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Flashcards in Dent 1.3 Deck (19):
1

what is added to Frit to creat different shades

--- Oxides (eg titianium oxide = yellow brown)

2

what two phases do compositions consist of when coming from the manufacture

Vitreous (glass) phase, and
Crystalline (nuneral/leucite) phase

3

what are some Characteristics of Crystalin phase

High thermal expansion
Content (10-20%) controls the CTE of the porcelain
contributes strength

4

when a crown is moved into the oven where it is heated under vacuum and the process called _______ takes place

Sintering (porcelain particles join together by flow on contact as a result of surface energy)

5

where is a fracture most common when proper bonding is present

fractures in the porcelain

6

when will a fracture occur trough the oxide layer

If the oxide layer is to thick

7

CTE of ceramic and metal must be compatible - metal slightly _______ then ceramic to put ceramic in a compression where it is ______

Higher, compatible

8

CTE

Coefficient of thermal expansion

9

what are the three stages of free Radical Polymerization

1) Initiation phase
2) propagation stage
3) termination stage

10

what substances are considered to be Thermoplastic

WAXES

11

why are waxes considered to have a high degree of THERMAL EXPANSION

due to weak secondary valence forces and transition forces

12

Define residual stress

internal stresses- independant of applied forces.

13

what causes residual stress

usually a result of non-uniform heating and cooling

14

Four properties of Waxes

melting range
tendency to flow
residual stresses
Largest CTE of all dental materials

15

what is the most accurate way to measure impression materials

By Weight

16

what acts as a retarder for Impression materials

Sodium Phosphate

17

what is the composition of alginate (5)

sodium alginate,
calcium sulfate,
sodium phosphate,
filler,
potassium flouride

18

what three environmental factors effect impression materials

- syneresis
-imbibition
-evaporation

19

what is syneresis

fluid loss during setting squeezing water from between polysaccharide or alginate chains
(shrinkage and distortion of cast)