Haemostasis and wound healing Flashcards
Understand the three components and processes of haemostasis
- Vasoconstriction: When injury occurs, the first thing the vessel does is constrict to minimise blood loss
- Platelet plug formation: The exposure of the ECM to the blood activates platelets which stick at the wound site.
- Coagulation cascade: Has two pathways (intrinsic and extrinsic). These pathways lead to the formation of thrombin, which then converts fibrinogen into fibrin, which forms a mesh that traps more platelets and erythrocytes. This forms a solid clot.
List the 3 components that platelets are attracted to
- Collagen
- Von Willebrand factor (vWF)
- Adhesive glycoproteins
State the importance of thrombin in the coagulation cascade
- Thrombin further enhances platelet aggregation
* Thrombin converts fibrinogen to fibrin which forms the fibrin mesh
Know the 2 groups of bleeding disorders
- Clotting factor deficiencies (2 types)
* Platelet disorders
List the 2 types of clotting factor deficiencies and their subtypes
Inherited clotting factor deficiencies (2):
• Haemophilia A (factor 8 deficiency)
• Haemophilia B (factor 9 deficiency)
Acquired clotting factor deficiencies:
• Liver disease e.g. cirrhosis, alcoholic hepatitis
• Drug-induced e.g. Warfarin
• Vitamin K deficiency
State the 4 types of platelet disorders
- Defective platelet adhesion
- Defective platelet activation
- Defective platelet aggregation
- Drug-induced e.g. antiplatelet drugs such as aspirin
vWF disease is the most common inherited bleeding disorder. Explain the importance of vWF in haemostasis
- Promotes platelet adhesion and platelet-to-platelet cohesion during primary haemostasis
- It is the carrier for FVIII in plasma. FVIII activates factor IX, which in turn activates factor
- Deficiency of vWF results in impaired platelet adhesion, activation, aggregation and ultimately impaired haemostasis
Explain the dental management of patients with bleeding disorders
- Identify the cause of the bleeding disorder and the severity
- Invasive dental procedures such as extractions pose the greatest risk of complications such as uncontrollable haemorrhage, airway compromise and haematoma infection
- For severe bleeding disorders, referral for specialist management in a hospital setting may be required
- For minor bleeding disorders, atraumatic extraction technique combined with local haemostatic measures can reduce the risk of complications occurring
Understand the mechanisms of wound healing and its 3 outcomes
- Involves proliferation and differentiation of different cell types and the laying down of connective tissue
- Aim is to restore normal tissue structure and function, however whether this is achieved depends on, type of tissue damaged, severity and whether the cause of the damage can be completely eliminated
In general, the outcomes of wound healing are:
• Regeneration (when original tissue is made, e.g liver. Is quite rare)
• Scar formation (Damaged tissue is repaired with connective fibrous tissue. Occurs with some regeneration.)
• Fibrosis (extensive replacement of normal tissue with connective tissue, leading to loss of function. It occurs when cause of damage persists, e.g fibrosis).
Explain healing by first intention
- Healingthat occurs when a clean laceration or a surgical incision is closed primarily with sutures, Steri-Strips, or skin adhesive. Occurs when the outline of the wound can be approximated
- Healing is mainly by regeneration of the epithelium
- Small scar formation where the ECM (basement membrane) was damage
- Minimal wound contraction
Explain healing by second intention
- Healingthat occurs when a wound is left open tohealby granulation, contraction, and epithelialization. Occurs when the outline of the wound cannot be approximated, and the wound needs to heal from the bottom.
- Examples: extraction socket, large wound, abscess and ulceration
- Repair is by both epithelial regeneration and scar formation
- More extensive scar formation
- Wound contraction
List the three stages of wound healing
- Proliferation
- Remodelling
- Maturation
Explain the proliferation phase of wound healing after a tooth extraction
- Proliferation
• Starts within 24 hours of extraction, at the end of the acute inflammatory response
• Socket is Infiltrated with macrophages and growth factors
• Growth factors stimulate angiogenesis and promote the migration, proliferation and activation of fibroblasts to deposit collagen
• Formation of granulation tissue appears 3 to 5 days after extraction
• The epithelium around the crest of the alveolus migrates down the socket walls during the first week
• The migration continues until it reaches the bed of granulation tissues situated underneath the blood clot
• It then migrates over this granulation tissue until it makes contact with the epithelium migrating from the other sides
• This process is called epithelialisation and it re-establishes epithelial continuity
Explain the remodelling phase of wound healing after a tooth extraction
- Underneath the new epithelial layer there is deposition of connective tissue by fibroblasts
- After several weeks, the granulation tissue develops into a scar
- Soft tissue forms much faster than bone
- Differentiation and proliferation of osteoblasts and osteoclasts, causing bone deposition and remodelling
Explain the maturation phase of wound healing after a tooth extraction
- The socket is filled with bone within 8 weeks
- Radiographic evidence of bone formation does not become apparent until 6 to 8 weeks following tooth extraction
- In 10-12 weeks, no longer able to distinguish outline of extraction socket
- Remodelling of the bone can go on for 6+ months; the final healing product of the extraction site may not be discernible on radiographs after 4 to 6 months
