Dental Porcelain and Metal-Ceramic Restorations

A set of educational flashcards covering key vocabulary and concepts related to dental porcelain and metal-ceramic restorations for exam preparation.

Dental Ceramics

Materials containing both metallic and non-metallic ions in their formula.

Powder-Slurry Ceramics

Ceramics that are mixed as powder with liquid to form a slurry for restorations.

Castable Ceramics

Ceramics that are cast by fusing ceramic ingots in a mold using the lost wax technique.

Machinable Ceramics

Ceramics designed to be carved into restorations using CAD-CAM technology.

Copy-Milling Technology

A method where impressions of a prepared tooth are used to create a die for restoration.

Pressable Ceramics

Ceramics that are pressed into molds using heat-softened ceramic ingots.

CAD- CAM technology

Restoration is design over that image by the aid of computer. Ceramic blocks are carved into restorations by the aid of computer- controlled milling machine

Advantages of Complete Ceramic Crowns

Superior aesthetics, excellent translucency, good tissue response.

Disadvantages of Complete Ceramic Crowns

Reduced strength, less conservative tooth reduction, high cost.

Indications for Using Complete Ceramic Crowns

Use in esthetic zones and presence of carious lesions.

Contraindications for Complete Ceramic Crowns

Where conservative restoration is feasible, molars, and teeth with constricted necks.

Preparation Sequence for Crowns

Incisal, axial, retention and resistance form establishment, margination and refinement.

Common Errors in Tooth Preparation

Excessive taper, insufficient reduction, variable shoulder width.

Uses of Metals in Dentistry

Substructures for PFM crowns, full metallic crowns, bridges, dentures.

Properties of Metals

High thermal conductivity, ductility, opacity, luster, and strength.

Forming Metal Objects

Heating metals beyond their melting range for shaping.

Casting

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

“lost-wax technique ”

used to create the mold space for the metal

Alloys

are formed when metallic atoms are dissolved within the atoms and crystals of another metal

Dental Alloy Requirements

Strong, biologically compatible, resistant to corrosion, easy to cast.

Composition of Noble Metals

Precious metals including gold, platinum, and palladium.

Noble Metals

also known as “Precious ” Metals

Noble Metals

What metals are resistant to corrosion and tarnish?

Gold

was the first metal successfully used

Copper & silver

added to enhance gold metals

GOLD ALLOY

is a soft metal and are expensive

Silver

found to discolor porcelain

Palladium

added to alloy eliminates discoloration and adds strength

Base Metal Alloys

most popular for PFM’ s. Contain NO noble metals or “Non-

Precious ”

Chromium content

Corrosion prevention by surface oxide layer of PFM is formed by

Nickel

What is the primary metal of PFM?

PFM Alloy Characteristics

Base metal alloys have no noble metals and prevent corrosion.

Advantages of Metal-Ceramic Restorations

Stronger than porcelain crowns and suitable for long-span bridges.

Disadvantages of Metal-Ceramic Restorations

Sufficient metal bulk required, potential display of metal at margins.

Special Properties of Metal Copings

Higher melting temperature than porcelain, oxide layer formation.

2.3-7.5 years

How many years a clinical durability of Metal Ceramic Restorations last?

Chemical Bonding in Metal-Ceramic Restoration

Ionic bonds establish between metal oxide layer and opaque porcelain.

Coefficient of Thermal Expansion Mismatch

Higher metal contraction affects porcelain bonding.

Production Methods of Metal Copings

Casting, burnishing, heat treating, CAD-CAM processing.

Classification of Dental Porcelain

High-fusing, medium-fusing, low-fusing, and ultra-low-fusing types.

Components of PFM Crowns

Core (metal framework), opaque porcelain layer for masking.

Characteristics of Dental Porcelain

Biocompatible, resistant to acid attack, not soluble in oral fluids.

Mechanical Properties of Porcelain

Brittle with low fracture toughness, can wear opposing dentition.

Advantages of Porcelain Fused to Metal Crowns

Stronger, aesthetically pleasing, less demanding preparation.

Indications for PFM Crowns

Complete coverage, anterior/posterior restorations, RPD retainers.

Contraindications for PFM Crowns

Poor oral hygiene, large pulp chambers in young patients.

Preparation for Posterior Crown Restoration

Specific techniques and considerations for posterior tooth preparations.

METAL CERAMIC ALLOYS

Alloys that are compatible with porcelain and capable of bonding to it

Gold-Platinum-Palladium

Contains primarily gold (80%-88%) and have excellent castability & fit. Failure usually occurs within the porcelain.

Gold-Palladium

Excellent castability & fit and Good porcelain-to-metal bond. Significantly improved physical properties

High-Palladium

Good castability & fit. Porcelain discoloration is a problem. May be sensitive to phosphate-bonded investments containing carbon

Base-Metal

Composed primarily of NICKEL (60-80%) & CHROMIUM (12-22%)

CHROMIUM

essential to provide passivation & corrosion resistance.

FRITTING

Components of porcelain are mixed, fused, quenched in water & then ground

into a fine powder.

FRIT

product of fritting

DEVITRIFICATION

A process that changes the glassy or vitreous state of porcelain to a crystalline state

- Process of Crystallization

- Occurs if porcelain is fired too often

DENTAL PORCELAIN

An early type of dental ceramics that has been modified to improve its properties. Most durable esthetic restorative material & when correctly glazed, is easily cleansed of stain or plaque.

QUARTZ (11% - 18%)

• Strengthener

• Serves to stabilize the mass at high temps.

• Acts as a matrix for the other materials to fuse around

• Provides OPACITY

KAOLIN (1% - 10%)

- Hydrated aluminum silicate

- Acts as a binder to increase the moldability of the unfired porcelain

FELDSPAR (70% - 90%)

- Mixture of Potassium aluminum silicate (potash) & albite (soda)

- Provides translucency

- Serves as a matrix for the high fusing quartz

- Contains glass modifiers

- Reduces softening temp. of the glass

- Increases coefficient of thermal expansion

- Contains alumina

- Acts as an intermediate oxide to increase viscosity & hardness of the glass network

Glazing Process

Application that gives porcelain a shiny surface.

Overglazes

A layer applied to porcelain restorations to prevent staining.

Autoglazing

A process that raises the body to a fusion temperature for surface finishing.

Feldspathic Porcelain Composition

Contains a vitreous matrix mainly made from feldspars.

Fritting Process in Porcelain Production

Mixing, fusing, quenching, and grinding porcelain components.

Devitrification in Porcelain

Process that crystallizes porcelain from glassy to crystalline state.

Opacifying Oxides in Porcelain

Used to mask the color of the metal framework in PFM crowns.

Dental Alloy Composition

Alloys formed when metallic atoms dissolve within another metal's crystals.

High-Palladium Alloys

Porcelain discoloration issues may arise with these alloys.