Materials for Inlays, Onlays, Crowns and Bridges

Chapter 7

DAE/DHE 203

Review: Inlay – indirect restoration; occlusal

surface excluding cusps

Onlay – indirect restoration; occlusal surface plus cusp(s)

Review: Crown – usually covers the clinical crown

of the natural tooth Can create “¾ crowns”

Bridge – replaces missing tooth/teeth Abutment vs. Pontic Cantilever, Maryland

Review: Cantilever Bridge

Maryland Bridge

Materials for Indirect Restorations:

Dental Ceramics – Porcelains Composites Metals

Uses for Dental Ceramics:

Crowns (Anterior – “jackets”) Veneers Fused to metal for crowns & bridges Denture teeth Inlays & Onlays All-porcelain crowns & bridges (without

metal substructure)

Characteristics of Ceramics: High melting point Low thermal & electrical conductivity High compressive strength & stiffness Low tensile strength Brittle (low toughness – able to fracture) Excellent esthetics Great biocompatibility

The Composition of Ceramics:

Metal oxide compounds Building block of ceramics = silica

Silicon dioxide molecule (SiO2) Can be amorphous or crystalline arrangement

Components mined from the earth Porcelains are white & translucent ceramics

Composition of Dental Porcelains: Three Main Components:

Feldspar – 75 - 85% (potassium-aluminum silicate)

Quartz – (silica)

Kaolin Clay – 3 –5 % (aluminum silicate)

Plus: glass modifiers leucite – strengthens & toughens; raises the

coefficient of thermal expansion pigments (metallic oxides) – color fluorescing agents

Types of Porcelain: High-fusing:

Fuses at 1300-1350° C Used for denture teeth Highest strength & stability

Medium-fusing: Fuses at 1100 - 1250° C Used for all-ceramic restoratives

Low-fusing: Fuses at 850 - 1050° C Used for PFM restorations

Properties of Porcelains: Great hardness

Excellent wear resistance Can rapidly abrade tooth enamel

Not ductile – very stiff (compressive & tensile strength)

Able to fracture; brittle Often used to veneer metals (PFM) Especially in stress-bearing areas (posterior)

Shrinkage occurs upon firing

Preparation of Porcelain:

1. Powders of quartz, feldspar, clay are blended2. Powder mixed with Water3. “Dentin” or Core Layer is painted onto die or

metallic framework4. Excess water removed from mixture thru

brushing or vibration of die – packs particles5. Placed in oven to “sinter” (heated below fusion point)

particles begin to coalesce (not melted) water is removed die is cooled

Preparation of Porcelain:

6. “Enamel” is painted onto porcelain core

7. Die is fired; cooled

8. Stains are painted onto outer surface

9. Final high-temperature firing – “glaze” finish

10. Cooled slowly Metals used as substructure must have similar

coefficients of thermal expansion as the porcelain to avoid in cracking porcelain

Preparation of Porcelain:

Porcelain-Fused-to-Metal:Advantages:

Strong core Supports porcelain Best for high-stress

areas Easy “seating” –

cementation Less expensive than

all-ceramic

Disadvantages: Esthetics not Perfect

Not as translucent Metallic margin Ions may discolor

porcelain Porcelain may

fracture from metal

All-Ceramic Restorations: Superior esthetics All-ceramics made of

reinforced porcelains Added glass, alumina,

leucite, magnesia, or zirconia

Change in composition to allow for better resistance to cracking

Video

CAD-CAM system:

Milled porcelain restorations “CAD” – computer-aided design “CAM” – computer-assisted machining “CEREC” – by Sirona Use porcelain blocks, milled in the office One-appointment indirect restorations Expensive start-up cost

“CEREC®” System:

“CEREC” System:

Video

“Procera®”

Lab uses computer stylus to measure die Data is transferred to a lab where an

aluminum oxide core is fabricated through milling

Core is sent back to lab for porcelain finish No metal substructure Video

“Procera”

“Cerpress®” Ceramic core made of “pressable” ceramic Used in “lost wax” technique Ceramic is heated and pressed into mold

space Porcelain is applied to core Bonded to tooth with composite bonding

adhesives

“Cerpress”

Composite Inlay Restorations: Intended for very large Class I or II

restorations Applied directly or indirectly Reduces concern of polymerization

shrinkage and marginal leakage Composite restoration fully cured outside

of mouth Similar to direct composite materials

Direct Composite Restoration:

The tooth is prepared The prep-site is lined with a lubricant The composite is placed and cured (but not

etched, bonded!) Remove the composite filling and finish cure The restoration is cemented into prep at same

appointment

Indirect Composite Restoration:

After tooth is prepped, an impression is taken A provisional filling material is placed The impression is sent to lab Lab fabricates the restoration from composite

material onto the die The restoration is cured fully The inlay is seated with composite cement at 2nd

appointment

Other Indirect Composites: Composite materials are also being used

for crowns, bridges, veneers, and onlays Fabricated in the lab “Sinfony”, Targis/Vectris”, “belleGlass” Allow for conservative prep designs Have great esthetics Use etch, bonding agent & resin cement

Uses for Metals:

Full metallic crowns, bridges Inlays, onlays Substructure for PFM’s Substructure/framework for partial

dentures Temporary crowns (prefabricated)

Properties of Metals: Composed of metallic elements (80 pure metals)

High thermal & electrical conductivity High ductility, opacity & luster High strength, high melting points Crystalline arrangement of atoms Various types of metals can be created by

“alloying” metals Mixing 2 or more metals Dental alloys must be resistant to corrosion

Forming Metal Objects:

Metal is relatively stable when in a solid state To mold metal, it must be heated beyond its

melting range Except the use of mercury in dental amalgam!

When cooled, metal forms a crystalline solid Casting – heating metal and pouring it into a

mold where it solidifies into a specific shape A “lost-wax technique” is used to create the mold

space for the metal

ALLOYS: Alloys have advantages over pure metals

alone: Stronger Harder Easier to fabricate Less expensive

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

Dental Alloy Requirements:

Strong & hard enough to withstand occlusal forces

Biologically compatible High resistance to corrosion & tarnish Easy to cast Not cost-prohibitive to use

Alloy Composition: Noble Metals – “Precious” Metals

Gold (Au) * Platinum (Pt) * Palladium (Pd) * Iridium, Ruthenium, Niobium, Osmium

Resistant to corrosion and tarnish Gold was the first metal successfully used

copper & silver added to enhance it

Gold Alloys: Gold is a soft metal Less gold in alloy improves

strength ADA-approved classes

based on properties of alloy Mixed with platinum,

palladium, copper & silver Gold alloys are expensive

Porcelain-Fused-to-Metal Alloys:

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 – “Non-Precious” Corrosion prevention by surface oxide layer

formed by Chromium content Primary metal is Nickel

Allergen (10% women, 1% men) Carcinogen? Video