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 uni 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
what is the thermal expansion coefficient of enamel and dentine?
enamel = 8.3ppm°C^-1 dentine = 11.4ppm°C^-1
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
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PMMA (acrylic resin)38
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DMS vocabulary11
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Amalgam47
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Bonding to Teeth13
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Cavity Lining Materials29
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Elastomeric Impression Materials12
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Metals and Alloys 227
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Partial Denture Alloys22
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Resin Modified Glass Ionomer Cements11
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Glass Ionomer Cements37
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Metals and Alloys 138
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Gypsum44
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Alginate Impression Materials39
