Dental Ceramics Flashcards
what is kaolin
clay
why is kaolin removed from dental ceramics
it is opaque but dental ceramics need to be translucent
what replaces kaolin
feldspar and silica
what is the process of conventional dental ceramics
powder is heated then rapidly cooled
milled to fine powder
binder added
mixed with distilled water and built up into restoration
what do feldspathic ceramics form when heated
leucite
what does leucite give the powder
physical and thermal properties
how is a crown fabricated
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
what is sintering
ceramic particles begin to fuse into a single mass
what happens to the material during sintering
contracts
what are the properties of conventional dental ceramics
aesthetics - good
chemical stability - good
biocompatibility - good
thermal properties - similar to tooth
dimensional stability - good
mechanical properties
what are the mechanical properties of dental ceramics
high compressive strength
high hardness
low tensile strength
low flexural strength
low fracture toughness
what is static fatigue
time dependent decrease in strength even in absence of any applied load
where can conventional feldspathic ceramic crowns be used
low stress areas
anterior crowns
how do you overcome problems with conventional ceramics
produce a strong coping
what are the 2 types of core used in a crown
alumina or zirconia
what does alumina act as
crack stoppers preventing cracks propagating through material and causing fracture
what are the problems of alumina cores
lack of flexural strength
only successful anteriorly
what zirconia is used in dentistry
Yttria stabilised
what does yttria make the material
hard
strong
tough
how is a zirconia core made
impression taken and model cast
digitally scanned
software creates bridge
milling
heat treated and stained
veneered with feldspathic porcelain
what are the problem with zirconia cored crowns
expensive equipment needed
could debond from core
cannot etch or bond
what is used for posterior teeth
monolithic zirconia
what is used for anterior teeth
lithium disilicate
what is used for anterior bridgework
lithium disilicate
