Autumn quiz II: Materials

Question 1

dental casting alloy ANSI/ADA types :

1,2,3,4?

Answer 1

1. Soft, restorations subjected to low stress, inlays
2. Medium, restorations subjected to moderate stresses, inlays and onlays
3. Hard, restorations subjected to high stresses, crowns, thick veneer crowns, short span, fixed prosthesis
4. Extra hard, restorations subjected to very high stress, thin veneer crowns, long span fixed prostheses, removable prostheses

Question 2

what were the two types of fabrications for leucite reinforced, lithium disilicate, and zirconia

Answer 2

leucite reinforced: pressed ingots (lab) or milled blocks

Lithium disilicate: pressed (lab) ingots, or milled blocks

Zirconia: porcelain fused zirconia ingots (bilithic) or milled blocks (monolithic)

Question 3

what is leucite reinforced material made of, whats brand name (when was it available), how can it be fabricated?
(whats leucite itself made of?)

Answer 3

leucite reinforced glass ceramic

• leucite is a mineral composed of potassium and aluminum tectosilicate.
• particle filled glass ceramics (scientific name: potassium aluminum silicate) are reinforced by leucite to make esthetic ,with functional strength. for use in anterior dentition and partial coverage for posterior teeth BEFORE invention of lithium disilicate

brand name; empress I and II

can be PRESSED or MILLED.

-available in 1990

Question 4

what is the composition of lithium disilicate, fabrication options, brand name?

Answer 4

• quartz , lithium dioxide, phosphate oxide, alumina and potassium oxide. Its a glass ceramic
• highly esthetic and strong restoration (bc of translucency options, interlocking of crystals)
• material can be ingots pressed, or monolithic blocks (CAD/CAM milling)
• BRAND NAME: IPS eMAX

Question 5

when should MT Multi IPS emax be used

whats the stregth/wall thickness

Answer 5

this is considered the ESTHETIC Lithium disilicate
(medium translucency with shade gradation)
-used for FULL CONTOUR crowns, full contour 3 unit bridges.
-strength: 850 MPa, thickness .8 anterior /1 mm posterior

– (most) efficient

Question 6

when should MT ips emax be used, whats its strength/wall thickness

Answer 6

MT= medium translucency 
this is "creative"?
-strength; 850 Mpa
thickness; .8 anterior /1 mm posterior
-used for full contour crowns and full contour 3 unit bridges

–efficient

Question 7

when should LT IPs emax be used, strength and thickness?

Answer 7

LOW translucency
-“allrounder”
-strength; 1200 Mpa
wall thickness; .4 mm anteriors, .6 posteriors
-used :full contour crowns, 3 unit bridges full contour, full contour 4 to multi unit bridges w max 2 pontics, crown frameworks, 3 to multi unit bridge frameworks with max 2 pontics..
can be monolithic or frameworks?

Question 8

when should MO IPS emax be used, strength, wall thickness

Answer 8

-Medium opacity. CLASSIC
-framworks ?
-strength 1150 MPa
wall thickness; .4 mm anterior, .6 mm posterior.
-used for crown frameworks and 3 to multi unit bridge frameworks with max 2 pontics.

Question 9

what is an ingot

Answer 9

a block of material (lithium disilicate, porcelain, or metal) in a uniform size and shape that can be utilized for casting, pressing a restoration or become part of a restoration

• for fabrication of a dental restoration the ingot is liquefied high temps and pressed through a casting ring.
• used in layering of porcelain ON zirconia (bilithic restorations)
• comes in a variety of translucencies for lithium disilicate to accommodate patients esthetics, clinicians demand for strength

Question 10

what does it mean to PRESS ingot

Answer 10

• take ingot and heat at a high temp. then heat pressuring under a vacuum, fabricating a restoration through an investment.
• mostly done at dental labs

Question 11

how many mpa are lithium disilicate in block form

Answer 11

130-160 MPa

Question 12

what do you do after the restoration is milled by a machine

temp/ shrinkage amount?

Answer 12

its placed in a ceramic furnace to be crystallized, strength increases to 500 MPa (bonded adhesively with a material?)
-metal lug on it assures positive lock in the mill.

-sintered at. 1500-1600 celsius to enact state change. shrinkage is 20-25%!! becomes stronger and more translucent w heating

Question 13

how does the composition change with crystallization of LDS

Answer 13

-LDS grows, interlocks and concentrates, increasing flexural strength

• • pre crystallized state; 40% isolated lithium metasilicate crystals in a glass matrix
• -ips e max CAD afterfiring; 70% lithium disilicate crystals in a glass matrix

Question 14

what are the crystal phases of zirconia

Answer 14

tetragonal and cubic

• tetragonal; used for toughening the zirconia
• cubic: used to increase translucency

balance o these determines strength and esthetics

Question 15

whats the flexural strength of the diff types of fabricated leucite reinforced, LDS, and zirconia

Answer 15

leucite reinforced; pressed and milled both 160-185 MPa (glaze up to 240 MPa)

LDS: ingots pressed and milled are 400-500 MPa, high values assumes bonded

Zirconia: porcelain fused zirconia(bilithic) is 1,000 MPa, and milled monolithic is 500-1500 MPa

Question 16

when would you use leucite reinforced

Answer 16

veneers, inlays, onlays (MUST BOND)

Question 17

when would you use lithium disilicate

Answer 17

veneers, inlays/onlays, crowns 1 mm bonded, bridges to 2nd premolar, 12 mm2 connectors (bridges) should give 12 square mm of volume

Question 18

when would you use zirconia

Answer 18

veneers, inlays/onlays, crowns 1 mm with no bond, bridges 12 mm squared in connector area, and anterior crowns in bilithic form

Question 19

how is strength meausred of materials (flexural/mpa)

Answer 19

• flexural strength: measured by applying a load to a material specimen that is supported at each end, which combines forces found in compression and tension
• MPa: a unit of measure that represents how much stress/pressure a material can withstand without failing.

Question 20

which materials need bonding

Answer 20

short zirconia or E-max crowns in posterior require bonding for retention

Question 21

whats the order of esthetic for zirconia, LDS, leucite reinforced and their methods

Answer 21

leucite reinforced pressed/milled > LDS pressed/milled AND zirconia PFZ (bilithic) and high translucency /polychromatic zirconia > zirconia milled and opaque (monolithic)

Question 22

can zirconia be made for thin veneers

Answer 22

yes can be very thin

Question 23

what dimension matters most for connectors

Answer 23

height is more important than width

LDS and zirconia both; 12 square mm