Healing

• What are the causes of tissue destruction?

  Traumatic excision (surgical or accidental) Physical, chemical & microbial agents Ischaemia which leads to infarction Hypersensitivity reactions
• What is the mechanism of healing?

  The healing process has two aspects:

   Contraction - mechanical reduction in the size of the defect

   Replacement of lost tissue Migration of cells to provide extra tissue to fill the gap.

  This can be accomplished in three ways:-◦ Repair ◦ Regeneration ◦ Reconstitution
• What is repair?

  The replacement of lost tissue by granulation tissue which matures to form scar tissue. Occurs in specialised cells which cannot proliferate e.g. muscle

  
• What is regeneration?

  Replacement of lost tissue by tissue similar in type• by proliferation of surrounding undamaged specialised cells• predominant where cells are capable of multiplication e.g. epithelium
• What is reconstitution?

  Co-ordinated regeneration of several types of lost tissue, reformation of whole organs or limbs e.g. liver reformation
• What is wound contraction?

  • After 2-3 days rapid contraction of wound, completed by day 14 Due to remodeling of tissue
  • Wound size reduced by up to 80% Contraction results in much faster healing as less new tissue has to be formed If contraction is prevented, healing is slow and a large ugly scar results
• What is the definition of Organisation?

  Definition: The replacement of necrotic tissue, fibrin and blood clot by living granulation tissue.
• What phases occur in the growth of granulation tissue?

  1) blood clot forms

  2) acute inflammation follows

  3) demolition
• Granulation tissue is formed by....

  the proliferation and migration of surrounding connective tissue elements
• What is the tensile strength of a wound?

  Initially low, fibrin holds cut edges together The wound increases in strength as collagen is formed
• How are skin wounds healed?

  By Primary or Secondary Intention

  (The difference is quantitative. The difference lies in the type of wound not the type of healing)
• What are the two main aspects of the mechanism of healing?

  Contraction and replacement of lost tissue
• How does contraction aid healing?

  Mechanical reduction in size of defect
• What are the three ways lost tissue is replaced in healing?

  Repair, regeneration and reconstitution
• What is repair?

  Replacement of lost tissue by granulation tissue that matures to form scar tissue
• Which tissues require repair to heal?

  Specialised cells that cannot proliferate
• What is regeneration?

  Replacement of lost tissue by tissue similar in type by proliferation of surrounding undamaged specialised cells
• What is reconsitution?

  Co-ordinated regeneration of several types of lost tissue causing the reformation of whole organs or limbs
• When does wound contraction occur?

  After 2-3 days until day 14
• How much can wounded retraction reduce wound size by?

  80%
• What happens if wound contraction is prevented?

  Healing is slow and a large scar forms
• What is organisation?

  The replacement of necrotic tissue, fibrin and blood clot by living granulation tissue
• What are the steps of organisation in healing?

  Blood clot forms, followed by acute inflammation and demolition, granulation tissue forms and scarring occurs on healing
• What increases the tensile strength of a wound?

  Collagen
• What is healing by primary intention?

  Wound fills with a clot and epithelium migrates into the wound, epithelial spurs are forms and granulation tissue forms and scar tissue remains
• What is healing by secondary intention?

  A blood clot forms in a large open wound and the socket heals from the base upwards
• Why might the healing process be delayed?

  Poor blood supply, presence of infection/foreign body, movement, increased age, nutrition, protein deficiency, lack of vitamin C, Glucocorticosteroids, colder temperature
• Why might a lack of vitamin C delay healing?

  Weak granulation tissue
• Why might protein deficiency cause a delay in healing?

  Deficiency in collagen formation
• Why might glucocorticosteroids delay healing?

  Inhibit formation of granulation tissue
• What is healing like in oral epithelium?

  Complete regeneration with scar tissue remaining in lining mucosa- lamina propria and submucosa heal by repair
• When a periodontal pocket heals after RSD, which tissues heal by secondary intention?

  Epithelium, connective tissue, periodontal ligament, cementum and alveolar bone
• Why might gingivae appear denser following RSD?

  Fibrous tissue develops and is less vascular