1. Lecture 5 Ceramic Material
BIOMATERIALS ENT 311/4
Lecture 5
Ceramic Material
Prepared by: Nur Farahiyah Binti Mohammad
Date: 3rd August 2008

2. Teaching Plan BIOCERAMIC
Describe, discuss and evaluate types o ceramic biomaterials.
Define and describe biomedical application of each ceramic biomaterial.
Evaluate effect of the physiological environment on ceramic biomaterials.
DELIVERY
MODE
Lecture
LEVEL OF COMPLEXITY
Knowledge
Repetition
Evaluation
COURSE OUTCOME
COVERED
Ability to describe the concept of biocompatibility & basic concepts of materials used in medical application
Ability to select biomaterials that can be used for different medical applications and explain the criteria that will lead to a successful implants

3. 1.0 INTRODUCTION
Ceramics are inorganic materials composed of non-directional ionic bonds between electron donating and electron –accepting elements.
Mechanical properties of ceramics:
Hard
Brittle
Allow for little deformation before failure
Can withstand high compression stress

4. 1.0 INTRODUCTION WHY CHOOSE CERAMIC AS BIOMATERIALS?
Have an appropriate mechanical properties for particular medical application such as dental crowns.
Biocompatible:
Relative inertness to the body fluid.
More resistant to degradation.
Have a similar chemistry and mechanical properties with natural bone → more often used as a part of orthopaedic implant (coating material) or as dental materials (crowns, dentures).
High wear resistance

5. 2.0 STRUCTURE OF CERAMIC
Ceramic may contain crystal or non-crystalline glassess

6. 2.0 ATOMIC STRUCTURE OF CERAMIC

7. 2.1 ATOMIC STRUCTURE OF CERAMIC
FACE CENTERED CUBIC

8. 2.1 ATOMIC STRUCTURE OF CERAMIC
BODY CENTERED CUBIC

9. 2.1 ATOMIC STRUCTURE OF CERAMIC
HEXAGONAL CLOSED PACK (HCP)

10. 2.2 MICROSTRUCTURE OF CERAMIC

11. 2.2 MICROSTRUCTURE OF CERAMIC
MICROSTRUCTURAL FEATURES

13. 3.0 BIOMEDICAL APPLICATION
DENTISTRY
Dental filling, Dental crown, dentures
Why widely used in dentistry
Relatively inert to body fluid
High compressive strength
Aesthetically pleasing apparent
ORTHOPAEDIC IMPLANT
Femoral head/ball of hip implant
Coating of hip stem
Acetabular inner cup of hip implant
Bone plates and screw

14. Acetabular component
Inner cup (Polymer or ceramic)
Outer cup (Metal)
Femoral component
femoral stem (metal)
neck (metal)
head/ball (metal or ceramic)

15. 4.0 DESIRED PROPERTIES OF BIOCERAMICS
In order to be classified as a bioceramic, the ceramic material must exceed such properties:
Should be nontoxic
Should be noncarcinogenic
Should be nonallergic
Should be non inflammatory
Should be biocompatible
Should be biofunctional for its lifetime in host

16. 5.0 TYPE OF BIOCERAMICS
5.1 RELATIVELY INERT (NON-ABSORBABLE) BIOCERAMICS
5.2 NON-INERT BIOCERAMICS (RESORBABLE) BIOCERAMICS
5.3 SURFACE REACTIVE (SEMI-INERT) BIOCERAMICS
Notes
Absorbable : Capable of being absorbed or taken in through the pores of a surface

17. 5.0 TYPE OF BIOCERAMICS
Relative reactivity of bioceramics in physiological enviroments:
Non-inert bioceramic
Surface reactive bioceramic

18. 5.0 TYPE OF BIOCERAMICS
Some typical room temperature properties of bioceramics and corticol bone

19. 5.1 RELATIVELY INERT (NON-ABSORBABLE) BIOCERAMICS
Maintain their physical and mechanical properties while in host.
Resist corrosion and wear
Have all the six (6) desired properties of implantable bioceramics.
Have a reasonable fracture toughness.
Typically used as structural-support implant such as bone plates, bone screw and femoral heads.

20. 5.1 RELATIVELY INERT (NON-ABSORBABLE) BIOCERAMICS
5.1.1 ALUMINA (Al203)
The main source of alumina or aluminium oxide is bauxite and native corundum.
Highly stable oxide – very chemically inert
Low fracture toughness and tensile strength – high compression strength
Very low wear resistance
Quite hard material, varies from 20 to 30 GPa.
Notes
Bauxite and corundum is type of minerals

21. 5.1 RELATIVELY INERT (NON-ABSORBABLE) BIOCERAMICS
Mechanical properties requirement:
Compressive strength: 4 -5 Gpa
Flexural strength : > 400MPa
Elastic modulus: 380 GPa
Density : 3.8 – 3.9 g/cm3
Generally quite hard : 20 to 30 GPa

22. 5.1 RELATIVELY INERT (NON-ABSORBABLE) BIOCERAMICS
ALUMINA
High hardness + low friction + low wear+ inert to in vivo environment
Ideal material for use in:
Orthopaedic joint replacement component, e.g. femoral head of hip implant
Orthopaedic load-bearing implant
Implant coating
Dental implants

23. 5.1 RELATIVELY INERT (NON-ABSORBABLE) BIOCERAMICS
5.1.2 ZIRCONIA (Zr202)
Pure zirconia can be obtained from chemical conversion of zircon, which is an abundant mineral deposit.

24. 5.1 RELATIVELY INERT (NON-ABSORBABLE) BIOCERAMICS
Has a high melting temperature and chemical stability.
The bending strength and fracture toughness are 2-3 and 2 times greater than alumina.

25. 5.1 RELATIVELY INERT (NON-ABSORBABLE) BIOCERAMICS
The improved mechanical properties plus excellent biocompatibility and wear properties make this material the best choice the new generation of orthopaedic implant.
Has already widely use to replace alumina and metals.

26. 5.1 RELATIVELY INERT (NON-ABSORBABLE) BIOCERAMICS
5.1.3 CARBON
Carbon can be made in many allotropic forms:
Crystalline diamond
Graphite
Nanocrystalline glassy carbon
Quasicrystalline pyrolitic carbon
Only pyrolitic carbon is widely utilized for implant fabrication.
Normally used as surface coating

27. 5.2 NON-INERT BIOCERAMICS (RESORBABLE) BIOCERAMICS
Chemically broken down by the body and degrade
The resorbed material is replaced by endogenous tissue
Chemicals produced as the ceramic is resorbed must be able to be processed through the normal metabolic pathways of the body without evoking any deleterious effect.
Synthesize from chemical (synthetic ceramic) or natural sources (natural ceramic)

28. 5.2 NON-INERT BIOCERAMICS (RESORBABLE) BIOCERAMICS
Examples of Resorbable Bioceramics
Calcium phosphate
Calcium sulfate, including plaster of Paris
Hydroxyapatite
Tricalcium phosphate
Ferric-calcium-phosphorous oxides
Corals

29. 5.2 NON-INERT BIOCERAMICS (RESORBABLE) BIOCERAMICS
5.2.1 Synthetic ceramic
Calcium phosphate and Hydroxyapatite
Can be crystallized into salts such as Hydroxyapatite.
Hydroxyapatite (HAP) has a similar properties with mineral phase of bone and teeth.
Important properties of HAP:
Excellent biocompatibility
Form a direct chemical bond with hard tissue

30. 5.2 NON-INERT BIOCERAMICS (RESORBABLE) BIOCERAMICS
Low values of mechanical strength and fracture toughness, thus cannot be used in load bearing materials.

31. 5.2 NON-INERT BIOCERAMICS (RESORBABLE) BIOCERAMICS
Application:
Bone substitute in a granular or a solid block.
Temporary scaffold which is gradually replaced by tissue
Orthopaedic and dental implant coating
Dental implant materials
Drawback:
Complicated fabrication process and difficult to shape

32. 5.2 NON-INERT BIOCERAMICS (RESORBABLE) BIOCERAMICS
Tricalcium phosphate
Composition similar to hydroxyapatite
Degrades faster than calcium phosphate
More soluble than synthetic HAP
Allow good bone in growth and eventually is replaced by endogenous tissue.

33. 5.2 NON-INERT BIOCERAMICS (RESORBABLE) BIOCERAMICS
5.2.2 Natural ceramic
Biocoral
Corals transformed into HAP
Biocompatible
Facilitate bone growth
Used to repair traumatized bone, replaced disease bone and correct various bone defect.
Bone scaffold

34. 5.3 SURFACE REACTIVE (SEMI-INERT) BIOCERAMICS
Direct and strong chemical bond with tissue
Fixation of implants in the skeletal system
Low mechanical strength and fracture toughness
Examples:
Glass ceramics
Hydroxyapatite
Dense nonporous glasses

35. 5.3 SURFACE REACTIVE (SEMI-INERT) BIOCERAMICS
5.3.1 Glass ceramics
Glass-ceramics are crystalline materials obtained by the controlled crystallization of an amorphous parent glass.
Controlled crystallisation requires:
specific compositions
usually a two-stage heat-treatmen
Controlled nucleation
Controlled crystallization will growth of crystal of small uniform size

36. 5.3 SURFACE REACTIVE (SEMI-INERT) BIOCERAMICS
Type of glass ceramic
Bioglass
Ceravital
Both are SiO2, CaO, Na2O and P2O5 systems
Bioglass composition manipulated to induce direct bonding with the bone
Must simultaneously form a calcium phosphate and SiO2 – rich film layer on surface of ceramic for this to happen
With correct composition will bond with bone in approximately 30 days

37. Bioglass structure

38. 5.3 SURFACE REACTIVE (SEMI-INERT) BIOCERAMICS
Glass ceramic properties

39. 5.3 SURFACE REACTIVE (SEMI-INERT) BIOCERAMICS

40. 5.3 SURFACE REACTIVE (SEMI-INERT) BIOCERAMICS

41. 5.3 SURFACE REACTIVE (SEMI-INERT) BIOCERAMICS
Application of Glass Ceramic
Orthopaedic and dental implant coating
Dental implant
Facial reconstruction components
Bone graft substitute material
Main limitation:
Brittleness
Cannot be used for making major load bearing implant such as joint implant

42. 6.0 BIODEGRADATION OF CERAMIC
DEFINITION
Biodegradation: chemical breakdown of a material mediated by any component of the physiological environment ( such as water, ions, cells, proteins, and bacteria).
Bioerosion is breakdown including chemical degradation or other process in which bond cleavage is not required (e.g. physical dissolution), of a material mediated by any component of physiological environment.

44. 6.1 UNCONTROLLED DEGRADATION
DEPEND ON TWO FACTOR
Mechanical environment
Stress induced degradation can occur in ceramics under tension.
If crack is formed in these materials, the tensile stress may lead to further dissolution at the crack tip and material fracture.
Ceramic porosity
Pores are stress raiser thus may increase the formation of cracks or the rate of their propagation.

45. 6.1 UNCONTROLLED DEGRADATION

46. 6.1 UNCONTROLLED DEGRADATION
Uncontrolled degradation will cause WEAR.
WEAR → the generation of fine wear particles that can lead to inflammation and implant loosening.

47. 6.2 CONTROLLED DEGRADATION
Degradation is desirable.
Controlled biomaterial degradation can be used as an important part of tissue engineering and drug delivery therapies.
For these application, the temporary nature of the material is ideal to promote localized tissue healing or release of a bioactive agent without the need for second surgery to remove implant.

48. 6.2 CONTROLLED DEGRADATION
Biodegradable ceramics are usually type of calcium phosphate, such as
Hydroxyapatite, HA (Ca10(PO4)6(OH)2)
Tricalcium phosphate, TCP (Ca3(PO4)2)
Biodegradable ceramic generally degrade by dissolution (influenced by the solubility of the ceramic formulation in media and the pH of the media) coupled with physical disintegration.

49. 6.2 CONTROLLED DEGRADATION
6.2.1 FACTOR THAT INFLUENCE DEGRADATION RATE
Chemical susceptibility of the material
Hydrated form forms such as hydrated calcium sulphate degrade faster than their nonhydrated counterparts.
hydrated calcium sulphate = gypsum is a common sulphate mineral which is white or colourless mineral. It is a source of plaster of Paris.

50. 6.2.1 FACTOR THAT INFLUENCE DEGRADATION RATE
2. Amount of crystallinity
Ceramic degradation depend on water penetration.
A more tightly packed crystalline material is less susceptible to dissolution than a ceramic that is mainly amorphous (unstructured).
Polycrystalline ceramics degrade more quickly than single crystal ceramic due to presence of grain boundaries.
Ceramic contain many smaller crystals is more susceptible to dissolution than one with fewer, larger crystal.
Dissolution = perlarutan/pembubaran

51. 6.2.1 FACTOR THAT INFLUENCE DEGRADATION RATE
Amount of media (water) available
High amount of water → increase degradation rate
Low amount of water → slower degradation rate
Material surface area to volume ratio
Highly porous ceramic will dissolve more quickly than the same ceramic with fewer pores due to increase in area for interaction with the environment.

52. 6.2.1 FACTOR THAT INFLUENCE DEGRADATION RATE
Highly porosity Low porosity

53. 6.2.1 FACTOR THAT INFLUENCE DEGRADATION RATE
5. Mechanical environment
Ceramic degradation is encouraged in areas with high mechanical stress, either due to
Implant site location
Presence of stress raiser in the device
Production of wear particles will caused inflammatory response → pH drop → accelerate degradation of material

54. Extra: Bone scaffold
Perfection regained: the perfect fit of the Sandia ceramic scaffolding in the model jaw also recreates the upper line of the original jawbone. The scaffold layering, which cross each other like a child's Lincoln Logs,
are approximately 500 microns apart to expedite passage of new bone and blood vessels.

55. The milled implant from a wax-embedded scaffold of hydroxyapatite.
Once the device is milled, the wax is melted out, and the implant is finished.
The porous structure of the scaffold allows bone to grow into it,
providing the future basis for the growth of new bone in a patient.

56. The underside of the final implant scaffold,
showing the modeled canal for the nerve path.
The final implant scaffold fit
tested in the patients jaw.

57. Attachment
Allotropy is the property of some chemical elements to be able to take two or more different forms, where the atoms are arranged differently by chemical bonds.
The forms are known as allotropes of that element.[1] The phenomenon of allotropy is sometimes also called allotropism.
For example, carbon has two common allotropes: diamond, where the carbon atoms are bonded together in a tetrahedral lattice arrangement,
and graphite, where the carbon atoms are bonded together in sheets of a hexagonal lattice.