Wound Healing and Repair PDF

Wound: is a rapid onset of injury that involves laceration or punctured skin (an open wound), surgical, or a a closed wound from blunt force trauma or compression. Healing involves the repairing of damaged tissues and resumption of normal...

Wound: is a rapid onset of injury that involves laceration or punctured skin (an open wound), surgical, or a a closed wound from blunt force trauma or compression. Healing involves the repairing of damaged tissues and resumption of normal function Wound healing involves either: A. Regeneration: - Complete restoration of the original tissue and structure of the damage - Restore the function of the tissue - No scar formation B. Repair: - Proliferation of connective tissue and restore some original structure - Leads to loss of function in the tissue - Scar formation Phases of wound healing (4 phases): a) Hemostasis (Stop bleeding) b) In ammation (new framework for blood vessel growth) c) Proliferation (pulls the wound closed) d) Remodeling (Final proper tissue) More details: A. Homeostasis (minutes): - Platelet aggregation - Neutrophil in ltration - In ammatory cell recruitment *This stage begins immediately after wounding and it stops bleeding by vascular constriction and brin clot formation B. In ammation (Days): - Neutrophil apoptosis - Macrophage migration - Angiogenesis - Granulation - Fibroblast proliferation C. Proliferation (weeks) - Re-epithelialization - Decreased blood vessels - Cellular apoptosis - Aligned C M brillar network Dense Type I collagen formation D. Maturation (21 days to 2 years) 1 of 5 fi fl fl fl fi fi  Phase 1- Hemostasis - This stage begins immediately after wounding and it stops bleeding by vascular constriction and brin clot formation Phase 2 – in ammation - Occur from ( 0 -4 days ) in ammation is a biological process that is de ned by blood vessel dilation soon after the hemostasis phase has ended. - The primary objective of vasodilation is to prevent infections throughout the healing process. - Mainly Neutrophils and macrophages play the role in this phase by removing the debris and prevent infection. - Is often associated with edema, erythema, heat and pain. Phase 3 – Proliferation - Occur ( 2-24 Days) - Main focus of the healing process lies in covering the wound surface, replacement of provisional brin matrix with new matrix of collagen brin, formation of granulation tissue and restoring the vascular network. Phase 4 – Remodeling - Occur (24 days– 1 year) - The new tissue slowly gains strength and exibility, and collagen bers reorganize, the tissue remodels and matures and there is an overall increase in tensile strength. - This is where collagen III is converted to collagen I, and the tensile strength continues to increase up to 80% of normal tissue. 2 of 5 fi fi fl fl fl fi fi fi  Wound assesment: is by using TIME clinical decision tool to assess and document wounds T: Tissue M: Moisture balance I: Infection E: Edges of the wound *Check slides 20 - 23 The di erences between Skin and Oral mucosa - In comparison to cutaneous wounds, oral mucosa supports rapid healing with minimal scarring - The oral mucosa is less reactive to in ammation during healing process with lower in ltration from macrophages, T-cells, and neutrophils - Oral epithelium has lower expression of transforming growth factor beta-1 (TGF-Beta1), a pro- brotic and pro-in ammatory cytokine recognized for its contribution to hypertrophic scars during wound healing Oral cavity - Saliva, a weak bu er with PH ranging from 5.5 to 7, has shown to accelerate wound re-epithelialization while constantly providing hydration and warm temperature - Saliva also contains histatins, antimicrobial peptides, and mucins that can aid in wound healing by assisting broblast proliferation, migration, releasing growth factors Factors a ecting wound healing: A. Local factors: - Oxygenation - Repeated trauma - Foreign body - Venous su ciency - Wound management and moisture balance - Infection - Mechanical stress, pressure, or friction B: Systemic factors: - Stress - Nutrition - Age and gender - Alcoholism and smoking - Ischemia - Obesity - Immunocompromised conditions - Medications and chemotherapy Complications: Infection Hypertrophic scar Abscess Keloid Hematoma contracture Dehiscence Exuberant granulation Necrosis 3 of 5 fi ff ff ffi ff fl fi fl fi  Bone healing and repair: A. Healing process in alveolar socket after tooth extraction: - The healing process begins immediately after extractions by formation of the blood clot. - The coagulation produce a brin meshwork that will seal o torn blood vessel and shrink the size of the wound. - The brin mesh provides a sca old for leukocytes migration, which starts after vasodilation of blood vessels within the PDL remnants. - The epithelium at the socket edges start to migrate over the organized clot, and new vessels start to form towards the center of the clot. - Osteoclast start resorption of the crestal bone, osteoblast start to form osteoid (immature bone) within the clot. - By the end of third week post extraction, primary healing concludes, the socket is lled with granulation tissue and poorly calci ed immature bone is evident. The surface of the socket is sealed with epithelium. - Bone remodeling continues by replacing immature bone with lamellar bone. The rst radiographic evidance of bone formation is not until 6-8 weeks post extraction, and the nal remodeled product is not seen until 4-6 months. B. Healing process modulated by grafting materials. - Bone grafts of any type can only regenerate bone through three possible mechanisms: 1- osteogenesis: transplanted osteoblasts and periosteal cells directly produce bone. 2- osteoconduction: Growth factors encourage mesenchymal cells to di erentiate into osteoblastic lineages 3- osteoinduction: provide matrix/sca old for bone growth. Grafts may develop bone from one, two, or all three of these mechanisms to varying degrees. 4 of 5 fi fi ff fi ff ff ff fi fi fi Nerve healing and repair: A. Neurapraxia - Segmental myelin damage with an intact axon - Usually caused by compression - Temporary focal conduction block resolves completely within 12 weeks once myelination is restored B. Axonotmesis: - Axonal injury where the connective tissue and nerve continuity remain intact - Caused by a crush mechanisim - Wallerian degeneration ensues and slow axonal regeneration follows at a rate of 1mm/day C. Neurotmesis - Complete physiological and anatomical transection of both axons and connective tissue - No spontaeuos regeneration occur without surgical intervention 5 of 5