There has been some disagreement as to whether the
pulp microcirculation is capable of functional regulation.
Pulp blood flow in anaesthetized animals is dependent
on alterations in systemic blood pressure.
Stealing perfusion of the surrounding tissues has been implicated
in the paradoxical decrease in pulp blood flow in
response to arterial infusion of well-known vasodilators
in other circulations.
“Stealing” of the blood supply to
the dental pulp is thought to occur when vasodilation
of the neighbouring tissues reduces the perfusion
pressure to the pulp, thus producing a decrease in the
blood flow to the pulp.
However, the passive view of
pulp microcirculation has been challenged by a body of
in vivo data: topical application or close intra-arterial
bolus injection of various vasoactive substances alter
pulp blood flow while systemic blood pressure is
unaltered.
Pulp blood flow in anaesthetized
animals of several species is under the influence of local
nerve impulses unrelated to systemic haemodynamics.
Perivascular sympathetic nerve fibres liberate
noradrenaline and possible neuropeptide Y causing a
reduction of pulp blood flow,
whereas intradental
sensory nerves liberate neuropeptides causing an
increase in pulp blood flow.
Reflex excitation of
the sympathetic nervous system causes pulp
vasoconstriction and a reduction in pulp blood flow.
Reflex activation of sensory axons causes pulp
vasodilatation spreading beyond the site stimulated as
a result of branching of sensory axons.
Beaded nerve
terminals are found in intimate association with
smooth muscle in the walls of arterioles and venules.
The peri-vascular nerve endings are adrenergic post-
ganglionic fibres containing noradrenaline, or
somatosensory nerve fibres containing substance P or
calcitonin gene-related peptides.
These nerve fibres
appear to participate in the regulation of the pulp blood
flow by affecting vascular smooth muscle tone, thereby
changing vessel diameter. Pulp blood flow is hence
considered to be predominantly under neural control.
The possible existence of a local vascular regulation
in the pulp has been proposed recently.
It is important in the confined and restricted circulation
that microvascular tone is modulated locally to match
the nutrient flow and tissue demands. Using an isolated
pulp arteriole preparation combined with in vivo
measurement of pulp blood flow and pulp oxygen
tension, it has been demonstrated that the pulp
vasculature is capable of responding to a range of
vasoactive mediators and the pulp microcirculation
may be controlled locally by endothelium-related
factors, metabolic (tissue-related) factors, as well as
humoral (blood-borne) factors.
It is important to study the pulp microcirculation
because of its brave but limited success in dealing with
injury in a restricted low compliance environment.
Studies of oxygen tension in the tissue and the individual
properties of the pulp vessels will help to understand
the mechanism that leads to necrosis in hypoxia and
anoxia following vessel collapse after progressive
spread in raised interstitial fluid pressure. Two practical
outcomes of this understanding would be the discovery
of therapeutic agents and strategies that could help the
pulp survive, and the developments of techniques for
measuring pulp blood flow clinically such that a true
diagnosis of the presence and extent of pulp
inflammation could be made. Both outcomes may
enable practitioners to diagnose and treat pulp diseases
at an early stage.
a result of branching of sensory axons.
Beaded nerve
terminals are found in intimate association with
smooth muscle in the walls of arterioles and venules.
The peri-vascular nerve endings are adrenergic post-
ganglionic fibres containing noradrenaline, or
somatosensory nerve fibres containing substance P or
calcitonin gene-related peptides.
These nerve fibres
appear to participate in the regulation of the pulp blood
flow by affecting vascular smooth muscle tone, thereby
changing vessel diameter. Pulp blood flow is hence
considered to be predominantly under neural control.
The possible existence of a local vascular regulation
in the pulp has been proposed recently.
It is important in the confined and restricted circulation
that microvascular tone is modulated locally to match
the nutrient flow and tissue demands. Using an isolated
pulp arteriole preparation combined with in vivo
measurement of pulp blood flow and pulp oxygen
tension, it has been demonstrated that the pulp
vasculature is capable of responding to a range of
vasoactive mediators and the pulp microcirculation
may be controlled locally by endothelium-related
factors, metabolic (tissue-related) factors, as well as
humoral (blood-borne) factors.
It is important to study the pulp microcirculation
because of its brave but limited success in dealing with
injury in a restricted low compliance environment.
Studies of oxygen tension in the tissue and the individual
properties of the pulp vessels will help to understand
the mechanism that leads to necrosis in hypoxia and
anoxia following vessel collapse after progressive
spread in raised interstitial fluid pressure. Two practical
outcomes of this understanding would be the discovery
of therapeutic agents and strategies that could help the
pulp survive, and the developments of techniques for
measuring pulp blood flow clinically such that a true
diagnosis of the presence and extent of pulp
inflammation could be made. Both outcomes may
enable practitioners to diagnose and treat pulp diseases
at an early stage.