Lecture 10: Ceramics

Question 1

what are some of the applications dental ceramics are used for?

Answer 1

inlays
onlays
single all ceramic crowns
short span all ceramic bridges
support for metal crowns and bridges
artificial denture teeth
orthodontic brackets
implants

Question 2

what are ceramics composed of and what do they form?

Answer 2

• metal oxygen atoms with ionic bonds like zirconium and aluminum
• arrays in a 3-D crystalline lattice

Question 3

what are the different types of ceramics?

Answer 3

glassy
glass dominated
crystalline
crystalline dominated

Question 4

what are glassy ceramics used for?
glass dominated? crystalline? crystalline dominated?

Answer 4

esthetics and veneers

better esthetics/strength

strongest, opaque, any dental restoration

improved strength, more opaque, cores for anterior posterior crowns, inlays/onlays

Question 5

what are the common compounds in the crystal phase?

Answer 5

leucite
fluroapatite
spinel
zirconia
alumina
lithium disilicate
lithium silicate/phosphate

Question 6

what are the common compounds in the glassy phase?

Answer 6

silica (quartz, silicone oxide)

Question 7

how are ceramics manufactured?

Answer 7

stacking (glass infusion)
pressing (HOT)
milling (CAD/CAM)
additive manufacturing (3D printing)
slip casting

Question 8

each type of ceramic requires ______

Answer 8

a specific method of manufacturing

Question 9

what are the matrix and fillers of resin-ceramic materials and why are they made ?

Answer 9

matrix: BisGMA, UDMA, TEGDMA
fillers: Zr-si, silica, zirconia, alumina

** resin ceramics are easier to fabricate, have properties closer to dentin, easier to repair, load bearing eg veneers

Question 10

what are the mechanical properties of ceramics?

Answer 10

• high compressive strengths and moduli
• low tensile strengths and elongation
• stiff and brittle relatively to alloys and polymers

Question 11

the hardness of ceramics is?

Answer 11

substantially higher than enamel and wear can be minimized if restoration surface is smooth

Question 12

what is the coefficient of thermal expansion (CTE)?

Answer 12

measure of how much material expands per unit length if heated 1 C

Question 13

why is the CTE important?

Answer 13

it is important for thermal compatibility due to ceramic being bonded to another material which can cause failure

Question 14

proper CTE matching is required because?

Answer 14

not all alloys are compatible with all ceramics (prevent failure)

Question 15

the glass phase allows what to pass through? crystalline phase?

Answer 15

• allows light to pass through
• reflects the light (absorbs and reflects)

Question 16

the value is the most critical for what?

Answer 16

color matching (amount of lightness or darkness)

Question 17

what are the parts of the porcelain fused metal?

Answer 17

• opaque porcline: masks darkness of oxidized metal
• gingival and incisal ceramics: overlap gives natural tooth color

Question 18

what are the characteristics of the bonding of ceramics and alloys?

Answer 18

• alloys have oxide layer
• bond results in chemisorption by diffusion (covalent bond) between ceramic and oxide layer
• roughness increases strength

Question 19

what are some causes of ceramic-alloy bonding failure?

Answer 19

• inadequate oxide layer
• high thermal residue stress
• secondary caries, tooth failure, periodontal disease

Question 20

what is the advantage of all ceramic restorations?

Answer 20

• better esthetics
• no dark color to mask
• entirely glass dominated ceramics

Question 21

what are the layers of all ceramic restorations?

Answer 21

• core (replaces alloy)
• veneering ceramic