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 I am starting with the end of the chapter first. We will discuss metals last and merge into the next section, which is about how metal restorations are fabricated. This section begins on page 158 of your text.

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 Leucite has been added to give strength to porcelains in HIGH-stress areas.

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 1300 degrees Celcius is the same as about 2375 degrees Fahrenheit Low-Fusing – this porcelain is created to fuse at a lower temperature to protect the metal substructure of the PFM – the higher temperatures will exceed the melting point of the alloys used in the PFM.

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: Powders of quartz, feldspar, clay are blended Powder mixed with Water “Dentin” or Core Layer is painted onto die or metallic framework Excess water removed from mixture thru brushing or vibration of die – packs particles Placed in oven to “sinter” (heated below fusion point) particles begin to coalesce (not melted) water is removed die is cooled

Preparation of Porcelain: “Enamel” is painted onto porcelain core Die is fired; cooled Stains are painted onto outer surface Final high-temperature firing – “glaze” finish 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 Show Patterson catalog – page 149+ blocks of porcelain for milling

“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 ADA Classes – Type I & II = softer alloys; used for inlays; Type III = hard alloys; used for crown & bridge; Type IV = extra hard for partial denture frames Since golds are expensive, alternative alloys have been used. Golds give excellent thin, margins and some providers still prefer it for some restorations. In fact, a new PFM has emerged which fuses porcelain to gold for the strength of a metal core but with the better esthetics that a gold core can give over a base metal alloy – this is an expensive alternative that some dentists are choosing again – “Captek” (Show picture)

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 Base Metal Alloys are also known as “NON-Precious”