DENTAL CERAMICS PT. 2

What’s glass infiltrated ceramics/ slip cast ceramics?

• specialized ceramics reinforced by an unique glass infiltration process

• involves condensation of an aqueous slip on refractory die 

In-Ceram was developed by infiltrating glass into a porous ceramic framework, creating a strong and esthetic glass-ceramic used in dentistry.

Types of In-ceram

1. In-ceram alumina core

2. In-ceram spinell core

3. In-ceram zirconia core

In-Ceram Alumina

• Made of alumina (Al₂O₃) particles infiltrated with glass

• Very strong and fracture-resistant

• Opaque appearance (less esthetic)

• Best for posterior crowns and short-span bridges

In-Ceram Spinell

• Made of magnesium–alumina (MgAl₂O₄), called spinel, infiltrated with glass

• Developed to improve translucency compared to alumina

• Lower strength than alumina

• More esthetic and natural-looking

• Best for anterior crowns where appearance matters

In-Ceram Zirconia

• Made of alumina + zirconia mixture infiltrated with glass

• Highest strength among the three types

• Least translucent (more opaque)

• Used for posterior crowns and long-span bridges that need extra strength

Differences between in-ceram alumina, spinell, and zirconia

Alumina: Strong but opaque

Spinell: Translucent but weaker

Zirconia: Strongest but most opaque

What are the machinable ceramics?

• Digital Systems

• Analogous Systems

What are the strengthening methods?

• Strengthening brittle materials:

  • Introduction of residual compressive stresses

  • Interruption of crack propagation

• Methods of designing to:

  • Minimize tensile stress through design

  • Avoid stress raisers

Ion exchange mechanism:

• This technique is called as chemical tempering and is the most sophisticated and effective way of introducing residual  compressive stresses.

• This process is best used on the internal surface of the  crown, veneer/inlay as the surface is protected from  grinding and exposure to acids.

Ion exchange mechanism (Chemical tempering):

• It is a chemical process used to strengthen glass-ceramics.

• In this technique, the material is heated and placed in a molten salt bath (usually containing potassium nitrate).

• Smaller sodium ions (Na⁺) on the glass surface are replaced by larger potassium ions (K⁺) from the salt bath.

• Because the larger ions occupy more space, they create compressive stresses on the surface of the material.

• These compressive stresses increase the strength and resistance of the ceramic to cracks and fractures.

• It is most effective when applied to internal surfaces (like the inside of a crown, veneer, or inlay) because these areas are protected from wear, grinding, or acid exposure, helping preserve the compressive layer.

Thermal tempering

• This is the most common method of strengthening glass.

• In dentistry silicone oil and other special liquids are used for quenching ceramics instead of water/air

Essentials of cad cam

1. Scanner/digitizer

2. Computer

3. Milling station

4. Ceramic blanks

5. Furnace

What’s the CAD-CAM Process?

1. Optical impression by an intraoral scanner

2. 3d reconstruction of dentitions on the monitor

3. CAD process (Virtual wax-up prstheses_

4. Fabrication of NC data

5. CAM process (Milling prostheses from the block)

6. Post treatments (Staining & glazing)

How can CAD-CAM be produced?

• by chairside milling units

• industrial milling processes

MOST COMMON CAD CAM SYSTEMS

1. Direct CAD-CAM Systems

2. Indirect CAD-CAM Systems

3. Cicero system

4. Lava system

5. Cerec scan

6. Copy milling