Overview
This lecture reviews intraoral and extraoral radiographic techniques, discusses common image errors, explains radiographic anatomy, and outlines criteria for prescribing dental radiographs.
Intraoral Radiographic Techniques
- Bitewings, paralleling, and bisecting angle techniques are common intraoral radiographs.
- Occlusal radiographs image the occlusal aspects to view the entire dental arch.
- Occlusal radiographs help detect salivary stones, supernumerary teeth, bone injury, swelling, or foreign objects.
Extraoral Radiographic Techniques
- Panoramic (pan) images provide a broad view of the maxilla, mandible, and surrounding structures.
- Panoramic radiographs are suitable for assessing tooth eruption patterns, large lesions, trauma, and impacted teeth.
- Panoramic images are supplementary; they do not replace bitewings or periapical (PA) images.
Radiographic Positioning and Errors
- The Frankfurt plane (tragus to infraorbital rim) should be parallel to the floor during panoramic imaging.
- Incorrect vertical angulation causes foreshortening (over-angulated) or elongation (under-angulated) of teeth roots.
- Horizontal angulation errors create overlapping contacts between teeth.
- Cone cut errors result from improper PID (position indicating device) placement.
- Patient movement during exposure decreases image sharpness, causing blurriness.
- Incorrect anterior/posterior positioning in pan imaging causes magnification (too far back) or minification (too far forward).
Radiographic Interpretation and Anatomy
- Amalgam appears radiopaque with irregular borders; gold is radiopaque with defined borders; composite can be radiopaque or radiolucent.
- Radiolucent (dark) areas include pulp, periodontal ligament space, fossae, canals, sinuses, and foramina.
- Radiopaque (white) areas include enamel, dentin, lamina dura, alveolar crest, and bone projections like processes or condyles.
- The number of natural teeth and dental restorations can be assessed radiographically.
Criteria for Prescribing Radiographs
- Radiographs are prescribed based on clinical findings, caries risk, and periodontal status, not on a fixed schedule.
- Children receive bitewings only when proximal surfaces are not visible.
- Adolescents typically need bitewings and sometimes a pan; full mouth series only if extensive disease is present.
- Adults receive radiographs as needed based on symptoms and disease risk.
Key Terms & Definitions
- Bitewing — intraoral image showing crowns of upper and lower teeth.
- Periapical (PA) — intraoral film showing entire tooth and root.
- Panoramic (Pan) — extraoral image providing an overview of both jaws.
- Occlusal Radiograph — captures the biting surfaces and dental arch.
- Frankfurt Plane — anatomical reference from ear tragus to infraorbital rim, used for head positioning.
- Radiolucent — appears dark on x-rays; indicates spaces or soft tissue.
- Radiopaque — appears white on x-rays; indicates dense structures.
- Foreshortening/Elongation — root distortion due to vertical angulation errors.
- Cone Cut — area of image not exposed due to PID misalignment.
Action Items / Next Steps
- Review radiographic positioning techniques and common errors.
- Study dental radiographic anatomy, focusing on radiolucent and radiopaque landmarks.
- Familiarize yourself with the guidelines for prescribing dental radiographs for various age groups.