INDICATIONS
Estimation of the pulpal vitality:
Monitoring of reactions to local and systemic pharmacological agents (including local anaesthetic solutions) may be undertaken with LDF
MECHANISM
The original technique used a light beam from a helium neon (He Ne) laser emitting at 632.8 nm. Other wavelengths of semi-conductor laser have also been used: 780 nm and 780 820 nm.
Laser light is transmitted to the dental pulp by means of a fibre optic probe placed against the tooth surface. Two equal-intensity beams (split from a single beam) intersect across the target area. The scattered light beams from moving red blood cells will be frequency-shifted whilst those from the static tissue remain unshifted in frequency. The reflected light, composed of Doppler-shifted (light reflected by a moving object is Doppler-shifted) and unshifted light, is returned by an afferent fibre within the same probe to photo detectors in the flowmeter and a signal is produced. The photo- detectors convert the interference pattern arising from the mixing of shifted and unshifted light into a semi- quantitative measurement of blood flow, termed the Flux signal, which is measured in arbitrary units. The received signal is calculated with a preset algorithm in the LDF machine. The LDF output signal or Flux can be simplified as a function of the product of red blood cells’ concentration as well as their mean velocity. In fact, Flux is the number of moving red blood cells per second times their mean velocities.
REF: IEJ, 42, 476—490, 2009
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