Dent 1.3

Question 1

what is added to Frit to creat different shades

Answer 1

— Oxides (eg titianium oxide = yellow brown)

Question 2

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

Answer 2

Vitreous (glass) phase, and

Crystalline (nuneral/leucite) phase

Question 3

what are some Characteristics of Crystalin phase

Answer 3

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

Question 4

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

Answer 4

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

Question 5

where is a fracture most common when proper bonding is present

Answer 5

fractures in the porcelain

Question 6

when will a fracture occur trough the oxide layer

Answer 6

If the oxide layer is to thick

Question 7

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

Answer 7

Higher, compatible

Question 8

CTE

Answer 8

Coefficient of thermal expansion

Question 9

what are the three stages of free Radical Polymerization

Answer 9

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

Question 10

what substances are considered to be Thermoplastic

Answer 10

WAXES

Question 11

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

Answer 11

due to weak secondary valence forces and transition forces

Question 12

Define residual stress

Answer 12

internal stresses- independant of applied forces.

Question 13

what causes residual stress

Answer 13

usually a result of non-uniform heating and cooling

Question 14

Four properties of Waxes

Answer 14

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

Question 15

what is the most accurate way to measure impression materials

Answer 15

By Weight

Question 16

what acts as a retarder for Impression materials

Answer 16

Sodium Phosphate

Question 17

what is the composition of alginate (5)

Answer 17

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

Question 18

what three environmental factors effect impression materials

Answer 18

• syneresis
• imbibition
• evaporation

Question 19

what is syneresis

Answer 19

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