Dental Cements

Front 1

What are the criteria of an acceptable cement?

Back 1

-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

Front 2

What is the composition of zinc phosphate cement?

Back 2

Powder: zinc oxide w/ up to 10% magnesium oxide

Liquid: Phosphoric acid (45-64%), water (30-35%), aluminum (2-3%), and zinc (0-9%)

Front 3

Describe how to mix zinc phosphate cement. (Per Fleck's cement)

Back 3

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.

Front 4

By what means does zinc phosphate cement cause retention?

Back 4

Mechanical interlocking only; no chemical bond

Front 5

What are advantages and disadvantages of ZP cement?

Back 5

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

Front 6

What is the composition of zinc polycarboxylate cement?

Back 6

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

Front 7

By what mechanism of adhesion does polycarboxylate cement work?

Back 7

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

Front 8

Is polycarboxylate cement used for cement-retained implant restorations?

Back 8

No; studies have shown that the fluoride in Durelon, for example, may corrode titanium and thus should not be used

Front 9

What component in glass ionomer cement allows for bonding to the tooth structure?

Back 9

Polyacrylic acid

Front 10

How are glass ionomer cements classified?

Back 10

I: luting crowns, bridges, ortho brackets

IIa: Esthetic restorative cements

IIb: Reinforced restorative cements

III: Lining cements, bases

Front 11

Describe the glass composition of glass ionomer.

Back 11

-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

Front 12

Describe the liquid composition of glass ionomer.

Back 12

-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

Front 13

Describe the composition of set glass ionomer cement.

Back 13

Undissolved glass particles with a silica gel coating embedded in an amorphous matrix of calcium and aluminum polysalts containing fluoride.

Front 14

What is the setting reaction of glass ionomer?

Back 14

-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

Front 15

What is the mechanism of adhesion of glass ionomer to the tooth?

Back 15

Chelation of the carboxyl groups of polyacrylic acid with the calcium of the apatite in enamel and dentin

Front 16

Describe RMGI.

Back 16

-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

Front 17

What type if reaction is glass ionomer?

Back 17

Acid-base reaction

Front 18

What are the different types of resin cements?

Back 18

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

Front 19

What is the composition of resin cements?

Back 19

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

Front 20

What type of reaction is resin cement?

Back 20

Polymerization reaction

Front 21

What are advantages of resin cements?

Back 21

-High strength

-Low oral solubility

-High micromechanical (and possible chemical) bonding to prepared enamel,dentin, alloys, and ceramic surfaces

Front 22

What are disadvantages of resin cements?

Back 22

-Technique sensitive

-More difficult sealing

-Higher film thickness

-Possible leakage and pulpal sensitivity

-Difficulty in removal of excess cement

Front 23

What are advantages of GIC?

Back 23

-Easy mixing

-High strength and stiffness

-Leaches fluoride

-Good resistance to acid dissolution

-Potential adhesive characteristics

-Translucency

Front 24

What are disadvantages of GIC?

Back 24

-Initial slow setting and moisture sensitivity

-Variable adhesive characteristics

-Radiolucency

-Possible pulpal sensitivity

Front 25

What are advantages of RMGI?

Back 25

-Dual cure

-Fluoride release

-Higher flexural strength than GIC

-Ease of handling

-Capable of bonding to composite

Front 26

What are disadvantages of RMGI?

Back 26

-Setting expansion that may lead to cracking of all ceramic restorations (and roots, if used for post cementation)

Front 27

What are advantages of zinc phosphate cement?

Back 27

-Low cost

-Long clinical history

-High rigidity

-Long working time

-Easy to use

Front 28

What are disadvantages of zinc phosphate cement?

Back 28

-No bond to tooth

-Slow setting time

-Moisture sensitivity during mixing

-Pulpal sensitivity

Front 29

Describe zinc oxide-eugenol cements.

Back 29

Powder: zinc oxide

Liquid: eugenol

Front 30

What is a major disadvantage of zinc oxide-eugenol as a temporary cement?

Back 30

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.