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319 Cards in this Set
- Front
- Back
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PFM Restorations
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-Most commonly used
-Provides good esthetics with excellent physical properties & longevity |
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Important ceramic dates:
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- 1907: Taggart introduces the lost wax process
- 1962: Weinstein metal ceramic restoration -1968: Price of gold fluctuates -1970: Introduction of gold substitute alloys - 1969- first biomedical application of zirconia - early 1990's: zirconia expands into dentistry |
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Alloy definition
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-mixture of two or more metals or metalloids that are mutually soluble in the molten state
-distinguished as binary, tertiary, quaternary, depending on the number of the metals within the mixture -alloying elements are added to alter the hardness, strength, and toughness of a metallic element, thus obtaining properties not found in a pure metal. -may be classified on basis of behavior when solidified |
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Classification of alloys
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-usage
-major element -nobility -principle three elements -dominant phase system |
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Precious alloys
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metal composed of elements considered precious such as Pt group, Au, Ag
-classification no longer used |
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Semiprecious Alloys
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-composed of precious and nonprecious
-classification no longer used |
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Nonprecious alloys
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-preferred term for base metal, mainly Ni and Cr
-classification no longer used |
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High Noble
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-Au content 40% weight or more, -Noble metal content 60% or more
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Noble
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-Noble metal content more than 25% and less than 60%
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Predominantly Base Metal
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-Noble metal content less than 25%
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Noble Metals
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-resistance to tarnish
-position in the periodic table -Au, Pt, Pd -Ir, Ru, Rh, Os |
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Favorable Characteristics of All Ceramic Restorations
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Metal Free
Highly esthetic Biocompatibility (proven to result in less plaque accumulation) Durability Longevity |
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All Ceramic Core Materials
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-Lithium disilicate
-Aluminum oxide -Zirconium oxide |
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Historical Background of All Ceramic Restorations
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-Land 1903: first Feldspathic porcelain crown
Mclean 1965: added Al2O3 to feldspathic porcelain to improve mechanical & physical -1969 - first biomedical application of zirconia -Early 1990s - zirconia expands into dentistry |
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Classification of All Ceramic Materials
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-Fusion temperature (high, medium, low)
-Fabrication technique (Milled, casted, split-cast, heat-pressed, sintered) -Strengthening mechanism (Alumina, Zirconia, Lithium disilicate, leucite reinforced, Glass infiltrated) |
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Categorization of Modern All-Ceramic Systems
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-Translucent ceramics (predominantly glass ceramics & particle-filled glasses): Feldspathic (ceramic by itself), Leucite reinforced, Lithium disilicate (very strong)
Feldspathic & Leucite are the weakest -Opaque, high-strength core (polycrystalline ceramics): zirconia or Alumina based |
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Feldspathic Ceramics (Amorphous Glass)
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-Highly esthetic
-Low physical properties (flexural strength 60-70 Mpa) -Layering of PFM & ceramic cores -Machinable blocks (VITA) were introduced in 1991 -Veneers, anterior single crowns, inlays & onlays (must be bonded with resin cement) |
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Leucite reinforced Glass Ceramics
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-Dispersion strengthening
-Heat pressed or milled -Inlays, onlays, veneers, & single crowns (mainly anterior & single crowns --> IPS Empress) -HIGH SUCCESS RATE: 1. Inlays & onlays: 90% after 8 years 2. Veneers: 94.4% after 12 years 3. Crowns: 95.2% after 11 years |
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Leucite reinforced CAD/CAM ceramics (IPS ProCAD)
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-In office milling of monolithic restorations (CEREC)
-Multi-layered blocks available -Single crowns, onlays, inlays, veneers |
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Lithium Disilicate Glass Ceramics
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-Either heat pressed or milled
-Anterior & posterior crowns (IPS Empress II) -3-unit fixed partial dentures with 1 pontic -Most distal potential abutment is 2nd premolar |
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IPS Empress II
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-IPS Empress II crowns --> 95.5% success after 10 years
-3 unit FPD IPS Empress II --> 70% success after 5 years (mainly connector fracture in less than recommended connector size) |
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Type I Gold Alloy
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-98% Au
-soft -indicated for single surfaces such as class V -was used for gold foil restorations -high noble |
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Type II Gold Alloy
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-77% Au
-Soft -indicated for inlays/onlays -high noble |
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Type III Gold Alloy
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-71% Au
-soft -indicated for crowns -hard to burnish margins -high noble |
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Type IV Gold Alloy
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-69% Au
-Hard -indicated for fixed partial dentures and removable partial denture frameworks -high noble |
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Composition of Gold Alloys
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-Au: Tarnish resistance
-Ag: strength -Cu: strength |
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Classification of Metal-Ceramic Alloys
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-high gold: Au 80-85%
-High noble: minimum 60% noble elements; at least 40% gold (Gold/platinum/palladium, gold/palladium, gold/palladium/silver) -Noble-minimum 25% noble; no gold required (silver palladium) -Base Metal - less than 25% noble; no gold required (Nickel/Chromium, Cobalt-Chromium/Beryillium, Titanium) |
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Specific requirements for metal ceramic alloys
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-ability to produce surface oxide for chemical bonding with porcelain
-coefficient of thermal expansion slightly greater than the porcelain veneer -Melting range higher than the fusing temp of porcelain -strength as any flexure of metal substructure will lead to porcelain fracture -Must not undergo distortion at the firing temp of porcelain (Sag resistant) -porcelain compatibility |
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Modifications of high gold alloys
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-increase melting temp (Pt)
-increase strength (Pt and Pd) -Reduced thermal COE (Pt) -Porcelain bonding (trace elements) |
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Strength/Minimal Cross sectional thickness
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-high gold: .5mm
-high noble low gold: .3mm -silver-palladium: .3mm -Base metal: .1mm |
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Casting Process
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-different investments are needed for different alloys
-metal mold equilibrium -balance casting shrinkage with mold expansion -melting temp: ability of investment material to withstand the casting temp |
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Lithium Disilicate Glass Ceramics
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-Newly developed pressable lithium disilicate (2005)
-Improved physical properties & translucency -Can be used for monolithic applications for single restorations -Apatite glass ceramics are recommended for layering -IPS Emax Anterior teeth are often pressed first, then cut back & layered with feldspathic porcelain for esthetics |
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IPS Emax Pressed Veneers & Onlays
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Very high success rate:
-Pressed onlays: 100% after 3 years -Crowns: 95.6% after 3 years |
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IPS Emax Monolithic Inlay retained FPDPs & full retainer FPDPs
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-Inlays retained FPDP: success rate 100% after 4 years
-Full retainer FPDP: 93% after 8 years |
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IPS Emax CAD
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-In office milling monolithic restorations
-2 stage crystallization (lithium, metasilicate, Lithium disilicate) -Anterior & posterior crowns, implant crowns, veneers, inlays & onlays -Success rate 100% for single crowns after 2 years |
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High Strength Oxide Ceramics
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-Alumina Based Restorations
-Zirconia Based Restorations |
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Alumina-Based Ceramic Restorations
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-Core material: Aluminum oxide
-Manufacturing techniques: Milled, Split-cast, Densely sintered -Systems: In-Ceram Alumina, In-Ceram Spinell, In-Ceram Zirconia, Procera -Indications: Complete & partial coverage restorations, veneers, & FPDP |
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In-Ceram Zirconia Resin Bonded FPD after 15 years (Zirconia Reinforced)
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-Mofidication of In-Ceram Alumina
-Addition of 35% partially stabilized Zirconia for strength -Slip casting or milled |
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Alumina Based Ceramics: Procera
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-99.9% high purity Al2O3
-Combined with a low-fusing veneering porcelain -Highest strength of the alumina-based materials (lower only to zirconia) |
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Zirconia Based Restorations
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-Bilayered restorations or monolithic
-Crowns, Resin bonded FPDP, Regular FPDP, Implants restorations & Abutments -Multiple systems available on the market: --> Lava: green milled & sintered --> Cercon: green milled & sintered --> Procera: densely sintered & milled --> DC-Zerkon: milled --> Denzir: milled |
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Zirconia
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-Polymorphic material
-Tetragonal phase at high temp. & monoclinic phase at room temp (Monoclinic phase is 4% bigger than the tetragonal phase) -Yttrium-oxide control volume expansion, stabilize it in the tetragonal phase -Transformation Toughening -Twice the flexural strength of Alumina (900-1200 Mpa) |
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Survival of Zirconia Restorations
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-88-100% after 2-5 year
-84-97% after 5-14 years Depends on manufacturing process (Cooling temperature/rate, etc) |
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Clinical Complications of Zirconia layered Restorations
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1. Mechanical Failure (Porcelain veneer fracture, Framework or coping fracture)
2. Tooth or Root Fracture 3. Biological Failure (RCT, Caries) Most common complication = veneer fracture |
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Veneered Zirconia Clinical Failure Modes
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-Cohesive failure in ceramic
-Procelain Chipping (most common) -Adhesive failure between framework & ceramic (delamination) -Fracture in core or framework |
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Zirconia-bilayered
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-No fracture in the frameworks
-Consistent chipping rate of veneering ceramic (3-25%) |
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Reduce cohesive failures of veneering porcelains
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-Matching CTE between core material & veneering ceramics
-Prolonged cooling rates (especially with thick frameworks) -Improved mechanical properties (Fusing temperature) -Framework design with optimal support for veneering porcelain -Adequate clinical procedures: minimizing occlusal adjustments (polishing/reglazing) |
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Castability/ Metal mold equilibrium
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-melting temp of alloy
-melting temp of mold |
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Types of Investments
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-gypsum-bonded investments; Gold alloy
-Phosphate-bonded investments: high noble and noble alloys -Silica-bonded investments: base mental alloys and removable partial denture frameworks |
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Melting Temp and Casting Shrinkage
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(melting temp and casting shrinkage from highest to lowest)
-High gold -High noble -Noble -Base metal *strength is inversely related to melting temp *fit is inversely related to casting shrinkage *cost increase with the increase of gold and noble content |
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Marginal Integrity
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-achieved with base metal alloys is generally inferior to that achieved with other ceramometal alloys
-casting shrinkage and oxide formation |
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Indications for High gold alloys
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-anterior all ceramic crowns
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Indications for High noble and noble alloys
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-single unit crowns both anterior and posterior and short span FPDs
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Indications for Base metal alloys
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-only indicated for long span FPDs. Biological complications and improper fit due to casting shrinkage is a concern
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Porcelain to metal bond four theories
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-Van der waals forces
-mechanical interlocking -compression bonding -chemical bonding |
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Van der Waals forces
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-attraction of charged atoms, generally weak forces, but create strong bond via numbers
-better surface preparation to improve porcelain wetting and improve the adhesion |
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Mechanical interlocking
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-air abrasion, increasing surface area
-removing contaminants |
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Relative Translucency
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Increased translucency correlated with improved esthetics is the primary advantage in using an all-ceramic restoration
Relative translucency (High to Low): -In-ceram spinell -IPS empress -Procere -E-max -Inceram Alumina -Zirconia - PFM |
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All Ceramic Restorations
(Summary) |
-High strength all ceramic material have expanded the indications for all ceramic restorations
-Precise attention to details with regard to tooth preparation, margin design & location, soft tissue management, impression & cementation techniques are crucial for success -Proper selection of material is paramount (esthetics vs strength) -Patient with all ceramic reconstructions should routinely wear an occlusal night guard -All ceramic FPDs should be limited to 3-4 units & should not extend beyond the 2nd premolar |
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Compression Bonding
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-porcelain is stronger under compression than tension
-slight COE mismatch between porcelain and compatible alloy -wraparound effect with the cut back |
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Chemical bonding
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-Major mechanism of attachment
-chemical bond between the tetravalent oxides in the opaque porcelain and the oxide layer of the metal -both ionic and covalent bonds form -different alloys varied in their requirements to oxidize (gold based alloys require longer oxidation time than base metal alloys to allow the non-noble trace elements to oxidize) |
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Improving bond strength to base metal alloys
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-combination of sandblasting, ultrasonics, and radio frequency glow discharge is suggested to effectively eliminate contaminants and improve the metal ceramic bond for base metal alloys
-other methods were suggested like tin plating, but most effective way is controlled oxidation |
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Oxide layer
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-plays important role in bonding to porcelain
-mono-molecular layer (bonding depends on controlled thickness of metal oxide layer) -most oxides formed during the degas cycle |
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Increased Oxide thickness layer with trace element content
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-base metal alloys produce more thicker oxide layer than noble and high noble alloys
-at least 50% new metal is needed in each casting procedure to make sure enough trace elements are present to produce the oxide layer |
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Modes of porcelain to metal bond failure
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-porcelain to porcelain failure
-metal oxide-metal oxide failure -metal-metal failure |
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Opaque porcelain
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-establish porcelain-metal bond, masks the dark metal substructure, initiate development of selected porcelain shade
-two coats preferred |
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Compatibility of metal ceramic systems
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-Chemical compatibility implies a bond strong enough to resist both transient and residual thermal stresses and mechanical forces
-thermal and mechanical compatibility include a fusing temp of porcelain that does not cause distortion of metal substructure -metal ceramic combo must be capable of simulating range of tooth characteristics |
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Compression Bonding
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-porcelain is stronger under compression than tension
-slight COE mismatch between porcelain and compatible alloy -wraparound effect with the cut back |
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Chemical bonding
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-Major mechanism of attachment
-chemical bond between the tetravalent oxides in the opaque porcelain and the oxide layer of the metal -both ionic and covalent bonds form -different alloys varied in their requirements to oxidize (gold based alloys require longer oxidation time than base metal alloys to allow the non-noble trace elements to oxidize) |
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Improving bond strength to base metal alloys
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-combination of sandblasting, ultrasonics, and radio frequency glow discharge is suggested to effectively eliminate contaminants and improve the metal ceramic bond for base metal alloys
-other methods were suggested like tin plating, but most effective way is controlled oxidation |
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Oxide layer
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-plays important role in bonding to porcelain
-mono-molecular layer (bonding depends on controlled thickness of metal oxide layer) -most oxides formed during the degas cycle |
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Increased Oxide thickness layer with trace element content
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-base metal alloys produce more thicker oxide layer than noble and high noble alloys
-at least 50% new metal is needed in each casting procedure to make sure enough trace elements are present to produce the oxide layer |
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Modes of porcelain to metal bond failure
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-porcelain to porcelain failure
-metal oxide-metal oxide failure -metal-metal failure |
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Opaque porcelain
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-establish porcelain-metal bond, masks the dark metal substructure, initiate development of selected porcelain shade
-two coats preferred |
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Compatibility of metal ceramic systems
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-Chemical compatibility implies a bond strong enough to resist both transient and residual thermal stresses and mechanical forces
-thermal and mechanical compatibility include a fusing temp of porcelain that does not cause distortion of metal substructure -metal ceramic combo must be capable of simulating range of tooth characteristics |
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Fabrication
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-materials selection
-manufacture method -skill |
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Favorable Characteristics of All Ceramic Crowns
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-metal free
-highly esthetic -bio-compatibility Durability -longevity |
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Ceramic core materials
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-lithium disilicate
-aluminum oxide -zirconium oxide |
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Ceramic Historical background
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-land 1903: first Feldspathic porcelain crown
-Mclean 1965: added Al2O3 to feldspathic porcelain to improve mechanical and physical -1969 first biomedical application of zirconia -Early 1990s zirconia expands into dentistry |
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Classification of all ceramic materials
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-Fusion temperature (high, medium, low)
-Fabrication technique (milled, casted, split-cast, heat pressed, sintered) -strengthening mechanism (alumina, Zirconia, lithium disilicate, leucite reinforced, glass infiltrated) |
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Categorization of Modern All-Ceramic systems
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-translucent ceramics (predominantly glass ceramics and particle filled glasses) Feldspathic, Leucite reinforced, lithium disilicate)
-opaque, high strength core (polycrystalline ceramics) *zirconia or Alumina based |
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Translucent Ceramics
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-Feldspathic Ceramics
-Leucite Reinforced -Lithium Disilicate |
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Feldspathic Ceramics (Amorphous Glass)
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-highly esthetic
-Low physical properties (flexural strength 60-70 Mpa) -Layering of PFM and ceramic cores -Machinable blocks (VITA) were introduced in 1991 -Veneers, anterior single crown, Inlays and onlays |
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Leucite Reinforced Glass Ceramics
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-dispersion strengthening
-heat pressed or mille -inlays, onlays, veneers and single crowns -high success rate |
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Success Rates of Leucite reinforced glass ceramics
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-Inlays and onlays: 90% after 8 years
-Veneers: 94.4% after 12 years -crowns: 95.2% after 11 years |
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Leucite reinforced CAD/CAM ceramics (IPS ProCad)
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-in office milling of monolithic restorations (CEREC)
-multi-layered blocks available -single crowns, onlays, inlays, veneers |
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Lithium Disilicate Glass Ceramics
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-either heat pressed or milled
-anterior and posterior crowns -3-unit fixed partial dentures with one pontic -most distal potential abutment is second premolar -newly developed pressable lithium discilicate (2005) -improved physical properties and translucency -can be used for monolithic applications for single restorations -apatite glass ceramics are recommended for layering |
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IPS Impress II Veneer and crowns (pressed) success Rates
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-IPS Empress II crowns: 95.5% success after 10 years
-3 unit FPD IPS Empress II: 70% success after 5 years (mainly connector fracture in less than recommended connector size) |
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IPS Emax Pressed Veneers and Onlays
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-very high success rate
-pressed onlays: 100% after 3 years -crowns 95.6% after 3 years |
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IPS Emax monolithic inlay retained FPDPS and Full retainer FPDPS
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-inlays retained FPDP: success rate 100% after 4 years
-full retainer FPDP 93% after 8 yrs |
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IPS Emax CAD
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-in office milling monolithic restorations
-two stage crystallization (lithium metasilicate, lithium disilicate) -Anterior and posterior crowns, implant crowns, veneers, inlays and onlays -IPS Emax CAD; Success rate 100% for single crowns after 2 years |
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High Strength Oxide Ceramics
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-Alumina Based Restorations
-Zirconia Based Restorations |
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Alumina-Based Restorations
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-core material: Aluminum oxide
-manufacturing techniques: Milled, split-cast, densely sintered -systems: In-ceram Alumina, in-ceram spinell, in-ceram zirconia, procera -Indications: complete and partial coverage restorations, veneers and FPDP (mainly anterior) |
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In-Ceram Zirconia Resin Bonded FPD (Zirconia Reinforced)
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-modification of in-ceram alumina
-addition of 35% partially stabilized zirconia for strength -slip casting or milled |
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Alumina Based Ceramics: Procera
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-99.9% high purity Al2O3
-combined with a low-fusing veneering porcelain -highest strength of the alumina-based materials (lower only to zirconia ) |
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Zirconia Based Restorations
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-Bilayered restorations or monolithic
-crowns, resin bounded FPDP, Regular FPDP, Implant restorations and abutments -multiple systems available on the market |
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Zirconia Based Restoration Systems
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-Lava: green milled and sintered
-Cercon: green milled and sintered -Procera: densely sintered and milled -DC-Zerkon: milled -Denzir: milled |
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Zirconia
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-polymorphic material
-tetragonal phase at high temp and monoclinic phase at room temp -Yttrium-oxide control volume expansion stabilize it in the tetragonal phase -transformation toughening -twice the flexural strength of alumina |
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Survival of Zirconia Restorations
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-88-100% after 2-5 yrs
-84-97% after 5-14 years |
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Clinical Complications of Zirconia layered Restorations
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1. Mechanical failure (porcelain veneer fracture, framework or coping fracture)
2. Tooth or Root Fracture 3. Biological Failure: (RCT, caries) |
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Veneered Zirconia Clinical Failure modes
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-cohesive failure in ceramic
-porcelain chipping (most common) -adhesive failure between framework and ceramic (delamination) -Fracture in core or framework |
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Delamination
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-fracture of the porcelain from the metal substructure
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Zirconia-bilayered
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-no fracture in the frame works
-consistent chipping rate of veneering ceramic (3-25%) -3-5 units FPDS, 31 metal ceramic and36 Zirconia-ceramic -survival rate of both types of restorations was 100% -minor chipping of veneering porcelain was found in 25% of the zirconia restoration and 19.4% of the metal ceramic restorations -major chipping was found in 5.6% of the zirconia-ceramic restorations and 2.8% of framework fracture |
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Reduce cohesive failures of veneering porcelains
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-matching CTE between core material and veneering ceramics
-prolonged cooling rates (esp. with thick frame works) -improved mechanical properties (fusing temp) -framework design with optimal support for veneering porcelain -adequate clinical procedures: minimizing occlusal adjustments (polishing/reglazing) |
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Relative translucency from High to Low
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-in-ceram spinell
-IPS impress -procera -E-max -inceram alumina -zirconia -PFM |
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Cement
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-binding element or agent used as a substance to make objects adhere to each other, or something serving to firmly unite
-a material that, on hardening will fill a space or bind adjacent objects-syn luting agent |
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Cementation
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-the process of attaching parts by means of cement
-attaching a restoration to natural teeth by means of a cement |
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Types of Dental Cements
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-Definitive luting agents
-provisional luting agent |
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Bonding Mechanisms
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-non-adhesive luting
-micromechanical bonding -molecular adhesion |
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Non-Adhesive Luting
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-fills the gap and prevents the entrance of fluids
-Ex. Zinc phosphate |
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Zinc Phosphate
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-longest track of any dental cement
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Micromechanical Bonding
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Luting agent penetrates into small, deep surface pits
-etching of the tooth and/or restoration improves the bond strength -Ex: Resin Cements |
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Molecular Adhesion
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-physical forces: bipolar, van der waals and chemical bonds (ionic and covalent) between molecules of two different substances
-Ex: polycarboxylates and class ionomers |
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Ideal Properties of a Dental Cement
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-Adhesion to tooth structure
-adhesion to restorative materials -adequate strength to resist functional forces -lack of solubility in oral fluids -ability to achieve low film thickness under cementation conditions -biocompatibility with pulpal tissues -possession of anticariogenic properties -radiopaque -relative ease of manipulation -esthetic/color stability |
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Classification of Definitive Dental Cements
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A. Conventional (water based)
1. Zinc Phosphate 2. Zinc Polycarboxylate 3. Glass Ionomer B. Contemporary (polymerizing) 1. Resin-modified glass ionomer 2. adhesive resin C. Nano-structured bioceramics (Ceramir) |
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Basic Requirements for Conventional dental Cements
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-ANSI/ADA Spec #96
*film thickness: Max 25 micrometers *comprehensive strength:Minimum 70 Mpa * Setting time: 2.5-8 minutes |
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Zinc Phosphate Cement
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-oldest cement with the longest track
-powder: zinc oxide (90%), magnesium oxide (8%) -liquid: Buffered phosphoric acid (67%) -acidic:pH: 3.5 at time of cementation |
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Advantages of Zinc Phosphate Cement
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-long clinical history of success
-standard to which other cements are compared -adequate mechanical properties with good retention and resistance form -low cost |
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Limitations of Zinc Phosphate cement
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-lack of bonding
-lack of fluoride release -potential pulp irritation (precaution should be taken that the preparation is not too close to the pulp) -high solubility |
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Zinc Phosphate cement/indications
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-full cast restorations
-porcelain fused to metal restorations -cast dowel and cores -zirconia and alumina based all ceramic restorations |
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Zinc Polycarboxylate Cement
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-introduced by Smith in 1968 as the first dental cement that adheres to the tooth structure
-Powder: Zinc oxide, magnesium oxide -liquid: polyacrylic acid and water |
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Advantages of Zinc Polycarboxylate cement
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-adhesion to tooth structure (enamel)
-biocompatible -available in pre-weighted capsules |
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Limitations to Zinc polycarboxylate cement
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-low compressive and tensile strengths
-thyxotropic -plastic deformation -not suited for restorations in high stress areas or long span fixed partial dentures |
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Zinc Polycarboxylate cement/indications
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-shouldnt be used for luting definitive restorations
-long term provisionalization |
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Glass-Ionomer (Glass polyalkenoate) cement
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-introduced in 1969 by Wilson and Kent
-combines fluoride release with adhesion to tooth structure -hydrous and anhydrous forms -Powder: finely ground calcium aluminosilicate glass -liquid: copolymers of polyacrylic acid (35%-65%), water, D tartaric acid |
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Glass-Ionomer Cement Advantages
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-bonds to tooth structure (chelation to Ca2+) comparable to polycarboxylate
-bacteriostatic during setting phase -fluoride release |
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Glass-Ionomer Limitations
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-pH lower than zinc phosphate during setting -post cementation sensitivity have been reported but it has not been supported by clinical trials
-weakened by early exposure to moisture -dessication produces shrinkage cracks in recently set cement |
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Glass-Ionomer Cement/Indications
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-full cast restorations
-porcelain fused to metal restorations -cast dowel and cores -zirconia and alumina based all ceramic restorations |
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Contemporary Dental Cements
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-stronger
-less soluble -micromechanical adhesion -higher film thickness (40 microns) -less biocompatible |
|
|
Resin modified glass ionomer
|
-introduced in the 1980's
-water soluble polymers or polymerizable resins added to conventional glass-ionomer |
|
|
Resin Modified Glass Ionomer Advantages
|
-adhesion to tooth structure
-fluoride release -good physical properties -resistant to water exposure -famous in private practice |
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|
Resin Modified Glass Ionomer limitations
|
- dehydration shrinkage like GIC
-long term water sorption leading to volumetric expansion due to the added resin |
|
|
Resin Modified Glass-Ionomer indications
|
-cast restorations
-zirconia based restorations -not indicated for glass ceramics or dowel and core restorations |
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|
Resin Cements
|
-micromechanical bonding
-3 types (adhesive resin, esthetic resin, self adhesive) -curing modes: self, dual, or light cure |
|
|
Resin Cement Advantages
|
-excellent physical properties
-adhesion to tooth structure -insoluble in oral fluids -esthetic (multiple shades) |
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|
Resin cement limitations
|
-technique sensitive
-polymerization shrinkage -film thickness -bio-compatibility |
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|
Adhesive Resin Cements
|
-primer is needed for bonding to tooth substrates
-silane coupling agent is needed for silica-based ceramics -curing mode options- can be light- dual or self-cured -several shades available |
|
|
Esthetic Resin Cements
|
-self etch or total etch
-silane or ceramic primer is needed for all-ceramic restorations -curing mode options can be light or dual cured -light cured cement is available for veneers -multiple shades available -try in pastes |
|
|
Self adhesive Resin cements
|
-self-etching, no phosphoric acid or special primer needed for bonding to tooth substrates
-curing mode options -can be light, dual or self- cured -usually available in universal, translucent and opaque shades |
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|
Ceramic Surface Treatment/Silica and particle reinforced ceramics
|
-etching of dental ceramic with a glassy matrix using hydrofluoric acid
-silicoating (eg. Rocratic system) -silane coupling agent |
|
|
Cementation of Zirconia Based Restorations
|
-conventional cementation: adequate R&R form
-self adhesive resin cement: compromised R&R form |
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|
Selection of Luting Agents
|
-no available product satisfies all requirements of an ideal luting agent
-in practice, several materials are needed to provide comprehensive pt care -Although contraindications exist for use of certain materials under certain situation, the best choice is nt always clear -unless a specific indication for a given luting agent exists, the least technique sensitive material should be utilized -bonding to enamel is more predictable than to dentin |
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|
Implant Restorations
|
-screw retained
-cement retained |
|
|
Cementation of implant restorations
|
-permanent cementation
-provisional cementation -long term provisional cementation |
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|
Eliminating Excess cement
|
-cementation technique
-verification radiograph -abutment design and margin location -retraction cord -stock abutment analogue can be used to eliminate excess cement before cementation |
|
|
Internal Relief/Cement Space
|
-die spacer
-enlarged digital die -venting -sand blasting -fit checker |
|
|
Cementation/Tooth preparation
|
-Temporary cement removal (eugenol inhibit resin polymerization-air abrasion, pumice, etching after pumice)
-The casting preparation (air abrasion 50 microns alumina, increase the in vitro retention 64%, other methods include steam cleaning, ultrasonic and organic solvent) |
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|
Cementation
|
-isolate the area of cementation (cotton rolls and place the salivary ejector)
-mix cement acording to the manufacturer's recommendations -apply a thin coat of the cement to the clean internal surface of the restoration -restoration seated with firm rocking pressure (dynamic seating) -reexamine accessible margin for complete seating -remove excess cement -reexamine occlusion -verification radiograph (implants) |
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|
ceramic glazing
|
-the final firing of porcelain in which the surface is vitrified and a high gloss is imparted to the material
-to cover with a glossy, smooth surface or coating to attain a smooth reflective surface |
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|
Autoglazing
|
-the contoured bique bake is raised to its fusion temperature and maintained for a time before cooling
-pyroplastic surface flow occurs, and a vitreous layer of surface glaze is formed -occlusal contact in porcelain is altered slightly during glazing -occlusal contact in porcelain is altered slightly during glazing |
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|
Overglazing
|
-seperate mix of powder and liquid is applied to the surface of shaped restoration and subsequently fired
-firing procedure is similar to autoglazing -there are variations among brands |
|
|
Surface Glaze
|
-reproduces the natural luster of an unrestored tooth
-creates highly polished surface that is good for ginigval health and inhibits plaque accumulation and reduce porcelain abrasiveness -enhances the strength of the restoration |
|
|
An evaluation of porcelain strenght and the effect of surface treatment found..
|
-porcelain treated with overglaze was STRONGER than porcelain treated with autoglaze or augtoglaze and polish
|
|
|
Reducing abrasiveness of ceramics by polishing and glazing
|
-smoothest surface should cause the least wear damage to opposing surfaces
-depending on intial roughness of ceramic surface, glazing may not adequately decrease surface roughness -the glassy layer may be of insufficient hickness to fill in scratches and grooves within the ground surface -certain conditions REQUIRE polishing or polishing follwed by glazing -repolishing ceramic surfaces periodically is recommended especially after acid exposure |
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|
Armamentarium contouring and polishing
|
-pencil
-adequate ventilation/vacuum -diamond burs (high/low speed) -aluminum oxide wheels -diamond wheels (embrasures) -busch silent stone -porcelain polishing kits -pumice/brasso and lathe |
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|
Characterization
|
to alter by application of unique markings, indentations, coloration and similar custom means of delineation on a tooth or dental prosthesis thus enhancing natural appearance
|
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|
Intrinsic Characterization
|
may be accomplished by incorporating colored pigments in the opaque, body or incisal powder
|
|
|
Extrinsic Characterization
|
surface staining (supplied with most commercially staining kits)
|
|
|
Characterization (more)
|
-feldspathic porcelain stains are metallic oxides combined with translucent porcelain over glazes
-optimum esthetics is achieved through intrinsic characterization |
|
|
Characterization wih stains will almost always
|
-decrease the translucency
-decrease the value (make the restoration more gray in appearance- white stain is the exception) |
|
|
Porcelain Stain Kits
|
-many are porcelain dependent
-all stains should be mixed thick (honey consistency) -all stains should be mixed with a glass rod or agate spatula (metal instruments introdcue SS oxides, which will turn black on crown surface when glazed) |
|
|
Basic Characterization Technique
|
-complete porcelain adjustments (contouring, occlusion, additions)
-clean or air abrade crown external surfaces -place securely on hemostats |
|
|
Basic Characterization technique (continued 2)
|
-compare crown shade (dry) to adjacent natural tooth/crown
-wet crown with stain medium -compare again to natural tooth -"wet" crown will appear as if you ONLY glazed it- make modifications to shade to WET crown |
|
|
Rule of Thumb
|
-if the value is too low to start, PUNT! In other words, strip the porcelain and start over
-if you can detect a shade discrepancy in the crown, confirm with patient and/or family member- consider redo or referring! |
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|
Advanced Characterization
|
-incisal translucency
-gingival shades -interproximal depth (on FPDs) -check/craze lines -incisal "halo" -enamel cracks -exposed incisal dentin -hypocalcified areas -gingival pink porcelains |
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|
The "art" of dentistry
|
-generally we use low-fusing porcelain
-firing range of 1750-1860 degrees F -delivered form lab in a bisque bake |
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|
Armamentarium
|
-pallete with various colors- these are pigmented colorants (iron oxides) containing small amounts of glass
-violet and blue -orange, honey (lt brown), dark brown -white -liquid-glycerin/water mix -Oven- Ney Mini-glze is a good one ($879) -sable-haired brushes |
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|
General sequence
|
-attach hemostat to PFM crown on lingual
-steam clean -add colors/characterization -dry in open oven door 6-10 min -glaze |
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|
Delivery of Gold Casting
|
1. seat, burnish margins, occlude, and Rubber wheel finish on Cast
2. remove provisional restoration 3. clean preparation and seat casting 4. evaluate proximal contacts a. reflected light (contact evident?) b. strenght of contact (use floss) c. size and location of contact 5. evaluate margins to assure complete seating 6. assess and adjust occlusion 7. finalize axial and occlusal contours 8. polish, re-eval 4-7 above |
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|
Die spacer
|
-a space should exist between the internal surface of the casting and the prepared surface of the tooth everywhere except immediately adjacent (1.0mm) to the margin. This space will provide adequate room for the luting agent. Die spacers will provide the relief space
|
|
|
die spacer (evaluation)
|
-at the prep margin there should be a 1 MM WIDE BAND of closely adapted metal to prevent disintegration and dissolution of the luting agnet
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|
Intaglio surface
|
-the internal surface of the casting (that portion that is in close approximation to the prepared tooth). No contact should exist between the die and the internal surface of the casting, except in the marginal area for approximately 1mm in width
|
|
|
First things first
|
-pick up the work from the lab (is it ready PRIOR to patinets apt)
-assess the work for marginal adaptation, occlusion, contour, color-Quality Assessment (QA) -send back to lab for modifications if not correct PRIOR to patient visit |
|
|
Check crown internally
|
-for positives (check die for abrasions) will abrade/crush die but not tooth-prohibits full seating on tooth
-holes in metal (porcelain) -porosity at margin |
|
|
check crown externally
|
-for roughness
-polish -cracks (porcelain) -design (is it what you requested?) -color (check with shade guide and Rx) |
|
|
First things first (after check crown)
|
-seat the patient
-update the health hx (take blood pressure) -ascertain any problems with the tooth in question -sensitivity, pain (anesthesia) -lost provisional restoration |
|
|
Assess the temporary
|
-is it in place?
-what do the periodontal tissues look like (healthy vs. inflammation) -if inflamed, where will your final restoration margin be located? -may be a significant esthetic problem with a PFM crown |
|
|
I lost my temporary
Etiology |
-hyper occlusion, causing temp to flex, de-bond or fracture
-poor R&R form of prep -poor flossing technique (overhangs?) -length of temporization (permanent cementation?) |
|
|
I lost my temporary
sequellae |
-hyper eruption of oppsing tooth (may require enameloplasty or restoration of opponent tooth)
-drift of adjacent teeth (may require orthodontic tooth movement to correct |
|
|
Remove the temporary
|
Armamentarium
-black spoon (four corners method- gently lift at the line angles), good palm/thumb grasp, finger rest -hemostat -with great care- F-L motion -don't extract the tooth -don't extract the foundation |
|
|
Assess the temporary (part 2)
|
-is there cement left?
-is the cement discolored or stained? -staining results from micro-leakage, and tooth may be hyper-sensitive!! -how to treat hypersensitivity? |
|
|
clean the tooth
anesthesia |
-if yes, how do you assess or confim the occlusion?
-if required, your temporary crown did not meet appropriate success criteria, or tooth was hyper sensitive during crown preparation and temporization |
|
|
clean the tooth
armamentarium |
-spoon excavator/explorer
-remove as much of the bulk cement as possible -wet cotton pellet/cotton pliers -"scrub" the prep -whip mix "preppies" -prepared pumice/water -does not contain fluoride; thus will NOT affect bonding -use with prophy cup with SLOW speed -rinse to remove excess |
|
|
Clean the tooth
|
LOOK!
-is there reamining cement on axial walls, occlusal or in proximal grooves or boxes -crown will NOT seat if debris (cement, pumice) remains on tooth ! -re-clean the tooth if necessary |
|
|
Adjusting the contact
|
-Gold: seperating disk>stone>cratex wheel>burlew wheel
-porcelain: seperating disk>busch silent stone -adjust contact from gingival up |
|
|
Open contact (after adjusting)
|
Gold: solder proximal, re-adjust following same sequence
-PFM: send back to the lab to have additional porcelain added (indicate where you want it added and how much) |
|
|
ADA specification #8
|
for dental cements: require <25 microns cement film thickness
|
|
|
Short margin
|
-if less than .3mm accept
-if greater than .3mm re-impress -verify crown fit on die -if short on die, re-impress or send back to lab for remake |
|
|
Short margin and closed
|
-verify crown fit on die
-if it fits the die, either the crown isn't fully seated on tooth (back to fit checker) or die was abraded/shortened in lab |
|
|
Open Margin
|
-if gold alloy, burnish (on die or "in air") and trial seat again
-if PFM or non-precious alloy, difficult (impossible) to burnish: re-impress |
|
|
GC fit checker
|
-silicone material
-<25 micron film -white color (all-ceramics? black) -used to show areas of binding between tooth/crown -marginal 1mm should show only metal! |
|
|
Cementation
|
-temporary cement removal
-eugenol inhibit resin polymerization (air abrasion, pumice, etching after pumice) -the casting preparation -air abrasion 50um alumina increase the in vitro retention 64% protect the margin at 60lbs pressure you can modify the margin qjuickly -other methods include steam cleaning, ultrasonic and organic solvent |
|
|
Tooth prep
|
-isolate with cotton roll
-etch the tooth when using all cements OTHER than ZnPO4 cement -use GC dentin conditioner -phoshoric acid -etchant that comes with the cement you've selected |
|
|
Cement removal
|
-when to remove depends on which cement you used
-for those that are more easily removed (ZnPO4, polycarboxyllate, Glass ionomer, RMGI) wait until fully set and remove (explorer, floss) -Comp resins: remove Prior to full seating (read instructions carefully) |
|
|
Post-cementation
|
-most cements require 24 hours to reach full set (except for CR)
-however most are sufficiently "set" within 2 hours of clinic -have patient avoid eating "sticky" food for first 2 hours -caution pt about post-op sensitivity (occurs in up to 50% of pts and can last for several weeks) if present, shoud improve and if not call -11-17% of all crowns and FPDs need RCT after cementation |
|
|
thick margin
|
-thin
gold: cratex wheel, re=polish ceramic: aluminum oxide stones, re-glaze or polish |
|
|
CAD/CAM
|
-stands for computer aided design and computer aide manufacturing
- impacted dentistry tremendously in the last 25 years -used both in dental offices and dental laboratories |
|
|
Objectives of CAD/CAM systems
|
-improve restoration quality and strength
-create restorations with natural appearance -make the fabrication process easier and faster -reduce production cost |
|
|
CAD/CAM production concepts
|
-chair side production
-laboratory centralized production |
|
|
Components of CAD/CAM system
|
-digitalizing tool/scanner: transforms geometry into digital data
-software: processes data -production technology: transforms the data set into the desired product |
|
|
CEREC-AC-BlueCam/Sirona
|
-introduced in 2009
-utilizes blue light emitting diodes (LEDs) -active triangulation technique -available for both in house milling or lab support through CEREC connect -five yr survival rate of CEREC restorations (90.2% to 93.8%) -no significant difference than lab made restorations |
|
|
E4D-Dentist System/D4D
|
-introduced in 2008
-laser scanner -doesn't require the use of a reflective agent -successive pictures are wrapped around the 3D model -trimmed occlusal record is scanned instead of the opposing arch |
|
|
Advantages of In-office scanning and milling units
|
-same day delivery of prosthesis
-instant analysis of tooth preparation and soft tissue management -eliminates many steps/materials -brand practice and pt satisfaction |
|
|
Limitations of In-office scanning and milling units
|
-cost: too expensive for widespread use
-technique sensitive -laboratory interaction? |
|
|
Laboratory and Centralized production
|
-scan a cast made from a conventional impression
-allows for digital design and subsequent automated fabrication of the prosthesis |
|
|
Zirconia-bilayered
|
-no fracture in the frame works
-consistent chipping rate of veneering ceramic (3-25%) |
|
|
Intra-Oral Scanning units
|
-iTero/Cadent
-Lava COS/3M ESPE -E4D/D4D -CEREC-AC-Bluecam/Sirona |
|
|
Soft Tissue management
|
-adequate isolation of sub-g margins of tooth preparations before making impressions is paramount
-digital impressions will not reduce the problems related to isolation of sub=g margins -digital impressions require even more definitive pre-impression isolation of tooth preparation margins than conventional impressions |
|
|
Digital Capturing of tooth prep margin
|
-margin of prep should be visible to be scanned
-unprepared tooth structure apical to the margin should be captured to identify and correctly mark the margin digitally |
|
|
Separation of the impression material from the impression tray occurs...
|
-mainly related to proper selection and application of tray adhesive
|
|
|
Distortion of conventional impressions before pouring
|
-elastic recovery
-proper impression technique -cross sectional thickness -impression disinfection -time of pouring -storage -inadvertent force applied to the tray and impression during transportation |
|
|
Digital Impressions vs. Conventional methods
|
-impression time
-adjustment and seating time -marginal integrity -inter-proximal contacts accuracy -occlusal registration accuracy -digital impressions performed as well as conventional impressions although the time required was significantly longer -dentists selected crowns made of digital impression in comparison to physical impressions in 68% of the time |
|
|
Marginal Accuracy
|
-marginal integrity achieved in in-vitro tests using the Lava Cos scanner was at least similar or better to what can be achieved with conventional VPS impresions
|
|
|
Advantages of Intraoral imaging units (digital impressions)
|
-elimination of impression materials
-re-scan small areas instead or remake impression -instant analysis of tooth preparation and tissue management -permanent record-computer aided -accuracy same or better than elastomeric materials -provides opposing impression and maxillo-mandibular record in the same setting -interaction with new technologies -lab interaction -ability to impress definitive restoration right after cementation |
|
|
Limitations of intraoral imaging units (digital impressions)
|
-cost
-time-variable based on system -isolation-no difference,may be more technique sensitive -the need to coat the teeth with a powder to minimize the noise in measurement -not for all procedures |
|
|
Properly Finished, Well-polished porcelain restorations...
|
-resist the formation of plaque and calculus
-are more resistant to stain -have improved marginal adaptation and integrity -are more easily cleaned -minimized the irritation of soft tissue -decrease the wear on opposing dentition (compared to an unglazed surface) -considerably increase the durability and service life of restoration |
|
|
Finishing
|
-focuses on contouring, adjusting (proximal contacts and occlusion), shaping and smoothing
-planes, smoothes and condenses the active surface -grooves resulting from the preceding instrument are eliminated in succeeding steps |
|
|
Polishing
|
-concentrates on achieving smooth surface luster
-producing a highly reflective surface -achieves the smoothest surface -grooves resulting from the preceding instrument are eliminated in succeeding steps |
|
|
Key Polishing Concepts
|
-always work from larger to smaller
work from coarse-medium-fine-extra fine sequence -polishing is most effective, with better clinical results, when a slower, optimal speed range is used, faster creates excess heat reducing efficiency and instrument life |
|
|
Finishing/Polishing PFM/All Ceramic sequence
|
-step 1: Diamonds: low pressure, low speed
-step 2: green and white stones (use green until shim stock is almost holding then use white) - Step 3: Brasseler CeramiPro Dialite (sequence blue, pink, gray) Wheels are for F&L surface and points are for occlusal and lingual of anterior teeth. -Step: 4 Polishing pastes (?) *beware of polishing highly characterized surfaces |
|
|
Blue Brasseler CeramiPro Dialite Polisher
|
-coarse
-reduce and slight contour |
|
|
Pink Brasseler CeramiPro Dialite Polisher
|
-medium
-pre-polish -no contour |
|
|
Gray Brasseler CeramiPro Dialite Polisher
|
-fine
-high gloss -luster polish |
|
|
Delivery and Cementation of single unit full coverage crowns sequence
|
-check the crown (internally & externally)
-seat the pt -update the health history -ascertain any problems with tooth in question -assess temporary -clean the tooth -try in crown |
|
|
Checking crown internally
|
-for positives (check die for abrasions) will abrade/crush die but not tooth -prohibits full seating on tooth
-holes in metal (porcelain) -porosity at margin |
|
|
Checking crown externally
|
-for roughness
-polish -cracks (porcelain) -design (is it what you requested?) -color (check with shade guide and Rx) |
|
|
Assessing Temporary
|
-is it in place
-what do the periodontal tissues look like (healthy vs. inflammation) -if inflamed, where will your final restoration margin be located? -may be significant esthetic problem with a PFM crown -is there cement left -is cement discolored or stained |
|
|
Losing Temporary Etiology
|
-hyper occlusion, causing temp to flex, de-bond or fracture
-poor R&R form of prep -poor flossing technique (overhangs?) -length of temporization (permanent cementation?) |
|
|
Losing Temporary Sequellae
|
-hyper eruption of opposing tooth (may require enameloplasty of restoration of opponent tooth)
-drift of adjacent teeth (may require orthodontic tooth movement to correct) |
|
|
Removing Temporary Armamentarium
|
-black spoon (UNC four corners method, gently lifting at line angles) good palm/thumb grasp, finger rest)
-hemostat (with great care F-L motion, dont extract the tooth or foundation) |
|
|
Temporary Staining
|
-results from micro-leakage, and tooth may be hyper sensitive
|
|
|
Anesthesia needed to clean cement from tooth
|
-if yes, how to assess or confirm the occlusion
-if required, your temporary crown did not meet appropriate success criteria, or tooth was hyper sensitive during crown preparation and temporization |
|
|
Cleaning the Tooth Armamentarium
|
-spoon excavator/explorer (remove as much of the bulk cement as possible)
-wet cotton pellet/ cotton pliers (scrub the prep) -whip mix preppies |
|
|
Whip Mix Preppies
|
-prepared pumice/water
-does not contain fluoride; this will not affect bonding -use with prophy cup (F, L, O surfaces) -brush (M, D surfaces) with slow speed -rinse to remove excess |
|
|
Crown Try-In sequence
|
-proximal contacts
-marginal adaptation -Fit Checker to confirm -retention -occlusion -contours, color, texture |
|
|
Checking Proximal Contact
|
-use un-waxed floss
-Hold the crown down while flossing (dental asst) -floss contact : if shreds, too tight; if doesn't catch,too loose or non-existent -visualize the contact (does light reflect through it -adjust the contact (if needed ) -locate the contact with articulating paper or floss |
|
|
Locating the Contact
|
-place articulating paper (thin) in the proximal contact area
-place the crown, press to place -remove-should leave location of proximal contact |
|
|
Adjusting the contact Armamentarium
|
-gold crown: separating disk>stone>cratex wheel>burlew wheel
-porcelain: separating disk>busch silent stone -use each on low speed with palm/thumb grasp -adjust contact from gingiva up |
|
|
Adjusting the contact
|
-may take several attempts
-after each attempt, replace crown, refloss, re-reflect light to visualize. Be sure crown is held firmly to place when assessing contact -repeat as necessary until floss test, visualization is correct |
|
|
Open Contact
|
-if contact was adjusted away or not there to begin with :
*Gold: solder proximal, re-adjust following same sequence *PFM: send back to lab to have additional porcelain added (indicate where you want it added and how much) |
|
|
Verifying Margins Armamentarium
|
-Sharp explorer (#17, G-20)
-tip is approx 40 microns in diameter -ADA specification #8 for dental cements requires <25microns cement film thickness -explore margins |
|
|
Margin possibilities
|
-Perfect fit: crown margin and prepared tooth meet simultaneously in time/space
-closed: contacts the tooth, short/closed, vertical overextension/closed, closed with lateral overhang -open: short/open, overextended/open, correct length/open (lateral overhand with opening) |
|
|
Detecting a Short margin
|
-direct tip of explorer toward the tooth margin
-you will feel or hear the margin click apical to the crown |
|
|
Detecting an Open margin
|
-direct the explorer tip in an occlusal direction
-tip with catch under the open crown margin (if open by more than 40 microns) |
|
|
Detecting an Overhang in margin
|
-direct explorer tip perpendicular to crown
-tip will hang on over hang -can detect explorer dropping off from crown to tooth when moved apically over margin |
|
|
Short and Closed margin
|
-if less than .3mm accept if greater than .3mm re-impress
-verify crown fit on die, if short on die, re-impress or send back to lab for remake -if it fits the die, either the crown isn't fully seated on tooth or die was abraded/shortened in lab |
|
|
Open margin
|
-if gold alloy, burnish on die or in air and trial seat again
-if PFm or non precious alloy, difficult/impossible to burnish: re-impress |
|
|
Thick Margin
|
-lateral overhang occurring
-thin with appropriate instrumentation *Gold: cratex wheel, re-polish *Ceramic: aluminum oxide stones, re-glaze or polish |
|
|
GC Fit Checker
|
-GC America (silicone material, <25 micron film, white color)
-used to show areas of binding between tooth/crown |
|
|
Fit Checker Method for Use
|
-mix equal amounts of material
-place liner in casting -seat tooth (cotton roll) -remove, assess internal contact -adjust, repeat |
|
|
Things to Look for with Fit Checker
|
-in gold, PFM crowns, you should see uniform thickness of material (white) on occlusal, axial walls
-marginal 1mm should show only metal -look for gold/gray areas showing through the white; adjust with round bur; repeat |
|
|
Crown Retention
|
-when seated does crown rock FL or MD
-does maxillary crown fall off -does crown move or lift when adjusting occlusion -if yes verify thickness of cement with Fit Checker, if excessive remake crown |
|
|
Adjusting occlusion
|
-evaluate occlusion without crown in place first
-evaluate with crown seated -check with Accufilm II, Shim stock and adjust as needed -Check, adjust lateral excursions (remove and non-functional contacts) |
|
|
Hyper-Occlusion in crown
|
-occlude it, armamentarium depends on how high it is in occlusion
*Gold: carbide, green/white xmas tree stone *PFM/Ceramic: diamond, green/white xmas tree stones -adjust to accufilm II, shim stock until adjacent teeth contact -re-polish after adjustment |
|
|
Hypo-Occlusion in crown
|
-Gold: solder (solder may or may not stay on cusp tip, or run into fossa areas)
-PFM/Ceramic: return to lab for porcelain addition -may need to re-articulate casts first or you could just guess -if grossly off, remake |
|
|
Adjust Contours
|
-does it look like a tooth
-change line angle, point angle positions -if gold crown what you wax is what you get, spend time in the waxing stage to save chair time Armamentarium: -gold: cratex, burlew wheel -PFM/Ceramic: diamonds, aluminum, oxide stones |
|
|
Over-contoured Crown
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-modify contours
-never assume that what is returned from the lab cannot be modified |
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Under-contoured Crown
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-assess if clinically significant (food impaction in gingival crevice etc) or an esthetic problem
-if yes to the above then remake (gold) or return to lab for additional porcelain to be added |
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Final Assessment
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-does pt approve of the occlusion and esthetics (color and contour)
-PFM/Ceramics: modify with surface characterization (staining) -if acceptable prepare the tooth and casting for cementation |
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Crown Finishing Procedures
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-metal crowns: polishing
-PFM/Ceramic: characterization and glazing of porcelain followed by polishing of the metal in PFMs and/or characterization and glazing, or polishing of porcelain in all ceramic crowns |
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Permanent Cementation
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-always allow 30 min for permanent cementation
-multi-step process involving preparation of the restoration and preparation of the abutment tooth and final assessment prior to pt dismissal |
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Cement removal
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-temporary cement removal (eugenol inhibit resin polymerization, air abrasion, pumice, etching after pumice)
-The casting preparation (air abrasion 50 microns alumina, increase the in vitro retention 64%, protect the margin at 60lbs pressure you can modify the margin quickly -other methods include steam cleaning, ultrasonic and organic solvent |
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Tooth Preparation for Cement
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-isolate with cotton rolls
-etch the tooth when using all cements other than ZnPO4 cement -use GC dentin conditioner or phosphoric acid or etchant that comes with the cement you have selected -after etching rinse and dry -replace cotton rolls , keep isolated, if saliva contaminates it, re-etch |
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Cementation Procedure
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-have cement mixed
-line the crown -seat crown with firm finger pressure -have pt bite on orangewood stick or cotton roll check margins with explorer-do they feel the same -remove cotton roll have pt occlude, does it feel the same to them -if yes to both have them bite firmly on cotton roll until set |
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Excess Cement Removal
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-when to remove excess depends on which cement is used
-for those that are more easily removed (ZnPO4, polycarboylate glass ionomer, RMGI) wait until fully set and remove (explorer and floss) -Comp resins: remove prior to full set |
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Post Cementation Evaluation
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-re-evaluate marginal adaptation
-re-evaluate proximal contacts (must be able to floss) -re-evalauate occlusion (adjust if needed, re-polish with appropriate instrumentation) |
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Post-Cementation Pt Instruction
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-most cements require 24 horus to reach full set, except for CR
-Most sufficiently set within 2 hours of clinic -have pt avoid eating stick foods for first 2 hours -caution pt about potential for post-op sensitivity (occurs in up to 50% pts, if present should improve, if not have them call) -11-17% of all crowns and FPDs need RCT after cementation |
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Ceramic Glazing
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-final firing of porcelain in which the surface is vitrified and a high gloss is imparted on the material
-cover with a glossy, smooth surface or coating to attain a smooth and reflective surface |
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Autoglazing
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-contoured Bisque bake is raised to its fusion temp and maintained for a time before coolin g
-pyroplastic surface flow occurs, and a vitreous layer of surface glaze is formed -occlusal contact in porcelain is altered slightly during glazing |
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Overglazing
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-separate mix of powder and liquid is applied to the surface of shaped restoration and subsequently fired
-firing procedure is similar to autoglazing -there are variations among brands -extrinsic stain is a type of overglazing |
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Surface Glaze
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-reproduces the natural luster of an unrestored tooth
-creates highly polished surface that is good for gingival health and inhibits plaque accumulation and reduce porcelain abrasiveness -Enhances the strength of the restoration -porcelain treated overglaze was stronger than porcelain treated with autoglaze or autoglaze and polish |
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Reduction of Abrasiveness of Ceramics by polishing and Glazing
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-smoothest surface should cause the least wear damage to opposing surfaces
-depending on the initial surface roughness of the ceramic surface, glazing many not adequately decrease the surface roughness -glassy layer may be insufficient thickness to fill in scratches and grooves within the ground surface -must polish interproximal areas bc these areas if left rough will accumulate plaque and can cause gingival inflammation -repolishing of ceramic surfaces periodically is recommended specially afer acid exposure |
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Ceramic Contouring and Polishing Armamentarium
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-pencil
-adequate ventilation/vacuum -diamond burs (high/low speed) -aluminum oxide wheels -diamond wheels (embrasures) -busch silent stone -porcelain polishing kits (Dialite) -pumic/brasso and lathe |
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Characterization Definition
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-to alter by application of unique markings, indentations, coloration and similar custom means of delineation on a tooth or dental prosthesis thus enhancing natural appearance
-should contour first -feldspathic porcelain stains are metallic oxides combined with translucent porcelain over glazes |
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Line Angles/Heights of Contour
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-moving the line angles laterally makes the tooth appear more wide
-moving the height of contour down shortens the look of the tooth -moving the line angles medially narrows the look of the tooth -raising the height of contour lengthens the look of the tooth |
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Intrinsic Characterization
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-may be accomplished by incorporating colored pigments in the opaque, body or incisal powder
-this achieves optimum characterization |
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Extrinsic Characterization
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-surface staining (supplied with most commercially staining kits)
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Characterization with Stains
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-will almost always
*decrease the translucency *decrease the value (make the restoration more gray in appearance-white stain is the exception) -if you cant decide on a shade go lighter because this can be made darker but a darker shade cannot be made lighter |
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Porcelain Stain Kits
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-many are porcelain dependent
-all stains should be mixed thick (honey consistency) -all stains should be mixed with a glas rod or agate spatula (metal instruments introduce SS oxides, which will turn black on crown surface when glazed) |
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Basic Characterization Technique
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-complete porcelain adjustments(contouring, occlusion, additions)
-clean or air abrade crown external surfaces -place securely on hemostats -compare crown shade (dry) to adjacent natural tooth/crown -wet crown with stain medium -compare again to natural tooth -wet crown will appear as if you only glazed it, make modification to shade to wet crown |
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Rules of Thumb for Characterization
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-if value is too low to start, PUNT! In other words, strip the porcelain and start over
-you can detect a shade discrepancy in the crown, confirm the patient and/or a family member-consider redo or referring |
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Advanced Characterization
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-Incisal translucency
-gingival shades -interproximal depth (on FPDs) -check/craze lines -Incisal halo -enamel cracks -exposed incisal dentin -hypocalcified areas -gingival pink porcelains |
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The Art of Dentistry
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-generally we use low-fusing porcelains with a firing range of 1750-1860 degrees F.
-delivered from lab in a bisque bake |
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Characterization Armamentarium
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-Palette with various colors-These are pigmented colorants (iron oxides) containing small amounts of glass
-violet and blue -orange, honey(light brown), dark brown -white -liquid-glycerin/water mix -oven-ney mini-glaze is a good one ($879) -sable-haired brushes |
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Characterization General sequence
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-attach hemostat to PFM crown on lingual
-steam clean -add colors/characterization -dry in open oven door 6-10 minutes -glaze -use a different brush for each color |
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The Basics of Dental Esthetics
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-Midline & plane of occlusion (consistent with facial references)
-Symmetry (gingival symmetry & long axis of teeth) -Integration |
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Esthetics Diagnosis
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Symmetry (pink space & black space)
Tissue contour (balance of gingiva) Tooth features (long axis of the teeth; size) Negative space (if you can fix negative space & symmetry problems, then esthetics become easy) |
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A good diagnosis & treatment plan for dental esthetics will:
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-Determine what clinical factors limit ability to achieve objective esthetic critera
-Define appearance -Identify strategies to overcome limitations to ideal restoration |
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Smile line is controlled by:
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-Black space (NEVER controlled by the incisal edge)
You can increase black space by increasing the length of the incisal embrasure Adjust the black space to adjust the smile line |
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Gingival Health & Biological Width:
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Biological width consists of lunctional epithelium & cementum, etc
Must have 3mm of tissue facial to anterior of any tooth - don't disturb this tissue (cement, bad margin, etc) If more than 3mm, then you can remove it by removing inflammation or by using a blade. |
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Gingival Health affected by:
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-Plaque mediated disease
-Modified by system factors -Affected by local factors |
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Gingival health vs Recession
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All gingiva will recede over 50 years & sick gingiva will recede much more quickly
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Gingival Health & Prostheses
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-FPDs "fail" most frequently due to caries
-But, FPDs may be replaced for esthetic reasons often related to gingival recession |
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Golden Proportion:
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The average tooth has a width to height ratio of 0.8
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Smile line is defined by...
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The incisal embrasures
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Problems with Shade Selection
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Subjective Faults:
-Differences in color perception -Ocular fatigue -Lack of education Metamerism & light selection Limitation of current shade "guides" Communication with laboratory |
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Perception
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That light that falls on the retina
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Apperception
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How the mind interprets the perception
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The Eye
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The Iris focuses the amount of light that is let in & then light falls on the retina. This light is then converted into nervous response/electrical response.
Rods --> are in the retina & see black/white & motion Cones --> see color (Women have more cones) There are 200x Rods for every Cone in the retina |
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How to Relax the Cones in the Retina...
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Used to be common practice to look at a blue card to relax the cones (NOT TRUE)
If you are taking a shade & you saturate your retina, then you should have a GRAY CARD to relax receptors |
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Color Blindness
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-Color blindness comes as a result of a lack of one or more of the types of cones/color receptors (red, green & blue)
-10% Males -0.4% Femails |
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Distractions in Shade Selection
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-Do not want a lot of distractions around because the information around the shade of the tooth can affect what we are actually looking at
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Brunessence
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-As the lens ages, a process known as brunescence occurs.
-The lens becomes denser & more opaque, allowing less light to reach the retina |
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Borders & Framing Color
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-If there is a lot of characterization to the teeth, then make sure the lab makes the crown with embrasure to frame the tooth the same way (framing can change the appearance of color)
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Definition of Color
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Color is the quality of an object or substance with respect to light reflected by it, usually determined visually by measurement of hue, saturation, & brightness
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Color Influenced By
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-characteristic of the light source
-degree which the object absorbs, transmits, reflects and scatters light -environment where the color is observed -human vision (light radiated from the object, modified by human perception) -teeth are slightly translucent and have depth of color, labs often ask what age the patient is so they know how translucent the teeth are |
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Metamerism
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-phenomenon when the same object may appear a different color in different light sources
-light in the dental office can be keyed to daylight -incandescent light causes yellow light to be bounced off the object and make it appear a different color |
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Color Measurement
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-hue
-chroma -value |
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Hue
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-color measurement
-the color itself |
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Chroma
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-intensity of the hue
-color measurement |
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Value
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-lightness or darkness of an object
-color measurement -eyes are more sensitive to value than hue or chroma because we have more rods |
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Translucency
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-4th dimension of color
-effects color -different amount of lights through the incisal edge |
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Sequence or Using the Vita Classic Shade Guide
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-select value
-select Hue -select chroma |
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Vita Classic Guide
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-can be divided by group or by value
-usually 1 is the lightest and 4 is the darkest but there are exceptions to the rule -all information in the tooth is in the incisal 2/3 -want to orient your shade tab so that the light coming off the tooth and shade tab at the same angle -color comes through where enamel is the thinnest (gingival 1/3) |
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Vita A group
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-reddish brown
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Problems with Vita Classic Shade Guide
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-derived through emphirical clinical experience
-color gaps -inaccurate interpolation (shades cannot be mixed to achieve a single intermediate shade) -not systematic (shades not set up to reflect Value chroma and hue) |
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Color sphere
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-is the color space composed of value or lightness, chroma,and hue
-shade distribution in color space |
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Shade selection
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-do at start of appoinment (eyes fatigue, dehydration of tooth)
-clean adjacent teeth -use natural daylight or diffuse light (5,500 degrees Kelvin) -18% Gray card used to relax receptors (minimized surrounding strong colors) -hold shade guide at arm's distance -make swift decisions -when in doubt always go with the lighter shade (higher value) as characterizing stains with only lower value |
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Problem with PFM crown
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-most error on being too light because of dessication and again this should be done at the beginning of the appointment so teeth are hydrated like normal
-pts are usually more receptive with lighter teeth than darker ones, if you miss with the hue make it darker but not lighter -metal is too thick or because the opaquer is too thick causing it to show through the body of the porcelain |
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Prosthodontics
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-dental specialty pertaining to the diagnosis, treatment planning rehabilitation and maintenance
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