lecture 11 - ceramics, glasses, and glass-ceramics

are ceramics/glasses organic or inorganic

inorganic

are ceramics/glasses metallic or non-metallic

non-metallic

what are some uses for ceramics/glasses

• eyeglasses

• diagnostic instruments

• drug carriers

what are ceramics mostly used to repair/replace

skeletal hard connective tissue

what 2 things do ceramic implant success depend on

• stable attachment to connective tissue (bulk implants)

• ability to stimulate repair and regenerate bone (particulates for bone grafting)

what are the 4 types of bioceramics

• type 1 - inert and dense

• type 2 - nearly inert, porous

• type 3 - bioactive

• type 4 - resorbable

what happens if a biomaterial is toxic

tissue dies

what happens if a biomaterial is non-toxic and bioinert

a fibrous capsule forms

what happens if a biomaterial is non-toxic and bioactive

native tissue/cells infiltrate the biomaterial

what happens if a biomaterial is non-toxic, bioactive, and degradable

native tissue replaces the biomaterial over time

most ceramics are biomaterials that are ____ and ____

non-toxic and bioactive (type 3)

what is an interfacial bond

the bond between ceramic and bone tissue

what does the strength of the interfacial bond depend on

how bioactive the material is

what does this graph show

% of interfacial bone tissue as a function of implantation time

how are type 1 ceramics implanted

through morphological fixation (like aluminum)

what do type 1 ceramics exhibit with a perfect fit

very thin fibrous capsule

how are type 2 ceramics implanted

through bone growing into the pores of the ceramic

type 2 ceramics can withstand ___ complex stress than type 1

more

because they are porous type 2 ceramics have ____ overall strength than type 1

lower

pore size should be how large to be conducive to bone ingrowth

>100microns → allows for cells and blood vessels to fit within pores to keep cells alive

type 3 ceramics are ___-reactive

surface

how are type 3 ceramics implanted

by chemically bonding directly with bone

how are type 4 ceramics implanted

embedded within bone to be slowly replaced by bone

because type 4 ceramics degrade, what 2 rates have to match

rate of degradation and rate of tissue formation

what does the density of a ceramic depend on

thermal processing (how high the temp is and how long it is kept at a certain temp for)

how are porous ceramics made

by adding a second phase that decomposes before densification (leaves behind pores)

what is sintering

a process that uses temp and time to help particles fuse

ceramics are also known as what

oxides

what is an example of a nearly inert crystalline ceramic

alumina (Al2O3)

why are alumina excellent for corrosion resistance

because they are already oxidized

what are 4 pros of alumina

• good compatibility

• high wear resistance

• high wettability

• low coefficient of friction

why is alpha-alumina used as a biomaterial

because the alpha form is the most thermodynamically stable