p.6
Challenges in Bonding and Cementation Techniques
Why can't certain ceramics be etched properly?
They lack a glassy phase.
p.12
Mechanical Bonding in Dental Materials
What is the purpose of enamelling a metal surface in dental restorations?
Enamelling a metal surface distributes stresses, provides rigid support, and inhibits crack propagation from cracks at the interface.
p.9
CAD/CAM Technology in Dental Restorations
What are the indications for using machinable materials in dental restorations?
Machinable materials, such as pure Zirconia, are indicated for all restorations.
p.1
Bonding Strategies for Different Materials
What should you do if a veneer comes off and the patient needs to look good for the next day?
Sandblast the area, use a metal primer, apply a layer of resin cement followed by a layer of composite, and then go through the normal workflow when the patient returns.
p.6
Challenges in Bonding and Cementation Techniques
What are the potential drawbacks of air-abrasion on zirconia?
It may introduce surface flaws that compromise strength and reliability.
p.6
Bonding Strategies for Different Materials
How does air abrasion improve bonding to ceramics?
It increases surface irregularity for micromechanical retention and exposes –OH groups for chemical bonding with silane coupling agents.
p.4
Mechanical Integrity of CAD/CAM Materials
Are CAD blocks indicated for multi-unit FPDs?
No, CAD blocks are not indicated for multi-unit FPDs.
p.6
Bonding Strategies for Different Materials
What chemical reaction occurs between silane coupling agents and ceramic surfaces?
Condensation reactions with silanol (SiOH) groups generated by hydrolysis of the alkoxy (or methoxy) group (RO3Si-).
p.9
Hybrid Ceramics and Their Advantages
What are the advantages of using infiltrated materials like InCeram Alumina/Zirconia?
Advantages include homogeneous blocks with fewer porosities leading to microcracks and better margins.
p.5
Glass-Based Ceramics and Their Properties
Why can't alumina ceramics be acid-etched?
Because hydrofluoric acid (HF) has no effect on Al2O3.
p.1
Types of Cements and Their Applications
Why might zinc phosphate be a good choice for cementing crowns?
Zinc phosphate is a good choice because it is cheap, easy to use, and suitable for crowns that are already opaque.
p.10
Challenges in Bonding and Cementation Techniques
What are the contraindications for crowning?
Bruxism/clenching and deep overbite, especially in the elderly.
p.4
Mechanical Integrity of CAD/CAM Materials
For what type of crown is PFM material used?
PFM crown, as the material needs to resist firing with metal.
p.9
Types of Cements and Their Applications
What is the recommended preparation for a crown in terms of margin and occlusal reduction?
A 1 mm margin for aesthetics (non-stress-bearing area) and 1.5 mm occlusally for force-bearing areas. If there are no opposing teeth, a more conservative approach can be taken.
p.9
Mechanical Integrity of CAD/CAM Materials
What are the advantages of using machinable materials in dental restorations?
Advantages include simplicity, durability, homogeneity (reduced microcracks), different aesthetic options, superior accuracy, and the availability of chairside options.
p.5
Glass-Based Ceramics and Their Properties
What are glass-infiltrated alumina and zirconia ceramics indicated for?
Posterior regions and substructures to mask dark underlying metal/discolouration.
p.12
Polycrystalline Materials in Dentistry
What is a notable optical property of Zirconia in dental restorations?
Zirconia has a notable opacity in dental restorations.
p.2
Bonding Strategies for Different Materials
What are the steps involved in bonding glass-based ceramics?
The steps involved in bonding glass-based ceramics are: 1) Air abrasion, 2) Etching with HF, 3) Silane treatment, 4) Etching the tooth with 37% orthophosphoric acid, 5) Applying resin-based composite luting material.
p.13
CAD/CAM Technology in Dental Restorations
What is one advantage of the Cerec CAD/CAM Chairside System?
It minimizes operator-dependent errors.
p.1
Types of Cements and Their Applications
What are some contemporary cements used in dentistry?
Contemporary cements include resin cements, resin-modified glass ionomer cements (RMGIC), self-adhesive composite resins, and compomers.
p.4
Mechanical Integrity of CAD/CAM Materials
What is one of the uses of CAD/CAM materials in dental restorations?
Single tooth restorations.
p.12
Glass-Based Ceramics and Their Properties
What is a common issue with dental ceramics during firing?
Shrinkage with firing is a common issue with dental ceramics.
p.9
Challenges in Bonding and Cementation Techniques
What are the disadvantages of using infiltrated materials in dental restorations?
Disadvantages include a limited number of burs which limits the finish, margin and fit to prep not being great, and higher costs (though improved with current technology).
p.8
Challenges in Bonding and Cementation Techniques
What effect can bleaching have on the surface integrity of ceramics?
Bleaching can extract alkaline ions from within ceramics, potentially causing surface roughening.
p.7
Bonding Strategies for Different Materials
What is the bonding mechanism of self-etch/self-adhesive cements?
Chemical and micromechanical bonding via 4-MET and MDP, which are acidic functional monomers that demineralize and penetrate the dentine and enamel.
p.7
Hybrid Ceramics and Their Advantages
What is the elastic modulus (EM) of hybrid ceramics and how does it compare to conventional ceramics and dentine?
The elastic modulus of hybrid ceramics is ~30 GPa, which is lower than conventional ceramics but similar to dentine.
p.3
Glass-Based Ceramics and Their Properties
How is lithium disilicate ceramic made pressable?
By pressure casting at 450-550°C for less than 1 hour to initiate enucleation, then cooling to room temperature.
p.11
Glass-Based Ceramics and Their Properties
What are two main causes of stress localization in glass-based ceramics?
Fabrication defects such as voids created during processing and sintering, and internal surface cracks that develop during firing and cooling.
p.13
CAD/CAM Technology in Dental Restorations
What is a drawback of the Cerec CAD/CAM Chairside System?
Subgingival placement of the margins.
p.6
Bonding Strategies for Different Materials
What is the ideal bond for ceramics?
A combination of mechanical and chemical pre-treatments.
p.4
Mechanical Integrity of CAD/CAM Materials
How does the survival rate of CAD/CAM materials compare to PFM?
CAD/CAM materials have a lower survival rate than PFM due to a higher incidence of veneer chipping.
p.9
Challenges in Bonding and Cementation Techniques
What are the potential disadvantages of the machining process for dental materials?
The machining process may create stresses in the material.
p.8
Hybrid Ceramics and Their Advantages
What are the three methods of monomer infiltration into ceramic pores?
Melt infiltration, solvent infiltration, and initiator infiltration.
p.8
Classification of Dental Ceramics by Composition
What are the advantages of traditional powder-slurry fabrication methods?
Highly translucent and allows for controlled shade (polychromatic).
p.7
Hybrid Ceramics and Their Advantages
What are hybrid ceramics and why were they created?
Hybrid ceramics are ceramic-resin materials created to combine the Young’s modulus of resin-based composites with the aesthetics of ceramics.
p.3
Glass-Based Ceramics and Their Properties
What is the shrinkage percentage associated with firing lithium disilicate CAD blocks, and how is it compensated?
Firing is associated with 2% shrinkage, which CAD accounts for by synthesizing an expanded restoration to compensate.
p.1
Types of Cements and Their Applications
What are 'legacy cements' in dental materials?
Legacy cements refer to traditional cements such as zinc polycarboxylate, zinc phosphate, and conventional glass ionomer cement (GIC).
p.10
Challenges in Bonding and Cementation Techniques
What are the advantages of crowning?
High abrasion resistance and chemical inertness.
p.1
Mechanical Integrity of CAD/CAM Materials
What is a potential exam question for DENT4206 regarding CAD/CAM materials?
Compare the mechanical integrity of different types of CAD/CAM materials and discuss their reinforcement strategies, such as those used for zirconia.
p.12
Glass-Based Ceramics and Their Properties
What is the minimum tooth reduction required for e.max restorations?
e.max restorations can now be done with a 1 mm reduction.
p.7
Challenges in Bonding and Cementation Techniques
What is a common cause of failure in bonding with veneers?
Cohesive failure within the veneer.
p.3
Glass-Based Ceramics and Their Properties
What is the main advantage of leucite-reinforced ceramics like Ivoclar IPS Empress?
They are low-strength etchable glass-based ceramics made by injection-moulding under heat and pressure, resulting in reduced shrinkage and increased flexural strength (~160 MPa).
p.5
Polycrystalline Materials in Dentistry
What are the indications for using polycrystalline materials in dentistry?
Posterior crowns, copings over dark underlying teeth, and monolithic bridges.
p.3
Glass-Based Ceramics and Their Properties
What is the composition of lithium disilicate CAD blocks in their initial state?
They start in a blue state composed of metasilicate and lithium disilicate nuclei, with flexural strength prior to firing of ~130 MPa.
p.11
Polycrystalline Materials in Dentistry
What is the role of yttria in stabilizing zirconia?
Yttria (yttrium oxide, Y2O3) is used to stabilize the tetragonal zirconia polycrystal (3Y-TZP), maintaining its structure at room temperature and opposing the opening of cracks by creating compressive stresses.
p.10
Challenges in Bonding and Cementation Techniques
Why is it usually preferred to have a patient in your clinic for a long time before crowning?
To know their oral hygiene habits.
p.9
Bonding Strategies for Different Materials
What are the key considerations for choosing a material and shaping a dental crown?
Considerations include how the papilla comes together, gingival margins, adjacent teeth, color of the underlying tooth, and the cementation system.
p.6
Polycrystalline Materials in Dentistry
What dental applications benefit from ceramics with no glass matrix?
Frameworks of fixed partial dentures (FPDs) and metal-free super-structures on implant abutments.
p.8
Hybrid Ceramics and Their Advantages
Why is polymerisation performed under high temperature and pressure?
To overcome polymerisation shrinkage, reduce size and number of defects, and reduce monomer release.
p.8
Classification of Dental Ceramics by Composition
What are the disadvantages of traditional powder-slurry fabrication methods?
Weak (FS 60-70 MPa), excessive shrinkage, and microporosities leading to inhomogeneity.
p.7
Hybrid Ceramics and Their Advantages
What is the flexural strength of hybrid ceramics compared to feldspathic glass?
Hybrid ceramics have a flexural strength of 150-160 MPa, which is higher than feldspathic glass (70-100 MPa).
p.13
Mechanical Integrity of CAD/CAM Materials
How do the survival rates of CAD/CAM systems compare to conventional crowns?
CAD/CAM systems have similar survival rates to conventional crowns.
p.10
Challenges in Bonding and Cementation Techniques
Why might crowning be more conservative than PFM in young patients?
Because young patients have large pulp chambers.
p.2
Glass-Based Ceramics and Their Properties
What are the aesthetic properties of glass-based ceramics?
Higher glass content in glass-based ceramics provides better aesthetic properties such as translucency, which mimics the optical properties of enamel and dentine.
p.2
Glass-Based Ceramics and Their Properties
Why are glass-based ceramics not suitable for posterior crowns?
Glass-based ceramics are not sufficiently strong for posterior crowns but can be used anteriorly, with fracture loads comparable to natural teeth in the premolar area.
p.2
Glass-Based Ceramics and Their Properties
What are the survival rates of inlays made from glass-based ceramics after 5, 8, and 10 years?
Inlays made from glass-based ceramics showed survival rates of 94.7% after 5 years, 90.6% after 8 years, and 85.7–89% after 10 years.
p.5
Glass-Based Ceramics and Their Properties
What is the composition of zirconia-reinforced lithium silicate ceramic (ZLS) like Vita Suprinity?
Glass ceramic enriched with 10% zirconia by weight.
p.8
Classification of Dental Ceramics by Composition
What are the advantages of pressed ceramics?
Improved mechanical properties, less risk of shrinkage, and they are translucent and aesthetic.
p.11
Glass-Based Ceramics and Their Properties
What are the aesthetic benefits of glass-based ceramics in dental materials?
Colour stability, translucency, and polishability.
p.11
Glass-Based Ceramics and Their Properties
How can the brittleness of ceramics be overcome?
By developing compressive strength in the surface of the materials through methods like chemical bonding with adhesive resin cements and thermal tempering.
p.13
Classification of Dental Ceramics by Composition
What is a key difference between CAD/CAM systems and conventional crowns?
There are distinct differences between the various types of ceramics used.
p.10
Challenges in Bonding and Cementation Techniques
What are the indications for crowning in young patients?
Young patients with large pulp chambers, high aesthetic demands, patient request, and metal allergy.
p.6
Bonding Strategies for Different Materials
How can the attachment of resin cement to ceramic be increased?
By using air abrasion to improve bonding.
p.6
Polycrystalline Materials in Dentistry
What are the mechanical properties of ceramics without a glass matrix?
They have higher strength due to a densely-packed crystalline network.
p.12
Glass-Based Ceramics and Their Properties
How can the abrasive wear of opposing tooth structure be reduced for maxillary anterior crowns?
Abrasive wear can be reduced by glazing the crown, although leucite used to enhance strength and optical properties can aggravate this effect.
p.12
Challenges in Bonding and Cementation Techniques
What materials are needed for repairing dental ceramics, and what is a limitation of the repair?
Repairs require hydrofluoric acid, silane, and composite, but the finish is never as good as the original.
p.7
Bonding Strategies for Different Materials
What happens during the light activation of resin cement?
Free radicals are formed that react with functional groups of the silane coupling agent and resin monomer to form a covalent polysiloxane (-Si-O-Si-) network.
p.5
Glass-Based Ceramics and Their Properties
What is the main advantage of zirconia over alumina in dental ceramics?
Zirconia has higher flexural strength (900-1200 MPa) and high fracture toughness (9-10 MPa m-1), which hinders the propagation of cracks.
p.3
Glass-Based Ceramics and Their Properties
Why are leucite-reinforced ceramics considered aesthetically advantageous for anterior teeth?
They offer high translucency for aesthetics in anterior regions, low translucency for discoloured teeth, and polychromatic blocks that are good for anterior teeth because the incisal edge is more translucent.
p.3
Glass-Based Ceramics and Their Properties
What are the four levels of translucency available for lithium disilicate ceramics?
MO (for discoloured prep), LT (posterior restorations), MT (brighter than LT but more translucent), and HT (inlays/onlays/veneers).
p.11
Glass-Based Ceramics and Their Properties
Why should glass-based ceramics be used cautiously in patients who brux?
Because they are brittle and have inferior tensile strength, which can lead to microcracks.
p.12
Mechanical Bonding in Dental Materials
What are the recommended crown design features to minimize stress concentration?
Careful preparation and crown design should minimize stress concentration, minimize tensile forces, and use shoulder and chamfer finishing lines to minimize oblique forces in the margins.
p.12
Challenges in Bonding and Cementation Techniques
Why is cementation considered technique-sensitive in dental restorations?
Cementation is technique-sensitive because it requires good technique and moisture control, and all steps must be followed to achieve a good result.
p.7
Types of Cements and Their Applications
What type of cement can be used without silica-coating and is self-adhesive?
Phosphate-modified composite resin (MDP) cement.
p.7
Bonding Strategies for Different Materials
How do total-etch resin cements bond to the tooth?
Largely through micromechanical means, as the tooth is etched as normal.
p.2
Bonding Strategies for Different Materials
What is the role of silane treatment in bonding glass-based ceramics?
Silane treatment acts as a coupling agent, bonding dissimilar materials by establishing a bond between ceramic and composite resin, and improving wetting.
p.8
Classification of Dental Ceramics by Composition
What is the main reason castable ceramics are not commonly used anymore?
They are not really used anymore due to advancements in other methods.
p.7
Hybrid Ceramics and Their Advantages
What is the composition of Vita Enamic, a type of hybrid ceramic?
Vita Enamic is a polymer-infiltrated ceramic network (PICN) with an inorganic ceramic network (leucite-based glassy phase and zirconia-reinforced) and an organic acrylic polymer infiltrate (e.g., UDMA and TEGDMA).
p.11
Polycrystalline Materials in Dentistry
What is transformation toughening and which material benefits from it?
Transformation toughening is a process where external stresses cause a metastable tetragonal phase to transform into a stable monoclinic phase, resulting in volumetric expansion that can compress crack tips. Zirconia benefits from this process.
p.2
Glass-Based Ceramics and Their Properties
For what dental applications are glass-based ceramics mainly used?
Glass-based ceramics are mainly used for veneers.
p.2
Glass-Based Ceramics and Their Properties
What is the flexural strength of glass-based ceramics like Vita TM Mark II?
The flexural strength of glass-based ceramics like Vita TM Mark II is 100 MPa.
p.8
Challenges in Bonding and Cementation Techniques
How does exposure to HCl affect ceramics compared to zirconia?
Exposure to HCl significantly increases roughness in ceramics compared to zirconia.
p.3
Glass-Based Ceramics and Their Properties
What is the primary benefit of leucite filler in dental ceramics?
Leucite filler dissolves preferentially in etching, creating micromechanical retentive features.
p.8
Classification of Dental Ceramics by Composition
What are the indications for using pressed ceramics?
Crown, core material, veneer, inlay/onlay.
p.8
Classification of Dental Ceramics by Composition
What are the disadvantages of pressed ceramics?
Equipment-heavy and time-consuming.
p.3
Glass-Based Ceramics and Their Properties
What happens to lithium disilicate CAD blocks after firing at 850°C for 20-25 minutes?
The lithium disilicate crystallizes as the lithium metasilicate reacts with the silicate, resulting in 70% lithium disilicate by volume, higher crystallinity, and altered grains.
p.2
Glass-Based Ceramics and Their Properties
How does adding filler to glass-based ceramics improve their properties?
Adding filler to glass-based ceramics improves their mechanical properties such as strength, thermal expansion, and contraction by interspersing small crystals in the ceramic structure, which impedes the propagation of cracks.
p.5
Polycrystalline Materials in Dentistry
What is the survival rate of Procera AllCeram after 5 and 10 years?
97% after 5 years and 93.5% after 10 years.
p.7
Hybrid Ceramics and Their Advantages
What is a disadvantage of hybrid ceramics compared to zirconia, LD, and In-Cerams?
Hybrid ceramics have lower fatigue-resistance compared to zirconia, LD, and In-Cerams.
p.3
Glass-Based Ceramics and Their Properties
What are the mechanical properties of tempered e.max CAD after firing?
It can withstand 350-450 MPa, with increased fracture toughness and flexure strength relative to leucite.
p.7
Hybrid Ceramics and Their Advantages
Why do hybrid ceramics have improved resistance to fracture?
The polymeric component allows hybrid ceramics to undergo slight plastic deformation, which improves resistance to fracture.
p.11
Glass-Based Ceramics and Their Properties
What is a major problem associated with glass-based ceramics in dental applications?
Propensity to fracture, which is related to the size, distribution, and nature of the crystalline phases.
p.11
Glass-Based Ceramics and Their Properties
What is the effect of ion exchange on dental ceramics?
Placing dental ceramics in a potassium nitrate salt tank cooler than the glass transition temperature causes Na+ ions on the ceramic's surface to exchange with K+ ions from the salt tank, compressing the silicate system.
