chapter 29

Normal Anatomy

Panoramic Images

Outline

NORMAL ANATOMIC LANDMARKS

Bony Landmarks of Maxilla and Surrounding Structures

Bony Landmarks of Mandible and Surrounding Structures

AIR SPACES SEEN ON PANORAMIC IMAGES

SOFT TISSUES SEEN ON PANORAMIC IMAGES

Learning Objectives

After completion of this chapter, the student will be able to do the following:

• Define the key terms associated with normal anatomy on panoramic images

• Identify and describe the bony landmarks of the maxilla and surrounding structures as viewed on the panoramic image

• Identify and describe the bony landmarks of the mandible and surrounding structures as viewed on the panoramic image

• Identify air spaces as viewed on the panoramic image

• Identify soft tissues as viewed on the panoramic image

Key Terms

Angle of mandible

Anterior nasal spine

Articular eminence

Coronoid notch

Coronoid process

Ear

External auditory meatus

External oblique ridge

Genial tubercles

Glenoid fossa

Glossopharyngeal air space

Hamulus

Hard palate

Incisive canal

Incisive foramen

Inferior border of mandible

Infraorbital foramen

Internal oblique ridge

Lateral pterygoid plate

Lingual foramen

Lingula

Lipline

Mandibular canal

Mandibular condyle

Mandibular foramen

Mastoid process

Maxillary sinus

Maxillary tuberosity

Mental foramen

Mental fossa

Mental ridge

Mylohyoid ridge

Nasal cavity

Nasal septum

Nasopharyngeal air space

Orbit

Palatoglossal air space

Pterygomaxillary fissure

Soft palate and uvula

Styloid process

Tongue

Zygoma

Zygomatic process of maxilla

A panoramic image allows the dental professional to view large areas of the mandible and the maxilla on a single projection. Just as dental professionals must be able to recognize normal anatomic landmarks on periapical images, they must also be able to recognize normal anatomic structures viewed on panoramic images. The recognition of landmarks enables dental professionals to interpret panoramic images accurately. Without a working knowledge of anatomy, normal anatomic structures may be mistaken for pathologic conditions.

To interpret the panoramic image and identify normal anatomic landmarks, dental professionals must have thorough knowledge of the anatomy of the maxilla and the mandible. Each normal anatomic landmark seen on a panoramic image corresponds to what is seen on the human skull. If dental professionals are familiar with the anatomy of the human skull, they will be able to identify normal anatomy viewed on a panoramic image.

The purpose of this chapter is to describe the normal anatomy of the maxilla and the mandible as viewed on a panoramic image. In addition to the normal anatomic landmarks, air space images and soft tissue images are also described in this chapter.

Normal Anatomic Landmarks

Bony Landmarks of Maxilla and Surrounding Structures

The maxilla forms the floor of the orbit of the eyes, the sides and floor of the nasal cavity, and the hard palate. The lower border of the maxilla supports maxillary teeth. This section reviews the bony landmarks of the maxilla and surrounding structures that can be viewed on a panoramic image.

Each of the following bony landmarks of the maxilla and surrounding structures is identified on Figure 29-1.

FIGURE 29-1 Normal anatomic landmarks of the maxilla and surrounding structures: 1, mastoid process; 2, styloid process; 3, external auditory meatus; 4, glenoid fossa; 5, articular eminence; 6, lateral pterygoid plate; 7, pterygomaxillary fissure; 8, maxillary tuberosity; 9, infraorbital foramen; 10, orbit; 11, incisive canal; 12, incisive foramen; 13, anterior nasal spine; 14, nasal cavity and conchae; 15, nasal septum; 16, hard palate; 17, maxillary sinus; 18, floor of maxillary sinus; 19, zygomatic process of maxilla; 20, zygomatic arch; 21, hamulus. (Modified from Dental Auxiliary Education Projects: Normal radiographic landmarks, New York, Teachers College Press, 1982 by Teachers College, Columbia University. All rights reserved.)

Mastoid Process

Description: The mastoid process is a marked prominence of bone located posterior and inferior to the temporomandibular joint (TMJ). The mastoid process is part of the temporal bone.

Appearance: On a panoramic image, the mastoid process appears as a rounded radiopacity located posterior and inferior to the TMJ area. The mastoid process is not seen on periapical images.

Styloid Process

Description: The styloid process is a long, pointed, and sharp projection of bone that extends downward from the inferior surface of the temporal bone. The styloid process is located anterior to the mastoid process.

Appearance: On a panoramic image, the styloid process appears as a long radiopaque spine that extends from the temporal bone anterior to the mastoid process. The styloid process is not seen on periapical images.

External Auditory Meatus

Description: The external auditory meatus (also known as the external acoustic meatus) is a hole, or opening, in the temporal bone located superior and anterior to the mastoid process.

Appearance: On a panoramic image, the external auditory meatus appears as a round or ovoid radiolucency anterior and superior to the mastoid process. The external auditory meatus is not seen on periapical images.

Glenoid Fossa

Description: The glenoid fossa (also known as the mandibular fossa) is a concave, depressed area of the temporal bone. The mandibular condyle rests in the glenoid fossa. The glenoid fossa is located anterior to the mastoid process and the external auditory meatus.

Appearance: On a panoramic image, the glenoid fossa appears as a concave radiopacity superior to the mandibular condyle. The glenoid fossa is not seen on periapical images.

Articular Eminence

Description: The articular eminence (also known as the articular tubercle) is a rounded projection of the temporal bone located anterior to the glenoid fossa.

Appearance: On a panoramic image, the articular eminence appears as a rounded radiopaque projection of the bone located anterior to the glenoid fossa. The articular eminence is not seen on periapical images.

Lateral Pterygoid Plate

Description: The lateral pterygoid plate is a wing-shaped bony projection of the sphenoid bone located distal to the maxillary tuberosity region.

Appearance: On a panoramic image, the lateral pterygoid plate appears as a radiopaque projection of bone distal to the maxillary tuberosity region. The lateral pterygoid plate is not seen on periapical images.

Pterygomaxillary Fissure

Description: The pterygomaxillary fissure is a narrow space or cleft that separates the lateral pterygoid plate and the maxilla.

Appearance: On a panoramic image, the pterygomaxillary fissure appears as a radiolucent area between the lateral pterygoid plate and the maxilla. The zygoma is often superimposed on this region and obscures the pterygomaxillary fissure. The pterygomaxillary fissure is not seen on periapical images.

Maxillary Tuberosity

Description: The maxillary tuberosity is a rounded prominence of bone that extends posterior to the third molar region.

Appearance: On a panoramic image, the maxillary tuberosity appears as a radiopaque bulge distal to the third molar region.

Infraorbital Foramen

Description: The infraorbital foramen is a hole, or opening, in bone inferior to the border of the orbit.

Appearance: On a panoramic image, the infraorbital foramen appears as a round or ovoid radiolucency inferior to the orbit. The infraorbital foramen may be superimposed over the maxillary sinus. The infraorbital foramen is not seen on periapical images.

Orbit

Description: The orbit is the bony cavity that contains the eyeball.

Appearance: On a panoramic image, the orbit appears as a round radiolucent compartment with radiopaque borders located superior to the maxillary sinuses. On most panoramic images, only the inferior border of the orbit is visible, where it appears as a radiopaque line.

Incisive Canal

Description: The incisive canal (also known as the nasopalatine canal) is a passageway through bone, that extends from the superior foramina of the incisive canal (located on the floor of the nasal cavity) to the incisive foramen (located on the anterior hard palate).

Appearance: On a panoramic image, the incisive canal appears as a tubelike radiolucent area with radiopaque borders. The incisive canal is located between the maxillary central incisors.

Incisive Foramen

Description: The incisive foramen (also known as the nasopalatine foramen) is an opening, or hole, in bone that is located at the midline of the anterior portion of the hard palate directly posterior to the maxillary central incisors.

Appearance: On a panoramic image, the incisive foramen appears as a small, ovoid or round radiolucency located between the roots of the maxillary central incisors.

Anterior Nasal Spine

Description: The anterior nasal spine is a sharp bony projection of the maxilla located at the anterior–inferior portion of the nasal cavity.

Appearance: On a panoramic image, the anterior nasal spine appears as a V-shaped radiopaque area located at the intersection of the floor of the nasal cavity and the nasal septum.

Nasal Cavity

Description: The nasal cavity (also known as the nasal fossa) is a pear-shaped compartment of bone located superior to the maxilla.

Appearance: On a panoramic image, the nasal cavity appears as a large radiolucent area superior to the maxillary incisors.

Nasal Septum

Description: The nasal septum is a vertical bony wall or partition that divides the nasal cavity into the right and left nasal fossae.

Appearance: On a panoramic image, the nasal septum appears as a vertical radiopaque partition that divides the nasal cavity.

Hard Palate

Description: The hard palate is the bony wall that separates the nasal cavity from the oral cavity.

Appearance: On a panoramic image, the hard palate appears as a horizontal radiopaque band superior to the apices of maxillary teeth.

Maxillary Sinus and Floor of Maxillary Sinus

Description: The maxillary sinuses are paired cavities or compartments of bone that are located within the maxilla, superior to maxillary posterior teeth.

Appearance: On a panoramic image, the maxillary sinuses appear as paired radiolucent areas located superior to the apices of maxillary premolars and molars. The floor of the maxillary sinus is composed of dense cortical bone and appears as a radiopaque line.

Zygomatic Process of Maxilla

Description: The zygomatic process of the maxilla is a bony projection of the maxilla, that articulates with the zygoma, or malar bone (cheekbone).

Appearance: On a panoramic image, the zygomatic process of the maxilla appears as a J- or U-shaped radiopacity located superior to the maxillary first molar region.

Zygoma

Description: The zygoma (also known as the malar bone or zygomatic bone) is the cheekbone, and it articulates with the zygomatic process of the maxilla.

Appearance: On a panoramic image, the zygoma appears as a radiopaque band that extends posteriorly from the zygomatic process of the maxilla.

Hamulus

Description: The hamulus (also known as the hamular process) is a small, hooklike projection of bone that extends from the medial pterygoid plate of the sphenoid bone. The hamulus is located posterior to the maxillary tuberosity.

Appearance: On a panoramic image, the hamulus appears as a radiopaque hooklike projection posterior to the maxillary tuberosity area.

Figures 29-2, 29-3, and 29-4 illustrate the normal anatomic landmarks of the maxilla and surrounding structures that can be viewed on a panoramic image.

FIGURE 29-2 Normal anatomic landmarks of the maxilla and surrounding structures seen on panoramic images: 1, external auditory meatus; 2, pterygomaxillary fissure; 3, infraorbital foramen; 4, orbit; 5, anterior nasal spine; 6, nasal septum; 7, nasal conchae; 8, hard palate; 9, zygomatic process of maxilla. (From Haring JI, Lind LJ: Radiographic interpretation for the dental hygienist, Philadelphia, 1993, Saunders.)

FIGURE 29-3 Normal anatomic landmarks of the maxilla and surrounding structures seen on panoramic images: 1, glenoid fossa; 2, articular eminence; 3, maxillary tuberosity; 4, maxillary sinus; 5, zygoma. (From Haring JI, Lind LJ: Radiographic interpretation for the dental hygienist, Philadelphia, 1993, Saunders.)

FIGURE 29-4 Lateral pterygoid plate. (From Haring JI, Lind LJ: Radiographic interpretation for the dental hygienist, Philadelphia, 1993, Saunders.)

Bony Landmarks of Mandible and Surrounding Structures

This section reviews the bony landmarks of the mandible and surrounding structures that can be viewed on a panoramic image. Each of the following bony landmarks of the mandible and surrounding structures is identified on Figure 29-5.

FIGURE 29-5 Normal anatomic landmarks of the mandible and surrounding structures: 1, condyle; 2, coronoid notch; 3, coronoid process; 4, mandibular foramen; 5, lingula; 6, mandibular canal; 7, mental foramen; 8, hyoid bone; 9, mental ridge; 10, mental fossa; 11, lingual foramen; 12, genial tubercles; 13, inferior border of mandible; 14, mylohyoid ridge; 15, internal oblique ridge; 16, external oblique ridge. (Modified from Dental Auxiliary Education Project: Normal radiographic landmarks, New York, Teachers College Press, 1982 by Teachers College, Columbia University. All rights reserved.)

Mandibular Condyle

Description: The mandibular condyle is a rounded projection of bone extending from the posterior superior border of the ramus of the mandible. The mandibular condyle articulates with the glenoid fossa of the temporal bone.

Appearance: On a panoramic image, the mandibular condyle appears as a bony, rounded radiopaque projection extending from the posterior border of the ramus of the mandible. The mandibular condyle is not seen on periapical images.

Coronoid Notch

Description: The coronoid notch is a scooped-out concavity of bone located distal to the coronoid process of the mandible.

Appearance: On a panoramic image, the coronoid notch appears as a radiopaque concavity located distal to the coronoid process on the superior border of the ramus. The coronoid notch is not seen on periapical images.

Coronoid Process

Description: The coronoid process is a marked prominence of bone found on the anterior–superior ramus of the mandible.

Appearance: On a panoramic image, the coronoid process appears as a triangular radiopacity posterior to the maxillary tuberosity region.

Mandibular Foramen

Description: The mandibular foramen is a round or ovoid hole in bone on the lingual aspect of the ramus of the mandible.

Appearance: On a panoramic image, the mandibular foramen appears as a round or ovoid radiolucency centered within the ramus of the mandible. The mandibular foramen is not seen on periapical images.

Lingula

Description: The lingula is a small, tongue-shaped projection of bone seen adjacent to the mandibular foramen.

Appearance: On a panoramic image, the lingula appears as an indistinct radiopacity anterior to the mandibular foramen. The lingula is not seen on periapical images.

Mandibular Canal

Description: The mandibular canal is a tubelike passageway through bone, that travels the length of the mandible. The mandibular canal extends from the mandibular foramen to the mental foramen and houses the inferior alveolar nerve and blood vessels.

Appearance: On a panoramic image, the mandibular canal appears as a radiolucent band outlined by two thin radiopaque lines representing the cortical walls of the canal.

Mental Foramen

Description: The mental foramen is an opening or hole in bone located on the external surface of the mandible in the region of the mandibular premolars.

Appearance: On a panoramic image, the mental foramen appears as a small, ovoid or round radiolucency located in the apical region of the mandibular premolars.

Mental Ridge

Description: The mental ridge is a linear prominence of cortical bone located on the external surface of the anterior portion of the mandible that extends from the premolar region to the midline.

Appearance: On a panoramic image, the mental ridge appears as a thick radiopaque band that extends from the mandibular premolar region to the incisor region.

Mental Fossa

Description: The mental fossa is a scooped-out depressed area of bone located on the external surface of the anterior mandible above the mental ridge in the mandibular incisor region.

Appearance: On a panoramic image, the mental fossa appears as a radiolucent area above the mental ridge.

Lingual Foramen

Description: The lingual foramen is a tiny opening, or hole, in bone located on the internal surface of the mandible near the midline.

Appearance: On a panoramic image, the lingual foramen appears as a small radiolucent dot located inferior to the apices of the mandibular incisors.

Genial Tubercles

Description: Genial tubercles are tiny bumps of bone that are located on the lingual aspect of the mandible.

Appearance: On a panoramic image, genial tubercles appear as a ring-shaped radiopacity surrounding the lingual foramen.

Inferior Border of Mandible

Description: The inferior border of the mandible is a linear prominence of cortical bone that defines the lower border of the mandible.

Appearance: On a panoramic image, the inferior border of the mandible appears as a dense radiopaque band that outlines the lower border of the mandible.

Mylohyoid Ridge

Description: The mylohyoid ridge is a linear prominence of bone located on the internal surface of the mandible that extends from the molar region downward and forward toward the lower border of the mandibular symphysis.

Appearance: On a panoramic image, the mylohyoid ridge appears as a dense radiopaque band that extends downward and forward from the molar region.

Internal Oblique Ridge

Description: The internal oblique ridge is a linear prominence of bone located on the internal surface of the mandible that extends downward and forward from the ramus.

Appearance: On a panoramic image, the internal oblique ridge appears as a dense radiopaque band that extends downward and forward from the ramus.

External Oblique Ridge

Description: The external oblique ridge is a linear prominence of bone located on the external surface of the body of the mandible.

Appearance: On a panoramic image, the external oblique ridge appears as a dense radiopaque band that extends downward and forward from the anterior border of the ramus of the mandible.

Angle of Mandible

Description: The angle is the area of the mandible where the body of the mandible meets the ramus.

Appearance: On a panoramic image, the angle of the mandible appears as a radiopaque bony structure where the ramus joins the body of the mandible.

Figures 29-6, 29-7 and 29-8 illustrate the normal anatomic landmarks of the mandible and surrounding structures that can be viewed on a panoramic projection.

FIGURE 29-6 Normal anatomic landmarks of the mandible and surrounding structures seen on panoramic images: 1, condyle; 2, coronoid notch; 3, coronoid process; 4, mandibular foramen; 5, mental foramen; 6, genial tubercles; 7, styloid process. (From Haring JI, Lind LJ: Radiographic interpretation for the dental hygienist, Philadelphia, 1993, Saunders.)

FIGURE 29-7 Normal anatomic landmarks of the mandible and surrounding structures seen on panoramic images: 1, mandibular canal; 2, hyoid; 3, internal oblique ridge; 4, angle of mandible. (From Haring JI, Lind LJ: Radiographic interpretation for the dental hygienist, Philadelphia, 1993, Saunders.)

FIGURE 29-8 Normal anatomic landmarks of the mandible and surrounding structures as seen on panoramic images: 1, inferior border of mandible; 2, submandibular fossa; 3, external oblique ridge; 4, soft tissue of ear. (From Haring JI, Lind LJ: Radiographic interpretation for the dental hygienist, Philadelphia, 1993, Saunders.)

Air Spaces Seen on Panoramic Images

This section reviews air space images that can be seen on a panoramic image. Each of the following air space images is identified on Figure 29-9.

FIGURE 29-9 Air spaces seen on panoramic images: 1, palatoglossal air space; 2, nasopharyngeal air space; 3, glossopharyngeal air space. (Modified from Dental Auxiliary Education Project: Normal radiographic landmarks, New York, Teachers College Press, 1982 by Teachers College, Columbia University. All rights reserved.)

Palatoglossal Air Space

Description: The term palatoglossal air space refers to the space between the palate (palato) and the tongue (glossal).

Appearance: On a panoramic image, the palatoglossal air space appears as a horizontal radiolucent band located superior to the apices of maxillary teeth.

Nasopharyngeal Air Space

Description: The term nasopharyngeal air space refers to the portion of the pharynx (pharyngeal) that is located posterior to the nasal cavity (naso).

Appearance: On a panoramic image, the nasopharyngeal air space appears as a diagonal radiolucency located superior to the radiopaque shadow of the soft palate and the uvula.

Glossopharyngeal Air Space

Description: The term glossopharyngeal air space refers to the portion of the pharynx (pharyngeal) that is located posterior to the tongue (glosso) and the oral cavity.

Appearance: On a panoramic image, the glossopharyngeal air space appears as a vertical radiolucent band superimposed over the ramus of the mandible. The glossopharyngeal air space is continuous with the nasopharyngeal air space superiorly and the palatoglossal air space inferiorly.

Figure 29-10 shows air spaces that can be viewed on a panoramic image.

FIGURE 29-10 Air spaces seen on panoramic images: 1, palatoglossal air space; 2, nasopharyngeal air space; 3, glossopharyngeal air space. (From Haring JI, Lind LJ: Radiographic interpretation for the dental hygienist, Philadelphia, 1993, Saunders.)

Soft Tissues Seen on Panoramic Images

This section describes soft tissues that can be seen on a panoramic image. Each of the following soft tissues is labeled on Figure 29-11.

FIGURE 29-11 Soft tissues seen on panoramic images: 1, tongue; 2, soft palate and uvula; 3, lipline; 4, ear. (Modified from Dental Auxiliary Education Project: Normal radiographic landmarks, New York, Teachers College Press, 1982 by Teachers College, Columbia University. All rights reserved.)

Tongue

Description: The tongue is a movable muscular organ attached to the floor of the mouth.

Appearance: On a panoramic image, the tongue appears as a radiopaque area superimposed over maxillary posterior teeth.

Soft Palate and Uvula

Description: The soft palate and the uvula form a muscular curtain that separates the oral cavity from the nasal cavity.

Appearance: On a panoramic image, the soft palate and the uvula appear as a diagonal radiopacity projecting posteriorly and inferiorly from the maxillary tuberosity region.

Lipline

Description: The lipline is formed by the positioning of the patient’s lips.

Appearance: On a panoramic image, the lipline is seen in the region of anterior teeth. Areas of teeth not covered by the lips appear more radiolucent; areas covered by the lips appear more radiopaque.

Ear

Appearance: On a panoramic image, the ear appears as a radiopaque shadow that projects anteriorly and inferiorly from the mastoid process. The ear is seen superimposed over the styloid process.

Figure 29-12 shows soft tissues that can be seen on a panoramic image.

FIGURE 29-12 Soft tissues seen on panoramic images: 1, tongue; 2, soft palate and uvula; 3, ear. (From Haring JI, Lind LJ: Radiographic interpretation for the dental hygienist, Philadelphia, 1993, Saunders.)

Summary

• The panoramic image allows the dental professional to view a large area of the maxilla and the mandible on a single projection.

• Knowledge of normal anatomic landmarks is necessary to interpret panoramic images; each normal anatomic landmark seen on a panoramic image corresponds to that seen on a human skull. Knowledge of the anatomy of the maxilla, the mandible, and adjacent bones as viewed on the human skull enables the dental radiographer to identify normal anatomy seen on a panoramic image.

• Knowledge of air spaces and soft tissues is necessary to interpret panoramic images.

• All anatomic landmarks, air spaces, and soft tissues viewed on a panoramic image are described in this chapter.

Bibliography

Haring, JI, Lind, LJ. Normal anatomy (panoramic films). In: Radiographic interpretation for the dental hygienist. Philadelphia: Saunders; 1993.

White, SC, Pharoah, MJ, Panoramic radiography. Oral radiology: principles of interpretation, ed 6, St. Louis, Mosby, 2009.

Quiz Questions

Identification

___ 1. Identify the normal anatomic landmarks labeled 1 to 15 in Figure 29-13.

FIGURE 29-13 (From Haring JI, Lind LJ: Radiographic interpretation for the dental hygienist, Philadelphia, 1993, Saunders.)

___ 2. Identify the normal anatomic landmarks labeled 1 to 16 in Figure 29-14.

FIGURE 29-14 (From Haring JI, Lind LJ: Radiographic interpretation for the dental hygienist, Philadelphia, 1993, Saunders.)