Zirconia Flashcards
What is the advantage and disadvantage of shorter sintering?
advantage: higher flexural strength (according to one study)
disadvantage: reduced translucency (small isolated pores cause light scatter)
Cesar Shang Recent Advances in Zirconia (2024)
What is the purpose of adding yttria to zirconia?
yttria stabilizes the tetragonal phase
- Pure zirconium dioxide is unstable at room temp and can transform from tetragonal to monoclinic, which can cause cracking and weakening.
What is the effect of increasing the yttrium content of zirconia?
increased percentage of cubic
more esthetic
less low-temperature degradation
less transformation toughening
Why zirconia over PFM?
1) technique-sensitivity of fabrication (did not have access to a lab with this skill
2) avoid chipping/fracture of veneering porcelain (only 2% instance, so maybe don’t mention this??)
How much volume change when zirconia changes phase from tetragonal to monoclinic?
5%
Is there potential for surface damage of zirconia with air particle abrasion?
APA can trigger tetragonal to monoclinic phase transformation, whereby transformation toughening can lead to increased mechanical strength. However, excessive sandblasting may cause damage to the zirconia surface, deteriorating the flexural strength of 3Y-TZP.
WORK ON THIS
Without priming, Relyx Unicem showed durable bond strength to air particle abrasion. With priming,
TKTK WORK ON THIS
Yang (2010) - Influence of air-abrasion on zirconia ceramic bonding using an adhesive composite resin
What happens during zirconia sintering?
heat causes densification via reduction of space between zirconia particles
as the particles fuse, they also grow in size, forming larger grains
the material shrinks in volume during sintering
Cesar Shang Recent Advances in Zirconia (2024)
How much does zirconia shrink during sintering?
20-25%
What happens if you sinter zirconia longer?
larger grain sizes
Ivoclean
What is it, and how does it work?
universal cleaning liquid designed to clean the intaglio or bonding surface of restorations after intraoral try-in
Ivoclean contains suspended zirconia particles that are attracted to phosphates in saliva and other contaminants. When rinsed off, these phosphate-laden particles are also removed, leaving a clean surface.
What is the effect of air particle abrasion on zirconia?
Airborne particle abrasion (APA) enhances bond strength and durability of resin-based materials to zirconia by increasing surface roughness, energy and wettability, promoting micromechanical interlocking, and facilitating surface decontamination.
Following APA, the application of a ceramic primer containing functional monomers, notably 10-MDP, has been deemed essential to promote chemical adhesion and ensure a longer-lasting seal for indirect restorations.
D’Allesandro et al (2024) - Is zirconia surface etching a viable alternative to airborne particle abrasion? A systematic review and meta-analysis of in vitro studies
What would happen if you had speed-sintered the zirconia?
it would be less translucent
one study reported increased flexural strength
but this study showed no difference in flexural strength, biaxial strength, or fracture toughness
Meta-Analysis Systematic Review on Zirconia speed sintering (2023)
At what temperatures does zirconia exist in its different phases?
monoclinic: below 1170˚C
tetragonal: 1170-2370˚C
cubic: above 2370˚C
What type of zirconia did you use?
BruxZir full strength (3Y - tetragonal)
1,000+ MPa flexural strength
What are criticisms of zirconia bonding?
1) lack of silane coupling
2) difficult to roughen or chemically modify zirconia
3) when you do roughen the surface, it’s not to the same level as acid etching on porcelain
4) long-term stability of MDP is questioned
What causes the “mother of pearl” effect in zirconia crowns?
The perception of iridescence is caused by light interaction with microscopic surface irregularities and the high refractive index of zirconia
What are the basic chemical forms of zirconia?
monoclinic (low-energy state)
tetragonal (high-energy state)
cubic
What are the preparation guidelines for your zirconia?
1mm ideal reduction, 0.5mm minimum
Chamfer or shoulder margin preferred; feather-edge is OK
Examples of MDP containing primers
Monobond Plus
Clearfil Ceramic Primer Plus
Z-Prime Plus
What is MDP?
10-methacryloxydecyl dihydrogen phosphate
Forms a stable chemical bond between the zirconia surface and the resin cement
- MDP’s phosphate group interacts with the zirconia’s oxide layer
- MDP’s methacrylate group can bond with methacrylate groups in resin cements
How many units is BruxZir Full Strength indicated for?
bridges up to 16 units
up to 2 pontics in the posterior
up to 4 pontics in the anterior
full-arch implant bridges
https://protecdental.com/products/crown-and-bridge/zirconia/#:~:text=Zirconia%20FC%20(Premium),one%20unit%20cantilever%20bridges
What is transformation toughening?
Transformation toughening describes a transformation from tetragonal to monoclinic phase that limits crack propagation, enhancing fracture toughness and flexural strength
When a crack starts to propagate through a matrix composed of tetragonal grains, the sudden loss of matrix constraint allows for spontaneous expasion of tetragonal into monoclinic grains (4% volume expansion in the monoclinic crystal).
The resulting compressive stresses will further inhibit crack growth.
What is the difference between 3Y-TZP, 4Y-TZP, and 5Y-TZP zirconia?
molarity of yttria (3Y = 3 molar, etc.)
Zirconia with higher yttria content has increased translucency.
- Increased translucency is due to more cubic phase.
Zirconia with lower yttria content has less translucency but better mechanical properties.
- Lower yttria zirconia has more tetragonal phase, which allows for an increased possibility of transformation toughening
What happens during zirconia sintering?
heat causes densification via recution of space between zirconia particles
as the particles fuse, they also grow in size, forming larger grains
the material shrinks in volume during sintering
Cesar Shang Recent Advances in Zirconia (2024)
Why did you air-particle abrade zirconia before bonding?
1) promotes micromechanical interlocking
2) increases surface area for bonding
What is the advantage of using a universal primer with MDP over a phosphate-based primer?
Universal adhesives have a higher wt% of 10-MDP than phosphate-based primers.
The 10-MDP molecule reacts chemically with the zirconium oxide surface via hydrogen bonds or ionic interactions (between the P-OH and Zr-OH groups, or between P-O− and partially positive Zr).
Other components in universal adhesives are methacrylate and dimethacrylate monomers (HEMA, bis-GMA, and UDMA), silane, and fillers. It is possible
that these components improve the bond strength to zirconia by increasing zirconia surface wettability and providing a moisture-stabilizing effect.
Consequently, the interface formed between 10-MDP and zirconia may become more hydrophobic and stable over time.
Lima - Bonding Efficacy of Universal Resin Adhesives to Zirconia Substrates: Systematic Review and Meta-Analysis (2023)
Bonding protocol for zirconia
1) Clean with Ivoclean
2) APA with alumina (50 microns)
3) prime with MDP primer (MonoBond Plus)
4) dual-cure or self-cure resing cement
Why can’t zirconia be etched with hydrofluoric acid?
Zirconia is a non-silica-based ceramic.
Why air particle abrasion for zirconia?
- micromechanical interlocking
- increased surface area for bonding
- increased wettability
Why resin bonding instead of RMGI?
resin is stronger - higher tensile and compressive strength than RMGI
less soluble
lasts longer
RMGI is prone to water sorption
RMGI:
comp. strength: 40-141 MPa
tensile strength: 13-24 MPa
solubility: .07-.4%
resin cement:
comp. strength: 200 MPa
tensile strength: 35 MPa
solubility: .13%
What form does pure zirconium oxide take at room temperature?
monoclinic
