Dental Ceramics

Question 1

what is kaolin

Answer 1

clay

Question 2

why is kaolin removed from dental ceramics

Answer 2

it is opaque but dental ceramics need to be translucent

Question 3

what replaces kaolin

Answer 3

feldspar and silica

Question 4

what is the process of conventional dental ceramics

Answer 4

powder is heated then rapidly cooled
milled to fine powder
binder added
mixed with distilled water and built up into restoration

Question 5

what do feldspathic ceramics form when heated

Answer 5

leucite

Question 6

what does leucite give the powder

Answer 6

physical and thermal properties

Question 7

how is a crown fabricated

Answer 7

ceramic powder mixed with water and applied to die with brush
crown built up using different porcelains for dentine and enamel
crown heated in furnace

Question 8

what is sintering

Answer 8

ceramic particles begin to fuse into a single mass

Question 9

what happens to the material during sintering

Answer 9

contracts

Question 10

what are the properties of conventional dental ceramics

Answer 10

aesthetics - good
chemical stability - good
biocompatibility - good
thermal properties - similar to tooth
dimensional stability - good
mechanical properties

Question 11

what are the mechanical properties of dental ceramics

Answer 11

high compressive strength
high hardness
low tensile strength
low flexural strength
low fracture toughness

Question 12

what is static fatigue

Answer 12

time dependent decrease in strength even in absence of any applied load

Question 13

where can conventional feldspathic ceramic crowns be used

Answer 13

low stress areas
anterior crowns

Question 14

how do you overcome problems with conventional ceramics

Answer 14

produce a strong coping

Question 15

what are the 2 types of core used in a crown

Answer 15

alumina or zirconia

Question 16

what does alumina act as

Answer 16

crack stoppers preventing cracks propagating through material and causing fracture

Question 17

what are the problems of alumina cores

Answer 17

lack of flexural strength
only successful anteriorly

Question 18

what zirconia is used in dentistry

Answer 18

Yttria stabilised

Question 19

what does yttria make the material

Answer 19

hard
strong
tough

Question 20

how is a zirconia core made

Answer 20

impression taken and model cast
digitally scanned
software creates bridge
milling
heat treated and stained
veneered with feldspathic porcelain

Question 21

what are the problem with zirconia cored crowns

Answer 21

expensive equipment needed
could debond from core
cannot etch or bond

Question 22

what is used for posterior teeth

Answer 22

monolithic zirconia

Question 23

what is used for anterior teeth

Answer 23

lithium disilicate

Question 24

what is used for anterior bridgework

Answer 24

lithium disilicate

Question 25

what is used for heavier occlusion

Answer 25

zirconia

Question 26

what cement is used for zirconia and lithium disilicate crowns

Answer 26

conventional or resin cements

Question 27

what type of ceramic is using in the ceraming process

Answer 27

lithium disilicate

Question 28

what is the advantage of lithium disilicate

Answer 28

good fracture toughness and good flexural strength