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Ceramics and Glasses > Ceramics and Glasses 2 > Flashcards

Ceramics and Glasses 2 Flashcards

1
Q

Bioceramic properties

A

high strength
high wear resistance
good biocompatibility
low coefficient of friction
excellent corrosion resistance

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2
Q

What causes high stength of Alumina

A

fine grained size due to precessing and sintering

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3
Q

How does grain size affect strength

A

Increased grain size, decreased strength
Due to increased surface area creating more friction and wear

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4
Q

What is the Modulus of Elasticity of Alumina

A

300 GPa

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5
Q

Where is alumina used

A

articulating surfaces of total joint prosthesis

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6
Q

Why would you select alumina instead of polyethylene for total joint prosthesis

A

Alumina had lower wear in comparison to polyethylene

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7
Q

Concerns for alumina

A
  • high modulus of elasticity limits bending in comparison to metals in dental applications
  • protein adhesion with biomolecule however wear molecules can induce foreign body response
  • Stress shielding (bone degeneration and implant loosening)
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8
Q

Zirconia

A

High bending strength
high toughness
lower modulus
more susceptible to wear than alumina
alumina-zirconia to improve toughness

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9
Q

Porous bioceramics

A

Inert and mechanically stable
bone grows into pores
low strength
as porosity increases, strength decreases due to increased exposed surface area

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10
Q

Bioactive glass

A

bioactivity HIGHLY dependent on the composition
bonds to bone/soft tissue
cannot be used for load-bearing applications
HIGHLY BRITTLE
can be used as filler/ coating

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11
Q

Class A bioglass

A

Most bioactive
bonds to both bone and soft tissue
governed by rate of dissolution of ions
Optimal rate of reaction
turns of body repair process
stimulates bone regeneration

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12
Q

Class B Bioglass

A

Less bioactive then class B
only bonds to bone
slower rate of reaction
osteoconductive not osteostimulative

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13
Q

Class C Bioglass

A

Fastest rate of dissolution
no bone formation

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14
Q

Class C Bioglass

A

Fastest rate of dissolution
no bone formation

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15
Q

Apex of glass triangle

A

No bioactivity
Bioinertness

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16
Q

Bottom of glass triangle

A

No glass formation

17
Q

How does class A bioglass enhance osteogenesis

A

Dissolution of ions
Silica gel layer forms of surface of the glass
Silica gel layer with calcium and phosphate from bodily fluid forms HCA layer
genes produce growth factors
cells proliferate and differentiate to produce a mineralized matrix (BONE)

18
Q

Cell proliferation

A

Formation of new cells via mitosis

19
Q

Cell Differentiation

A

Stem cells become a specific type of cell via specific cues

20
Q

bonding bioglass to bone

A

stage 1and 2:
- Alkali-proton exchange
- alkali (Na) from bioglass surface and proton (H) from bodily fluids to form Si-OH bonds
Stage 3:
- Polycondensation of Si-OH bonds to form a hydrated silica gel layer
- Silica-rich glasses form a thick silica layer to protect the glass. Formation of the fibrous capsule (Bioinert) (apex of triangle)
Stage 4:
Absorption of Ca, PO4, and CO3 from the body onto the silica gel layer
Stage 5:
HCA layer via crystallization
1. Nucleation (1st crystal) on Ca and P from bioglass
2. Growth (more crystal formation) from additional Ca, PO4, and CO3
3. Crystallization: formation of HCA similar to native bone
Step 6/7:
- the presence of the HCA layer enhances the absorption and desorption of growth factors
- HCA layer decreases the length f time that macrophages are needed at the implant site
Step 8/9:
- Osteoprogenitors attach on HCA surface
Class A: Rapid cellular proliferation and differentiation
Class B: takes several weeks for cell differentiation
Class C: No differentiation
Step 10/11: Class A only
- Osteoprogenitor cells colonize glass surface producing growth factors to stimulate mitosis and matrix production
- Mineralization of matrix with osteocytes embedded in collagen-HCA matrix

21
Q

Factors of rapid osteogenesis of class A

A
  • Control of the population of cells capable of entering active phases of cell cycle
  • Complete mitosis of cells with accurate replication of genes
  • Cellular differentiation into phenotype capable of synthesizing full complement of ECM proteins that make up mature osteocytes
  • controlled rate of dissolution provides critical concentration of biologically active ions to the cells resulting in the activation of genes responsible for osteogenesis
22
Q

Calcium Phosphate Ceramics

A
  • Forms the majority of mineral phase for native bone
  • Solubility and speed of hydrolysis of calcium phosphate dependant on Ca/P ratio
    (Increased with decreased Ca/P ratio)
  • Ca/P ratio less than 1:1 not suitable for biological implantation
23
Q

How do you make calcium phosphate ceramics

A
24
Q

What factors affect rate of resorption of HA with Calcium Phosphate ceramics

A

Larger Surface area faster resorption
Lower crystallizaton faster resorption
Intersitial (Smaller) Substitution ( Same size)

25
Q

Mechanisms of Degration of Calcium Phosphate ceramics

A

Phsiochemical dissolution: pH
Physical Disintergration: Chemical attack on grain boundaries
Biological Factors: Phagocytosis

26
Q

bonding bioglass to bone

A

Stage 1and 2:
- Alkali-proton exchange
- alkali (Na) from bioglass surface and proton (H) from bodily fluids to form Si-OH bonds
Stage 3:
- Polycondensation of Si-OH bonds to form a hydrated silica gel layer
- Silica-rich glasses form a thick silica layer to protect the glass. Formation of the fibrous capsule (Bioinert) (apex of triangle)
Stage 4:
Absorption of Ca, PO4, and CO3 from the body onto the silica gel layer
Stage 5:
HCA layer via crystallization
1. Nucleation (1st crystal) on Ca and P from bioglass
2. Growth (more crystal formation) from additional Ca, PO4, and CO3
3. Crystallization: formation of HCA similar to native bone
Step 6/7:
- the presence of the HCA layer enhances the absorption and desorption of growth factors
- HCA layer decreases the length f time that macrophages are needed at the implant site
Step 8/9:
- Osteoprogenitors attach on HCA surface
Class A: Rapid cellular proliferation and differentiation
Class B: takes several weeks for cell differentiation
Class C: No differentiation
Step 10/11: Class A only
- Osteoprogenitor cells colonize glass surface producing growth factors to stimulate mitosis and matrix production
- Mineralization of matrix with osteocytes embedded in collagen-HCA matrix

Ceramics and Glasses (2 decks)

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