Normal Radiographic Anatomy for the INBDE

Understanding what normal radiographic anatomy is important in order to be able to identify when a radiographic finding is abnormal.

Tooth Anatomy 

We can zoom in and see some additional structures:

Additional landmarks:

Some additional pulp features:

In some radiographs, the gingiva can be visible. This will appear as:

Additional supporting structures include cancellous/trabecular bone and cortical bone:

Maxillary Region

There are several other anatomic features that can be recognized in maxillary periapicals.

Intermaxillary suture

• Linear or slightly undulating radiolucent line between maxillary central incisors

‍Lateral fossa

• Diffuse radiolucent region apical and overlying maxillary lateral incisor

Canine fossa

• Diffuse radiolucent region distal to the maxillary canine

Anterior nasal spine

• diffuse , v-shaped radiopaque region apical to maxillary central incisors

Incisive foramen

• Oval radiolucency in region of maxillary central incisors

Nasopalatine canal

• Radiolucent channel between maxillary central incisors

Nasal septum

• Vertical radiopaque line at midline superior to central incisor

Nose

• Outline of soft tissue

Nasolabial fold

• Outline of soft tissue

Zygomatic arch

• Broad, radiopacity projected mostly superior and posterior to maxillary molars

Zygomatic process of maxilla

• U-shaped, radiopaque line in region of maxillary molars

Floor of maxillary sinus

• Bottom portion of the pyramidal-shaped cavity above the roots of the maxillary premolars and molars

• The nasal cavity and sinuses can have many variations
• The nasal cavity and sinus can be normal, not visible, or large
• The paranasal sinuses can vary in size, shape, and internal septations
• The sinuses have many variants related to their outline, shape, and internal appearance
• The size of the maxillary sinus increases as an individual ages until skeletal maturity is gained

This characteristic “Y” shape is commonly tested!

Maxillary tuberosity

• Radiopaque, rounded prominence distal to maxillary molars

Hamulus

• Hook-like, radiopaque process projected posterior to maxillary tuberosity

Mandibular Region 

Periapical radiographs in the mandibular posterior region can include anatomic features of the mandible.

Genial tubercles

• Poorly defined, irregular, radiopaque region apical to mandibular central incisors

Mental ridge

• Radiopaque, triangular shaped area below the mandibular anterior teeth

Mental foramen

• Round or oval radiolucency in apical region of mandibular premolars or first molars

• Variant of normal: two on one side or posteriorly positioned (this could be real or tube angulation)

Submandibular gland fossa

• Poorly defined, broad radiolucency apical to mandibular molars and premolars

Inferior Alveolar Canal

• Curvilinear, radiolucent channel in posterior mandible

• Variant of normal: anterior looping (shown below), multiple canals, canal diameter large or small

Mental fossa

• Poorly defined, broad, radiolucent region superimposed on mandibular incisor roots

Nutrient canals 

• Radiolucent lines extending between tooth roots

Lingual Foramen

• Round, radiolucent point apical to mandibular central incisors

Sialolith

• Round or oval-shaped radiopacity located on the inside of the mandible
• Due to the calcification and formation of stones in the major salivary glands

Mandibular tori

• Broad radiopacity overlaying the roots of posterior mandibular teeth

Cervical burnout

• This term refers to the radiolucency found just below the CEJ on the root due to anatomical variation or a gap between the enamel and bone covering the root
• It can appear similarly to caries

Sinus pneumatization

• The continuous physiological process that causes the paranasal sinuses to increase in volume
• Although it it seems like there is pathology between the roots of tooth 3 and 5, it is just the expanded sinus

‍Panoramic Features

There are several common anatomic features recognizable in the panoramic radiograph.

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1. Mandibular ramus- Broad radiopaque region in the mandible that connects the body to the condyle and coronoid process
2. Mandibular angle- Junction of the posterior and inferior border of the mandibular ramus
3. Condyle- Oval radiopaque process that extends posteriorly and superiorly from the mandibular ramus
4. Coronoid process- Triangular radiopaque process that extends anterior and superiorly from the ramus
5. Sigmoid notch- Concavity between the condyle and coronoid process
6. Antegonial notch- Concavity on inferior border of the mandible
7. Cervical spine- Irregular, radiopaque column behind the mandible and maxilla
8. Hyoid- Radiopaque process inferior or even superimposed onto the mandible
9. External auditory meatus- Radiolucent oval behind the mandibular condyle
10. Styloid process- Pointed radiopacity behind the mandibular ramus
11. Glenoid fossa- Thin radiopaque concavity where the condyle meets 
12. Articular eminence- Radiopaque convexity in front of the glenoid fossa

Soft tissue features can also superimpose onto the panoramic radiograph.

1. Tongue- Creates an arch that superimposes over the mandibular teeth and portions of the maxillary teeth
2. Soft palate- Creates an arch that superimposes above the tongue
3. Epiglottis- Radiopaque structure seem behind the tongue 
4. Oropharynx- Creates a column of soft tissue that superimposes behind the mandible
5. Nasopharynx- Creates a column of soft tissue that superimposes behind the mandible and is located above the oropharynx

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Now that you know what normal looks like, make sure to check out INBDE Bootcamp's Radiographic Bone Lesions To Know!