Download As Cohen and Burns10 reported, response to current

Pulp blood flow
The vitality of the pulp is determined according to the health of
the vascular supply, not of the sensory fibres. The pulp receives its
blood supply through thin-walled arterioles entering through the
apical and accessory foramina. These arterioles run longitudinally
through the centre of the pulp, branching out to its periphery where
they form a capillary network in the subodontoblastic area. These
capillaries do not enter the dentin; they drain into the venules that
run alongside the arterioles and pass out through the same apical
foramen. The diagnosis of dental pulp status is frequently given
insufficient attention by many dentists. Vitality testing is an
essential aid for dental pulp health status monitoring, especially
after traumatic injuries and for the correct diagnosis concerning
pulp disease and apical periodontitis. Current routine methods
include thermal stimulation, electrical or direct dentine stimulation,
assessment of the integrity of the Aδ nerve fibers in the dentinepulp complex by briefly applying the stimulus to the outer surface
of the tooth and indicate that the nerve fibers are functioning, but
does not give any indication of blood flow within the pulp. These
testing methods have the potential to produce an unpleasant and
occasionally painful sensation and inaccurate results (false positive
or negative can be obtained in many instances). Many studies have
shown that blood circulation and not innervation is the most
accurate determinant in assessing pulp vitality, as it provides an
objective differentiation between necrotic and vital pulp tissue.
Laser Doppler flowmetry (LDF)
LDF is an accurate, noninvasive,reproducible, reliable method
of assessing blood flow in microvascular systems with a diode that
projects an infrared light beam through the crown and pulp
chamber. LDF is a non-invasive method of assessing and
measuring the blood flow of pulp tissue. Laser light is directed
onto the tooth under investigation by securing a fiber-optic probe
against the tooth surface. The laser light from the probe passes
along the enamel prisms to the enamel–dentine junction and the Sshaped dentinal tubules, which act as light guides, to the pulp.
Fig (1) A laser Doppler flowmeter (Moor Instruments,
Axminster, UK).
Measurment the pulp blood flow by LDF
LDF passes a laser light through tooth structure, light
bounces off erythrocytes (red blood cells), is returned to a receiver
channel in laser probe, and is recorded as pulpal blood flow. It
requires natural tooth structure and can’t be used through
restorations. Test teeth must be isolated in a manner that precludes
laser light interacting with gingival RBCs and being recorded
together with those from pulpal blood cells. The device is also
prone to pick up sound, like air currents (environmental issues),
therefore the results are questionable due to lack of reproducibility,
sensitivity to environment and its sizeable costs.
The response to currentclinical tests indicates only that
sensory fibres arevital. However, 10%–16% of the results of these
tests are false. The nervous system, which is highly resistant to
inflammation, may remain reactive, even though all surrounding
tissues have degenerated; therefore testing the sensory supply may
give a positive response when the pulp is damaged (i.e., a falsepositive result). This test may also leave the patient with an
unpleasant sensation.A false-negative result (i.e., no response) may
be obtained in cases of calcific metamorphosis, recently
traumatized teeth and incomplete root formation.
Different methods may be used to assess the blood flow in the
pulp: for example, isotope clearance, local hydrogen-gas
desaturation and labelled microspheres.Because of the limitations
on the use of isotopes with humans, these methods remain
experimental (in vitro).A study to determine whether a change in
tooth temperature can trigger pulpal blood flow concluded that
this method of assessing blood flow in the pulp was not clinically
reliable.
LDF light beam is scattered through moving red cells and static
tissues. Its frequency shifts when the beam passes through moving
red blood cells, but remains constant when the beam passes
through static tissue. The LDF technique takes about an hour to
produce recordings, making it impractical for dental practices
unless its time frame can be shortened to a few minutes.
In dentistry, LDF was used to assess pulpal blood flow as an
indication of the vitality of traumatized teeth. LDF was also used
to assess gingival blood flow in flaps after ridge augmentation and
during Le Fort Iosteotomy, and to assess blood flow in intact teeth
in animals and in man. LDF used to study pulpal blood flow with
He-Ne light, a general purpose for LDF, rather than one optimized
for measuring pulpal blood flow. Pettersson and Oberg designed an
LDF instrument for measuring blood flow in human pulp and used
it to assess the viability of pulp in intact and traumatized teeth.
They used an infrared laser diode with a longer wavelength that
gave better penetration than the He-Ne wavelength. Sasano and
others designed and developed a transmitted laser-light flow meter
that used high-powered laser light to monitor the pulpal blood flow
of teeth rather than the conventional light flow-meter apparatus.
LDF is reported to be technique-sensitive: its readings are affected
by the movement of the patient, a nonfixed probe or a mobile
tooth. The technique yields false-positive results when used for
endodontically treated teeth and when the gingival blood flow is
measured.Moreover, intracoronal and extracoronal scattering of the
laser beam calls for special precautions such as covering the
gingiva and the crown of the tooth. Laser Doppler flowmetry is an
established technique for the real-time measurement of
microvascular red blood cell perfusion in tissue. Pulpal blood flow
can now be measured non-invasively in the clinic by means of
laser Doppler flowmetry. The method is noninvasive, and the
probe needs not actually touch the surface of the tissue.
Laser Doppler signals from the tissue are recorded in Blood
Perfusion Units, which is a relative, arbitrary units scale defined
using a carefully controlled motility standard, comprising a
suspension of latex spheres, polystyrene microspheres in water
undergoing Brownian motion. The validation criteria of the pulp
vitality test achieved through the laser Doppler technique are
related to the level of the flux signal and the presence of the
pulsatile character of the acquired signal, synchronised with the
cardiac frequency. Pulpal blood flow measurement with use of
laser Doppler flowmeter is a reliable, objective and harmless
method for evaluating the pulp condition. This technique is
characterized by high sensitivity and allows observing blood flow
in real time. However, the method has some limitations. Back
scattered light, recorded by the probe applied to the crown of a
human tooth, can be contaminated by signal derived from
periodontal tissues and mucous membrane. Therefore, the use of a
rubber dam was proposed to isolate the examined tooth and
enhance the validity of recordings. Moreover, results can be
falsified by movement artefacts; hence good probe stability seems
to be the crucial factor in achieving reliable measurements. Both
hand−held probe application technique and custommade splint
support enable to obtain stable and reproducible readings. the laser
Doppler flowmeter cannot be calibrated in absolute units of blood
flow. Changes in perfusion level can be observed only in series of
measurements, when latter results are compared to the previous
ones, recorded from the same tooth in similar condition. In the
pictures obtained from the histopathological analysis of the
extracted lower central incisors tissues, features typical for a
normal pulp were present – odontoblast layer, cell−free zone and
central area with blood vessels.
Fig(2) Histopathological picture of the pulp of the
tooth 31 extracted prior to orthodontic treatment
Moreover, inflammatory cells or atrophy that are tissue pathology
indicators, were not observed. Therefore, it seems reasonable to
regard the perfusion value 4.80 PU, registered in tooth 31 before
extraction, as corresponding to blood flow level in a healthy pulp
of lower incisor in examined patient. Initial perfusion values
measured in remaining teeth were similar, mean 4.65 PU; hence it
may be assumed that their pulp also functions The available
published studies, concerning the blood flow measurements with
the use of laser Doppler flowmetry, describe the impact of
orthodontic forces on pulpal blood flow applied for a short period
of time a few weeks maximum.
All researches focused on upper incisors reaction In
orthodontically extruded teeth no changes were observed in the
perfusion of pulp tissue while in intruded teeth a temporary
decrease in blood flow occurred when orthodontic force was being
Applied. Perfusion measurements in pulp tissue in the some studies
showed an increase of blood flow in the pulp tissue of lower teeth
under orthodontic treatment. Blood flow in vessels of the dental
pulp, elevated during treatment, returned to the basic level after the
removal of fixed appliance. Reversible character of changes in
vascular system of dental pulp was demonstrated both in studies
evaluating pulpal perfusion and estimating pulp sensitivity to
electric stimuli. Light absorbed by red blood cells in the capillary
plexus is scattered and undergoes a shift in frequency according to
the Doppler principle; light absorbed by stationary objects does not
undergo a shift in frequency. A signal is produced which measures
the flux of the blood cells (number of red blood cells times mean
velocity). The proportion of Doppler-shifted light is detected by a
photodetector. The detected signal is weak and therefore highly
amplified; a mathematical calculation using Fourier analysis can be
used to gain more meaningful information . A trace of signals from
vital and nonvital teeth is shown in Fig. 4. Fourier analysis of the
traces has revealed a heart beat frequency in the vital tooth, but not
in the non-vital tooth and is therefore an effective discriminator.
This technique is more objective and reliable than sensitivity
testing in assessing and following up the pulp status of traumatized
teeth. Several reports have found earlier positive responses with
LDF when compared with sensitivity testing in traumatized teeth
therefore avoiding unnecessary invasive treatment. In addition,
LDF offers the advantage of storing data, allowing initial baseline
measurements to be compared objectively with subsequent LDF
measurements. There has been little use of LDF on decayed or
heavily restored teeth.
The device is technique sensitive and requires preparation of a
putty splint to hold the probes, and a patient who is relaxed and not
anxious. It is necessary to ensure that the reflected signal only
comes from the pulp; this may be readily achieved with an opaque
putty splint or by isolating the teeth with rubber dam. In the case of
following up teeth that have had traumatic injuries, reusing the
putty splint ensures that the probe is reapplied to the same site and
therefore to the same part of the pulp unless growth prevents
repositioning of the splint. The available LDF equipment has
primarily been developed for medical use and is expensive. It is
probably for this reason that LDF has generally not been used as a
routine special investigation in dental practice. It has been used to
observe the effects of local anesthetic solutions on pulp blood flow
during anesthesia.
fig (3) A LDF probe showing laser light guides
fig (4) A LDF probe applied to a sectioned tooth
showing the passage of light via the enamel prisms and
dentinal tubules to the pulp
Fig(5) A LDF trace showing signals from two teeth; the upper is from
a vital tooth while the lower is from a nonvital tooth.
Assessment of dental pulp status
fig(6) Fourier analysis of the LDF traces reveals thevital tooth to have a
heart beat frequency (lower) while there is no such frequency peak for
the non-vital tooth (upper)
fig(7) Two probes have been placed in a putty
impression splint for accurate location on the teeth
while the trace is being recorded
Fig(8) The splint in position on the patient’steeth
Pulp Blood Flow in Vital and Nonvital
Teeth Measured by Laser Doppler
Flowmetry
Prepeared by
Bushra Habeeb Ahmad