1.11 Cast-Restorations: Inlays, Onlay, Crowns, and Bridge Materials for Cast Restorations

Direct veneer

A bonded composite veneer in which little to no tooth structure is removed and is considered reversible

Indirect veneer

A porcelain veneer in which the facial tooth surface is prepped and is not reversible

Retainer

The seated crown portion of a dental bridge

Pontic

The replacement of a missing tooth in a bridge

Abutment

The prepared teeth used as the support for a bridge unit

1. Tooth destruction

2. Orientation

3. Location of tooth

4. Condition of neighboring teeth

What are the 4 principles used to determine the appropriate restoration to be used?

• Type and size

• Location in the mouth

• Oral habits of the patient

• Patient’s wishes

• Opinion of the clinician

The choice for a given restoration must be based on which factors?

Die

A positive replica of a single tooth

• Wax patterns for cast restorations

• Register patient occlusion

• Simulate gingiva and hold teeth on processing dentures

• Border molding impression trays

• Cheek and tongue protection in orthodontics

What are uses of waxes in dentistry?

Low thermal conductivity

What causes high coefficient of thermal expansion in dental waxes?

High

Dental waxes are easily deformed under stress and have ______ coefficients of thermal expansion

Pattern waxes, processing waxes, and impression waxes

What are the 3 types of waxes used in dentistry

Inlay pattern waxes

Waxes that are hard at room temperature and blue or purple in color and used to fabricate crowns

Casting pattern waxes

Waxes that are softer and used for partial frameworks and are green, red, or blue in color

Baseplate waxes

Waxes that tend to be harder and more brittle, are supplied in sheets, and are pink in color

• High thermal and electrical conductivity

• Ductility

• Opacity

• Luster

• High strength

• Tend to dissolve in saline solution producing atoms with a positive charge

What are the characteristics of metal?

Alloy

A combination of metals allowing production of metals with varying physical and mechanical properties

Casting

A process of heating a metal and pouring it into a mold where it solidifies into a specific shape

True

T/F: Strong metallic bonds are a result of the high stiffness and thermal stability of metals

True

T/F: Metals with many small crystals tend to be harder and have higher elastic limits than metals with fewer, larger crystals

False

T/F: Pure metals are harder and stronger than alloys

Elastic deformation

A recoverable strain in which atoms move but return

Plastic deformation

A permanent deformation in which atoms move but do not rebound when force is removed

Elastic modulus

The property that describes the stiffness of material

Elastic limit

The property that describes the amount of stress required to produce permanent deformation

Strain hardening

The process of bending a metal beyond its maximum flexibility to increase hardness; used for gold foil

Annealing

Heating process to eliminate the effects of strain hardening, returns the metal back to the starting value

Tarnish

A chemical interaction between a metal and its environment resulting in a discoloration of the metal surface and is usually reversible

Corrosion

Irreversible active deterioration and loss of ions

Gold, platinum, and palladium

What are the most commonly used noble metals in dentistry due to corrosion/tarnish resistance

Increases

As the percent of gold decreases, the hardness of the alloy _______

True

T/F: Gold is a great option for heavy clenchers and grinders

Nickel-chromium

What is the base metal alloy used in fusing metal to porcelain?

Sagging

Gold alloys for PFMs are made with higher melting temps to prevent _______ during porcelain baking

Silver

Which type of metal gives a greening effect?

Passivation

The formation of a protective surface oxide film composed of chromium that achieves corrosion resistance

True

T/F: Ceramics have low thermal and electrical conductivity, high compressive strength and stiffness, and low tensile strength

True

T/F: Porcelain abrades enamel

1. Has a small tube connecting a wax pattern to a sprue base

2. Provides a channel for molten metal to flow through during the casting process

3. Serves as a route creating an opening of ingate for the mold

What are 3 characteristics of a sprue?

1. Wax pattern

2. Invest

3. Burnout

4. Cast with alloy

5. Polish

What is the proper sequence in casting a restoration for a patient?