the contacts, so proximal enamel and dentin can be examined where an explorer cannot reach. A periapical is designed to show the apex and surrounding bone, and its geometry does not reliably open the posterior contacts.

   Source: ADA/FDA Selection of Patients for Dental Radiographic Examinations; Iannucci & Howerton, Dental Radiography (purpose of the bitewing image)Report a problem with this question

2. 2. A patient reports swelling and pain under the tongue at mealtimes, and the dentist suspects a salivary stone in the floor of the mouth. Which projection displays the buccal and lingual cortical plates and the floor of the mouth in one view?

   • A.A mandibular anterior periapical, with the receptor parallel to the long axes of the teeth
   • B.A lateral cephalometric projection, with the head held in a device for repeatable geometry
   • C.A cross-sectional mandibular occlusal, with the central ray aimed perpendicular to the receptor✓ Answer
   • D.A topographic maxillary occlusal, with the central ray aimed by the bisecting-angle principle

   In the cross-sectional occlusal the beam passes down the long axis of the receptor, producing a bird's-eye view in which the buccal and lingual plates and the soft tissue of the floor of the mouth are separated rather than superimposed on the teeth. That separation is what allows a sialolith in a submandibular duct to be seen.

   Source: Iannucci & Howerton, Dental Radiography — cross-sectional mandibular occlusal projection and its indicationsReport a problem with this question

3. 3. Before placing an implant at the mandibular first molar site, the dentist needs the faciolingual width of the ridge and the exact position of the mandibular canal. Which imaging study answers that question?

   • A.A periapical of the site, whose paralleling geometry records ridge height and width without distortion
   • B.A cone-beam computed tomography scan, whose volume shows axial, coronal and sagittal views✓ Answer
   • C.A panoramic image, whose single survey view reproduces the arches at life size in every dimension
   • D.A cross-sectional occlusal, whose geometry separates the buccal and lingual plates from the roots

   Width in the faciolingual direction and the position of a canal inside bone are three-dimensional measurements, and only volumetric data reconstructed into multiplanar slices supplies them without superimposition. Two-dimensional projections compress that third dimension, and the panoramic image also magnifies unequally in the horizontal and vertical directions.

   Source: ADA Council on Scientific Affairs statement on cone-beam computed tomography; Iannucci & Howerton, Dental Radiography (CBCT and implant site assessment)Report a problem with this question

4. 4. An orthodontist wants a standardized, reproducible image to evaluate the relationship of the teeth to the jaws and the facial profile, and to monitor changes as the patient grows. Which image type is designed for that purpose?

   • A.A Waters projection, taken with the head tipped back so the maxillary sinuses are displayed
   • B.A panoramic image, taken with the patient biting a block so both arches appear on one image
   • C.A lateral cephalometric projection, taken with a head-positioning device so geometry repeats✓ Answer
   • D.A full mouth series, taken with receptor holders so every tooth-bearing area is recorded

   The cephalostat holds the head in the same relationship to the beam and the receptor at every visit, so images taken months or years apart can be superimposed and compared. Reproducible geometry, not coverage, is what makes this projection the tool for following dentofacial growth and planning orthodontic or orthognathic treatment.

   Source: Iannucci & Howerton, Dental Radiography — extraoral cephalometric projection; ADA/FDA selection criteria, evaluation of dentofacial growth and developmentReport a problem with this question

5. 5. A patient has a mandibular molar with spontaneous pain and a sinus tract on the facial gingiva, and the dentist wants to see whether a radiolucency has formed at the root ends. Which image is indicated, and what must it include?

   • A.A panoramic that includes both arches plus the condyles and the whole temporomandibular joint
   • B.A periapical that includes the whole tooth plus about 2 to 4 mm of bone beyond the apices✓ Answer
   • C.An occlusal that includes the whole mandibular arch plus both cortical plates around the roots
   • D.A bitewing that includes the crowns of both arches plus the crestal bone between the teeth

   A lesion of endodontic origin sits in the bone around and beyond the apex, so the image is only diagnostic when a margin of periapical bone is recorded past the root ends. An image that stops at the apices cannot show the extent of the radiolucency, and a bitewing does not record the apices at all.

   Source: Iannucci & Howerton, Dental Radiography — purpose of the periapical image and criteria for a diagnostically acceptable periapicalReport a problem with this question

6. 6. A patient with generalized periodontitis needs posterior images showing how far the crestal bone has receded from the cementoenamel junctions. Which choice best meets that need, and why?

   • A.Maxillary occlusal images, because they display the alveolar crest of a large area of the arch
   • B.A panoramic image, because it displays crestal bone at the resolution of an intraoral image
   • C.Horizontal bitewings, because the wide receptor captures the full root length of both arches
   • D.Vertical bitewings, because the upright receptor records more crestal bone and root surface area✓ Answer

   Turning the receptor so its long axis is vertical extends the field further toward the apices, so bone levels that have moved apically still fall inside the image. A horizontal bitewing is framed on the crowns and crestal bone and will cut off the crest once loss is advanced.

   Source: Iannucci & Howerton, Dental Radiography — vertical bitewing indication in periodontal diseaseReport a problem with this question

7. 7. A new adult patient brings a recent panoramic image from another office, and the dentist still prescribes posterior bitewings. What is the radiographic reason for prescribing them?

   • A.Panoramic images cannot record metallic restorations, so recurrent caries beneath them is hidden
   • B.Panoramic images magnify and superimpose structures, so early proximal caries can be missed✓ Answer
   • C.Panoramic images record only the mandible in focus, so maxillary contacts never appear at all
   • D.Panoramic images are read only for the third molars, so the rest of the arch is not interpreted

   Rotational geometry gives the panoramic image inherent magnification, unequal horizontal and vertical distortion, superimposition of adjacent teeth and lower resolution, so incipient lesions at the contacts are not reliably visible. The bitewing keeps the receptor close to the teeth with the beam through the contacts, which is why it remains the caries survey.

   Source: ADA/FDA Selection of Patients for Dental Radiographic Examinations; Iannucci & Howerton, Dental Radiography — limitations of panoramic imagingReport a problem with this question

8. 8. A new adult patient presents with heavy calculus, several broken-down teeth and mobility in more than one sextant. Which radiographic approach fits the ADA/FDA patient selection criteria?

   • A.A full mouth series, because clinical evidence of generalized oral disease is the stated indication✓ Answer
   • B.Periapicals of the mobile teeth, because imaging is directed only at symptomatic regions
   • C.Posterior bitewings only, because caries detection is the priority for every new adult patient
   • D.A panoramic image, because one survey view of both arches covers all tooth-bearing areas

   The selection criteria make the full mouth series the preferred examination when the clinical examination shows generalized oral disease, because every tooth-bearing area then has a plausible reason to be imaged. Imaging is still prescribed by the dentist after the clinical examination, so the finding of generalized disease is what justifies the wider survey.

   Source: ADA/FDA Selection of Patients for Dental Radiographic Examinations — new adult patient with clinical evidence of generalized oral diseaseReport a problem with this question

9. 9. An assistant reviews a premolar bitewing: the contacts are open, the crowns of both arches and the alveolar crests are recorded, density and contrast allow enamel, dentin and pulp to be told apart, and no root apices appear. How should this image be judged?

   • A.It is acceptable only after the software is used to bring out the missing apical structures
   • B.It must be retaken, because the vertical angulation clearly cut the apices from the image
   • C.It is diagnostically acceptable, because a bitewing is not intended to record the root apices✓ Answer
   • D.It must be retaken, because every intraoral image has to include the apices and apical bone

   An image is judged against the criteria for the image type that was prescribed, not against a single universal checklist. The bitewing is defined by crowns, open contacts and crestal bone, so the absence of apices is expected, and post-acquisition adjustment cannot add anatomy that was never inside the field.

   Source: Iannucci & Howerton, Dental Radiography — features of a diagnostically acceptable bitewing imageReport a problem with this question

10. 10. An assistant is arranging a newly acquired full mouth series in the imaging software using the ADA-recommended anatomical arrangement. Where do the images of the patient's right maxillary posterior teeth belong?

    • A.On the viewer's right, because the series is arranged as though the viewer stands behind the patient
    • B.On the viewer's left, because the images are placed in the order the operator exposed them
    • C.On the viewer's right, because maxillary images are always arranged from the patient's viewpoint
    • D.On the viewer's left, because the series is arranged as though the viewer faces the patient✓ Answer

    The anatomical arrangement puts the series in the same orientation as the patient seen from the front, so the patient's right side falls on the viewer's left and the left side on the viewer's right. Keeping one convention for every series is what prevents a lesion or a restoration from being charted on the wrong side.

    Source: Iannucci & Howerton, Dental Radiography — anatomical (labial) arrangement of a full mouth series recommended by the American Dental AssociationReport a problem with this question

11. 11. In an anatomically arranged full mouth series, how are the maxillary and mandibular images oriented with respect to each other?

    • A.Maxillary and mandibular roots both point down, with the occlusal planes along the top edge
    • B.Maxillary roots point up and mandibular roots point down, with the occlusal planes facing each other✓ Answer
    • C.Maxillary roots point down and mandibular roots point up, with the occlusal planes outermost
    • D.Maxillary and mandibular roots both point up, with the occlusal planes running parallel

    The arrangement reproduces the jaws as they sit in the head, so maxillary roots rise toward the top of the mount, mandibular roots hang toward the bottom, and the two occlusal planes meet in the middle with a slight upward curve posteriorly. Orienting by anatomy is how arch and side are confirmed on a digital image.

    Source: Iannucci & Howerton, Dental Radiography — anatomical arrangement and orientation of a full mouth seriesReport a problem with this question

12. 12. Using the Universal Numbering System for the permanent dentition, which pair of teeth is correctly identified?

    • A.Number 3 is the maxillary left first molar and number 30 is the mandibular left second molar
    • B.Number 3 is the maxillary right second molar and number 30 is the mandibular left first molar
    • C.Number 3 is the maxillary right first molar and number 30 is the mandibular right first molar✓ Answer
    • D.Number 3 is the maxillary right first premolar and number 30 is the mandibular right second molar

    Numbering runs continuously from the maxillary right third molar at 1 across to the maxillary left third molar at 16, then drops to the mandibular left third molar at 17 and returns to the mandibular right third molar at 32. Counting forward from 1 places the first molar at 3, and counting back from 32 places the lower first molar at 30.

    Source: American Dental Association Universal Numbering System, permanent dentition (teeth 1 through 32)Report a problem with this question

13. 13. In the Universal Numbering System for the primary dentition, letters A through T follow the same path used for the permanent teeth. Where does the lettering begin and end?

    • A.A is the maxillary right second primary molar and T is the mandibular right second primary molar✓ Answer
    • B.A is the maxillary left second primary molar and T is the mandibular left second primary molar
    • C.A is the maxillary right primary central incisor and T is the mandibular left primary lateral incisor
    • D.A is the mandibular right second primary molar and T is the maxillary right second primary molar

    The lettering starts at the same corner of the mouth as the permanent numbering, the patient's upper right, and travels across the upper arch to J at the upper left, then drops to K at the lower left and finishes at T on the lower right. Because a primary quadrant ends in a second molar, both A and T are second primary molars.

    Source: American Dental Association Universal Numbering System, primary dentition (teeth A through T)Report a problem with this question

14. 14. A periapical of the mandibular premolars shows a well-defined round radiolucency near the apex of the second premolar. The tooth is caries-free, responds normally to pulp testing, and the lamina dura is intact around the apex. What does this most likely represent?

    • A.The periapical cyst, an epithelium-lined cavity that develops from a long-standing apical granuloma
    • B.The mental foramen, a normal opening of the mandible that transmits the mental nerve and vessels✓ Answer
    • C.The nutrient canal, a narrow marrow channel that carries vessels between the bony trabeculae
    • D.The periapical granuloma, a chronic inflammatory lesion at the apex of a tooth with a necrotic pulp

    A radiolucency is only pathologic when the clinical picture supports it, and an intact lamina dura with a vital, caries-free tooth argues against a lesion of pulpal origin. The mental foramen lies near the premolar apices and is superimposed on them by projection, which is why it is the classic false positive for apical pathology.

    Source: Iannucci & Howerton, Dental Radiography — normal radiographic anatomy of the mandible (mental foramen) and interpretation of periapical radiolucenciesReport a problem with this question

15. 15. A dentist is reviewing images of a patient who has several different kinds of restorations. Which description of how these materials appear on the image is correct?

    • A.Amalgam appears sharply radiopaque, while acrylic may appear nearly radiolucent✓ Answer
    • B.Amalgam appears moderately radiolucent, while acrylic is the most radiopaque material
    • C.Porcelain appears completely radiolucent, while gutta-percha blends into the pulp space
    • D.Cast gold appears radiolucent, while stainless steel crowns leave only a faint outline

    How light or dark a material looks depends on how much of the beam it absorbs: dense metals such as amalgam, cast gold and stainless steel absorb heavily and appear white with sharp borders. Acrylic and some older composites are close in density to soft tissue, so a restoration made of them can be mistaken for recurrent caries.

    Source: Iannucci & Howerton, Dental Radiography — radiopaque and radiolucent appearance of dental restorative materialsReport a problem with this question

16. 16. On a periapical of the maxillary canine region, two radiopaque lines meet above the root to form an inverted Y shape. Which structures form this landmark?

    • A.The lateral wall of the nasal fossa crossing the floor of the maxillary sinus in that same region✓ Answer
    • B.The zygomatic process crossing the lower border of the maxillary tuberosity above the molars
    • C.The median palatal suture crossing the border of the incisive foramen behind the incisors
    • D.The anterior nasal spine crossing the nasal septum at the midline above the maxillary incisors

    Both the sinus and the nasal fossa are air spaces bounded by thin cortical bone, and where their bony walls cross in the canine region the superimposed cortical lines form the inverted Y. Recognizing it as normal anatomy keeps it from being read as a lesion and confirms that the image is of the maxillary canine area.

    Source: Iannucci & Howerton, Dental Radiography — normal radiographic anatomy of the maxilla (inverted Y formation)Report a problem with this question

17. 17. Two periapicals of the same area are exposed, the second with the tubehead shifted toward the mesial. Between the two images the crown of an impacted canine moves in the same direction as the tubehead shift. Where does the crown lie?

    • A.Buccal to the roots, because the buccal object rule is reversed in the mandibular arch
    • B.In the plane of the roots, because objects between the roots move with the tube head
    • C.Buccal to the roots, because an object that moves with the tube shift lies toward the cheek side
    • D.Lingual to the roots, because an object that moves with the tube shift lies toward the tongue✓ Answer

    The buccal object rule, remembered as same lingual, opposite buccal, follows from projection geometry: a structure farther from the receptor is displaced more by a change in beam angle, so it appears to travel with the tube. The rule holds in both arches, and two views at different angles are needed because one image cannot separate depth.

    Source: Buccal object rule (SLOB, tube-shift or Clark's rule); Iannucci & Howerton, Dental Radiography — localization of impacted teeth and foreign objectsReport a problem with this question

18. 18. A patient who is moving away asks the office to send her radiographic images to her new dentist. What is the correct handling of that request?

    • A.The images belong to the patient as originals once paid for, so the office sends them and keeps none
    • B.The images may go to the new dentist on a phone request, since both offices are treating her
    • C.The images are deleted after transfer, because the receiving office now holds the only record
    • D.The images stay in the record the practice keeps, and copies go out with her written authorization✓ Answer

    Radiographic images are part of the dental record, which the practice owns and must retain, while the patient controls where the information goes; the HIPAA Privacy Rule requires a signed authorization before protected health information is disclosed to another provider at the patient's direction. How long the record must be kept is set by the state in which the practice operates, so the office follows its own state's requirement.

    Source: HIPAA Privacy Rule, 45 CFR 164.508 (authorization for disclosure) and 45 CFR 164.524 (access to records); ADA principles on ownership of the dental recordReport a problem with this question

Practice questions only — not real exam items, and not affiliated with or endorsed by the Dental Assisting National Board. Questions are written to the domains published in DANB's current RHS and ICE exam outlines, and cover digital radiography only, matching DANB's statement that film-based concepts are no longer tested. This bank does not cover the chairside assisting or dental anatomy component exams. What a dental assistant is legally allowed to do — including who may expose radiographs and what training a state requires first — is set by each state's dental board and is deliberately out of scope here. Exam format, eligibility, and scoring are set by DANB and change from time to time; confirm the current requirements with DANB and your state board before you register. Official DANB exam outlines →