GIC properties Flashcards
(14 cards)
List the properties of GIC
Adhesion
Fluoride
Biocompatibility
Solubility
Dimensional change
Fracture resistance and wear
Thermal expansion
Colour and translucency
Radiopacity
Describe the adhesion property of GIC
• Chemically bonds to enamel and dentine
The higher the mineral content, the greater the bond. • In the order of strongest to the weakest bond: Enamel, sclerotic dentine, sound dentine, caries affected dentine
Describe the fluoride property of GIC
- The fluoride ions are not a structural component of the matrix thus they leach out
- Following placement, the initial fluoride release is quite high but declines rapidly during the first week and stabilises to a low but constant level over 2 – 3 months.
- Glass ionomer has the potential to act as a fluoride reservoir
- Advantages: remineralisation of surrounding tooth structure, inhibition of plaque formation and possible reduction in the recurrence of caries
Describe the biocompatibility property of GIC
- Gingiva and oral mucosa are very tolerant to glass ionomer
- Freshly mixed glass ionomer is very acidic with pH of 1.6, although it rises in an hour
- GIC should not placed directly over exposed pulp.
- Provided 0.5mm of dentine is between the glass ionomer and the pulp, pulpal reaction is relatively benign
- In deeper cavities, a spot application of calcium hydroxide should be placed on the deepest spot
Describe the solubility property of GIC
- Solubility of the slow set autocure cements is high if not adequately protected against water contamination
- The surface of glass ionomer can be damaged in the presence of low pH, so application of acidulated phosphate fluoride solution (pH 3.0) will lead to partial dissolution
- In conditions such as severe xerostomia, autocure glass ionomer will only last for a year, resin- modified glass ionomer appear to be more resistant to dissolution
Describe the dimensional change property of GIC
- RMGIC contracts approximately 3% by volume on setting
- Resin-modified glass ionomers show a small initial shrinkage at the time of light activation due to the polymerisation of the resin component
- Overtime, the set material will take up water and expand to some degree and will negate any setting shrinkage
Describe the fracture resistance and wear property of GIC
- Susceptible to brittle fracture as it lacks rigidity compared with hybrid composite and amalgam
- Avoid occlusal bearing load and bending
- Silver cements improves abrasion resistance
- Limited wear resistance, should not be used in direct contact with opposing teeth
- Sensitive to acid which can lead to increased erosion and wear
Describe the thermal expansion property of GIC
• Glass ionomers are very similar to tooth structure in their thermal behaviour
Describe the colour and translucency property of GIC
- Both autocure and resin-modified provide adequate colour matching and transluency
- For autocure, translucency will take several days to develop
- Some resin-modified glass ionomers have been shown to susceptible to darkening with time
- Titanium Oxide needs to be added to restore to a clinically acceptable colour. Eg. Ketac Ag, Riva Silver
Describe the radiopacity property of GIC
- Radiopacity can be achieved by incorporation of barium (Ba), strontium (Sr) or lanthanum (La)
- Most glass ionomers are more radiopaque than dentine and enamel
Describe the indication of luting cements, mentioning:
- Powder to liquid ratio
- Radiopacity
- Setting rate
- Used to cement crowns, bridges, inlays and ortho appliances
- Has tensile strength and abrasion resistance
- Presence of continuing fluoride release
- Setting rate: fast
- Powder to liquid ratio: less than restorative material
Describe the indication of restorative GIC cements, mentioning
- Radiopacity
- Setting rate
- Autocure: slow resistance to water uptake and loss
- Resin- modified: fast set, immediate resistance to water uptake
- Radiopaque
- Adhesion through the ion-exchange mechanism = strong and eliminates leakage
Describe the indication of lining cements, mentioning:
- Powder to liquid ratio
- Radiopacity
- Used as a thermal barrier in restorations
- Powder to liquid ratio: less than restorative type
- Radiopaque: always
Describe the indication of GIC base cements, mentioning:
- Powder to liquid ratio
- Radiopacity
- Setting rate
- Used in combination with composite resin
- Setting rate: fast set
- Powder to liquid ratio: 3:1 or greater
- Always use the strongest available material with highest possible powder content and restore completely
- Radiopaque: always
