Cavity Lining Materials

Question 1

What is the purpose of a lining material?

Answer 1

Prevent gaps within the restorative material and act as a protective barrier over the pulp.

Question 2

Why is it important to place a liner under an amalgam restoration?

Answer 2

Amalgam has a very high thermal diffusivity and thermal conductivity. So a liner acts to protect the pulp from temperature that could be transferred through the restoration.

Question 3

What is a cavity base?

Answer 3

Thick mix placed in bulk.
Dentine replacement used to minimise the bulk of the material or block out undercuts.

Question 4

What is a cavity lining?

Answer 4

Thin coating of material over exposed dentine.

Question 5

What is the purpose of a liner?

Answer 5

Protection from thermal, chemical or bacterial stimuli.
Therapeutic- calm down inflammation within the pulp and promote plural healing.
Palliative- reduce patient symptoms prior to definitive treatment being carried out.

Question 6

What are the ideal properties of a lining material?

Answer 6

Easy to mix
Long working time
Short setting time
Low thermal conductivity
Similar thermal expansion and thermal diffusivity to dentine.
High compressive strength
EM similar to dentine
Radiopaque
Form a chemical bond to dentine
Low solubility
Cariostatic
Biocompatible

Question 7

What type of setting reaction occurs in setting calcium hydroxide?

Answer 7

Chelation reaction between zinc oxide and butylene glycol disalicylate.

Question 8

What is the name of setting calcium hydroxide?

Answer 8

Dycal.

Question 9

What is the mode of action of setting calcium hydroxide?

Answer 9

High alkaline pH of Dycal kills cariogenic bacteria.
The cement causes irritation tot he odontoblast layer of dentine, tertiary dentine forms and this forms a calcified bridge, walling off the base of the cavity to the pulp.

Question 10

Why must you always cover setting calcium hydroxide with RMGI?

Answer 10

It is very unstable and soluble, if the cavity leaks, then the lining will disappear.

Question 11

What is a use of setting calcium hydroxide?

Answer 11

Place over an exposed pulp.

Question 12

What reaction occurs in zinc oxide eugenol cement?

Answer 12

Acid base reaction between zinc oxide and Eugenol.

Question 13

Why can ZOE not be used under amalgam restorations?

Answer 13

Low compressive strength- would crumble under the pressure of amalgam packing into the cavity.

Question 14

Why can ZOE not be placed under a composite restoration>

Answer 14

Eugenol inhibits the set of resin based filling materials, softens them and causes discolouration.

Question 15

Why is resin modified ZOE better than conventional ZOE?

Answer 15

Resin modified ZOE has resin added, which does not take part in the setting reaction but gives it a stronger back bone to the set material.

Question 16

What is the generic name for resin modified ZOE?

Answer 16

Kalzinol.

Question 17

Why is glass ionomer a good lining material?

Answer 17

Bonds directly to dentine and seals the dentine tubules.
Bond directly to composite that is placed over it.
Releases fluoride over time.

Question 18

Why is RMGI (vitrebond), the gold standard cavity lining material?

Answer 18

Least soluble
Releases benzoyl iodide and benzoyl bromides which can kill some remaining bacteria present
Bonds directly to composite.

Question 19

Which material should be used as a liner when the dentine quality is poor?

Answer 19

RMGI (vitrebond).

Question 20

When should setting calcium hydroxide be used?

Answer 20

When the cavity approaches the pulp.

Question 21

What criteria need to be met for you to apply a direct pulp cap?

Answer 21

Dentine surrounding the exposure is sound
Red, homogenous and blood filled tissue is observed on the surface of the pulp wound, with no yellowish, liquefied areas or dark non-bleeding zone.
Haemostats can be achieved within 203 minutes.

Question 22

What is the role of a direct pulp cap?

Answer 22

induce hard tissue formation by odontoblasts that sea the exposure and contribute to pulp vitality.

Question 23

What clinical and radiographic signs will be evident, if direct pulp capping has been successful?

Answer 23

Mineralised barrier over the pulp.
- dentine bridge.
Positive pulp vitality tests.
Pulp tissue free from inflammation and no PA pathology.

Question 24

What are some limitations of setting calcium hydroxide?

Answer 24

Poor bonding to dentine.
Mechanical instability and continuous resorption after placement.
Dentine bridge that forms can be porous, allowing micro-organisms access to the pulp.