Ceric restorative materials Flashcards
What are the four main groups of materials used in dentistry?
Ceramics, composites, metals, polymers
What is a ceramic?
Inorganic, non metallic material comprising of compounds formed between metallic and non metallic elements by wintering at high temps
What are the different microstructures of ceramics?
Glassy, crystalline or a mixture of both
What is a drawback of porcelain?
Weak - easily cracks therefore contraindicated for posterior teeth
What is feldspathic porcelain?
Porcelain with improved strength but still only used anteriorly
What are the different types of dental ceramics?
Feldspathic, Leucites, Lithium disilicates, Alumina, Zirconia
Examples of lithium disilicate ceramics?
EMAX, empress
How can ceramics be classified?
Lots of different ways eg indications, composition, processing methods, firing temp, microstructure etc
What are the different processing techniques for ceramics?
Condensation, hot isostatic pressing, computer aided milling
How are ceramics processed using the condensation technique?
Foil adapted over the die
Ceramic layered over the die
It is vibrated to allow excess water to rise to the surface which can be blotted away
Restoration is fired
Function of wrapping the die in foil before ceramic layering?
Allows space for cement
What is hot isostatic pressing?
Similar to lost wax technique
Heat pressing a pre fabricated ingot
Which processing technique do EMAX crowns use?
Hot isostatic pressing
Advantage of CAD/CAM milling?
Can allow for a single visit
Quicker
Reduces human error
Disadvantage of computer aided milling?
Machine is high cost
Which type of tools are required for computer aided milling for ceramics?
Diamond encrusted
Which type of tools are required for computer aided milling of zirconia?
Carbide
What is the three stage process of computer aided milling?
Roughing, finishing, detailed sequence
Benefit of pressed ceramics?
Superior margin fit which is especially useful where margin detail is not ideal
What are the two types of microstructure for feldspathic ceramics?
Conventional (porcelain), Leucite reinforced (porcelain)
What are some optical properties of feldspathic porcelain?
High translucency and colour stability
The ceramic thickness can impact light transmission
What are the physical properties of feldspathic porcelain?
Microcracks form during function
Leucite reinforced is stronger
Not suitable for posterior restorations or areas of high masticatory load
Glazed feldspathic porcelain can damage the opposing dentition 40x more than a gold restoration
Disadvantage of glazed feldspathic porcelain?
Wears away opposing dentition at a quick rate
How to cement feldspathic porcelain?
Acid etch
Use of a silane coupling agent
Dual, light or self cure or self adhesive resin
What are the two main processing techniques for lithium disilicate?
Ingot two stage crystallisation via pressing
CAD three stage crystallisation process
What are the optical properties of lithium disilicate?
Very good, maybe better than porcelain
What are the two techniques for staining lithium disilicates?
Cut back technique
Layering technique
What type of ceramics are EMAX and Empress?
Lithium disilicate
Indications of lithium disilicate restorations?
Anterior or posterior
Contraindications of lithium disilicate ceramics?
Not for deep subgingival preps in patients with bruxism or greatly reduced dentition
What are the preparation design requirements for lithium disilicate crowns?
No angles or sharp edges
Prepare margins with deep chamfer or rounded shoulder
Smooth finish line
Even reduction of the anatomical shape
Ensure the indicated dimensions match the stipulated minimum wall thickness that manufacturer recommends
How do you cement lithium disilicate restorations?
Conventionally or adhesively
RMGIC if prep is retentive and moisture control is difficult
Adhesive cementation is best - etch, apply silane, apply adhesive, apply resin cement
What type of material is Nobel Procera AllCeram?
Alumina
Applications of alumina in crown and bridge work?
Nil
Applications of alumina?
Implant abutments for Nobel pearl implants
Orthodontic brackets
Filler for composite and bone cement materials
Indications for alumina restorations?
PJC - anterior teeth but insufficient strength for posterior
In-ceram alumina - Implants for single teeth, anterior three unit fixed partial denture, inlays, anterior crowns
What are the preparation design requirements for alumina restorations?
Axial reduction of 0.8 - 1.0mm
Occlusal reduction of 2mm
Don’t use sharp line angles, boxes with butt shoulders etc
Keep margins supragingivally wherever possible, or equigingival
What do we use to cement alumina restorations?
GIC or RMGIC
Can do air abrasion on the fitting surface to increase surface area and follow up with a phosphate based coupling agent
What is the purpose of doing air abrasion on the fitting surface of alumina crowns?
Increases the surface area to aid adhesion
Which type of coupling agent should be used with alumina restorations?
Phosphate based
What are the three allotropic forms of zirconia?
Monoclinic, tetragonal, cubic exceeding
Which allotropes of zirconia need to be stabilised?
Tetragonal and cubic phases
Benefit of zirconia?
Strength
What are the preparation requirements for a zirconia restoration?
Monolithic - Axial reduction of 0.8mm
Veneering porcelain - axial reduction of 1.5mm, occlusal reduction of 1.2-1.5mm
What are the optical properties of zirconia?
White opacity - good for masking things
Staining can be added for aesthetics
What are the physical properties of zirconia?
Tougher and stronger than conventional glass ceramics
Hardness - can pose concerns for wear of opposing teeth especially for bruxists
What is the risk of zirconia for bruxists?
Wear of opposing teeth
What is the toughest and strongest ceramic?
Zirconia
Indications for zirconia?
Fixed dental prosthesis excluding veneers
Three used fixed dental prosthesis
Material of choice for resin bonded bridges
How is zirconia cemented?
Cannot be etched
Fitting surface prepared by sandblasting
Apply MDP containing ceramic primer
Use a self adhesive resin cement which doesn’t require separate etching or bonding
