Dental Radiography and Staff Protection

Radiographs

• Used to diagnose:
  • Interproximal caries
  • Periapical infection
  • Impacted teeth
  • Dental fractures
• Follow up on treatment outcomes

Protection of Dental Staff

• Best method: use of shielding (solid walls with a lead glass window)
• Radiographer should stand:
  • At 90 degrees to or behind the radiation source
  • At least 6 feet (2 m) from the radiation source
• If insufficient distance, wear a lead or lead-free apron with thyroid shielding
• 6-feet rule applies to panoramic and cephalometric imaging
• For CBCT imaging, stand behind a radioprotective barrier

Protection of Patient

• Additional techniques to reduce radiation burden:
  • Lead or lead-free apron with thyroid collar
  • Rectangular collimation of the x-ray beam
  • Correct focus-to-skin distance (minimum 8 inches/20 cm)
  • More radiation-sensitive image receptors
• Rectangular collimation:
  • Limits surface being irradiated to image receptor size, reducing radiation dose by about 50%
  • Decreases scatter in patient's tissues, resulting in better image quality
• Focus-to-skin distance:
  • Ideal minimum distance: 8 inches (20 cm) to reduce low-energy x-radiation
• Image receptors:
  • Fast image receptors recommended to minimize exposure time and radiation dose
  • E- or F-speed film or digital image receptors recommended for lower radiation doses

Radiographic Image Receptors

Analog Film

• Direct Film:
  • Film of choice for intraoral radiography
  • Highly sensitive to x-rays
  • Only E- or F-speed film recommended
• Disadvantages:
  • Double exposures
  • Difficulty sharing films and storing chemicals/processor
• Indirect Film:
  • Used in panoramic and cephalometric imaging
  • More sensitive to light than x-rays
  • Short exposure time, but images are less sharp

Digital Film

• Photostimulable Phosphor Storage Plates (PSPPs):
  • Referred to as indirect digital imaging
  • Image captured in analog format, converted to digital image when scanned
  • Come in different sizes, can be used for intraoral or extraoral applications
  • Disadvantages:
    • Susceptible to scratches, bite marks, and creasing
    • Damage to phosphor layer is irreversible and visible in the image
• Solid-State Sensors:
  • Known as direct digital receptors
  • Display radiographic image instantaneously after exposure
  • Disadvantages:
    • Bulky and not easy to position in the patient's mouth
    • Shielded wire cable can be damaged by repeated biting

Radiographic Techniques

Intraoral Radiography

• Patient size and cooperation must be considered
• Technique selection:
  • Timer must be accurate for short exposure times
  • Radiation-sensitive image receptors recommended
  • Rectangular collimation of the radiation beam advised
  • Film positioning devices or image receptor holder recommended

Techniques

• Periapical Radiography:
  • Show crown of the tooth and at least 3 mm beyond the apex
  • Two techniques:
    • Paralleling Technique:
      • Most accurate technique for intraoral radiographs
      • Image receptor parallel to the long axis of the teeth
      • X-ray beam directed perpendicular to the image receptor
    • Bisecting Angle Technique:
      • Image receptor positioned close to the teeth
      • Central x-ray directed perpendicular to a line bisecting the angle created by the tooth and image receptor
      • Drawbacks:
        • Elongation or foreshortening (vertical angulation errors)
        • Interproximal overlap (horizontal angulation errors)

Extraoral Radiography

• Panoramic Imaging:
  • Obtained through tomography
  • Image magnified by a factor of around 1.3
  • Some machines enable bitewing look-alike images
• Cephalometric Imaging:
  • Used in orthodontics and orthognathic surgery
• Cone Beam Computed Tomography (CBCT):
  • Delivers higher radiation than traditional radiographic techniques
  • Ideal for imaging hard tissues, including bone and teeth
  • Indications:
    • Localization of impacted canines and third molars
    • Visualization of maxillofacial pathologies for assessing extension or surgery planning
    • Visualization of the condyles and glenoid fossa
    • Visualization of the maxillary sinuses
• Ultrasound Imaging:
  • Excellent for investigating soft tissues
  • Does not involve ionizing radiation
  • Appropriate for fine-needle aspirations