Wound Healing

Question 1

Epithelialization

Answer 1

• Any free edge of normal epithelium continues to migrate until it comes into contact with another free edge of epithelium, where it is signaled to stop growing
• This is known as contact inhibition

Question 2

Migration

Answer 2

• Proliferation of germinal epithelial cells

Question 3

Stages of wound healing 3

Answer 3

• Inflammatory stage
• Fibroplastic Stage
• Remodeling stage

Question 4

Inflammatory Stage

Answer 4

• Begins the moment tissue injury occurs and usually lasts 1 to 5 days
• 2 phases
  
  • Vascular phase
  • Cellular phase

Question 5

Vascular Phase

Answer 5

• The initial vasoconstriction of disrupted vessels that slows blood flow into the area of injury, promoting blood coagulation, followed by vasodialation that opens small spaces between endothelial
• Simultaneous lymphatic obstruction causes collection of fluid in the tissue called edema

Question 6

Cellular Phase

Answer 6

• Polymorphonuclear leukocytes (neutrophils) adhere to the sides of blood vessels (margination), migrate through the vessel walls (diapedesis) to destroy bacteria and other foreign materials, digesting necrotic tissue

Question 7

Fibroplastic Stage

Answer 7

• Strands of fibrin derieved from blood coagulation crisscross the wound forming a latticework on which fibroblasts begin laying down ground substance and tropocollagen
• Mucopolysaccharides cement the collagen fibers together

Question 8

Fibroplastic Stage lastas and Phases

Answer 8

• Lasts 2-3 weeks
• Migratory phase
• Proliferative phase

Question 9

Migratory Phase

Answer 9

• Epithelial migration continues, leukocytes dispose of foreign and necrotic materials, capillary ingrowth begins, and fibroblasts migrate into wound along fibrin strands

Question 10

Proliferative Phase

Answer 10

• Proliferation increases epithelial thickness
• Collagen fibers are haphazardly laid down by fibroblasts
• Budding capillaries begin to establish contact with their counterparts from other sites in wound

Question 11

Remodeling Stage

Answer 11

• Initial collagen replaced by new collagen
• Increasing tensile strngth
• Stronger wound
• Accounts for about 70% of wound healing time, several months

Question 12

Factors that impair wound healing

Answer 12

Foreign material

Necrotic tissue

Ischemia

Wound tension

Question 13

Necrotic tissue

Answer 13

• Serves as a barrier to the ingrowth of repearitive cells
• Serves as a niche for bacteria
• Nutrient source for bacteria, especially with hematoma growth

Question 14

Ischemia

Answer 14

• Decreases blood supply leading to
  
  • Further necrosis
  • Lessens delivery of antibiotics, oxygen and nutrients

Question 15

Primary Intention

Answer 15

• Edges of wound are placed in essentially the same anatomic position they held before injury

Question 16

Secondary Intention

Answer 16

• A gap is left between the edges of an incision or wound
• Sockets heal by secondary intention

Question 17

Teritary Intention

Answer 17

• The healing of wounds through the use of tissue grafts to bridge the gap between wound edges

Question 18

Healing of Extraction Sockets

Answer 18

• The empty socket consists of cortical bone with a rim of epithelium (gingiva) at the coronal portion
• The socket fills with blood,
• which coagulates and seals the socket from the oral enviroment

Question 19

Timeline of extraction socket healing

Answer 19

• 1st week Inflammatory Stage
  
  • WBC remove bacteria and begin to break down debris, bone fragments
  • Fibroplasia the ingrowth of fibroblasts and capillaries and the accumulation of osteoclasts on the crestal bone
• 2nd week
  
  • Granulaton tissue
  • Osteios deposition along alveolar bone lining
• Epithelixation are commonly complete by week 3-4
• As bone fills socket, the epithelium moves toward the crest and eventually becomes level with adjacent crestal gingiva
  
  • `4-6 months

Question 20

Bone healing

Answer 20

• Same as ST healing
  
  • Inflammation, fibroplasia, remodeling
• Osteoclasts and osteoblasts reconstitute and remodel the damaged bone
• Osteoblasts rebuild bone and are derived from
  
  • Periosteum
  • Endosteum
  • Circulating pluripotential undifferentiated mesenchymal cells

Question 21

Implant integration, failure

Answer 21

• If implant had an epithelial barrier and allowed to develop a biologic bond with bone, epithelial migration down into the bone along implant would be resisted
• If implant had a CT barrier, epithelium would migrate down the implant, externalizing it and implant failure

Question 22

Succesful Implant integration

Answer 22

• An osseointegrated implant with dorect bone to implant contact
• Surface epithelium migrantion along the implant is halted by the direct bone to implant integration

Question 23

Wound healing around Implants has 2 factors

Answer 23

• Bone to implant healing
  
  • Bone healing must occur before any ST forms btw bone and implant
• ST to implant healing

Question 24

How to maximize bone to implant healing

Answer 24

• Short distance btw bone and the implant
• Viable bone at or near the surface of the implant
  
  • No micromovement
  • No over heating
• AN implant surface reasonaly free of contamination

Question 25

Implant surface

Answer 25

The surface of pure titanium implants are completely covered by a thick layer of titanium oxide

This stabilizes the surface and is the site of osseointegration

Question 26

Prep of implant site, bone considerations

Answer 26

• Regardless of how much care is give to not damage the bone during implant prep
  
  • A superficial layer of bone along the surface of a prepared impant site becomes nonviable as a result of thermal and vascular trauma
• Although the living cells in bone die, the inorganic bone strucure remains
• Under the influence of local growth factors, bone cells directly underlying this bone structure and bloodborne undifferentiated mesenchymal cells repopulate and remodel the bony scaffold with osteoblasts, osteoclasts, and osteocytes

Question 27

Guided Tissue Regeneration

Answer 27

• To selectively aid the bone forming process in its race to cover a surface before ST fills the site
• Woven membranes are used that have a pore size adequate to allow oxygen and other nutrients to reach the bone grown beneath the membrane while keeping fibroblasts and other tissue elements outside the membrane
• This excludes st and guides bone into desired position

Question 28

3 types of nerve injuries with implants

Answer 28

• Neurapraxia
• Axonotmesis
• Neurotmesis

Question 29

Neuropraxia

Answer 29

• Injury to the nerve that causes no loss of continuity of the axon or endoneurium
• But does cause disruption of the myelin sheath
• Caused by compression of the nerve or ischemia
  
  • Common when implant is placed into the inferior alveolar canal, copressing the nerve

Question 30

Axonotmesis

Answer 30

• Injury to nerve that causes loss of axon continuity
• But preserves the endoneurium
• Caused by a crushing injury
  
  • Over aggressive retraction of mental nerve can cause Axonotmesis (crusing)
  • Or Neurotmesis (stretching) depending on severity

Question 31

Neurotmesis

Answer 31

• Injury to nerve that causes loss of axonal and endoneurium continuity
• Caused by severe contusion, stretching, laceration, or local anesthesia toxicity
• Cutting of the inferior alveolar nerve during the removal of a deeply impacted third molar can cause neurotmesis