Lecture 13 - Metal Ions/Cell Health

Question 1

Metal Sensitivity Rates

Answer 1

Vary with gender

• Differences in home/work environments
• Increased rates in mining, metal refining, electroplating, printing, etc.

Question 2

Biological Response to Metal Sensitivity

Answer 2

• Dermatitis: skin response to excessive inflammation

- Implant site infection (poor integration)

Question 3

Dermatitis

Answer 3

• Side effect of metal hypersensitivity (rash on skin)
• Direct response to metallic contact (side effect of external metallic support devices and general indicator of systemic challenge)
• Activation of T-cells by metal-peptide complex produces more T-cells and cytokines (recruit macrophages, cell accumulation and release of lytic enzymes that leads to tissue damage)

Question 4

Metallic Dermatitis

Answer 4

• Ni, Cr, Co, Au, Pt
• No initial sensitivity (Ni) in solid state (low solubility)
• Multiple exposure all can provoke skin inflammation (sweat, saliva, etc., getting metal into solution)

Question 5

T-Cell Response to Metals

Answer 5

• Metal-peptide complex activated T-cells produce variety of cytokines to bring inflammatory response cells (T_H1, T_H2)
• Presenting hapten to T-cells which initiates T-cell response (directly bind to MHC, uptake and processing-takes exogenous antigen, phagocytose it, combine with MHC, present at surface)

Question 6

Exogenous Antigen

Answer 6

MHC Class II

Question 7

Metal Recognition by T-cells

Answer 7

Metal ion must be bound to MHC via proteins (Metal-MHC/peptide-complex recognized by T-cell)

(1) Hold antigen and show to T-cell
(2) T-cell produces cytokines
(3) Cytokines bring macrophages to area
(4) Macrophages phagocytose and break down antigen
(5) Macrophages spit out lytic enzymes to help kill/reduce # of antigen
- Cytokines and lytic enzymes causes tissue inflammation/necrosis
- Gives dermatitis and promotes reduction/integration of implant

Question 8

Necrosis

Answer 8

Cell death

Question 9

Patch Test

Answer 9

• Place metal or metal solution over skin for 2-3 days
• Examine skin for irritation several days after removal
• Discrepancies/variances in tests (location, activity, etc.)
• Requires patient return for evaluation
• Less invasive

Question 10

Blood Test

Answer 10

• Patient blood sample
• Incubate with metal or metal ion
• Quantify changes in T-cell (lymphocyte proliferation test-how much proliferation have T-cells undergone, if lots of T-cells then they likely have seen metal before and are sensitive)
• Higher cost (technical skill, send to lab)

Question 11

Implant Site Inflammation

Answer 11

• On top of common inflammation
• Immune response to metals initially thought to be simple inflammatory response to corrosion products, but repeated loosening of implant experienced
• Connection between sensitivity and loosening (not good enough bond between implant and tissue around)

Question 12

Prolonged Inflammation

Answer 12

• Excess of production of cytokines
• Large number of macrophages
• Led to necrosis of bone around implant
• Resorption of bone as osteocytes die
• Causes loosening of joint because strong fixation prevented (requires revision)

Question 13

Osteocyte

Answer 13

Bone cell formed when osteoblast becomes imbedded in matrix it secreted

Question 14

Alloying Additions in Metal Implants

Answer 14

• Add to tailor chemical and physical properties

- Focused on corrosion resistance, mechanics, and bone integration

Question 15

Corrosion in Metal Implants

Answer 15

• In metals, reaction in presence of water
• Utilize pourbaix diagrams to help predict if metal corrodes (heavily dependent on chemistry of fluid, addition of chloride ions decreases passivated and immunity regions)