Cavity lining materials

Question 1

constituents of setting calcium hydroxide liner

Answer 1

2 pastes
base
- calcium hydroxide 50%
- zinc oxide 10%
- zinc iterate >1%
- Plasticiser - 40%

catalyst
- butylene glycol disalicylate reactive agent

Question 2

initial Ph of setting calcium hydroxide

Answer 2

12

Question 3

CaOH liner - effects on the tooth

Answer 3

bactericidal to cariogenic bacteria
- due to high alkaline pH
high Ph irritates odontoblast layer
- results in production of tertiary dentine
- eventually forms calcified bridge walling base of cavity off from pulp

Question 4

properties of setting calcium hydroxide liner

Answer 4

quick setting time
radiopaque
easy to use
BUT
low compressive strength
unstable and soluble
- if cavity leaks lining will disappear
- may even disappear in contact with moist dentine

Question 5

types of zinc oxide based cements

Answer 5

zinc phosphate
zinc polycarboxylate
zinc oxide eugenol
resin modified ZOE
EBA ZOE

Question 6

zinc phosphate cement - features

Answer 6

acid base reaction
powder and liquid
easy to use
cheap

Question 7

zinc phosphate cement - powder constituents

Answer 7

zinc oxide 90%
- main reactive ingredient
magnesium dioxide >10%
- gives white colour
- increases compressive strength
other oxide - alumina and silica
- improve physical properties
- alter shade of set material

Question 8

`zinc phosphate cement - liquid constituents

Answer 8

aqueous solution of phosphoric acid
oxides which buffer the solution
- aluminium oxide - ensures even consistency of set material
- zinc oxide - slows reaction giving better working time

Question 9

zinc phosphate disadvantages

Answer 9

low initial pH - approx 3
- can cause pulpal irritation - can take 24 hours to return to near
exothermic setting reaction
not adhesive to tooth or restoration
not cariostatic
final set takes 24 hours
brittle
opaque

Question 10

how does zinc polycarboxylate cement differ from zinc phosphate ?

Answer 10

phosphoric acid replaced with polyacrylic acid
can bond to tooth surfaces
less heat of reaction
low initial pH but returns to neutral more quickly

Question 11

zinc polycarboxylate cement disadvantages

Answer 11

difficult to mix
difficult to manipulate
opaque
soluble in oral environment at low pH
lower modulus and compressive strength than zinc phosphate

Question 12

ZOE cements - uses

Answer 12

linings in deep cavities
- under amalgam restorations
temporary restorations
root canal sealer
- 24 hours set
periodontal dressings
- fast setting, 5 minutes

Question 13

ZOE properties

Answer 13

adequate working time
relatively rapid setting time
low thermal conductivity
low strength
radiopaque
high solubility
- disintegration of material
- eugenol when liberated can have therapeutic effect on pulp reducing pain

Question 14

Kalzinol is an example of…

Answer 14

resin modified ZOE

Question 15

dycal is an example of…

Answer 15

setting calcium hydroxide

Question 16

Vitrebond is an example of…

Answer 16

resin modified glass ionomer cement

Question 17

Purpose of a cavity liner

Answer 17

pulpal protection from
- chemical stimuli from unreacted chemicals in filling material, or the initial pH
- thermal stimuli e.g. exothermic setting reaction of composite to heat conducted through metal fillings
- bacteria and endotoxins

therapeutic
- calms inflammation within pulp and promotes pulpal healing
palliative
- reduce patient symptoms prior to definitive treatment being carried out

Question 18

What is microleakage?

Answer 18

the penetration of oral fluids and bacteria and their toxins between the restorative and cavity walls

Question 19

lining materials - ideal properties

Answer 19

ease of use
good thermal properties
good mechanical properties
radiopaque
good margins seal
insoluble
cariostatic
biocompatible
compatible with restorative materials