NEET MDS Lessons
Radiology
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
- Maxillary Central Incisors:
- Vertical Angulation: +40 to +50 degrees
- Maxillary Lateral Incisors:
- Vertical Angulation: +40 to +50 degrees
- Maxillary Canines:
- Vertical Angulation: +45 to +55 degrees
- Mandibular Central Incisors:
- Vertical Angulation: -15 to -25 degrees
- Mandibular Lateral Incisors:
- Vertical Angulation: -15 to -25 degrees
- Mandibular Canines:
- Vertical Angulation: -20 to -30 degrees
Posterior Teeth
- Maxillary Premolars:
- Vertical Angulation: +30 to +40 degrees
- Maxillary Molars:
- Vertical Angulation: +20 to +30 degrees
- Mandibular Premolars:
- Vertical Angulation: -10 to -15 degrees
- 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.
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.