Fractures of the Zygomatic Arch

• Structures: Zygomatic arch, zygomatic bone.
• Best Views:
  • Submento-Vertex View: Provides a clear view of the zygomatic arch and helps assess fractures.
  • Waters View: Useful for visualizing the zygomatic bone and maxillary sinus.
  • Reverse Townes View: Can also be used to visualize the zygomatic arch.

Base of Skull

• Structures: Base of the skull, cranial fossae.
• Best Views:
  • Submento-Vertex View: Effective for assessing the base of the skull and related fractures.

Maxillary Sinus

• Structures: Maxillary sinus, zygomatic bone.
• Best Views:
  • Waters View: Excellent for visualizing the maxillary sinus and any associated fractures.

Fractures of Zygoma

• Structures: Zygomatic bone, zygomatic arch.
• Best Views:
  • Waters View: Good for assessing zygomatic fractures.
  • PA View: Provides a frontal view of the zygomatic bone.
  • Reverse Townes View: Useful for visualizing the zygomatic arch.

Nasal Septum

• Structures: Nasal septum, nasal cavity.
• Best Views:
  • PA View: Useful for assessing the nasal septum and any associated fractures.

Condylar Neck Fractures

• Structures: Mandibular condyle, neck of the condyle.
• Best Views:
  • Lateral Oblique View (15°): Good for visualizing condylar neck fractures.
  • Transpharyngeal View: Useful for assessing the condylar region.

Medially Displaced Condylar Fractures

• Structures: Mandibular condyle.
• Best Views:
  • Lateral Oblique View (30°): Effective for visualizing medially displaced condylar fractures.

Coronoid Process of Mandible

• Structures: Coronoid process.
• Best Views:
  • PA View of Skull: Can help visualize the coronoid process.

Fractures of Ramus and Body of Mandible

• Structures: Mandibular ramus, body of the mandible.
• Best Views:
  • Lateral Oblique View (15°): Useful for assessing fractures of the ramus and body of the mandible.

Horizontal Favorable and Unfavorable Fractures of Mandible

• Structures: Mandible.
• Best Views:
  • Lateral Oblique View (30°): Effective for evaluating horizontal fractures.

Bony Ankylosis of TMJ

• Structures: Temporomandibular joint.
• Best Views:
  • CT Scan: Provides detailed imaging of bony structures and ankylosis.

Fibrous Ankylosis of TMJ

• Structures: Temporomandibular joint.
• Best Views:
  • CT Scan: Useful for assessing fibrous ankylosis.

Internal Derangement of the Disk

• Structures: TMJ disk.
• Best Views:
  • MRI: The best modality for evaluating soft tissue structures, including the TMJ disk.

Disk Perforation

• Structures: TMJ disk.
• Best Views:
  • MRI: Effective for diagnosing disk perforation.

Arthrography

• Structures: TMJ.
• Best Views:
  • Arthrography: Can be used to assess the TMJ and visualize the disk and joint space.

Common Problems in Film Processing

1. Light Radiographs

• Causes:
  • Under Development:
    • Temperature too low
    • Time too short
    • Depleted developer solution
  • Under Exposure:
    • Insufficient milliamperage
    • Insufficient kVp
    • Insufficient exposure time
    • Film-source distance too great
    • Film packet reversed in the mouth

2. Dark Radiographs

• Causes:
  • Over Development:
    • Temperature too high
    • Time too long
    • Accidental exposure to light
    • Improper safe lighting
    • Developer concentration too high
  • Over Exposure:
    • Excessive milliamperage
    • Excessive kVp
    • Excessive exposure time
    • Film-source distance too short

3. Insufficient Contrast

• Causes:
  • Improper processing conditions (under or over development)
  • Depleted developer solution
  • Contaminated solutions

4. Film Fog

• Causes:
  • Excessive kVp
  • Improper safe lighting
  • Light leaks in the darkroom
  • Contaminated developer solution

5. Dark Spots or Tines

• Causes:
  • Contaminated solutions
  • Film contaminated with developer before processing
  • Film in contact with tank or another film during fixation

6. Light Spots

• Causes:
  • Insufficient washing
  • Film contaminated with fixer before processing
  • Film in contact with tank or another film during development

7. Yellow or Brown Stains

• Causes:
  • Insufficient washing after fixation
  • Depleted fixer solution
  • Contaminated solutions

8. Blurring

• Causes:
  • Movement of the patient during exposure
  • Movement of the X-ray tube head
  • Double exposure
  • Misalignment of the X-ray tube head (cone cut)

9. Partial Images

• Causes:
  • Top of film not immersed in developing solution
  • Film in contact with tank or another film during processing

10. Emulsion Peel

• Causes:
  • Excessive bending of the film
  • Improper handling of the film

11. Static Discharge

• Causes:
  • Static discharge to film before processing (results in dark lines with a tree-like image)

12. Fingerprint Contamination

• Causes:
  • Fingerprint contamination during handling of the film

13. Excessive Roller Pressure

• Causes:
  • Excessive roller pressure during processing can lead to artifacts on the film.

Bisecting angle technique 

Bisecting angle technique is a method used in dental radiography to obtain radiographs of teeth and surrounding structures. This technique involves positioning the X-ray beam perpendicular to an imaginary line that bisects the angle formed by the long axis of the tooth and the film or sensor. Here are the general guidelines for angulations when using the bisecting angle technique:

Anterior Teeth

1. Maxillary Central Incisors:
   • Vertical Angulation: +40 to +50 degrees
2. Maxillary Lateral Incisors:
   • Vertical Angulation: +40 to +50 degrees
3. Maxillary Canines:
   • Vertical Angulation: +45 to +55 degrees
4. Mandibular Central Incisors:
   • Vertical Angulation: -15 to -25 degrees
5. Mandibular Lateral Incisors:
   • Vertical Angulation: -15 to -25 degrees
6. Mandibular Canines:
   • Vertical Angulation: -20 to -30 degrees

Posterior Teeth

1. Maxillary Premolars:
   • Vertical Angulation: +30 to +40 degrees
2. Maxillary Molars:
   • Vertical Angulation: +20 to +30 degrees
3. Mandibular Premolars:
   • Vertical Angulation: -10 to -15 degrees
4. Mandibular Molars:
   • Vertical Angulation: -5 to -10 degrees

Key Points

• Positioning: The film or sensor should be placed as close to the tooth as possible, and the X-ray beam should be directed perpendicular to the bisecting line.
• Patient Comfort: Ensure that the patient is comfortable and that the film or sensor is properly stabilized to avoid movement during exposure.
• Technique Variability: The exact angulation may vary based on the individual patient's anatomy, so adjustments may be necessary.

Radiation Biology

-X- and g -rays are called sparsely ionizing because along the tracks of the electrons set in motion, primary ionizing events are well separated in space.

Alpha-particles and neutrons are densely ionizing because the tracks consist of dense columns of ionization.

X-rays, gamma rays, electrons, and protons are all low LET forms of radiation in that their density of ionization is sparse. In general, they penetrate tissues deeply and result in less intracellular radiation injury.

High LET forms of radiation, such as heavy nuclear particles (e.g. fast neutrons), penetrate tissues less deeply and cause more radiation injury to biologic material.

Cells are most sensitive to Radiation when:

General guidelines for vertical angulations for common dental radiographs in children:

Anterior Teeth

1. Maxillary Central Incisors:
   • Vertical Angulation: +40 to +50 degrees
2. Maxillary Lateral Incisors:
   • Vertical Angulation: +40 to +50 degrees
3. Maxillary Canines:
   • Vertical Angulation: +45 to +55 degrees
4. Mandibular Central Incisors:
   • Vertical Angulation: -10 to -20 degrees
5. Mandibular Lateral Incisors:
   • Vertical Angulation: -10 to -20 degrees
6. Mandibular Canines:
   • Vertical Angulation: -15 to -25 degrees

Posterior Teeth

1. Maxillary Premolars:
   • Vertical Angulation: +30 to +40 degrees
2. Maxillary Molars:
   • Vertical Angulation: +20 to +30 degrees
3. Mandibular Premolars:
   • Vertical Angulation: -5 to -10 degrees
4. Mandibular Molars:
   • Vertical Angulation: -5 to -10 degrees

DENTAL X-RAY TUBE

The dental X-ray tube is surrounded by a glass envelope that houses a vacuum.
The glass prevents low-grade radiation from escaping. The vacuum insures the protection of the equipment from catastrophic failure. Production of X-rays generates enormous amounts of heat; the vacuum prevents the risk of combustion and ensures the proper environment for conduction of electrons.

There are two separate energy sources, one that powers the energy potential between the cathode ?lament and the anode, and the other being
the controls for the cathode ?lament. The latter essentially is the on and off switch of the X-ray unit.

The cathode ?lament is heated which causes electrons to be emitted.

These electrons are then accelerated by the electrical potential of the circuit.

Between the two points is a tungsten target.
When electrons strike the target, X-rays are produced.

HALF-VALUE LAYER

- Property of a material whereas the thickness (mm) reduces 50% of a monochromatic X-ray beam.
- Half-value layer of a beam of radiation from an X-ray unit is about 2 mm of aluminum (Al).

PRIMARY RADIATION

- Is the main beam produced from the X-ray tube. 

SECONDARY RADIATION

- Produced by the collision of the main beam with matter which causes scatter.