DENTAL CEMENTS

SILICATE CEMENTS
1. Composition
2. Properties
  1. Silicate is the strongest of all dental cements. It has a compressive strength of 180 Mpa.
  2. Setting time is 3 - 8 min.
  3. • Its hardness (70 KHN) and coefficient of thermal expansion is closer to dentin.
  4. • It is a severe irritant to the pulp. At the time of insertion it has a pH of 2.8 and even after one month, it remains below 7.
  5. • Silicate has high solubility and disintegrates readily in oral fluids. They become stained over a period of time.
  6. • It has anticariogenic property due to release of fluoride and so the incidence of secondary caries and contact caries is less.
  7. • Its refractive index is similar to enamel and dentin. It
  8. is used as an anterior esthetic restorative material.
GLASS IONOMER CEMENT
1. Composition
  1. itaconic acid reduces viscosity of liquid and inhibits gelation
2. Classification
  1. Type I
    1. Luting cement
  2. Type II
    1. Restorative cement
  3. Type III
    1. Liner
  4. Type IV
    1. Fissure sealant
  5. Type V
    1. Orthodontic cement
  6. Type VI
    1. Core build up cement
  7. Type VIII
    1. Posterior packable GIC for
  8. Type IX
    1. atraumatic restorations
3. Properties
  1. GIC has low fracture toughness and wear resistance.
    1. Ionic Bond found
  2. ii) Very sensitive to moisture, especially during initial setting reaction.
    1. During this period, absorption of water leads to weak cement and over drying will lead to cracks in the cement.
    2. Therefore, the surface of cement should be protected by coating with varnish or cocoa butter during setting.
  3. iii) Bonds chemically to tooth structure
    1. The bond of enamel is always higher than that of dentin.
  4. iv) Relatively biocompatible -
    1. The pulpal reaction is greater than ZOE but less than zinc phosphate cement.
  5. v) Anticariogenic property is due to fluoride release.
    1. Most anticariogenic effect
4. Modifications
  1. Miracle Mix (or) silver cermet
    1. Silver-Tin alloy powder is added to GIC powder.
    2. None of the properties were improved and it gave a gray or blackish colour to the cement
    3. It is also called as silver alloy admix.
  2. Glass cermet or cermet
    1. Glass and metal (Silver-tin-titanium) powders were sintered at high temperature and made to react with liquid.
    2. It improved the fracture toughness and wear resistance and at the same time maintained the esthetics.
  3. Resin modified GIC
    1. BisGMA, TEGDMA are added to powder and HEMA to the liquid. With exposure of light polymerization is achieved
    2. provide rapid setting to minimize acidity allowing early finishing
    3. eg VITREMER*
5. Stages of setting
  1. Decomposition
  2. Migration
  3. Post set hardening
  4. Maturation
Calcium Hydroxide
1. Composition
2. Application
  1. For direct and indirect pulp capping.
  2. • In apexification technique.
  3. • In pulpotomy (apexogenesis)
  4. • As a root canal sealer
  5. • As a root canal disinfectant
  6. • As a cavity liner and base
    1. preferred agent
3. Properties
  1. solubility in water is high. So it sh exposed at the margins when used as a liner
  2. Solubility is higher when exposed to phosphoric acid and ether, so care should be taken during acid etching and application of varnish.
  3. • The cement is alkaline in nature. It has a pH of 11. The high alkalinity and its consequent antibacterial and protein-lysing effect helps in formation of "Reparative dentin".
  4. • It is an effective antibacterial agent.
ZINC OXIDE EUGENOL
1. Classification
  1. Type I
    1. For temporary cementation
  2. Type II
    1. For permanent cementation
  3. Type III
    1. Temporary filling material and base
  4. Type IV
    1. Cavity liners
2. Composition
3. Properties
  1. Solubility is highest among dental cements.
  2. • Least irritating among all dental cements, so called as pulp friendly cement.
  3. It has obtundant (or) soothing effect on the pulp in
  4. deep cavities.
4. Copal Varnish
  1. ZnO Resin
    1. Addition of Zn Acetate Accelerate Setting time
ZINC PHOSPHATE CEMENT
1. Composition
2. Setting reaction
  1. Phosphoric acid reacts with zinc oxide forming zinc phosphate. Aluminum of the liquid is essential for cement formation. It forms complexes with phosphoric acid to form zinc alumino phosphate gel
3. properties
  1. Initial acidity with pH of 4.2, becomes neutral after 48 hours.
  2. - Retentive by mechanical retention sandblasting of crowns or inlays
  3. - Similar strength to GIC, high CS, low tensile strength.
  4. - Low solubility once set
  5. - Fast setting
  6. - Moisture adversely affects cement
Zinc PolyCarboxylate Cement
1. Composition
2. Properties
  1. Because of the larger size of the polyacrylic acid molecules, it is less irritant to pulp than zinc phosphate cement.
  2. • The pH of liquid is 1.7 and that of freshly mixed cement is 3-4. After 24 hours, pH of the cement is 5-6.
  3. • Cement bonds chemically with the tooth structure due to chelation of the carboxyl group with calcium in the tooth structure.
  4. • Unlike ZnPo, cement, adhesion is better to smooth surface than rough surface.
  5. These cements are good thermal insulators and so can be used as base material.