Cavity Lining Materials Flashcards
what are some disadvantages of restorative materials?
- may not make intimate contact with the tooth surface
- heat release during setting/curing
- release of chemicals (pulpal irritants)
what is the function of a lining material used in conjunction with restorative materials?
- prevents gaps
- acts as a protective barrier
what is the difference between a cavity base and a cavity lining?
Cavity base = thick mix placed in bulk (dentine replacement)
Cavity lining = thin coating over exposed dentine
what is the purpose of a liner?
- pulpal protection
- therapeutic/calm down inflammation within pulp
- palliative to reduce patient symptoms prior to definitive treatment being carried out
what does a liner protect the pulp from?
- chemical stimuli in the filling material (initial pH of material also)
- thermal stimuli (exothermic setting & heat conduction of materials)
- bacteria and endotoxins (microleakage)
what are the ideal properties that should be seen in a lining material?
- 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
explain the ideal usage tendencies of a lining material that are desired?
- easy to mix
- long working time
- short setting time (command set ideal)
why is it important that the thermal conductivity of a lining material is low?
to prevent heat expelled from exothermic reactions/conduction of heat through metal materials irritating the pulp
what is meant by the thermal expansion coefficient of a material?
the change in length per unit length for a temperature rise of 1°C (ppm°c^-1)
what should the thermal expansion coefficient of a lining material be?
should try to match the thermal expansion coefficient of the tooth
why is it important that lining materials have high compressive strength properties?
to allow placement of filling without it breaking
what is an example of a liner material?
setting calcium hydroxide
what is an example of a base material?
zinc oxide based cements
what is an example of a material that can be used as a cavity base OR liner??
glass ionomer & resin modified glass ionomer
what are the two main constitutes of setting calcium hydroxide liner?
base & catalyst
what is the setting calcium hydroxide liner base aspect composed of?
- calcium hydroxide
- zinc oxide
- zinc stearate
- N-ethyl toluene sulphonamide
what is the setting calcium hydroxide liner catalyst aspect made up of?
- butylene glycol disalicylate
- titanium dioxide
- calcium sulphate
- calcium tungstate
what is the setting reaction of a setting calcium hydroxide liner?
a CHELATION reaction between the ZnO and the butylene glycol disalicylate
what is the initial setting calcium hydroxide liner cement’s pH?
around 12
what are some positive properties of CaOH liner?
- quick setting time
- radiopaque
- easy to use
what are some negative properties of CaOH liners?
- low compressive strength
- unstable and soluble (if cavity leaks then the lining will disappear)
what are some uses of Zinc Oxide Eugenol (ZOE) Cements and related materials?
- linings/base in deep cavity
- temporary restorations
- root canal sealer
- periodontal dressings
what are some properties of zinc oxide eugenol?
- adequate working time
- relatively rapid setting time
- low thermal conductivity
- low strength (20MPa)
- radiopaque
what is the most common material used for lining cavities?
glass ionomer
why are glass ionomer cements ideal lining materials? (in terms of properties)
- 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
when should calcium hydroxide be used as a liner over glass ionomer?
calcium hydroxide should only be used when the cavity approaches the pulp/ pulp is exposed
when calcium hydroxide liner is placed, what else also needs to be done before placing final restoration?
covered with RMGIC to protect the Ca(OH)2 and prevent dissolution beneath the restoration
what are the different zinc oxide based cements?
- zinc phosphate
- zinc polycarboxylate
- zinc oxide eugenol
- resin modified ZOE
- ethoxybenzoic acid
