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30 Cards in this Set
- Front
- Back
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What are the criteria of an acceptable cement? |
-Adequate resistance to dissolution in oral environment -Film thickness of 25 um or less -Must develop an adequately strong bond through mechanical interlocking and adhesion -High strength in tension, shear, and compression -Good fracture toughness to resist stresses at the restoration-tooth interface -Good manipulation properties (ie working and setting times) -Must be biologically acceptable |
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What is the composition of zinc phosphate cement? |
Powder: zinc oxide w/ up to 10% magnesium oxide Liquid: Phosphoric acid (45-64%), water (30-35%), aluminum (2-3%), and zinc (0-9%) |
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Describe how to mix zinc phosphate cement. (Per Fleck's cement) |
1. Use a chilled glass slab 2. 0.8 g of powder (2 capfuls filled up to the shoulder) poured on the slab and flattened into a rectangle. 3. Divide powder into quarters; then divide one quarter into 2 eighths; then one eighth into 2 sixteenths 4. Drop 0.3 mL liquid (12 drops) onto slab 5. Incorporate 1/16 and mix for 15 seconds, spreading out over a large surface area to dissipate the heat. Add the 2nd 1/16 and mix for 15 secs, then 1/8 and mix for 15 secs, then 1/4 and mix for 20 secs, then 2nd 1/4 and mix for 20 secs, then final 1/4 and mix for 35 seconds. |
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By what means does zinc phosphate cement cause retention? |
Mechanical interlocking only; no chemical bond |
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What are advantages and disadvantages of ZP cement? |
Advantages: mixed easily, set sharply to relatively strong mass Disadvantages: pulpal irritation due to acidity, lack of antibacterial action, brittle, lack of adhesion, solubility in oral fluids |
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What is the composition of zinc polycarboxylate cement? |
Powder: zinc oxide, 1-5% tin or magnesium oxide; sometimes 10-40% aluminum oxide or other reinforcing filler, small percentage of stannous fluoride Liquid: ~40% aqueous solution of polyacrylic acid or an acrylic acid copolymer -Molecular weight of polymer ranges 30K-50K, accounts for viscous nature -Acid concentration 32-42% by weight |
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By what mechanism of adhesion does polycarboxylate cement work? |
Chemical bond; bonds to the calcium ions on the surface of the enamel and dentin, bond is greater to enamel due to higher calcium concentration |
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Is polycarboxylate cement used for cement-retained implant restorations? |
No; studies have shown that the fluoride in Durelon, for example, may corrode titanium and thus should not be used |
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What component in glass ionomer cement allows for bonding to the tooth structure? |
Polyacrylic acid |
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How are glass ionomer cements classified? |
I: luting crowns, bridges, ortho brackets IIa: Esthetic restorative cements IIb: Reinforced restorative cements III: Lining cements, bases |
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Describe the glass composition of glass ionomer. |
-All contain silica, calcia, alumina, fluoride. -Ratio of alumina to silica accounts for its reaction with polyacrylic acid -Barium, strontium, and other high atomic number metal oxides are added for radioopacity -Glass particles are ground to sizes ranging from less than 15 um to about 50 um, depending on use indication |
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Describe the liquid composition of glass ionomer. |
-Previously, aqueous polyacrylic acid was used, but now they are copolymers of itaconic, maleic, or tricarboxylic acids -Tartaric acid: rate-controlling additive; allows wider range of glasses to be used, improves handling properties, decreases viscosity, lengthens shelf life, increases working time, shortens setting time |
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Describe the composition of set glass ionomer cement. |
Undissolved glass particles with a silica gel coating embedded in an amorphous matrix of calcium and aluminum polysalts containing fluoride. |
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What is the setting reaction of glass ionomer? |
-When the powder and liquid are mixed, the acid begins to dissolve the glass, releasing sodium aluminum, calcium, and fluorine ions. -Water serves as the reaction medium -Calcium ions serve as the cross linking agent for polyacrylic acid, which is then replaced by aluminum ions over the next 24 hours |
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What is the mechanism of adhesion of glass ionomer to the tooth? |
Chelation of the carboxyl groups of polyacrylic acid with the calcium of the apatite in enamel and dentin |
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Describe RMGI. |
-Also known as hybrid ionomer cement. -Liquid: HEMA, water solution of polyacrylic acid, polyacrylic acid modified with methacrylate monomer -Powder: fluoroaluminosilicate glass particles of aconventional GIC plus initiators, such as camphorquinone,for light curing and/or chemical curing |
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What type if reaction is glass ionomer? |
Acid-base reaction |
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What are the different types of resin cements? |
Chemical or self-cured - used to cement metal and opaque ceramic core restorations Light-cured - used for any light cured indications or dual cured Dual-cured - used for translucent restorations; begin curing with light and continue with chemical reaction |
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What is the composition of resin cements? |
For powder-liquid materials: Powder: finely divided borosilicate or silica gass with fine polymer powder and organic peroxide initiator Liquid: mixture of bis-GMA and/or other dimethacrylate monomers containing and amine promoter for polymerization In light-cured and dual-cured versions, light sensitive polymerization systems such as diketones (eg camphorquinone) and amine promoters are present |
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What type of reaction is resin cement? |
Polymerization reaction |
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What are advantages of resin cements? |
-High strength -Low oral solubility -High micromechanical (and possible chemical) bonding to prepared enamel,dentin, alloys, and ceramic surfaces |
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What are disadvantages of resin cements? |
-Technique sensitive -More difficult sealing -Higher film thickness -Possible leakage and pulpal sensitivity -Difficulty in removal of excess cement |
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What are advantages of GIC? |
-Easy mixing -High strength and stiffness -Leaches fluoride -Good resistance to acid dissolution -Potential adhesive characteristics -Translucency |
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What are disadvantages of GIC? |
-Initial slow setting and moisture sensitivity -Variable adhesive characteristics -Radiolucency -Possible pulpal sensitivity |
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What are advantages of RMGI? |
-Dual cure -Fluoride release -Higher flexural strength than GIC -Ease of handling -Capable of bonding to composite |
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What are disadvantages of RMGI? |
-Setting expansion that may lead to cracking of all ceramic restorations (and roots, if used for post cementation) |
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What are advantages of zinc phosphate cement? |
-Low cost -Long clinical history -High rigidity -Long working time -Easy to use |
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What are disadvantages of zinc phosphate cement? |
-No bond to tooth -Slow setting time -Moisture sensitivity during mixing -Pulpal sensitivity |
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Describe zinc oxide-eugenol cements. |
Powder: zinc oxide Liquid: eugenol |
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What is a major disadvantage of zinc oxide-eugenol as a temporary cement? |
Eugenol inhibits the setting of composite, so if used as a temporary cement, the final prosthesis should not be cemented with a resin cement unless the tooth has been thoroughly cleaned of residual eugenol. |
