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