GIC properties Flashcards
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
