Normal Anatomy and Developmental Anomalies of the Maxillofacial Region
Normal anatomy on imaging
Know the radiographic appearance of key structures: cortical vs cancellous bone, the mandibular canal and mental foramen, the maxillary sinus and its septa, the nasal cavity and turbinates, the pterygoid plates, and the temporomandibular joint. Recognize normal radiolucencies (e.g., incisive canal, genial tubercles, submandibular fossa) and radiopacities (e.g., torus, stylohyoid ligament ossification). Understand how projection geometry alters apparent position (e.g., the mandibular canal appears to move with tube angulation).
Developmental anomalies
Know common anomalies: dens invaginatus, dens evaginatus, taurodontism, gemination vs fusion (fusion has a shared pulp, gemination has a single root with split crown), concrescence, hyperdontia/supernumerary teeth, hypodontia, and eruption disturbances. Understand cleft lip/palate imaging, and the appearance of developmental cysts (e.g., nasopalatine duct cyst, dentigerous cyst). Recognize syndromes with maxillofacial findings (e.g., cleidocranial dysplasia with supernumerary teeth).
Traps
Questions test whether a radiolucency is normal vs pathologic (e.g., incisive canal vs nasopalatine duct cyst), and whether an anomaly is gemination or fusion. Watch for confusion between ghost images and true structures on panoramic images.
Rule of thumb
If a radiolucency is symmetric, has corticated borders, and matches a known anatomic space, suspect normal anatomy; if it expands, displaces teeth, or is asymmetric, suspect pathology.