|SECTION VI||STRUCTURES VISIBLE ON A PANORAMIC RADIOGRAPH|
The objective for this section is to prepare the reader to perform the following:
- Based on relative location and shape, identify key structures already discussed in this text as they appear on a panoramic radiograph.
Now that you have learned the location and shape of many bony structures within the head, it is possible to look at a radiograph and identify many of these structures based on their shape and location. In order to do this, you need to know that the denser structures in the head (i.e., the bones and teeth) will appear on the radiograph as whiter (or radiopaque). Further, the least dense structures in the head (like foramina passing through bones, sinuses, and nerve canals) will appear on the radiograph as darker structures (called radiolucent). A panoramic radiograph can be taken with a device that rotates around the jaws so that the operator can view structures from the right, front, and left on one film. It is as though you could take the horseshoe-shaped mandible with its teeth and rami and flatten it out with its inner surface lying flat on a table and the outer (lateral) surface visible as one flat object.
With this simple background, and your knowledge of the shape and location of structures in the skull, study the radiograph in Figure 14-52 and see how many of the following structures you can identify without looking at the answers. MATCH the following lettered items with the corresponding number and arrow on the radiograph. Use the clues only if needed.
- Mandibular teeth. Note that each tooth has one or more roots embedded into the bony (opaque) alveolar processes. How many teeth there? If you know that all anterior teeth are present, count the premolars in each quadrant. Are they all there? Can you see the radiolucent, very thin (almost invisible) periodontal ligaments around each root?
- Maxillary teeth. Note that each tooth has one or more roots embedded into the bony (opaque) alveolar processes. How many are there?
- Body of the mandible
- Angle of the mandible
(Clue: It is the inferior posterior corner of the horizontal body of the mandible where it joins the vertical ramus.)
(Clue: It is the vertical part of the mandible.)
- Coronoid process
(Clue: It is shaped like the point of a king’s crown.)
- Condylar process
(Clue: It articulates within the concavity of the temporal bone called the mandibular [articular] fossa).
- Sigmoid notch
(Clue: This notch is between the coronoid and condyloid processes.)
- Mandibular canal
(Clue: It is a radiolucent canal with its mandibular foramen where the inferior alveolar nerve enters the mandible.)
- Mental foramen
(Clue: It is a radiolucent circle near the ends of the premolar roots where the mental nerve branch of the inferior alveolar nerve splits off and exits the mandible to innervate the lower lip and chin on that side.)
- Maxillary tuberosity
(Clue: It is the bump of bone behind the last maxillary molar.)
- Maxillary sinus
(Clue: It is the radiolucent area in proximity to the roots of the maxillary molars and premolars.)
- Hard palate composed of the palatal processes of maxillae and palatine bones.
- Mandibular (articular) fossa
(Clue: It is the depression on the base of the cranium in the temporal bone where the condyle of the mandible fits.)
- Articular eminence
(Clue: It is the opaque bump of temporal bone anterior to the mandibular fossa that deflects the condyles and the mandible downward [opening the mouth] as it moves forward.)
- Articular disc space
(Clue: It is a radiolucency between the condyle and the fossa.)
- Nasal passageway (also called nasal fossa)
(Clue: This hollow radiolucent space is located superior to the maxillary anterior teeth.)
- Nasal septum: VOMER and vertical plate of ETHMOID bone
(Clue: The septum separates the right and left halves of the nasal passageways.)
- Hyoid bone
(Clue: This bone appears to float below the mandible since the infra- and suprahyoid muscles attached to it are radiolucent and are not visible.)
ANSWERS: A—18 (there are 14 mandibular teeth; two premolars are missing), B—2 (there are 14 maxillary teeth; two premolars are missing), C—16, D—14, E—13, F—7, G—12, H—8, I—19, J—17, K—1, L—3, M—6, N—10, O—9, P—11, Q—5, R—4, S—15