5 - Ceramics

Question 1

5.8 Pigments can be added to frit to produce various shades

1. Titanium oxide?
2. Manganese oxide?
3. Iron oxide?
4. Cobalt oxide?

Answer 1

1. Yellow brown
2. Lavendar
3. Brown
4. Blue

Question 2

5.8 Pigments can be added to frit to produce various shades

5. Copper/chromium oxide
6. Nickel oxide
7. Lanthanide oxide

Answer 2

5. Green
6. Brown
7. Fluorescence

Question 3

5.12 What are the two phases of feldspathic dental porcelain?

Answer 3

1. Vitreous (glass) phase
2. Crystalline (mineral/leucite) phase
   - High thermal expansion
   - Content (10-20%) controls the thermal expansion coefficient (CTE) - contributes strength

Question 4

5.19 Describe the process of condensation and sintering of porcelain products

What is the “first firing” called?

Answer 4

First, the wet crown is dried at the door of the oven to drive off remaining water. It is then moved into the oven where it is heated under vacuum and the process called sintering takes place.

The porcelain particles join together by flow on contact as a result of surface energy. Gas bubbles escape via grain boundaries and porosities are reduced.

The first firing is the Biscuit Bake

Question 5

5. 30 Ceramic-metal bond failures

- Where would a properly bonded ceramic-metal specimen fracture?

Answer 5

In the porcelain

Question 6

5.30 Ceramic-metal bond failures

Where would a fracture occur if the oxide layer is too thick?

Answer 6

Fracture through the oxide layer

Question 7

5.31 One of the requirements for a ceramic-metal system is for ________ to be compatible.

Answer 7

CTE (co-efficient of thermal expansion) - metal slightly higher than ceramic to put ceramic in compression where it is stronger