Ceramics

Question 1

Increasing the porous microstructure: Pros and Cons

Answer 1

Pros: More tissue integration, but a decrease in strength

Question 2

Processing and material microstructure properties can mainly be manipulated by altering the following two factors

Answer 2

Temperature and Pressure

Question 3

Ceramics are mainly used to replace the following biological material:

Answer 3

hard connective tissues

Question 4

Type I Bioceramics

Answer 4

Dense, nonporous, no biological interface, normally made from Alumina (Al2O3)

Question 5

What is one way to induce morphological fixation?

Answer 5

You can press fit

Question 6

What is fibrous capsule?

Answer 6

scarring, discontinuity, and loosening

Question 7

Type II Bioceramics

Answer 7

porous, non load bearing, derived form coral or animal bones e.g: HA COATING.

Question 8

Porosity decreases these two types of stress, but doesn’t really change this type of stress

Answer 8

decreases tensile and compressive, doesn’t really change torsional strength

Question 9

2 ways to make slightly porous materials

Answer 9

drill a larger piece down, or use a bead technique called powder sintering

Question 10

What is important when considering making something porous for tissue ingrowth?

Answer 10

Must allow diffusion of oxygen and nutrients to maintain inner tissue ingrowths.

Question 11

Type III Bioceramics

Answer 11

exists between being resorb able and inert, elicits a biological “bond” at interface such as buildup of a more bioactive material. e.g. HA itself

Question 12

Sequence of interfacial events

Answer 12

Original substrate—chemical bonds— water absorbtion–adsorbtion of salts onto surface—crystalization—absorbtion of larger biomolecules– cells start to interact with these biomolecules—release of factors–cellular proliferation.—generation of bone matrix and crystallization

Question 13

Hydroxyapatite (HA)

Answer 13

Ca and PO4 crystals co precipitated in collagen matrices

Question 14

What level (type) is a biomaterial with HA considered?

Answer 14

Type III

Question 15

Using powdering techniques etc. you can add HA to the surface of devices to do what?

Answer 15

Add a bioactive layer that is slowly degraded by osteoblasts, but not necessarily replaced with bone. (Type II)

Question 16

Type IV Bioceramics

Answer 16

Bioresorbable typically made from calcium phosphate, designed to eventually be replaced by bone

Question 17

How do you alter the tensile and compressive strength of type IV bioceramics?

Answer 17

Alter the volume and porosity of the unit

Question 18

What is a major challenge when creating a bioresorbable material?

Answer 18

Matching degradation rate with tissue integration rate.

Question 19

How do you alter the degree of crystallinity in a bioceramic?

Answer 19

Processing temperature, pressure, and pH. For example, calcium phosphate under higher temperatures can lead to beta tricalcium phosphate, or tetra calcium phosphate.

Question 20

Bond strength as a function of time: Why would a bioactive fixation have such a variant strength as a function of time?

Answer 20

A bioactive fixation would vary with degradation vs. tissue ingrowth.

Question 21

At what pressure does bone naturally heal?

Answer 21

30 MPa

Question 22

Bioglass or bioactive fixations can be problematic because:

Answer 22

over time, they can get stronger and stronger, eventually negatively stress shielding the bone.

Question 23

Describe Wolff’s Law

Answer 23

strong implants can stress shield, or cause bone fracture.