Dental Materials 2

Front 1

Name two classic luting cements?

Back 1

Zinc phosphate cement
ZnO eugenol

Front 2

How do classic luting cements set?

Back 2

Acid base reactions

Front 3

Are classic luting cements adhesive?

Back 3

They are not strictly adhesive to tooth tissue or to restorations.

Front 4

Describe micromechanical adhesion

Back 4

Consists of intimate wetting and permeation of microscopic roughness of adherend by the adhesive

Front 5

Described chemical adhesion

Back 5

Consists of both intimate wetting and permeation described above and the 'attractive' interaction between adherend and adhesive.

Front 6

Which two luting cements are adhesive?

Back 6

-Ionomer cements
-Resin cements

Front 7

Give an example of an Ionomer cement. Why are they adhesive?

Back 7

Poly-F ( Zinc polycarboxylate)
Adhesive due to the polyacid. (acid base cement)

Front 8

How do resin cements achieve adhesion?

Back 8

Micromechanical attachment to tooth structures and to surfaces of restorations (adheres by wetting and permeation)

Front 9

What is the key role of resin cements?

Back 9

Cementation of ceramics

Porcelain is brittle therefore needs to be bonded to avoid fracture. An all porcelain restoration CANNOT be successfully cemented with traditional luting cements.

Front 10

Give two examples of resin cements.

Back 10

-Panavia
-Nexus

Front 11

When is Panavia 21 used?

Back 11

To cement metals to tooth:
>resin retained bridges
>metal/ceramic crowns

Front 12

What are the properties of Panavia 21?

Back 12

It is an anerobic curing resin cement
Claims chemical adhesion through phosphate esters in resin.

Front 13

What is Nexus 2?

Back 13

It is a 'dual curing' resin cement.

Front 14

When is Nexus 2 used?

Back 14

To cement translucent 'optically linked' restorations

Front 15

Name a mixed resin ionomer cement

Back 15

Rely-X Luting cement

Front 16

What is the difference between dentine bonding agents and resin cements?

Back 16

DBAs are resin materials used to make dental composite adhere to bond to both dentine and enamel.
Resin cements are resin materials used to cement a restoration (Usually made by indirect means) to tooth tissue and or restorations already present.

Front 17

What is a ceramic?

Back 17

Any man-made solid produced by fusion of mineral substances in a kiln.

Front 18

What is porcelain?

Back 18

A ceramic based on K-Al-Silicate

Front 19

Porcelain is brittle coz its full of cracks. List some strengthening mechanisms.

Back 19

-Glaze
-Use of permanent platinum matrix
- Porcelain fused to metal (pfm)
- porcelain bonded to dental enamel (resin bonded crown)
-Non-porcelain substitutes (glass ceramics, cad-cam ceramics)

Front 20

How does glaze strengthen porcelain?

Back 20

It reduces size of flaws in the surface of porcelain and increases its resistance to crack propagation.

Front 21

How does use of a permanent platinum foil matrix help?

Back 21

It inhibits crack propagation from the fitting surface.

Front 22

What is sintering?

Back 22

Method of making objects from powder by heating the material below its melting point until particles adhere to each other

Front 23

Name a non-porcelain dental ceramic

Back 23

Procera

Front 24

Give two disadvantages of dental ceramics?

Back 24

- thick connectors in bridgework
-heavy tooth preparations may be needed.

Front 25

How are castable glass ceramics bonded to tooth?

Back 25

bis-GMA composite resin

Front 26

Give two advantages of porcelain?

Back 26

-good aesthetics
-good longevity when used correctly

Front 27

What is a precious metal?

Back 27

Metal containing metals of high economic value e.g. gold

Front 28

What is a noble metal?

Back 28

A precious metal that is resistant to tarnish. Excludes silver

Front 29

What are low gold alloys?

Back 29

Alloys containing <75% gold

Front 30

What are gold-substitute alloys?

Back 30

Precious metal alloys not containing gold

Front 31

What are base metal alloys?

Back 31

alloys not containing precious metals to impart their corrosion resistance.

Front 32

What is the sequence of use of amalgam?

Back 32

-Proportioning (by weight or volume)
-Trituration (by hand or machine)
-Dispensing- packing,condensing,carving
- SLOW SETTING
-Polishing

Front 33

What is a wrought alloy?

Back 33

An alloy that has been mechanically worked in the solid or semi-solid state

Front 34

What is the gold composition of high gold alloys?

Back 34

80 to 90% Gold

Front 35

What are the benefits of high gold alloys?

Back 35

-Good corrosion resistance
-good bonding to porcelain

(Tin and indium migrate to surface on heating and produce oxides which aid chemical bonding of porcelain to alloy)

Front 36

What are the limitations of high gold alloys?

Back 36

-Creep of alloys may occur during the firing of porcelain, since alloys have a comparatively low melting range
-low modulus thus minimum alloy thickness of 0.5mm required

Front 37

How does porcelain stay on the metal?

Back 37

1. Micromechanical interaction
2. Chemical bonding (via oxide mixing)

Front 38

What are the advantages of Cobalt-Chromium casting alloys?

Back 38

- corrosion resistance
-biocompatible in mouth
-cheaper than gold alloys

Front 39

Which alloys can be used for porcelain fused to metal crowns?

Back 39

-Medium gold alloys
-silver palladium casting alloys
-nickel chromium casting alloys

Front 40

Why are porcelain fused to metal alloys stronger?

Back 40

- metal substructure supports the porcelain
-decreased crack propagation by bonding the inner porcelain surface to the metal
-the outer surface of porcelain is under tension therefore reduced crack propagation