Cavity Lining Materials

Question 1

what are some disadvantages of restorative materials?

Answer 1

• may not make intimate contact with the tooth surface
• heat release during setting/curing
• release of chemicals (pulpal irritants)

Question 2

what is the function of a lining material used in conjunction with restorative materials?

Answer 2

• prevents gaps

- acts as a protective barrier

Question 3

what is the difference between a cavity base and a cavity lining?

Answer 3

Cavity base = thick mix placed in bulk (dentine replacement)

Cavity lining = thin coating over exposed dentine

Question 4

what is the purpose of a liner?

Answer 4

• pulpal protection
• therapeutic/calm down inflammation within pulp
• palliative to reduce patient symptoms prior to definitive treatment being carried out

Question 5

what does a liner protect the pulp from?

Answer 5

• chemical stimuli in the filling material (initial pH of material also)
• thermal stimuli (exothermic setting & heat conduction of materials)
• bacteria and endotoxins (microleakage)

Question 6

what are the ideal properties that should be seen in a lining material?

Answer 6

• easy to use (mix, long working time, short setting time)
• low thermal conductivity
• should match the thermal expansion coefficient of tooth
• low thermal diffusivity
• high compressive strength
• similar modulus to dentine
• radiopaque
• LOW solubility
• fluoride releasing/antibacterial
• biocompatible

Question 7

explain the ideal usage tendencies of a lining material that are desired?

Answer 7

• easy to mix
• long working time
• short setting time (command set ideal)

Question 8

why is it important that the thermal conductivity of a lining material is low?

Answer 8

to prevent heat expelled from exothermic reactions/conduction of heat through metal materials irritating the pulp

Question 9

what is meant by the thermal expansion coefficient of a material?

Answer 9

the change in length per uni length for a temperature rise of 1°C (ppm°c^-1)

Question 10

what should the thermal expansion coefficient of a lining material be?

Answer 10

should try to match the thermal expansion coefficient of the tooth

Question 11

what is the thermal expansion coefficient of enamel and dentine?

Answer 11

enamel = 8.3ppm°C^-1
dentine = 11.4ppm°C^-1

Question 12

why is it important that lining materials have high compressive strength properties?

Answer 12

to allow placement of filling without it breaking

Question 13

what is an example of a liner material?

Answer 13

setting calcium hydroxide

Question 14

what is an example of a base material?

Answer 14

zinc oxide based cements

Question 15

what is an example of a material that can be used as a cavity base OR liner??

Answer 15

glass ionomer & resin modified glass ionomer

Question 16

what are the two main constitutes of setting calcium hydroxide liner?

Answer 16

base & catalyst

Question 17

what is the setting calcium hydroxide liner base aspect composed of?

Answer 17

• calcium hydroxide
• zinc oxide
• zinc stearate
• N-ethyl toluene sulphonamide

Question 18

what is the setting calcium hydroxide liner catalyst aspect made up of?

Answer 18

• butylene glycol disalicylate
• titanium dioxide
• calcium sulphate
• calcium tungstate

Question 19

what is the setting reaction of a setting calcium hydroxide liner?

Answer 19

a CHELATION reaction between the ZnO and the butylene glycol disalicylate

Question 20

what is the initial setting calcium hydroxide liner cement’s pH?

Answer 20

around 12

Question 21

what are some positive properties of CaOH liner?

Answer 21

• quick setting time
• radiopaque
• easy to use

Question 22

what are some negative properties of CaOH liners?

Answer 22

• low compressive strength

- unstable and soluble (if cavity leaks then the lining will disappear)

Question 23

what are some uses of Zinc Oxide Eugenol (ZOE) Cements and related materials?

Answer 23

• linings/base in deep cavity
• temporary restorations
• root canal sealer
• periodontal dressings

Question 24

what are some properties of zinc oxide eugenol?

Answer 24

• adequate working time
• relatively rapid setting time
• low thermal conductivity
• low strength (20MPa)
• radiopaque

Question 25

what is the most common material used for lining cavities?

Answer 25

glass ionomer

Question 26

why are glass ionomer cements ideal lining materials? (in terms of properties)

Answer 26

• low thermal conductivity & diffusivity
• thermal expansion similar to dentine
• high compressive strength
• radiopaque
• good marginal seal
• less soluble than other liners
• fluoride release
• can bond to composite resin
• don’t require surface treatment

Question 27

when should calcium hydroxide be used as a liner over glass ionomer?

Answer 27

calcium hydroxide should only be used when the cavity approaches the pulp/ pulp is exposed

Question 28

when calcium hydroxide liner is placed, what else also needs to be done before placing final restoration?

Answer 28

covered with RMGIC to protect the Ca(OH)2 and prevent dissolution beneath the restoration

Question 29

what are the different zinc oxide based cements?

Answer 29

• zinc phosphate
• zinc polycarboxylate
• zinc oxide eugenol
• resin modified ZOE
• ethoxybenzoic acid