Reading the panoramic film

Correct answer: D. The patient's head was rotated to the left

• A. Excessive chin depression produces an exaggerated downward curve of the occlusal plane, the so-called frown, with the anterior teeth blurred and the condyles displaced to the edge of the film, but the two sides stay symmetrical.
• B. Rotating to the right would produce the mirror image, magnifying the left side.
• C. Positioning too far forward narrows the anterior teeth and blurs them, but again it does so symmetrically.
• D. Correct. In panoramic imaging the side placed further from the film and closer to the source is magnified. Turning the head to the left carries the right side away from the receptor, so the right structures widen while the left, now closer, narrows. The rule is that the side that appears wider is the side that moved away.

Correct answer: A. The right earring, projected across the midline

• A. Correct. Panoramic imaging produces ghost images: an object between the source and the centre of rotation projects across to the opposite side, higher, larger and blurred. The right earring therefore appears over the left side. The real left earring also appears, on its own side and sharper.
• B. The true left earring image would sit on the left but would be sharp and in its correct anatomical position rather than projected up over the antrum.
• C. Nothing in the history suggests trauma or surgery, and the ring shapes correspond directly to the jewellery.
• D. Antroliths are irregular mineralised concretions within the sinus and would not appear as concentric rings that match the earrings the patient is wearing.

Note: The practical lesson comes first: all jewellery, hairpins, dentures and removable appliances come off before a panoramic exposure. When a ghost appears, remember it projects to the opposite side, higher and magnified.

Correct answer: D. Waters projection

• A. The submentovertex, or base, view shows the zygomatic arches and the skull base from below, and is used for medial or lateral displacement of the arches.
• B. A lateral cephalometric film superimposes the two sides and is used for orthodontic and orthognathic analysis, not for sinus assessment.
• C. The reverse Towne view is used for condylar neck fractures and demonstrates the condyles and the posterior skull.
• D. Correct. The Waters, or occipitomental, projection tips the head so the petrous ridges drop below the antral floors, giving an unobstructed view of both maxillary sinuses. It is the standard plain film for sinusitis and for orbital floor and midface fractures.

Correct answer: C. Normal anatomy, the shadow of the nose

• A. A supernumerary such as a mesiodens would be radiopaque with recognisable enamel and dentin density and a defined outline.
• B. A soft tissue calcification would be a discrete radiopacity with sharp borders, not a diffuse shadow following the contour of the nose.
• C. Correct. On a maxillary occlusal projection the tip of the nose and the nasal cartilages cast a soft tissue shadow across the anterior region. Recognising normal soft tissue superimposition prevents unnecessary investigation. Soft tissue shadows are diffuse and lack the density and defined outline of bone or tooth structure.
• D. A retained root would show tooth density, root form and often a residual canal outline.

Correct answer: A. The hyoid bone

• A. Correct. The hyoid bone appears frequently on panoramic films as a curved radiopacity below the mandible, often superimposed over the mandibular body or projected bilaterally. It is normal anatomy and needs no action.
• B. A carotid atheroma appears as a vertical linear or nodular calcification at about the level of C3 to C4, adjacent to the greater cornu of the hyoid, and its recognition warrants medical referral.
• C. The epiglottis may appear as a soft tissue shadow in the airway but is far less dense and does not have this curved bony outline.
• D. The styloid process runs downward and forward from the skull base near the mastoid. When elongated and mineralised, as in Eagle syndrome, it appears as a slender spike, not a broad curved body.

Correct answer: D. Cone beam computed tomography

• A. A single periapical film is two-dimensional and cannot resolve buccal from palatal without a second angled exposure.
• B. Panoramic imaging has substantial distortion in the anterior midline and considerable superimposition in that region.
• C. An occlusal film adds a second plane and, paired with a periapical using the tube shift rule, can localise reasonably. But when precise three-dimensional relationships matter, CBCT is superior.
• D. Correct. CBCT gives true three-dimensional localisation, showing the mesiodens in relation to the incisor roots, the nasopalatine canal and the cortical plates, which determines the surgical approach and reduces the risk of damaging adjacent structures.

Correct answer: D. Same lingual, opposite buccal

• A. This misstates the mnemonic; the L stands for lingual.
• B. The first S refers to the object moving in the same direction as the tube, not to a superior position.
• C. The B stands for buccal, which is the whole point of the rule.
• D. Correct. SLOB stands for same lingual, opposite buccal. When the tube head is shifted and a second image taken, an object that moves in the same direction as the tube lies lingually or palatally, and an object that moves in the opposite direction lies buccally. It is also called Clark's rule or the tube shift technique.

Correct answer: A. Buccal

• A. Correct. The tube moved distally and the object moved mesially, which is the opposite direction. By SLOB, opposite means buccal. Working through it deliberately, rather than reciting the mnemonic, is what makes these items reliable.
• B. An object within the canal would not shift relative to the root at all; it would stay superimposed on it in both projections.
• C. A palatal object would have moved distally, following the tube in the same direction.
• D. The tube shift technique resolves buccal from lingual, not apical position, and an object apical to the root would not shift laterally in this way.