DM - cement: crowns, posts and bridges

Question 1

When cementing a post and core what surfaces does the luting cement lie on?

Answer 1

all surfaces of post
all contacting surfaces of core

Question 2

what marker can be placed to accommodate luting cement thickness?

Answer 2

die relief

Question 3

what is the function of luting cement?

Answer 3

added retention
seals the space between restoration and tooth

Question 4

what are the 2 types of luting cements?

Answer 4

active
passive

Question 5

what is an active luting cement?

Answer 5

bonds to tooth and restoration chemically
has a role in retention - mechanical interlocking
creates a marginal seal

Question 6

what is a passive luting cement?

Answer 6

fills gap between tooth and restoration
no bond between tooth and restoration
retention due to tooth prep

Question 7

in what ways can tooth prep create renetion?

Answer 7

taper
prep height
surface roughness and mechanical interlocking

Question 8

list the general ideal properties of a luting cement

Answer 8

biocompatible
retentive
mechanical
marginal seal
low film thickness
ease of use
pseudoplastic
radioopaque
aesthetic
antibacterial

Question 9

why must a luting cement be biocompatible?

Answer 9

it contacts tooth tissue and periodontal tissues

Question 10

what mechanical properties should a luting cement have?

Answer 10

high tensile strength
fracture toughness
fatigue strength
wear resistance

Question 11

what properties must a luting cement have to create a marginal seal?

Answer 11

low solubility

Question 12

what does low film thickness allow for in a luting cement?

Answer 12

full seating of restoration
good marginal adaptation

Question 13

why should a luting cement be pseudoplastic?

Answer 13

coats fit surface of restoration without slumping but flows readily on fitting under pressure

Question 14

list types of passive luting cements?

Answer 14

zinc phosphate
zinc polycarboxylate
GI
RMGI

all are water based as aqueous acid

Question 15

what luting cement is the oldest and routinely used by 30% UK dentists?

Answer 15

zinc phosphate

Question 16

what are the components of zinc phosphate luting cement?

Answer 16

powder: zinc oxide, 10% magnesium oxide
liquid: aqueous phosphoric acid

Question 17

what is the working time of zinc phosphate?

Answer 17

3-6mins

Question 18

how is zinc phosphate mixed?

Answer 18

gradual incorporation of powder over large area on mixing slab
fluid is slaked - small amount powder added to fluid 1 min before to extend setting time

Question 19

what can be used when mixing zinc phosphate to increase its working time?

Answer 19

chilled slab

also increases its strength

Question 20

describe the setting reaction of zinc phosphate luting cement

Answer 20

acid base reaction
exothermic
viscosity increases rapidly
shrinks slightly on setting

Question 21

is zinc phosphate antibacterial?

Answer 21

no

Question 22

what does the pH of zinc phosphate depend on?

Answer 22

thickness of mix

Question 23

describe the mechanical properties of zinc phosphate luting cement

Answer 23

good compressive strength
low tensile strength (brittle)
high solubility

Question 24

what are the components of zinc polycarboxylate?

Answer 24

powder: zinc oxide, 10% magnesium oxide
liquid: aqueous copolymer of polyacrylic acid (30-40%)

alternatively - acid freeze dries and added to powder, distilled water added

Question 25

describe the setting reaction of zinc polycarboxylate luting cement

Answer 25

acid dissolves in zinc oxide

Question 26

what is the working time of zinc polycarboxylate luting cement?

Answer 26

30-40 seconds can be extended by adding tartaric acid, mixed on a cold glass slab

Question 27

what pH is zinc polycarboxylate?

Answer 27

3-4 less injurious on pulp

Question 28

is zinc polycarboxylate antibacterial?

Answer 28

yes

Question 29

what is zinc polycarboxylate adhesive to?

Answer 29

enamel and dentine some metals (base metal alloys via oxide layer)

Question 30

describe the mechanical properties of zinc polycarboxylate luting cement

Answer 30

lower compressive strength higher tensile strength reaches 80% full strength in 1 hour soluble in acid

Question 31

describe the presentation of GI luting cement

Answer 31

powder: fluoro-alumino-silicate glass liquid: aqueous poly alkenoic acid alternatively - acid freeze dried and added to powder, distilled water added

Question 32

describe the setting reaction of GI luting cement?

Answer 32

chemical set dissolution of calcium ions, then aluminium gelation hardening

Question 33

setting time of GI luting cement?

Answer 33

initial set 3-6 mins hardening can take 7 days

Question 34

why may GI initially cause pulpal inflammation?

Answer 34

acidity

Question 35

compared to ZnO cements, describe the mechanical properties of GI

Answer 35

better compressive strength low tensile strength and fracture toughness less soluble

Question 36

what are the constituents of RMGI cement?

Answer 36

GI plus monomer e.g., HEMA, Bis-GMA

Question 37

What are the advantages of RMGI compared to GI?

Answer 37

low solubility improved biocompatibility improved fluoride release improved physical properties (tensile strength) improved adhesion to tooth tissue

Question 38

what are the disadvantaged of RMGI?

Answer 38

can undergo hygroscopic expansion - may lead to crack propagation avoid under conventional all ceramic crowns

Question 39

what is the name of RMGI luting cement?

Answer 39

FUGI PLUS

Question 40

what indirect restorations are suitable for the use of RMGI luting cement?

Answer 40

zirconia core/ CAD CAM crowns

Question 41

what are the constituents of resin based luting cements?

Answer 41

silanated filler resin - Bis GMA

Question 42

how are resin-modified luting cements cured?

Answer 42

chemical and light

Question 43

what indirect restorations are suitable for conventional resin based luting cements?

Answer 43

all ceramic restorations indirect composite or quartz fibre posts - veneers, dentine bonded crowns

Question 44

what indirect restorations are suitable for chemically adhesive resin based luting cements?

Answer 44

resin retained bridges metal veneers poorly retained indirect restorations

Question 45

how are resin based luting cements bonded to ceramic?

Answer 45

bond to tooth in conventional way - acid etch, rinse, dry, dentine bonding agent bond to fit surface of ceramic - etch with hydrofluoric acid, just before cementing silane coupling agent air dry

Question 46

why can hydrofluoric acid only be used by the lab?

Answer 46

very toxic must be neutralised tends to slump

Question 47

how do you bond to a base metal alloy?

Answer 47

roughen fit surface with 50um aluminia grit chemically adhesive resin luting cement - modified bis GMA resin

Question 48

how do you bond to precious metal alloys?

Answer 48

chemically adhesive resin luting cement modify fit surface