Overview
This lecture explains the basics of dental x-rays, including how they work, the main types used in dentistry, how to interpret them, and introduces the buccal object rule for object localization.
How Dental X-Rays Work
- High-voltage electricity heats a filament, releasing electrons that hit a tungsten target, producing x-rays.
- X-rays are high-frequency, high-energy waves (photons) between UV and gamma rays on the spectrum.
- X-rays pass through tissue; denser tissues block more x-rays, creating lighter (radiopaque) areas on the image.
- The receptor (film or digital sensor) captures the pattern of x-ray attenuation to make the image.
Types of Dental X-Rays
- Intraoral x-rays: Receptor inside the mouth, best for teeth and supporting structures.
- Extraoral x-rays: Receptor outside the mouth, best for skull, jaws, and big-picture views.
- Bitewing x-rays: Show upper and lower teeth together, used for detecting cavities and bone loss.
- Periapical x-rays: Focus on the area around the tooth root apex, used to diagnose abscesses, cysts, and bone pathology.
- Occlusal x-rays: Beam comes from above or below, used for trauma and eruption patterns.
- Panoramic x-rays: Extraoral, provide a wide view of all teeth and jaws.
- Cephalometric x-rays: Extraoral, show skull and jaw relationships, important for orthodontics.
Reading Dental X-Rays
- Radiopaque (light/white): Dense tissues (enamel, bone, metal fillings).
- Radiolucent (dark): Less dense tissues (pulp, air spaces, cavities, infections).
- Enamel: Brightest, hardest part of the tooth.
- Dentin: Slightly less bright, second hardest layer.
- Pulp: Darkest area, contains nerve and blood vessels.
- Lamina dura: Whiter bone border near teeth, denser bone.
- Periodontal ligament (PDL): Thin dark line between bone and tooth root, holds tooth in place.
- Bone loss and cavities show as darker or missing areas on x-rays.
- Fillings and crowns appear very radiopaque (white or bright).
- Cervical burnout: Normal darkening near tooth neck, not a cavity.
The Buccal Object Rule
- The buccal object rule helps determine if an object is closer to the cheek (buccal) or tongue (lingual).
- Take two x-rays at different angles; if the object moves in the same direction as the tube head, it is lingual; if opposite, it is buccal.
- Known as the SLOB rule: "Same Lingual, Opposite Buccal."
Key Terms & Definitions
- Radiopaque — Appears white on x-ray; resists x-ray passage.
- Radiolucent — Appears dark; allows x-ray passage.
- Enamel — Hard, outermost tooth layer, most radiopaque.
- Dentin — Tooth layer under enamel, less dense.
- Pulp — Central part of the tooth with nerves/blood vessels, radiolucent.
- Lamina dura — Dense bone lining of tooth socket, radiopaque.
- PDL (Periodontal Ligament) — Space holding tooth to bone, thin and dark on x-ray.
- Bitewing — X-ray type showing crowns of upper/lower teeth.
- Periapical — X-ray showing entire tooth and root tip.
- SLOB Rule — "Same Lingual, Opposite Buccal" for object localization.
Action Items / Next Steps
- Review bitewing and periapical x-ray images to identify anatomical structures and pathologies.
- Practice determining buccal vs. lingual object positions using the SLOB rule.
- Prepare for a quiz on dental x-ray terminology and reading basics.