Lecture 5 Flashcards

(25 cards)

1
Q

Which ions have been reported to induce angiogenic activity in biological conditions?

A

Silicon

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1
Q

What are the conditions for bioactivity?

A

bonding between tissue and material (chemical or biological)

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2
Q

What are some features of non-oxide ceramics? How do they compare to alumina and zirconia?
Are there any limitations?

A

silicon nitride = biocompatible
supports bone growth on elongated grains
crack deflection

better mech properties than alumina
better stability than zirconia

very expensive and hard to machine

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3
Q

What are the benefits and limitations of porosity? What is the minimum size?

A

allows for better tissue integration but decreases strength

min size is 100um

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4
Q

How does bone bonding onto HA work?

A

saturates with Ca and potassium to form bone-like layer between HA and host bone

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5
Q

Compare HA and beta TCP - what is the combination ratio?

A

HA = insoluble
beta-TCP = resorbable, good in vivo but mechanically unstable

GOOD to combine - 60 HA 40 TCP

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6
Q

What are some features of calcium phosphate ceramics?

A

Group of ceramics
HA and beta TCP
not good for load bearing
highly dissolvable = less strong

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7
Q

What are some features of bioactive glass?

A

forms oxides
quenching = amorphous forming = brittle
direct bonding to bone
can be used to composite with polymers

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8
Q

Do ceramics have a high or low young’s modulus? How does this compare with cortical bone?

A

High - ~20x cortical bone

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9
Q

What is zirconia-toughened alumina (ZTA)?

A

10-20% volume

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10
Q

What does stress do to material? How does water affect it?

A

crack propagation
inducces phase transformation
makes it toucher
water can trigger degradation too

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11
Q

What are the 2 main phases of zirconia? How can they be both stable at room temp?

A

monoclinic = stable @ room temp
tetragonal = stable @ high temps (stabilised with yttria)

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12
Q

What are some features of zirconia? Bioinert or bioactive?

A

BIOINERT
stronger and tougher than alumina

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13
Q

What are some features of alumina? Bioinert or bioactive?

A

BIOINERT
doesn’t leach anything
thinnest tissue
good wear resistance
can be strengthened with zirconia

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14
Q

What materials are not as strong but bioactive?

A

Calcium phosphates, bioactive glasses and calcium silicates

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15
Q

What materials are strong but bioinert?

A

Zirconia and alumina

16
Q

What types of dental implants use ceramics?

A

Dental crowns = alumina and zirconia
Bone defect fillers = granules of bioactive glass

17
Q

What ceramic is used for ball-socket hip joints?

18
Q

When would ceramics be used?

A

High strength high wear resistance joints
bioactive coatings
dental implants

minimal loading profile

19
Q

What are some properties of ceramics?

A

brittle
strain to failure < 0.5%
corrosion and wear resistance
bioinert and bioactive

20
Q

What are the different types of crystallinity?

A

purely, semi and amorphous?

21
Q

What are ceramics?

A

inorganic compounds with ionic and covalently bonded attoms

22
Q

What ion would you add to existing calcium phosphate ceramic material to achieve better vascularization?

23
Q

What are the 6 stages of carbonated HA formation on the surface of bioactive glasses?

A

Rapid ion exchange
increase in pH which attacks the silicon network
Condensation and polymerisation of the surface
Interaction between calcium and potassium ions
Glass dissolving and ions crystalising
Bone forming

24
What is the ultimate compressive strength required for load bearing applications?
1000MPa