Oral Radiology Series: Types of Radiographs and How to Read Them

Categories of Radiographs

• Intraoral Images (Direct):
  • Receptor inside the mouth
  • X-ray photons directly interact with the receptor
  • Examples:
    • Periapical (PA)
    • Bitewing (BW)
    • Occlusal image
• Extraoral Images (Indirect):
  • Specialized screen placed outside mouth
  • X-rays contact screen before film
  • Examples:
    • Panoramics (Pans)
    • Cephalometrics (Cephs)
    • Cone Beam Computed Tomography (CBCT)

Intraoral Imaging

Periapical (PA)

• Captures roots of teeth including their apices
• Used for detecting manifestations of pulpal or periodontal disease
• Identifies radiolucency at root apex (endodontic condition indicator)
• Vertical positioning for anterior; horizontal for posterior
• Anatomy visible: enamel, dentin, pulp, amalgam restorations
• Terms:
  • Lamina dura: Radiopaque line, dense border of alveolar bone
  • Periodontal ligament space: Radiolucent line within lamina dura

Bitewing (BW)

• Focuses on crowns and alveolar bone height
• Effective for posterior caries detection and bone level checks
• Exposed horizontally, occasionally vertically
• Identifies: bone levels, calculus deposits

Occlusal Films

• Receptor placed flat on occlusal plane
• Captures from canine to canine
• Useful for detecting: alveolar bone fractures, impacted/missing/supernumerary teeth
• Preferred for pediatric patients

Extraoral Imaging

Panoramic X-rays

• Panoramic spin around the head
• Screens jaw pathology and third molars
• Systematic approach recommended for viewing
  • Start global, then local

Cephalometrics (Cephs)

• Gathers information on the entire head
• Lateral Ceph: Side profile view
  • Used in orthodontics
  • Superimpose for before/after comparison
• Posterior Anterior (PA) Ceph: Front-back view
  • Historically used for transverse asymmetry

Cone Beam Computed Tomography (CBCT)

• Provides 3D radiographic images
• Views: Axial, Sagittal, Coronal
• Common uses:
  • Implant planning (bone quality/quantity)
  • Endodontics, orthodontics, TMJ, and pathology analysis

Specialized Views

Waters View

• Anterior view of paranasal sinuses, midface, orbits
• Useful for mid facial fractures, sinus issues

Towne's View

• Visualizes condyles and neck of mandible
• Eliminates mastoid and zygoma superimposition

Submento Vertex View

• Base projection of the skull
• Useful for diagnosing basilar skull fractures

Techniques for Intraoral Imaging

Bisecting Angle Technique

• Central ray aimed perpendicular to bisector between tooth and receptor
• Creates equal triangles

Paralleling Technique

• Receptor parallel to tooth axis; central ray perpendicular
• Less distortion, uses XCP device

Common Errors in Radiography

Common Digital Imaging Errors

• Elongation: Due to angulation or bent receptor
• Cone Cut: Misalignment of x-ray beam and receptor
• Under/Overexposure: Incorrect settings
• Double Exposure: Two images on one plate

Panoramic Imaging Errors

• Motion: Causes wave-like lines
• Chin Tilt Errors: Big smile or frown effect
• Ghosting: Detection lag translates object across image

Conclusion

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