Haemostasis and Wound Healing

• Wound healing = the replacement of damaged tissue by regeneration or repair. The completion of bony remodelling of the alveolar bone after removal of a tooth, may take months or even years (depending on age of patient).
• Haemostasis is defined as the natural process to arrest haemorrhage following tissue trauma. There are 3 components:

  1. Vascular response - constriction of blood vessels
  2. Platelet aggregation and adhesion - results in the formation of a platelet plug. This occurs within a few minutes, stops further blood loss but is unstable and easily dislodged
  3. Clotting cascade to produce fibrin. This is vital for survival of the host. Fibrin production at the site of damage helps to stabilise clot. It takes hours to form a mature clot (hence post-op advice to avoid hard physical work, excessive rinsing etc.)
• Primary haemostasis involves the vascular response and platelet aggregation and adhesion. Secondary haemostasis includes the insoluble fibrin mesh that is incorporated into and around the platelet plug. This mesh serves to strengthen and stabilise the blood clot.
• Haemostasis normally takes 5-10 mins - can be aided with compression of the socket, and pressure with gauze until satisfied bleeding has arrested.
• Functions of the clot:

  • Arrest haemorrhage
  • Protect the wound from contamination
  • Provide substrate for further healing to take place
• How long does it take for a clot to become stable?

  24 hours
• How does the stabilisation time of the clot relate to post-op instructions?

  No smoking or vigorous exercise, no rinsing for 24 hours, and encourage gentle cleaning around the area.
• There are are live cells within the clot, but it has no blood supply. The clot requires blood supply to maintain existence or will necrose and fall out.
• What do we call it if the clot fails?

  Dry socket or alveolar osteitis
• When does dry socket/alveolar osteitis typically present?

  48 hours post-extraction
• The fate of the clot is to be replaced by granulation tissue, which is rich in blood supply and fibrous tissue (process of organisation). The blood supply migrates from surrounding tissue (i.e. Bone and gingivae) whilst dead cells are removed by macrophages. It takes several days to establish mature granulation tissue.
• Functions of granulation tissue:

  • Continue protective function
  • Allow further repair to occur
  • Establish ideal vascular bed for epithelial coverage to advance from edges of wound
• How long does it take for granulation tissue to form?

  5-10 days
• Is granulation tissue alive or dead?

  Has a rich blood supply, so a living tissue.
• Migration of epithelium occurs very quickly once blood supply is present (e.g. Epithelial versus connective tissue reattachment in periodontal disease). It usually takes around 2-3 weeks.
• What do we call the process of thickening of epithelium to protect itself from trauma?

  Keratinisation
• Epithelial coverage of wound re-establishes the integrity of the host. Initially it is only very thin, so easily damaged. The wound may still appear red. The epithelium becomes thicker and will eventually start to keratinise.
• Bone formation - under the epithelial coverage socket healing continues with:

  Differentiation of osteoblasts, laying down matrix for bone formation, early osteoid seen after 3/52

  Callus (immature woven bone) 6/52

  Bony remodelling continues with process of resorption of alveolar bone depending on functional stresses from teeth either side of extraction site. Radiographic evidence of cortical bone of socket wall may remain for years especially in the elderly.