CDA Essentials 2019 • Volume 6 • Issue 4

32 | 2019 | Issue 4 S upporting Y our P ractice to where you started. Look for landmarks (See Landmarks of the Mandible - below.) Bear in mind that some landmarks will not be visible on every image, even in normal cases and look for symmetry between right and left. If something is the same on both sides, it’s usually—but not always—normal. • Count the teeth in the mandible. Make sure there is a normal complement of teeth. • Trace the entire outline of the maxilla. Trace the bony borders of the maxilla along the crest of the alveolar process. Look for three vertical radiopaque cortical lines in the posterior half of the maxillary sinus—they may not always be present, but you should look for them: (1) posterior wall of the sinus, (2) infratemporal surface of the zygomatic bone, and (3) posterior wall of the maxilla. Also look for the pterygoid plates. (See Landmarks of the Maxilla - p. 33). • Count the teeth in the maxilla. Make sure there is a normal complement of teeth. 3. Look for (and at) soft-tissue structures adjacent to and associated with the mandible and maxilla. 4. Look at the properties of the basal bone and alveolar processes of the maxilla and mandible to assess if they are normal. 5. As you systematically examine your images and identify and assess the radiographic appearance of each structure, continually ask yourself if what you see can be explained as normal. 6. List your observations As you trace and examine these structures, write down your observations. For the novice, these observations should be cross-checked using the Radiology Observation Checklist (see p. 39) with the image set. 7. Determine the basic nature of the disease • Is it normal? The first fork in the road ALWAYS involves asking yourself, “Is what I’m looking at on this radiographic image set a variation of normal or is this abnormal?” • If abnormal, is it developmental or acquired? The second fork in the road, once you decide that something is abnormal, is considering whether the abnormality is developmental or acquired: is this something the patient has always had (developmental conditions) or do these radiographic findings represent a condition your patient has picked up along the way? These latter conditions are said to be “acquired.” • If acquired, which disease categories can be ruled out? You’ve read this heading correctly. First, try to figure out what something is NOT before honing in on what conditions it might be. This reduces the number of categories from which the lesion could stem. Acquired conditions will generally fit (albeit with exceptions) into one of seven broad categories: 1. Infection/inflammatory 2. Traumatic 3. Cyst/cyst-like 4. Metabolic/systemic disease 5. Benign tumour 6. Fibro-osseous 7. Malignant tumour Do NOT try to guess which category best explains your findings; first determine which categories can be ruled out. 8. Formulate a working diagnosis Once the number of possible acquired disease categories have been narrowed down, determine what the possibilities are to help you reach a differential diagnosis, starting with the most likely condition to the least likely condition. As a practitioner, you would include clinical, histological or patient history information. You would then make a working diagnosis, consider special testing methods and treat the patient.  Landmarks of the Mandible • Condylar head. Is it inclined backwards? Is there evidence of destruction or fracture? Are there any interruptions in its cortical outline? • Mandibular ramus. Is it symmetrical on both sides? • Coronoid process. Look at its length; an elongated coronoid process may be associated with an inability to open. • Inferior border of the mandible. It should appear as a ribbon-like radiopacity. • External oblique ridge • Mylohyoid ridge • Mandibular canal. Appears as a fairly uniform neurovascular bundle that terminates at the mental foramen. • Mental foramen. Take care to not mistakenly identify these two radiolucencies as pathoses, as they can be highly variable in location and size. • Mental fossa • Lingual foramen • Submandibular gland fossa • Cervical spine