CAD/CAM Materials- Fixed Restorations

CAD is Computer-Aided Design

Digital design of the restoration on a computer

Some examples of CAD include

Crown contour, contacts, occlusion, and margins

CAM is Computer-Aided Manufacturing

Machine production of the restoration

How does CAM work?

Commonly milling; printing is expanding for some materials and workflows

The simple digital workflow is 1. scan 2. design and 3. manufacture. What are the steps of scanning

1. Intraoral or lab scan

2. Captures teeth, margins, and occlusion

3. Replaces or reduces conventional impressions

The simple digital workflow is 1. scan 2. design and 3. manufacture. What are the steps of design?

1. Software creates the restoration form

2. Operator adjusts contours, contacts and thickness

3. Virtual tools help detect under reduction

The simple digital workflow is 1. scan 2. design and 3. manufacture. What are the steps of manufacturing?

1. Milling is the main subtractive method

2. Some workflows also use printing

3. Final finishing may include staining, glazing, or polishing

What are some advantages of CAD/CAM as opposed to conventional techniques?

1. More predictable fit and accuracy

2. No impression material for many workflows

3. Magnified view helps detect preparation problems

4. Better reproducibility and easier data storage

What are some limitations of CAD/CAM as opposed to conventional techniques?

1. High initial equipment cost

2. Training is required

3. Software and maintenance costs continue over time

4. Digital speed does not replace sound preparation principles

Digital workflow can be faster and cleaner, but it still depends on

Preparation quality, moisture control, margin clarity and correct material selection

Examples of temporary materials

• PMMA

• Bis-acryl / resin block composites

Examples of glass ceramics

• Lithium disilicate

• Strong esthetics

• Usually bonded with adhesive protocols

Examples of polycrystalline ceramics

• Zirconia

• High strength and toughness

• Different cementation logic from glass ceramics

What are some examples of common temporary CAD/CAM materials that are used for provisional crowns and longer-term temporary restorations?

• PMMA blocks

• Bis-acryl or resin composite blocks

What is the benefit of using CAD/CAM temporary materials?

• They protect prepared teeth

• Maintain function and esthetics

• Help evaluate contour, occlusion, and patient comfort

A good provisional is not only a placeholder, it teaches whether

Contours, occlusion, margins and patient comfort are acceptable

What are some indications for temporary materials?

• Interim crowns and bridges

• Diagnostic or transitional restorations

• Longer provisional phases compared with direct chairside temporary materials

What are some limitations for temporary materials?

• Not final definitive ceramics

• Lower wear resistance and strength

• Color and surface quality are usually less ideal than definitive esthetic ceramics

Zirconia provides strong tooth-colored restorations, especially where forces are higher. It is not automatically the best choice everywhere, but it is a very reliable material. Why is zirconia known for its strength?

• Very high flexural strength compared with glass ceramics

• Excellent fracture toughness

• Useful in higher-load areas

Zirconia provides strong tooth-colored restorations, especially where forces are higher. It is not automatically the best choice everywhere, but it is a very reliable material. Why is zirconia known for its biocompatibility?

• Inert and well tolerated

• Chemically stable

• Used in crowns, bridges, and implant restorations

Zirconia provides strong tooth-colored restorations, especially where forces are higher. It is not automatically the best choice everywhere, but it is a very reliable material. Why is zirconia known for its durability?

• Wear and fatigue resistance support long-term function

• Maintains shape and fit over time

• Can be used as a monolithic restoration

What kind of zirconia has the highest strength, lower translucency, and is a common choice for posterior and high-stress situations?

3Y-TZP

4Y zirconia is

• Middle ground

• More translucent than 3Y

• Balances esthetics and strength

Which type of zirconia is more translucent, weaker than 3Y, and more useful where esthetics matter more?

5Y Zirconia

What is the correlation between strength and translucency?

As translucency increases from 3Y to 5Y, strength generally drops

What are some indications for zirconia?

1. Posterior crowns

2. Fixed partial dentures

3. Implant-supported restorations

4. Situations needing high strength

When using zirconia, it is still not always the first esthetic choice for every anterior case. What kind of zirconia improves appearance?

4Y, 5Y. Earlier zirconia was more opaque

What kind of material is a glass ceramic that is crystalline-dominated and used in pressed & CAD/CAD forms?

Lithium disilicate (E.max)

What are some benefits of lithium disilicate?

• Strong esthetics and translucency

• Good bonding capability

• Versatile for single-unit restorations

• Can be etched and silanted

• Adhesive bonding supports retention and fracture resistance

Which one is stronger, leucite ceramics or lithium disilicate?

Lithium disilicate

Which one is stronger, zirconia or lithium disilicate?

Zirconia

Lithium disilicate =

Esthetics + adhesive dentistry

Lithium disilicate is often used for

• Veneers

• Inlays and onlays

• Anterior crowns

• Selected posterior single crowns

• Resin-bonded restorations (Maryland Bridges)

The best application for lithium disilicate is

Single unit, esthetic, bondable restorations

Which material is HF etched + silane + resin bonding

Lithium disilicate

What does cementation depend on?

1. The material

2. Preparation design and retention form

3. Tooth substrate: enamel bonds better than dentin

4. Soft tissue and moisture control

What does conventional cementation rely on?

• Preparation geometry and material strength

• Often acceptable for zirconia with good retention form

• Examples include RMGI in selected situations

What does adhesive cementation rely on?

• Bonding to tooth and restoration

• Very important for many glass ceramics

• Often improves retention and supports conservative preparations

T/F: Zirconia is hydrofluoric acid etchable

False

What are the mechanical steps of surface treatment for zirconia?

1. Air abrasion and sandblasting with small aluminum oxide particles

2. Creates micro retention on intaglio surface

What are the chemical steps of surface treatment for zirconia?

Use an MDP-containing primer or compatible resin system

Why should you NOT use phosphoric acid as a zirocnia cleaner?

Because phosphate contamination interferes with bonding (MDP-containing primer)

T/F: Because lithium disilicate is a glass ceramic, it can be etched

True

What are the mechanical-chemical steps of surface treatment for lithium disilicate?

• Hydrofluoric acid etch of intaglio

• Then silane application

What is the clinical result of hydrofluoric acid etch + silane of lithium disilicate?

1. Creates a strong bond to resin cement

2. Supports veneers, inlays/onlays, and crowns

When considering your prep design, how much reduction is needed?

• Enough space is needed for material thickness

• Under-reduction creates weak or overcontoured restorations

When considering your prep design, how should your margins be?

• Smooth and readable

• Digital systems still depend on visible margins

When considering your prep design, how should your internal form be?

• Rounded internal line angles are friendlier to ceramics

• Avoid sharp stress concentrators

Accepted features of preparation guide for digital dentistry

1. Smooth and continuous finish lines

2. Rounded internal line angles

3. Clearn, readable margins for scanning

4. Even reduction with enough material space

NOT accepted features of preparation guide for digital dentistry

1. Sharp line angles

2. Lipping of finish lines

3. Rough or irregular margins

4. Under-reduced areas that force over contouring

Every material needs minimum thickness to function safely. What if it is too thin?

Fracture risk increases

Every material needs minimum thickness to function safely. What if it is too thick?

If too thick from under-reduced tooth prep, contours become bulky

Zirconia often tolerates ______ sections better than glass ceramics

thinner

Lithium disilicate generally needs more ______ and ______ ______

Thickness, bonding support

What are 5 common, simple and preventable mistakes?

1. Choosing material by popularity instead of indication

2. Confusing zirconia cementation with glass-ceramic bonding

3. Under-reducing and leaving inadequate material thickness

4. Creating rough or unreadable margins

5. Ignoring moisture control during adhesive procedures