Ceramics

Question 1

Definition of ceramic

Answer 1

Simple compounds of metallic and non-metallic elements e.g. almost all solids that are neither metals nor polymers.

Question 2

Definition of glass

Answer 2

A material e.g. ceramic or polymer, that has been cooled to a rigid condition without crystallising.

Question 3

Crystalline define

Answer 3

Exhibit long range and periodic anatomic order

Question 4

Amorphous define

Answer 4

Lack of long-range atomic order (glasses)

Question 5

Important properties of ceramics

Answer 5

• Flexural strength: forces that are applied as ceramics are brittle, they can chip
• Fracture toughness: how strong the material is
• Chemical solubility: otherwise will start dissolving
• Antagonistic wear
• Translucency: how they appear

Question 6

What are the 3 types of all ceramic systems?

Answer 6

1. Polycrystalline (oxide) ceramics - without a glass phase e.g. Procera Al2O3/ZrO2, Cercon, lAVA
2. Glass-infiltrated ceramics (With a glass phase) e.g. In Ceram Al2O3/ZrO2
3. Glass ceramics (with a glass phase) e.g. Empress I/II

Question 7

Which type of ceramic system is the most aesthetic?

Answer 7

Glass ceramic

Question 8

Which type of ceramic system is the most strongest?

Answer 8

Polycrystalline (oxide) ceramics

Question 9

What are glass ceramics used for?

Answer 9

Inlays and onlays, veneers, anterior single crowns

Question 10

What are glass infiltrated ceramics used for?

Answer 10

Substructures for anterior and posterior single crowns

Question 11

Systems for glass infiltrated ceramics

Answer 11

In-Ceram (Alumina Al2O3)
In-Ceram Spinnell (Al2O3+MgO2)
In-Ceram Zirconia (Al2O3+ZrO2)

Question 12

What are oxide ceramics used for?

Answer 12

AlZr Cores for anterior and posterior crowns

Zr anterior and posterior bridgework

Question 13

What is the most common cause of failure in all ceramic restorations?

Answer 13

Fracture

Question 14

Why do porcelains fracture?

Answer 14

• No moveable defects/dislocations (as in metals) to dissipate stress
• Flaw leads to stress concentrations, especially with tensile forces
• If a crack starts to propagate, less stress required to continue propagation and the crack accelerated quickly
• Fracture stress determined by the largest flaw

Question 15

Traditional (Feldspathic) Porcelain disadvantages

Answer 15

• Fracture resistance low
• Construction technique sensitive: shrinking due to fusing when fired, skill level required to achieve good aesthetics
• Hardness

Question 16

What are some areas of development to counteract disadvantages of traditional ceramic restorations?

Answer 16

2 Solutions: provide support for using a stronger substrate or produce ceramics that are stronger and tougher.
1. Better fracture resistance: laminate to metal to decrease influence of internal flaws, adapted to substructure,
Dispersion strengthening of glasses: alumina added to glass to increase strength and high strength crystalline ceramics as a core

Question 17

Leucite-reinforce glass ceramics e.g. IPS Impress

Answer 17

Indications: crowns, inlays, onlays and veneers