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Skull anatomy

Posterioranterior projection 
The PA Skull view is used to detect abnormalities caused by trauma or developmental delays, particularly in the mediolateral dimensions of the skull such as asymmetric growth. It demonstrates the frontal and ethmoid sinuses as well as the orbits, nasal anatomy, coronoid process of the mandible, and a frontal view of the mandible.

Areas of cortical bone that are thinner than other areas may mimic disease by appearing more radiolucent than the surrounding bone. Typically, cortical bone is thinner in the area of the mandibular incisive fossa and submandibular fossa. In the maxilla, the incisive fossa in the globulomaxillary region appears radiolucent.

The radiopaque outline of the orbit is seen bilaterally, traversed by the petrous portion of the temporal bone mid-orbit. The radiopaque innominate line traverses upward from the upper outer portion of the orbit bilaterally. The radiolucent frontal sinus is visualized between the upper inner area of the orbits and may vary greatly in size and shape. The sphenoid and ethmoid sinuses are seen as radiolucent areas located between the mid and lower inner portions of the orbit.

In the center of the image is the nose and its associated anatomy: inferior nasal turbinates, nasal septum, and the nasal turbinates. The nasal septum appears as a vertical radiopaque line floored by the radiopaque nasal fossa and hard palate and sided by the middle nasal turbinates superiorly and the inferior nasal turbinates laterally.

Radiolucent areas lateral to the orbits are the mastoid air cells. Just below the mastoid air cells begins the radiopaque coronoid process of the mandible which extends downward to the mandible. The mandibular canal is visible as it runs most of the length of the rami, ending in the mental foramen at the area of the second mandibular premolar. The shadow of the cervical vertebrae begins in the area of the nasal anatomy and extends downward past the mandible to the bottom of the film, where they are seen much more clearly.

Lateral skull 
This view is used to demonstrate the skull and facial bones, visualizing the hard palate, nasopharyngeal soft tissues, and paranasal sinuses. In orthodontics this view is used to assess facial growth.

This view shows all of the sinuses which appear as a large cluster radiolucent areas. The frontal sinus is the smallest and most superior, with the maxillary sinus below it, bordered by the hard palate which runs consistent with the floor of the maxillary sinus. The ethmoid and sphenoid sinuses are visualized posterior to the maxillary sinus. Adjacent to the posterior wall of the maxillary sinus is the pterygomaxillary fissure which appears triangular in shape and slightly radiopaque. The pterygoid plates are posteriorly adjacent to the fissure.

The soft palate is an ill-defined radiopaque area between the hard palate and the mandible.

Other radiolucent areas include the oropharyngeal airspace running from the oral cavity to the trachea, and the nasopharyngeal air space running from the maxillary sinuses to the trachea.

The cervical vertebrae are visible and well-defined. The mastoid air cells appear as a slightly radiolucent area in the skull above the process of the second vertebra.

Waters view 
This view is particularly useful for evaluating the maxillary sinuses which appear radiolucent. Other radiolucent structures seen include the ethmoid air cells, orbits, nasal turbinates, frontal sinus, and nasal cavity. Radiopaque structures seen include the nasal septum, body of the zygoma, frontal process of the zygoma, zygomatic arch, coronoid process of the mandible, and crista galli.

Submentovertex (SMV) view 
Radiolucent structures demonstrated on this view include the ethmoid sinus, mastoid air cells, and maxillary sinus. Radiopaque structures demonstrated include the base of the skull, mandibular condyles, coronoid process of the mandible, lateral and medial pterygoid plates, nasal septum, and zygomatic arch. Structures of a medium density that are commonly seen include the carotid canal, foramen spinosum, foramen ovale, and foramen magnum.

Normal radiographic anatomy of the tempomandibular joint
A panoramic image of the TMJ typically includes 2 views of each condyle; one with the mouth wide open and one with the mouth closed. Radiopaque anatomy demonstrated typically includes the mandibular condyle, articular eminence, soft palate, and maxillary tuberosity. Radiolucent structures seen include the maxillary sinus, external auditory meatus, and pterygomaxillary fissure.

Virginia Commonwealth University
School of Dentistry
Department of Oral Diagnostic Sciences
Lyons Dental Building
520 North 12th Street
Richmond, Virginia 23298-0566
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