Materials for Inlays, Onlays, Crowns and Bridges Chapter 7 DAE/DHE 203
Jan 15, 2016
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