Quiz April

What are difference between base and liner? What are the ideal requirements of dental cements when used for cavity base? What are the main differences between resin cement and conventional cements? What is the main function of calcium-hydroxide cement? How GIC bond to tooth structure?

Liners: materials that are placed as thin coatings, and their main function is to provide a barrier against chemical irritation. They do not function as thermal insulators. Selected primarily for pulpal medication. Base: cement base (1 to 2 mm) function as barriers against chemical irritation, provide thermal insulation, and resist forces applied during condensation of the restorative material.

6. When used for cementation or luting, they should have: sufficient low viscosity to give a low film thickness, adequate working time, optical properties for cementation of translucent restoration. 7. When used for cavity bases and liners: protect the pulp from effects of other restorative materials, thermal insulation under large metallic restorations, chemical protection, electrical barrier to galvanism, rapid strength to permit packing of a filling materials and high modulus of elasticity to prevent fracture due to masticatory forces.

Resin cements Basically its fluid composite, achieved by reduce amount of fillers. Advantages: Good compressive and tensile strengths. High tensile strength than conventional cements. Resistance to water dissolution. Relatively resistant to acid dissolution. Can enhance strength of ceramic restoration.

3- Light- cured calcium hydroxide cements: Its recently available and easy of application. Ca (OH)2 + Bis-GMA + barium sulphate + light sensitive material Properties: The pH (11-12). This degree of alkalinity stimulate odontoblast cells to produce reparative dentine. Easy manipulation Rapid hardening in thin layer Good sealing, high solubility, low compressive st. 5 MPa, they have antibacterial effect.

Bonding Ionic bond Chelation of carboxyl groups of the polyacids with calcium in the apatite of enamel and dentine. To achieve long lasting bond, the prepared surface must be clean and dry to remove a smear layer.

In the following multiple-choice questions, one or more responses may be correct 1. Glass ionomer cement is used in which of the following ways? a. As a base for thermal and mechanical protection of the pulp under composite restorations b. For cementation of orthodontic bands c. For retention of cast metallic restorations d. For cementation of ceramic crowns

2. An increased amount of powder in a cementing consistency mix of zinc phosphate cement does which of the following? a. Decreases the solubility b. Increases the strength c. Decreases the film thickness d. Increases the setting time

3. The components of zinc oxide-eugenol cement may include which of the following? a. Ethoxybenzoic acid (EBA) in the eugenol to improve strength b. Alumina or acrylic polymer in the powder to improve strength c. Zinc acetate in the powder as an accelerator d. Zinc oxide and eugenol formulated as pastes in separate tubes

c. Increases in temperature and humidity shorten the setting time. 4. Which of the following statements are true for zinc oxide-eugenol cements? a. Zinc oxide powder is added to the eugenol liquid on a treated paper pad in six equal increments. b. Equal lengths of the base paste and the accelerator paste are mixed together until the mix has a uniform color. c. Increases in temperature and humidity shorten the setting time. d. The reaction is not reversible if there is moisture

5. Hybrid ionomer introduced to overcome some of the following disadvantages of GIC. a. moisture sensitivity b. short working time c. short setting time d. Low flouride relase

2. Which of the following statements are true? a. The marginal adaptation of a casting to the tooth is affected by the film thickness of the cement. b. Typical values of film thickness and compressive strengths of glass ionomlr cements are 25m and 90 to 220 MPa, respectively. c. The retaining action of glass ionomer cement is primarily one of mechanical bonding between surface irregularities of the tooth and casting by the cement. d. Glass ionomer cement is as strong in tension as it is in compression.

3. Which of the following statements are true for glass ionomer cements? a. The powder is added to the liquid in two portions to control the consistency of the mixture. b. Total mixing time varies between 30 and 60 seconds. c. Cooling the mixing slab slows the setting reaction. d. Once the cementing or primary consistency is obtained, the base consistency is achieved by the addition of powder to the mix.

4. An increased amount of powder in a cementing consistewy mix of zinc phosphate cement does which of the following? a. Decreases the solubility b. Increases the strength c. Decreases the film thickness d. Increases the setting time

5. The components of zinc oxide-eugenol cement may include which of the following? a. Ethoxybenzoic acid (EBA) in the eugenol to improve strength b. Alumina or acrylic polymer in the powder to improve strength c. Zinc acetate in the powder as an accelerator d. Zinc oxide and eugenol formulated as pastes in separate tubes

6. Which of the following statements are true for zinc oxide-eugenol cements? a. Zinc oxide powder is added to the eugenol liquid on a treated paper pad in six equal increments. b. Equal lengths of the base paste and the accelerator paste are mixed together until the mix has a uniform color. c. Increases in temperature and humidity shorten the setting time. d. A mix appears thick at the start of mixing, but after 30 seconds of additional spatulation it becomes more fluid.

7. Which of the following statements about hybrid ionomer cements are true? a. Some hybrid ionomer cements are not recommended for cementation of all-ceramic inlays, onlays, or crowns because of their water sorption. b. They release more fluoride than glass ionomer cements. c. They have no measurable solubility when tested by lactic acid erosion. d. The powder is incorporated into the liquid within 30 seconds to give a mousse-like consistency.

8. The components of zinc polycarboxylate cements include which of the following? a. Zinc polyacrylate crystals in water b. A solution of polyacrylic acid in water c. Zinc oxide powder d. A paste of zinc oxide and one of acrylic acid

9. Which of the following statements are true? a. The pH of the mix of zinc polycarboxylate cement is initially acidic but the acid is weakly dissociated. The pH increases to neutrality in several days. b. Hybrid ionomer cements cause minimal postoperative sensitivity. c. Glass ionomer cement acts as an obtundant like zinc oxide-eugenol cement.

10. Which of the following statements are true for zinc polycarboxylate cements? a. The powder is incorporated into the liquid within 30 seconds. b. The working time can be extended by use of a cooled glass mixing slab. c. After a cement loses its luster and becomes stringy, it is ready to be used.

11. Which of the following statements apply to the comparison of zinc polycarboxylate and zinc phosphate cement? a. The viscosity of zinc polycarboxylate cement increases more rapidly with temperature than that of zinc phosphate cement. b. Zinc polycarboxylate cements provide superior clinical retention of crowns compared with zinc phosphate cements. c. Both cements depend primarily on mechanical bonding for retention clinically. d. When first mixed, zinc polycarboxylate cements are slightly more acidic than zinc phosphate cements.