delicate structures called fibrils. At this point,
blood cells and plasma are enmeshed in the
network of fibrils to form the clot. Therefore,
fibrils are responsible for tightly binding the
platelet plug, stabilizing the plug, and affixing it
to the site of injury. Resulting in a semi-solid,
gelatinous mass, it is termed the hemostatic
clot or thrombus. This definitive clot prevents
excessive bleeding from the site of the injury.
Within approximately 9 to 18 minutes, the fibrin
clot is produced. (Diagram 2) Under these
physiological conditions, it is important to note
that if any defect or deficiency of platelets or
coagulation factors exists, disorders of the
hemostatic system can result.1,2,5
Finally, anticlotting mechanisms (broadly termed
fibrin degradation products) in the fibrinolynic
pathway are activated to prevent the formation
of more clots and to allow for the dissolution of
the definitive clot.4,5 The expected outcome is
accomplished: repair of the injured blood vessel
wall results and bleeding ceases.
Laboratory Assessment of Hemostasis
Many of the bleeding disorders can be diagnosed
and monitored by way of laboratory testing.
When a significant disorder occurs in the
vascular or platelet phase a clinical bleeding
problem is observed immediately after injury, or
during invasive medical or dental procedures.
Conversely, when a significant disorder affects
the coagulation phase, the clinical bleed will
most likely not be observed until several hours or
longer after the injury or invasive procedure.
Various laboratory screening tests can be ordered
by the dentist when the patient reports a bleeding
disorder: when the patient responds positively
to a family history of a bleeding disorder; or
when the clinician observes a sign/symptom of
a bleeding problem during the clinical exam.
Patients with unknown bleeding problems should
be referred to their physician or to a hematologist
for further evaluation. Laboratory tests provide
an assessment of adequate numbers of platelets,
proper functioning of platelets, sufficient levels