Glass Ionomer Cements Flashcards
What is a glass ionomer
Group of materials that use silicate glass powder in an aqueous solution of poly acrylic acid
What is a cement
A substance that hardens to act as a base, liner, filling material or adhesive. To bind structures to each other or the tooth surface
What are the most important characteristics of a restorative material?
Aesthetics
Biocompatibility
Strength
Speed
Patient and case related factors to think about with restorability?
Patient compliance
Aesthetics
Caries risk
Aesthetic concern
Why would you treat a patient with GIC?
High caries risk
Temporary solution needed
Less cooperative patients
What are its constituents?
Constituents-
Liquid-
Poly acrylic acid
Water- hydrates the hydrogel
Itaconic acid- increases working time
Modifiers
Itacontic acid- promotes reactivity
Maelic acid- causes cement to lose moisture sensitivity faster
Classifications- based on its use?
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Class I luting cements
II restorative material
III bases and liners
IV pits and fissure sealants
V orthodontic luting
VI Core build up
VII command set (high flouride)
VIII ART
IX paediatric
Advantages of GIC?
Ability to bond to enamel and dentine
Moisture tolerant
Tooth coloured
Flouride leaching
Good biocompatibility
Chemical bond
Coefficient of thermal expansion is similar to dentine
Disadvantages of GIC?
Poor wear resistance
Vulnerability to acid erosion
Low fracture toughness- poor in high occlusal load areas
Low flexural strength
Finishing and polishing times
Types of GIC?
Conventional GIC
Conventional Reinforced GIC
Resin modified GIC (light activated, combines properties of a resin material and GIC)
Talk about the constituents of GIC
Glass powder- replacing calcium with strontium or lanthanum increases radiopacity, reduced particle size improves the physical properties, flouride improves the handling properties- slows the setting time to increase the working time
Tartaric acid
Water- essential component
PAA- increased molecular weight or concentration of PAA molecules improves the physical properties
Describe the setting reaction of GIC
Acid base reaction- PAA plus water—-hydrogen ion release
Hydrogen ions cause aluminosilicate glass to release calcium and aluminium ions - dissolution phase- which replace the H+ ions in the acid
This causes the PAA matrix (made of 2(FAS-core) to release calcium ions- this is the hardening phase, and silicone hydrogel- that is the gelation phase, rising pH, important to isolate
What is reinforced GIC
Modified conventional GIC
Compare reinforced GIC to conventional GIC and what effect does this have clinically?
Improved compressive and flexural strength, hardness, wear resistance and solubility.
Improved outcomes in load bearing areas
Improved clinical handling
Improved radiopacity
Examples of reinforced GIC
Chemflex and Fuji IX
Indications for Fuji IX (a type of reinforced GIC)
Deciduous teeth
Adult-
Restorations- class I, II and V restorations
As a core build up
Base/liner- sandwich technique
What is then definition of a resin modified GIC?
Materials set by an acid base reaction in an aqueous environment in the presence of a photoplymerisation reaction
What are the key chemical reactions with reinforced GIC?
HEMA goes to camphourquinone which goes to poly-HEMA
HEMA (2-hydroxyethyl-methacrylate)
What is reinforced GIC in relation to conventional GIC
Conventional GIC plus resins and photoinitiators goes to resin modified GIC
What is the setting reaction for RMGIC? N
Acid base reaction : Polyalkenoic acid in the presence of HEMA plus water releases hydrogen ions
Hydrogen ions cause aluminosilicate glass in the presence of camphorquinone to release calcium and aluminium ions
The aluminosilicate glass is activated by light to cause the PAA matrix (2(FAS-core-polyHEMA) to release calcium ions (hardening phase) and silicone hydrogel
What are the benefits/ importance of the setting reaction for Resin modified GIC?
Immediate hardening can cause
3 setting phases: ionic cross linking, photopolymerisation (light), free radical cure (dark)
What are some examples of RMGIC?
Vitremer and Fuji II LC
Indications of Fuji II LC?
Deciduous teeth
Adult-
Restorations- class III and class V (cervical erosion, abractions, root surface caries)
Core build up
As a base/liner- sandwich technique
Caution with RMGIC?
Increased risk of allergy due to HEMA
Hydrophilic- if it absorbs too much water it will expand
Potential for disolcouration
What can you do to prevent adverse effects when using RMGIC
Trimming and polishing under water coolant to prevent dehydration and shrinkage
What about mixing RMGIC?
Powder and liquid ratio measurement prone to errors
Less expensive
Increased porosity
Centrifugal frequency 2950 rpm
3 seconds in 80 mm diameter orbit
What about isolation for RMGIC?
Careful to find balance between desiccation and excessive moisture contamination during placement
Avoid salivary contamination of the cavity - use cotton wool rolls and slow suction
What about adhesion for GIC
No separate bonding agent needed- can sometimes use a conditioner
Mechanism is micromechanical interlocking (cement tags) and chemical bonding (ionic bond between calcium in the enamel and dentine and carboxyl ions in the GIC), (calcium phosphate polyalkenoate bond)
Bond is compromised if the tooth surface is contained with blood or saliva
Talk about the finishing and polishing of GIC
Finishing - contouring for optimal marginal finish and occlusal anatomy
Polishing- smoothing the surface with abrasives to create low surface roughness and high surface lustre
Initially use hand instruments to shape
Use steel burs with Vaseline (avoid water to prevent expansion) to remove excess
Place protective resin
When fully set (24 hours+ for conventional)
Use rotary abrasives (so flex disks, tungsten carbide burs and diamond finishing burs)
Note the manufacturer’s instructions- may vary by brand, RGMI less susceptible it can be placed on the same day as placement
Why caution with finishing and polishing GIC? And what to do about this?
Heat generation may damage the pulp.
Resins may be placed as a varnish after placement and hardening to protect the GIC during the setting process
Talk about the stages of flouride release for GIC
Flouride enters the tooth from the restoration
Equilibrium is reached between tooth surface and restoration
Flouride leaches into salvia
Tooth and restoration depleted of flouride
Topical replenishment of flouride reacharges the cement
Talk about the indications for Fuji II LC, Fuji IX and Fuji triage
Fuji II LC primary teeth, triple cure
Fuji triage - temp, paediatric, elderly, fissure protection, root surface protection
Fuji IX - temp, self cure
What are the benefits and disadvantages of Fuji as a base/liner
Bacteriostatic
Thermal insulation
But
Does not lay down reparative dentine
Need 0.5mm thickness of dentine - if less than 0.5mm between it and pulp then CaOH liner first
What are some examples of GI base/ liners?
Vitrebond
GIC as a luting cement- describe
Similar composition to GIC restorative material
Smaller glass particle size to allow thinner film thickness
Example of GI luting cement?
FujiCem2
Describe ART
Minimally invasive approach which involves removal of caries using hand instruments alone
Usually without use of anaesthesia
Then restoration with adhesive materials e.g. GIC
Technique has helped to bridge the gap in the provision of treatment to rural communities, senior citizens, children and dental phobic patients.
Combines both restorative and preventive care, and causes minimal discomfort to patients.
Describe the ART procedure
Isolate the tooth to be restored with cotton wool rolls.
Clean the tooth with water and cotton wool pledgets.
Widen the entrance to the lesion with hand instruments.
Remove all carious tissues with an excavator
Clean the cavity and occlusal surfaces with cotton wool pledgets and water.
Provide pulpal protection with calcium hydroxide liner if necessary.
Condition the cavity walls and occlusal surfaces of the tooth according to the manufacturerís instructions.
Mix the glass-ionomer cement according to instructions and insert the material into the cavity, overfilling slightly.
Apply pressure with a gloved finger to the occlusal surface of the tooth, thus condensing the restoration (finger-press technique)
Check for correct occlusion.
Remove any excess material with a carver or similar flat plastic instrument
Readjust the bite if necessary, making sure that the occlusal fissures are sealed
Apply Vaseline to the restoration to protect the glass-ionomer during the initial setting reaction.
Instruct the patient to avoid eating for about an hour to allow the material to set completely.
