3.Ceramic Biomaterials

Question 1

define a ceramic material

Answer 1

Inorganic material consisting of * two or more metallic and nonmetallic elements*, and characterized by a combination of ionic and covalent bonds.

Question 2

mechanical properties of ceramic biomaterials

Answer 2

-high melting temperature
-low conduction of electricity and heat=Good heat and electricity insulators
-high hardness
-Brittle and fragile materials
-low ductility
-High resistance to compression NOT in tension
-Low coefficient of friction and wear rates
-Very susceptible to microcracks

Question 3

Electronegativity

Answer 3

Chemical property that describes the tendency of an atom or a functional group to attract electrons.

Question 4

chemical properties

Answer 4

high chemical inertness = stability of their strong bonds
nigh wetting degrees and surface tension = cell and protein adhesion

Question 5

NOT all ceramics are bioactive (True or false)

Answer 5

True

Question 6

High mechanical properties only in compression (True or False)

Answer 6

True

Question 7

Ceramic biomaterials always establish strong interactions with bone (True or False)

Answer 7

False
NOT all ceramics are bioactive

Question 8

Ceramic biomaterials always display high mechanical properties (True or False)

Answer 8

False
High mechanical properties only in compression

Question 9

Classification of ceramics by form

Answer 9

powders
coatings
bulk shapes

Question 10

Classification of ceramics by composition

Answer 10

oxides
non-oxides
composites

Question 11

Ceramic oxides (properties + examples)

Answer 11

resistant to oxidation
electrically insulating
low thermal conductivity
Ex.: alumina
zirconia
magnesium oxide

Question 12

Ceramic non-oxides (properties + examples)

Answer 12

low oxidantion resistance
electrically and thermally conducting
ex.: carbides
nitrides
silicates

Question 13

Classification of ceramics based on the reactivity with biological fluids

Answer 13

Bioinert
Bioactive or surface reactive
Biodegradable or resorbable

Question 14

Bioinert ceramics (ex..)

Answer 14

Aluminium oxide (Al2O3)
Zirconium oxide (ZrO2)
Sintered HA
Carbons

Question 15

Bioactive or surface reactive ceramics (ex.:)

Answer 15

bioactive glass
sense hydroxyapatites
HA = hydroxyapatite
HCA = hydroxycarbonate apatite
A-W = apatite - wollastonite

Question 16

Biodegradable or resorbably ceramics (ex.:)

Answer 16

Hydroxyapatite
Tricalcium phosphate

Question 17

[evolution of biomaterials] 1st generation

Answer 17

bioinert ceramics
non-absorbable
structural functions (joint or tissue replacement)
isolated by a non-adherent fibrous capsule
ex.:
-zirconia (ZrO2)
-alumina (Al2O3)
-carbons, mainly pyrolytic and as fibres in composites

Question 18

[evolution of biomaterials] 2nd generation

Answer 18

Biodegradable
Resorbable
Dissolved after a specific time
ex.:
-calcium phosphates
-calcium sulfate
Bioactive
Surface reactive
tightly bonded to living tissues
ex.:
-hydroxyapatite ceramics (HA)
-hydroxycarbonate apatite (HCA)
-glassees
-glass ceramics

Question 19

[evolution of biomaterials] 3rd generation

Answer 19

scaffolds of biologically active molecules
driving living tissue regeneration
ex.:
-Ca-P osteoinductive ceramics
-Bioglass
-Porous biactive and biodegradable ceramics
-Advanced bioceramics: mesoporous materials, organic-inorganic hybrids

Question 20

[evolution of biomaterials] ideal bioceramics

Answer 20

tissue regeneration and perform natural functions

Question 21

steps of foreign body reaction

Answer 21

1.surgeon implants biomaterial
2.biomaterial adsorbs a layer of proteins
3.cells interrogate the biomaterial (neutrophills and macrophages)
4.cell fuse to form giant cells and secrete protein signalling agents (cytokines)
5.in response to the cytokines, fibroblasts arrive and begin synthesizing collagen
6.the biomaterial is encapsulated in a acellular collagenous bag

Question 22

tissue response to Bioninert bioceramics

Answer 22

minimal tissue response

Question 23

tissue response to surface reactive bioceramics

Answer 23

-partial solubility
-chemically stable
-direct chemical bond with bone with fibrous encapsulation

Question 24

tissue response to Biodegradable bioceramics

Answer 24

-fully resorbably (high solubility)
-absence of a fibrous tissue layer
-replaced by the regenerated tisse

Question 25

[key definitions] Bioceramic

Answer 25

Any ceramic, glass or glass-ceramic that is used as a biomaterial

Question 26

[key definitions] Bioactive Material

Answer 26

A material which has been designed to induce specific biological activity

Question 27

[key definitions] Biactivity

Answer 27

A phenomenon by which a biomaterial elicits or modulates biological activity

Question 28

[key definitions] Bioresorption

Answer 28

The breakdown of a structure within a biological environment and the consequent assimilation of resulting components into that environment

Question 29

[key definitions] Bioabsorption

Answer 29

Process whereby substances are absorbed by the tissues and organs in a living system

Question 30

Main properties of Bioinert Ceramics

Answer 30

Very stable in physiological conditionsànegligible chemical variations;
Do not react with the host=foreign body;
Excellent corrosion and wear resistance

Question 31

Examples of Bioninert Ceramics

Answer 31

Aluminum oxide (Al2O3)
Zirconia oxide (ZrO2)
Silicon carbide (SiC)
Silicon nitride (Si3N4)

Question 32

Aluminum oxide or Alumina (Al2O3)

Answer 32

Excellent biocompatibility, wear and
corrosion resistance
* Extremely hard, BUT low tensile and
bending strengths
* Insoluble in water, but slightly soluble in
strong acids
* Low surface roughness + high
wettability=very low friction coefficient

Question 33

Aluminum oxide or Alumina (Al2O3) used in

Answer 33

orthopedics and dentistry
-hip prostheses
-knee prostheses
-crown

Question 34

Aluminum oxide or Alumina (Al2O3) implants or biomaterials have critical clinical issues

Answer 34

-fatigue
-overload

Question 35

Why is Pure zirconia not used

Answer 35

Large residual stresses and cracks after cooling

Question 36

What is the reason for including stabilizing oxides? (in bioinert ceramics)

Answer 36

Stabilizing oxides (yttrium oxide, Y2O3, and magnesium oxide, MgO) => prevent volume expansion during phase
transformation;
Stabilize the tetragonal and/or cubic phases à partially stabilized zirconia (PSZ) - multiphase ceramic material.

Question 37

scaffolds

Answer 37

Porous are useful for cell and tissue ingrowth, along with degradation

Question 38

Bioactive Glass – 2 mechanisms of bioactivity

Answer 38

1.Bone bonding
2. Osteogenic ability

Question 39

Bone Bonding

Answer 39

carbonated hydroxyapatite (CHA) layer formation on the glass surface

Question 40

Osteogenic ability

Answer 40

dissolution products (Ca, Si) stimulate bone cells at gene level

Question 41

Are there any advantages in the lab production of CaP?

Answer 41

“Engineered composition” => similar in composition, biodegradation, bioactivity, and osteoconductivity to the biological apatites (constituent of bone and teeth)

Question 42

Calcium phosphates (CaP)

Answer 42

Occur in normal (bone) and pathological calcification (arteries) in the body;
Can also be synthetically produced in the laboratory;
Integrate with tissue and are eventually replaced by host tissue

Question 43

How can we control the degradation rate?

Answer 43

Composition
Crystallite size
Degree of crystallinity
Chemical composition
+
Biological environmental conditions (pH, [calcium], [phosphate])

Question 44

Hydroxyapatite (HA) – Ca10(PO4)6(OH)2

Answer 44

-Osteoconductive material + high compressive strength
-Ability to establish a high interfacial bone–implant strength
-Brittle => coatings on metallic implant surfaces

Question 45

Hydroxyapatite (HA) – impact of ionic substitutions

Answer 45

• Altered solubility and dissolution
• Improve specific properties (e.g.,
  mechanics, surface structure)
• Improved bone formation
• Antibacterial properties

Question 46

Major factors determining the physical properties

Answer 46

-grain size
-sensity
-porosity
-impurities

Question 47

Major factor determining the chemical properties

Answer 47

Solubility

Question 48

Calcium Phosphate Cements

Answer 48

-Calcium phosphate phases mixed with an aqueous solution to forma paste;
-Forms a hardened mass with similar compressive strength similar to cancellous bone.

Question 49

Advantages of Calcium Phosphate Cements

Answer 49

• Injectability
• Easy handling;
• Incorporation of drugs or biomolecules into the aqueous phase.