Materials for Inlays, Onlays, Crowns and Bridges

1. Materials for Inlays, Onlays, Crowns and Bridges Chapter 7 DAE/DHE 203

2. Review: • Inlay – indirect restoration; occlusal surface excluding cusps • Onlay – indirect restoration; occlusal surface plus cusp(s)

3. 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

4. Review: Cantilever Bridge Maryland Bridge

5. Materials for Indirect Restorations: • Dental Ceramics – Porcelains • Composites • Metals

6. 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)

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. Preparation of Porcelain:

15. 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 Porcelain-Fused-to-Metal:

16. 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

17. 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

18. “CEREC®” System:

19. “CEREC” System: Video

20. “Procera®” • Lab uses computer stylus to measure die • Data is transferred to a lab where an aluminumoxide core is fabricated through milling • Core is sent back to lab for porcelain finish • No metal substructure • Video

21. “Procera”

22. “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

23. “Cerpress”

24. 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

25. 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

26. 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

27. 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

28. Uses for Metals: • Full metallic crowns, bridges • Inlays, onlays • Substructure for PFM’s • Substructure/framework for partial dentures • Temporary crowns (prefabricated)

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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