Cavity Lining Materials Flashcards
What is the purpose of a lining material?
Prevent gaps within the restorative material and act as a protective barrier over the pulp.
Why is it important to place a liner under an amalgam restoration?
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.
What is a cavity base?
Thick mix placed in bulk.
Dentine replacement used to minimise the bulk of the material or block out undercuts.
What is a cavity lining?
Thin coating of material over exposed dentine.
What is the purpose of a liner?
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.
What are the ideal properties of a lining material?
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
What type of setting reaction occurs in setting calcium hydroxide?
Chelation reaction between zinc oxide and butylene glycol disalicylate.
What is the name of setting calcium hydroxide?
Dycal.
What is the mode of action of setting calcium hydroxide?
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.
Why must you always cover setting calcium hydroxide with RMGI?
It is very unstable and soluble, if the cavity leaks, then the lining will disappear.
What is a use of setting calcium hydroxide?
Place over an exposed pulp.
What reaction occurs in zinc oxide eugenol cement?
Acid base reaction between zinc oxide and Eugenol.
Why can ZOE not be used under amalgam restorations?
Low compressive strength- would crumble under the pressure of amalgam packing into the cavity.
Why can ZOE not be placed under a composite restoration>
Eugenol inhibits the set of resin based filling materials, softens them and causes discolouration.
Why is resin modified ZOE better than conventional ZOE?
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.