Overview
This lecture covers intraoral and extraoral radiographic techniques, common errors in dental radiography, image interpretation, and the clinical decision-making process for prescribing radiographs.
Intraoral Radiographic Techniques
- Intraoral radiographs are taken inside the mouth and include bitewings, paralleling, bisecting, and occlusal radiographs.
- Occlusal radiographs show the occlusal aspect and are used to visualize the entire arch, not as a standalone image.
- Occlusal films help detect salivary stones, supernumerary teeth, bone injuries, abnormal growths, or foreign objects.
- Advanced bone loss is best evaluated with periapical (PA) images, not occlusal films.
Extraoral Radiographic Techniques
- Panoramic (pan) images are extraoral and show both the maxilla and mandible for assessing eruption patterns, trauma, or large lesions.
- Panoramic radiographs are not suitable for diagnosing occlusal caries, periapical pathology, or periodontal bone loss.
- Patient positioning for pan: Frankfurt plane (tragus to infraorbital rim) must be parallel to the floor; incorrect positioning causes image distortion.
Image Analysis and Common Errors
- Improper receptor placement can miss the tooth apex on a PA film.
- Foreshortening (roots look short) is due to excessive vertical angulation; correct by decreasing angulation.
- Elongation (roots look long) is due to insufficient vertical angulation; correct by increasing angulation.
- Overlapping contacts are caused by incorrect horizontal angulation.
- Cone cuts occur when the PID (position indicating device) is misaligned.
- Patient movement during x-ray exposure reduces image sharpness, making images blurry.
Interpretation and Identification
- Radiopaque (white) structures: enamel, dentin, lamina dura, alveolar crest, bone projections (e.g., process, condyle).
- Radiolucent (dark) structures: pulp, periodontal ligament space, fossa, canal, foramen, orbit, sinus.
- Amalgam restorations are radiopaque with less-defined borders; composite restorations are well-defined and often radiopaque.
- Implants are radiopaque; no visible roots indicate no natural teeth are present.
Prescribing Dental Radiographs
- Radiographs are prescribed based on clinical indications and individual needs, not on a fixed schedule.
- Children: bitewings only if proximal surfaces are not visible; more frequent films if disease risk is high.
- Teenagers: bitewings and pan; full-mouth series only for extensive disease/treatment.
- Adults: clinical signs determine the type and frequency of radiographs; focus on caries risk and periodontal status.
Key Terms & Definitions
- Intraoral Radiograph — X-ray taken inside the mouth (e.g., bitewing, PA, occlusal).
- Occlusal Film — Shows the chewing surface and entire dental arch.
- Panoramic Image — Extraoral x-ray showing the whole maxilla, mandible, and adjacent structures.
- Foreshortening — Shortened tooth image due to increased vertical angulation.
- Elongation — Lengthened tooth image due to decreased vertical angulation.
- Radiopaque — Appears white on x-ray film; represents denser materials.
- Radiolucent — Appears dark on x-ray film; represents less dense or hollow structures.
- Frankfurt Plane — Reference line from ear tragus to infraorbital rim, parallel to the floor during pan imaging.
Action Items / Next Steps
- Review the guidelines for prescribing dental radiographs.
- Practice identifying radiographic errors and anatomical landmarks on sample images.
- Prepare for upcoming reading on intraoral and extraoral radiographic interpretation.