All-Ceramic Systems in Dentistry

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Questions and Answers

What is the impact of Yttria on zirconia ceramics?

  • Increases translucency while decreasing strength
  • Reduces the phase stability of zirconia
  • Eliminates all chipping occurrences
  • Enhances phase stability and toughness (correct)

Which of the following is a primary application of zirconia restorations?

  • Long-term bridges and crowns (correct)
  • Gingival grafts
  • Temporary restorations in orthodontics
  • Direct composite fillings

What is a common failure mode associated with porcelain-veneered zirconia restorations?

  • Chipping and delamination (correct)
  • Thermal expansion mismatch
  • Corrosion of the zirconia
  • Discoloration of the zirconia

Which technique is NOT commonly used to veneer zirconia infrastructures?

<p>Sintering (A)</p> Signup and view all the answers

Which phase of zirconia is characterized by high strength and is commonly used in dental applications?

<p>Tetragonal (T) (A)</p> Signup and view all the answers

What property of zirconium makes it similar to metals?

<p>Mechanical properties (D)</p> Signup and view all the answers

What is a key advantage of monolithic zirconia restorations?

<p>Higher strength and improved esthetics (B)</p> Signup and view all the answers

What is a disadvantage of traditional porcelain veneering of zirconia?

<p>Increased risk of delamination (B)</p> Signup and view all the answers

What is the primary reason for using stabilizing oxides in zirconia ceramics during cooling?

<p>To prevent volume expansion and ceramic cracks (A)</p> Signup and view all the answers

At what temperature does zirconia begin its phase transformation from monoclinic to tetragonal?

<p>1170°C (D)</p> Signup and view all the answers

Which group of zirconia ceramics is characterized by the highest translucency and reduced mechanical properties?

<p>7-8 mole % Y-TZP (C)</p> Signup and view all the answers

What phenomenon occurs in zirconia that allows it to resist crack propagation?

<p>Transformation toughening (C)</p> Signup and view all the answers

In zirconia ceramics, what does the term 'PSZ' stand for?

<p>Partially Stabilized Zirconia (D)</p> Signup and view all the answers

Which composition of zirconia contains the highest amount of alumina?

<p>0.25 weight % alumina (C)</p> Signup and view all the answers

What measurement of flexural strength is commonly associated with opaque zirconia?

<p>1,200 to 1,500 MPa (C)</p> Signup and view all the answers

Which zirconia ceramic restoration is suitable for full mouth restorations?

<p>Full mouth restorations with two pontics (D)</p> Signup and view all the answers

What is the effect of adding yttria content to zirconia regarding its phases and translucency?

<p>Increases cubic phases but reduces strength. (D)</p> Signup and view all the answers

Which of the following zirconia types has a flexural strength of 800 to 900 MPa?

<p>6-7 mole % yttria stabilized zirconia (C)</p> Signup and view all the answers

In which of the following applications can VITA ENAMIC be used?

<p>Definitive single-tooth restorations (B)</p> Signup and view all the answers

What characterizes the material Lava Ultimate?

<p>It contains a resin matrix with ceramic particles. (C)</p> Signup and view all the answers

How does 7-8 Y-TZP zirconia compare to 6-7 mole % yttria when it comes to flexural strength?

<p>6-7 mole % yttria has higher strength. (B)</p> Signup and view all the answers

What percentage of the inorganic ceramic part makes up VITA ENAMIC?

<p>86 wt.% (C)</p> Signup and view all the answers

What is a characteristic of hybrid ceramics?

<p>They consist of ceramic reinforced with resin. (B)</p> Signup and view all the answers

Which ceramic system category does IPS e-Max ceramics belong to?

<p>Reinforced glass ceramics (C)</p> Signup and view all the answers

Flashcards

Pure Zirconia Phase Transformation

Pure zirconia undergoes phase transformations from monoclinic to tetragonal to cubic as temperature increases, and reverts from cubic to tetragonal to monoclinic during cooling. The tetragonal-monoclinic transformation is associated with volume expansion.

Tetragonal-Monoclinic Transformation

This phase transformation in zirconia, happening during cooling, is accompanied by a volume change (expansion) of about 3-4%.

Transformation Toughening

A physical property of zirconia where the tetragonal to monoclinic phase transformation during cooling helps to absorb energy during crack propagation, making the material more resistant to fracture.

Partially Stabilized Zirconia (PSZ)

A metastable form of zirconia, typically used in ceramics, created by adding other oxides to stabilize its tetragonal structure at room temperature.

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Yttria-Stabilized Tetragonal Zirconia Polycrystal (Y-TZP)

A type of zirconia material used in dental restorations. Different concentrations of yttria affect the material's strength and translucency.

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3-4 mole % Y-TZP

A strong zirconia material primarily used in dental restorations; characterized by a high concentration of yttria.

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5-6 mole % Y-TZP

A more translucent zirconia material used in dental restorations; characterized by a mid-range yttria content.

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7-8 mole % Y-TZP

A very translucent zirconia material used in esthetic dental restorations; least of the three for strength, highest yttria content.

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Alumina Addition

Adding alumina to zirconia to influence its properties, such as strength and translucency.

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All-ceramic systems

Dental restorations made entirely from ceramic materials, categorized by their composition and microstructure.

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Zirconia with Yttria

Adding yttria to zirconia increases cubic phases, improving translucency but reducing strength compared to pure zirconia.

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Flexural Strength of Zirconia

Zirconia with 6-7 mole% yttria has a strength of 800-900 MPa, while 7-8 mole % has 600-700 MPa.

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Glass-based (Feldspathic) ceramics

Ceramic restorations primarily composed of glass-like materials, often used for crowns and bridges. These often require additional porcelain veneering for optimal aesthetics.

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All-Ceramic Systems

Categories of ceramic materials for dental restorations, including glass-based (feldspathic), reinforced glass ceramics, glass-infiltrated alumina, zirconia, and resin-based ceramics.

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Reinforced glass-ceramics

Ceramic restorations with added reinforcing elements which enhance strength, commonly used for crowns and bridges.

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Resin-Based Ceramics

Hybrid materials combining ceramic particles (around 80% by weight) in a resin matrix. They offer a combination of esthetics and toughness.

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Zirconia ceramic

A polycrystalline ceramic based on zirconium oxide, characterized by high strength and a color similar to tooth enamel.

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Glass-infiltrated alumina

Ceramic restoration that has alumina embedded in it, offering good strength and translucency.

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Vita Enamic

Sintered ceramic matrix with polymer filled pores. Composed of 86 wt% inorganic ceramic and 14 wt% organic polymer.

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CAD/CAM Technology

Computer-aided design and computer-aided manufacturing technology for fabricating dental restorations using digital models.

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Zirconia Polymorphs

Different crystal structures of zirconia (Monoclinic, Tetragonal, Cubic).

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Monolithic Zirconia Restoration

A zirconia restoration without a veneer, characterized by improved translucency and strength.

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Veneering techniques

Methods used to apply porcelain to zirconia frameworks for improved esthetics.

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Chipping

A failure of the veneering porcelain on a zirconia restoration.

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Delamination

Separation of the porcelain veneer from the zirconia substructure.

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Study Notes

All-ceramic Systems

  • Categories:
    • Glass-based (Feldspathic)
    • Reinforced Glass ceramics (IPS Empress, IPS e.Max ceramics, Vita Suprinity, Celtra Duo)
    • Glass-infiltrated alumina (In-ceram, Spinel)
    • Zirconia ceramic
    • Resin-based ceramics (ceramic reinforced resins) (Vita Enamic, Lava Ultimate, Visio ligne, CeraSmart, Brilliant, Grandio)

Classification

  • Category IV (Non Silica Based): Zirconia ceramic
    • Zirconium is a polycrystalline ceramic without any glass component.
    • Sintered Zirconium ceramic has a strength of 900-1500 MPa.

Material Science

  • Zirconium is a crystalline dioxide of zirconium.
  • Its mechanical properties are similar to metals, sometimes called "ceramic steel".
  • Its color is similar to tooth color.

Unfavorable Circumstances

  • Chipping: failure within the veneering porcelain
  • Delamination: failure at the porcelain-zirconia interface

Monolithic Restorations

  • Combines the strength of zirconia with improved esthetics due to higher translucency.

Crystallographic Phases

  • Zirconia is monoclinic at room temperature and stable to 1170°C.
  • Above 1170°C, it transforms to tetragonal.
  • Further above 2370°C, it becomes cubic.

Transformation Toughening

  • During cooling, a tetragonal-to-monoclinic transformation occurs at ~1070°C, which leads to volume expansion of approx. 3-4%.
  • This transformation can cause cracks if not controlled by stabilizing oxides.
  • Propagating crack can trigger zirconia grains to transform.

Indication

  • Zirconia provides versatility for placing restorations throughout the mouth.
    • Single crowns
    • Implant abutments
    • Full-mouth restorations

Current Zirconia Classification

  • Classified based on yttria content. Types include:
    • 3-4 mole % Y-TZP (strong, mainly tetragonal)
    • 5-6 mole % Y-TZP (more translucent)
    • 7-8 mole % Y-TZP (most translucent, reduced mechanical properties)

Opaque Zirconia

  • Contains 3 mole % yttria and 0.25 weight % alumina.
  • Flexural strength is 1200 to 1500 MPa.

Next Generation Monolithic Zirconia

  • 4Y-TZP with reduced alumina concentration (0.05% weight) for higher translucency (e.g., Lava Plus, Cercon ht).

More Recent Versions

  • Increased yttria content (3-6 mole %) results in increased cubic phase and thus improved translucency.
  • However, this can compromise strength. (e.g. BruxZir Anterior, Lavaâ„¢ Esthetic, KATANAâ„¢ HT, and Cercon XT)

Zirconia Strength

  • Zirconia with 6-7 mole % yttria has a flexural strength of 800-900 MPa (STZ).
  • 7-8 mole % Y-TZP zirconia has a flexural strength of 600-700 MPa (UTZ).

Category V: Resin-based Ceramics

  • Resins with ceramic reinforcements
    • Lavaâ„¢ Ultimate (Resin Nano Ceramic): 80% (by weight) nano-ceramic bound in the resin matrix.
    • VITA ENAMIC: sintered ceramic matrix with a polymer material-filled pores.
      • 86 wt.% inorganic ceramic
      • 14 wt.% organic polymer

VITA ENAMIC Indications

  • Crowns, onlays/inlays, veneers
  • Implant-supported single crowns
  • Fabricated with CAD/CAM

VITA ENAMIC Contraindications

  • FPD restorations
  • Parafunctional habits (e.g., bruxism)

Loading Indication

  • Anterior loading ∼25 kg
  • Premolar loading ∼35kg
  • Molar loading ∼100 kg

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