FACTOR

ADVANTAGES

DISADVANYAGES

E speed film

* Most effective method of reducing patient dose.
The risk is reduced by a factor of 2.
Contains large tubular grains which increases speed.
The exposure time is 0.2 sec compared to regular film which is 0.9 sec

Decreases image sharpness

Collimation

The radiation risk is reduced by a factor of 5.
Greatest decrease in overall radiation risk from dental x ray.
Increased image quality due to reduced scattered radiation.
Rectangular collimators do better than round.

Intensifying screens

Decreases 85-90% of scattered radiation.
Useful for extra oral radiography.
Sensitive to both visible light and x rays.

1. Decreases resolution
2. Decreases sharpness
3. Not useful for intraoral radiography

Lead aprons and collars

Reduces 94% of scattered radiation to the gonads.
Protects gonads from radiation exposure.
Thyroid collars reduce the exposure of this gland by 92%.

High kVp

Provides x ray photons with high penetration.
Reduces patient radiation exposure.
Provides low contrast images which ae useful for periodontal diagnosis

1. Decreases contrast
2. Provides long gray scale contrast which is not suited for detecting caries of periapical disease

Long TFD

41 cm TSD results in less patient exposure and best diagnostic image than with 20cm fsfd.
Long TSD decreases thyroid dose because it produces less divergent x ray beam.

1. Increase in exposure time

Grid

Preferentially removes scattered photons that reach the film.
Increases film contrast.
Decrease film fog

1. Increased patient radiation dose or exposure

Filtration

Selective removal of low energy x ray photons occurs by conventional aluminium filtration.
Decreases patient exposure with no loss of radiographic information.

1. Image quality suffers due to reduced contrast and sharpness
2. Increase in exposure time