Wound Repair Flashcards
- Noted with abrasions
- Renewal of epithelium occurs within hours after injury
- Completion occurs at 24 – 48 hours
- Free edge of epithelium migrate until it contacts the opposite edge
- Signal is terminated in CONTACT INHIBITION
- Occurs over wound bed but under scabbing/superficial blood clot
- Occurs faster with moisten substrate over wound
- Epithelium does cross over desiccated surface
Epithelialization
- Also called LAG PHASE:
- No increase in wound strength
- Due to little collagen deposition
- FIBRIN principle material holding wound together
- Has little tensile strength
- 2 phases of the it
- Vascular
- Cellular
Inflammatory phase
____ phase of inflammatory phase
• Vasoconstriction of disrupted vessels
• Coagulation (platelets and fibrin)
• Clot formation 5-10 minutes
• Vasodilation
• Increases permeability to site to allow healing factors and cells to
reach injury site
• Mediated by histamine and prostaglandins (E1 and E2) from WBCs
• Causes EDEMA (leak of cells and fluid to site of injury)
Vascular phase
Does vasodilation or constriction occur first in inflammation?
Vasoconstriction
____ phase of inflammatory phase
• PMN (neutrophils) arrive within 24 hrs of injury
• Margination:
• PMNs stick to side of blood vessels
• Diapedesis:
• PMNs migrate through vessel walls
• Degranulation:
• PMNS releasing lysosomal enzymes to destroy bacteria/foreign
materials/necrotic tissue
• Macrophages continue clearance of debris
CELLULAR PHASE
_______ are the dominant cell of fibroblastic phase of wound healing
• Fibroblasts
- Fibroblasts are the dominant cell
- Deposits ground substance and TROPOCOLLAGEN over fibrin lattice
- Ground substance contains mucopolysaccharides →cement collagen fibers together
- Secretes FIBRONECTIN
- Stabilize fibrin
- Assists in recognizing foreign material
- Chemotactic factor to aid recruitment of fibroblasts and macrophages
- Angiogenesis occurs:
- Increase vascularity (from wound edges inward)
- Causes raised and red color of wound
- Superfluous fibrin strands removed by plasmin
- Excessive collagen deposited in haphazard manner
- Increases tensile strength (~ 5-7 days after injury →timing for suture removal)
- 70%-80% tensile strength compared to uninjured tissue
Fibroblastic phase of wound healing
What percentage of the tensile strength is retained after healing in the fibroblastic phase compared to normal skin areas around it?
70-80%
____ phase of wound healing
• Increase in collagen ORGANIZATION AND STRENGTH
• Collagen oriented in direction to better resist tension
• Type III collagen replaced by Type I
• Excess collagen removed →scar softens
• Wound strength never reaches above 80% - 85% of
uninjured tissue
• Peak tensile strength at 60 days
• Wound erythema decreases as vascularity decreases to site
• Wound contraction occurs by migration of wound edges
toward each other
Remodeling phase
FACTORS THAT IMPAIR WOUND HEALING
- Dirt, wood, glass, suture, bacteria
- “Non-self” material causes chronic inflammation
- Decreases fibroplasia
- Bacteria proliferation causing infection
- Destroys host tissue with bacteria byproducts
- Non-bacteria causes a harbor for bacteria
• Foreign material
FACTORS THAT IMPAIR WOUND HEALING
- Free bony fragment in extraction site is classic example
- Barrier to ingrowth of reparative cells
- Serves as a protected niche for bacteria
- Hematoma formation:
- Nidus for bacteria, as well as food source for bacteria
- Blood clot is small and functional, hematoma is large and of no use
• Necrotic tissue
FACTORS THAT IMPAIR WOUND HEALING
- Decreased blood supply, resulting in poor oxygen delivery to needed site
- Increases wound infection by halting delivery of PMNs, WBCs, antibodies, ABX
- Results from:
- Poorly designed flaps
- Tight sutures
- Internal pressure from edema/hematoma
- Hypotension during surgery
• Ischemia
FACTORS THAT IMPAIR WOUND HEALING
• Wounds closed under tension will cause ischemia at
margins with eventual opening (dehiscence)
• If suture removed too early, the wound under tension will
reopen and heal with excessive scar formation
• Tension
• Overgrowth of tissue within border of wound edges • Any race • Common in pediatrics • Regresses with time • Common on flexor surfaces
HYPERTROPHY
• Overgrowth beyond border of wound edges • Common in darker skin/hereditary • Rare in pediatrics • Grows for years • Common on upper body, head/neck
KELOID
- Triple therapy:
- Surgical excision
- Corticosteroid injection
- 40 mg/cc injection intralesional
- 2-3 times per month for 6 months
- Silicone pressure dressing
- Worn 12-24 hours per day
- For 2-3 months
Keloid/Hypertrophy Treatment
MOst healing of extraction sockets is via ______ intention
Secondary intention
______ intention
• Edges of wound returned to anatomic position
• Wound edges directly next to each other
• Little loss of tissue
• Minimal scar
• Closure stabilized and accomplished with
sutures/staples/adhesives
• Examples:
• Lacerations
• Well reduced bone fractures
Primary intention
\_\_\_\_ intention • Wound is allowed to granulate in • May be packed by surgeon with gauze or drain • Granulation results in broad scar • Slower healing process • Examples: • Gingivectomy • Tooth extraction • Poorly reduced fracture
SECONDARY INTENTION
_____ intention
• Delayed primary closure
• Related to contaminated wounds
• Wound cleaned, debrided and observed
• Closure attempted after 4-5 days
• Purposely left open to observe for any signs and
symptoms of infection or further tissue necrosis
• Skin grafting or flaps can be used to cover these type of
wounds
TERTIARY INTENTION
(what point in extraction wound healing?)
• Immediately after extraction:
• Remnants of periodontal ligament remain attached to the lamina dura
• Gingival epithelial margin is separated at the crest
• Coagulated blood seals socket
Immediately
(what point in extraction wound healing?)
• Inflammatory phase
• WBCs break down and digest bacteria and debris
• Fibroplasia begins
• Fibroblast proliferate forming granulation tissue
• Neovascularization penetrates clot
• Clinical correlation: Localized osteitis, “dry socket,” occurs if this
phase fails
• Epithelium begins to migrate down towards first granulation tissue
it comes into contact with
• First week
(what point in extraction wound healing?)
- Granulation tissue increase and matures
- Small socket may close off at 14 days, molars by 3 weeks
• Second week
(what point in extraction wound healing?)
- Almost all sockets will have epithelial closure by 21 days
- Deposition of early bone (osteoid) within the socket
• Third and Fourth week
(what point in extraction wound healing?)
• Continued resorption and recontouring of alveolus
• Total resorption of lamina dura by 1 year
• Clinical correlation:
• What is time frame to wait before building a final prosthesis?
• Four to six months
• Where do osteogenic cells responsible for bone repair come from? 3 places
- Periosteum
- Endosteum
- Circulating pluripotential mesenchymal cells
• Factors most important to proper bone healing
- If low oxygenation →cartilage will form instead of bone
- If severe →fibrous tissue may never calcify →fibrous union
• VASCULARITY
• Factors most important to proper bone healing
- Intermaxillary fixation (IMF), bone plates, direct wires
- Mobility prevents fibrous tissue from ossifying →fibrous union, non-union,
• IMMOBILITY
What are the 3 phases of nerve repair?
Degeneration and Regeneration
- Myelin sheath dissolved in isolated segments (slows nerve conduction)
- Symptoms: paresthesia, dysesthesia, hyperesthesia, hypoesthesia
• Segmental demyelination
• Axons and myelin sheath of nerve distal to site of interruption undergo disintegration in their
entirety
• Axons proximal to the site of interruption undergo some degeneration generally a few Nodes of
Ranvier away
• Wallerian Degeneration
• Growth cone (growth of new nerve fibers from proximal nerve stump) starts growing down
remnant Schwann cell tube
• Progresses 1 mm per day
• Continues until site innervated by the nerve is reached
• New myelin sheaths may form as axons increase in diameter
• Abnormal nerve healing →NEUROMA
• Mass of aimless nerve fibers
• Painful when disturbed (temperature, pressure, etc…)
• Regeneration
• Spontaneous and subjective altered sensation that IS NOT PAINFUL/UNCOMFORTABLE
• Paresthesia
• Spontaneous and subjective altered sensation that IS PAINFUL/UNCOMFORTABLE
Dysesthesia
• Excessive sensitivity of a nerve to stimulation
Hyperesthesia
• Decreased sensitivity of a nerve to stimulation
Hypoesthesia
• No sensation when stimulated
Anesthesia
