Dental Restorative Materials: GICs W9 Flashcards
What are the two types of Glass Ionomer Cements?
GIC
Resin Modified GIC
What are the contraindications to using GIC?
- In stress bearing
- Class I, II, IV
- Cusp replacement
- xerostomia patients
- in mouth breathers
- in areas requiring high aesthetics
What are some indications of using GIC?
- Restoration in permanent teeth
- Small Class I, III, V
- Abrasion/erosion
- Restoration in primary teeth: I, V, Rampant and nursing bottles
- Luting and cementing- inlay, only crown, veneers, orthodontic brackets
- Endodontics
- Sandwich technique
- Atraumatic restorative treatment
What are disadvantages of GIC?
- Brittle
- Low fracture resistance
- Low Modulus of Elasticity
- Water Sensitive during setting
- Radiolucency
What are advantages to GIC?
- Adhesion to tooth structure
- Biocompatible
- Anticariogenic
- Conservation tooth prep
- Aesthetic
- Less technique sensitive
- Little shrinkage and good marginal wear
- Low solubility
What are essential components of GIC?
- Poly acid
- FAS Glass
- Water
- Tartaric acid
What are the 3 steps of GI setting reaction?
- Acid attack (dissolution)
- Hydrogel (gelation)- water protections, prevents dissolution
- Maturation (hardening)- water addition, prevents dehydration
What is rapidly released in the setting reaction?
Ca2+ loosely bound to glass
What is not involved in the setting reaction?
F and Na, combine and released as NaF
What happens in the stage 1 acid attack?
- Carboxylic acid attacks the surface of the glass releasing metal ions
- COOH + H20 → COO- + H30+
What happens in stage 2 hydrogel?
- COO- + M form salt bridge, ionic crosslinking
- Ca is released more rapidly, forms initial crosslink
- must be protected from additional water to prevent loss of metal cations
What happens in stage 3 maturation?
- Al is released more slowly, replaces Ca overtime
- Takes up to 7 days, Al has stronger crosslink
- Water uptake, takes up to several months
- Water loss leads to cracking, chalky appearance
What is the role of tartaric acid?
- Controls the setting characteristics
- Delays set, cement is easier to mix and speeds up set
- Ca preferentially binds to tartaric acid forming calcium tartrate instead of salt bridge matrix
What is the role of water?
- Solvent for polyacrylic acid
- prevents contamination and dehydration
- medium where setting reaction takes place- provides a means for ion transport
- Component of set cement- chemically bound and provides stability to restoration
What does water contamination do?
- Loss of translucency
- Susceptible to erosion
What does dehydration do?
Chalky appearance, cracking and softening
What are the 2 types of water in GIC?
- Loosely bound: removed easily by drying
- Tightly bound: cannot be removed
How do you prevent contamination/dehydration?
- Use a rubber dam or cotton rolls and suction for isolation
- Place a covering for the GI restoration
What is the best covering for GIC?
Light-polymerised bonding agent:
- acts as a glaze
- improved aesthetics
- decreases cracking and loss of translucency
- increase in strength
How is fluoride released?**
- It is a by product of the setting reaction.
- Occurs over a period of time. Peaks at 24 hrs and stabilises at 3-4 months
- Buffering: F released in acidic conditions
- Reservoir effect: F taken up by GIC and can be recharged with F
How does GIC adhere to tooth surface?
- Micro-mechanical interlocking
Removal of smear layer with conditioner before placement of GIC restoration with 10-25% polyacrylic acid.
Direct bonding with tooth and cement, as acid displaces P042- and Ca2+ ions on enamel and dentine surface, the in surface energy increases
- True chemical bonding = interfacial zone of ion exchange between carboxyl groups of cement and ca2 of tooth.
What product decreases cracking?
Light-polymerised bonding agent
You have stabilised the health of your patients gums, but they aren’t happy with the look of tooth 21. What material can you use to restore 21?
RMGIC- because chemical retention is not needed.
What is the atraumatic restorative technique?
- Hand instruments to remove caries
- GIC used
- Unreliable electrical power supplies- where there are no drills!
- Suitable for middle/low income countries
What is the open sandwich vs closed sandwich?
- Open: GIC exposed to oral environment, used with no enamel is at gingival margin
- Closed: CR completely encases GIC, used when enamel is at gingival margin
What is the open/closed sandwich technique?
- When you layer restorative materials in a cavity prep
- Combines desirable properties of various materials
- GIC placed as a liner/base, CR on top
What are the issues of concern with RMGI?
- Light curing: varies with depth, lower layers receive less light. Placed in layers less than 2mm
- Cytotoxic to pulp: unreacted HEMA
What are the improved properties of RMGIC?
- Greater working time
- Set on demand
- Fewer problems with water
- Immediate finishing
- Better aesthetics
- Higher tensile strength and fracture toughness
- Resistance to microleakage
- Bond to CR
What is the setting reaction of RMGI?
- Neutralisation - acid base reaction
- Addition polymerisation- free radical polymerisation of methyl acrylate, light activated and chemically activated polymerisation
How and why do you expand the clinical use of GIC?
- Resin added to GIC
- Because normal GIC has poor aesthetics, slow setting reaction and sensitivity to water in initial setting
Your patient has short-duration pain on the carious mandibular first molar.
Pulp testing was conducted, and the tooth was determined to be vital. You take a radiograph.
Your diagnosis is reversible pulpits. You want to perform caries control and re-evaluate the tooth in four to six week.
What can you do in the mean time?
Remove caries
Cavity condition- wash out and dry
Bulk fill material- carve it back
Light cure/time cure
Your patient is a drug user and is seeking dental treatment. You identify rampant caries where isolation and control of the soft tissue can be very difficult. What is an ideal restorative material for this patient?
GIC- helps with sensitivity
How does GIC differ from other restoratives?
- Adheres to enamel and dentine
- Anticariogenic fluoride activity
- Moisture tolerant
What is the difference between a liner and a base?
And what type of GIC are these placed under?
- Liner: placed under the restoration near pulp, a chemical barrier and reduces micro leakage.
- Base: thicker and reduces chemical irritation, and thermal protection. Place where injured pulp.
Type III
What type of GIC would you use for core build up?
VI (6)
Type I and II GICs are used for?
Type I: Luting (cementing crowns)
Type II: restoration: aesthetics and restorative reinforced
What components added to FAS increases fluoride release?
SrO, SrF2
What is the proper name for Glass Ionomer?
Glass Polyalkenoate
How are GICs made?
- Fuse the components (SiO2, AL2O3, AlF3) at a high temp and shock cool them.
- Ground the substances into particles between 20-50nm
- Ions released from glass are important for setting, solubility and release of F.
How do the forms of GICs differ?
When acid and base in powdered form and adding water.
A vacuum dired polyacid
In Stage 1 Dissolution, what metals ions are released first and then after?
First: Na, Ca, Sr
Second: Al
What gives GICs their radiopacity?
Strontium Sr2+
What is a trivalent vs divalent cation?
Trivalent: Aluminium
Divalent: Calcium
Describe the final set state of a GIC
Al and Ca cross-bridges with poly acid surrounded by silica gel.
What is the term “true chemical bonding?”
Interfacial zone of ion exchange
Tooth bonded to material directly
Between carboxyl groups of the cement, and Ca2+ of tooth.
Adherences of GIC to tooth structure.
What are the components of RMGI?
- Powder: fluroaluminisilicate glass particles BASIC
- Monomer: hydrophilic HEMA, dimethacrylate added to acidic liquid
- Initiator system: CQ or Dual cure (acid/base + monomer light cure)
- Liquid: poly acrylic acid copolymer ACID contains initiator system
What is the monomer, photo initiator and base used in RMGICs?
HEMA, CQ, Fluoroaluminisilicate
What class would you use RMGICs on?
Class I, II, III for primary
Class V for permanent
Why do we use open/closed sandwich technique?
- Reduced post op sensitivity
- Protect pulp
- Fluoride release
- Can be placed in single bulk layer
- Radioopqaue
What is a cermet?
- Ceramic and metal
- Metal reinforced GI - fused with Au,Ag Ti,
- Improved radiopacity
- High compressive strength
What type of GIC is not recommended for ART?
RMGIC- can’t light cure
What type of water reduces the risk of cracking overtime?
tightly bound
A cavity to be restored with GIC should be conditioned with…?
Polyacrylic acid
What does the GIC release that restores and protects teeth?
Fluoride
Why is GIC the best restorative material in children?
It can bond to enamel and dentine
What is the mechanism of adhesion of GIC with tooth surface?
Carboxyl group
