Cavity Lining Materials Flashcards
(45 cards)
Describe cavity lining materials
Intermediate restorative materials lining the cavity, applied before the placement of the restorative, not temporary but permanent.
What is the purpose of the cavity lining materials
Protection, palliative and therapeutic barrier to stop penetration through the dentinal tubules to protect the pulp.
What are the choices we have for using cavity lining materials before we add the restorative
Nothing
Cavity varnish
Cavity liner
Cavity base
What are some of the cavity lining material groups that we can use
- Varnishes
- Calcium Hydroxide cements
- Zinc oxide based cements
- Glass ionomer cements
- Resin modified glass ionomer cements
- Visible light cured resins
- Calcium silicate based cements
AY BAWS CAN I HABE DE NOTE PLZ
Based on the kind of restorative we use different cavity lining materials to protect the pulp
What kind of pulp protection do cavity varnishes provide
Chemical protection
What kind of pulp protection do cavity liners provide
Pulp medication
Thermal/electrical protection
What kind of pulp protection do cavity bases provide
Thermal/electrical protection
Mechanical protection
What is cavity varnish designed to do
- Seal dentine
- Reduce diffusion through dentin
- Decrease microleakage
- No strengthening
- Does not bond chemically to dentin
Describe the composition of cavity varnish
- Natural resins e.g. copal
- Synthetic resins e.g. polystyrene
- Solvent e.g. alcohol, acetone, ether
- Some calcium hydroxide and/or zinc oxide
What does cavity liner seal and do
Seals exposed dentin
Promotes health of the pulp and adheres to the tooth structure and has antibacterial action
Name some types of cavity liner
Calcium hydroxide
Zinc Oxide eugenol
Zinc oxide non-eugenol
What does cavity base do
Replaces dentin Blocks out undercuts Insulation High strength Minimises bulk of restorative as it is quite thick
What is an undercut
When the cavity goes into the dentin and errr yh the cavity base can fill that
Name some cavity base materials
- Reinforced zinc oxide eugenol
- Visible light cured resins
- Zinc phosphate
- Zinc polycarboxylate
- Glass ionomer
- Resin modified glass ionomer
What are the 2 forms of zinc oxide eugenol cement
Two paste or powder-liquid form
Describe the composition of the powder component of zinc oxide eugenol cement
- Main component (ZnO/MgO)
- Fillers SiO2, Al2O3
- Dicalcium phosphate, mica or rosin - Improves mixing
- Zinc salt 1% accelerates set
Describe the composition of the liquid component of zinc oxide eugenol cement
- Eugenol or oil of cloves
- other oils may also modify viscosity
- Acetic acid 1% - accelerates set
- Water - small amount - essential to set
Describe the setting reaction of zinc oxide eugenol cement
- Acid-base reaction
- Reaction of zinc oxide with eugenol to form zinc eugenolate, a chelate complex
- Water initiates the reaction and is a by product of the reaction
ZnO + 2HE ZnE2 + H2O
Describe the basic features of the chemical structure of eugenol
A substituted phenol
Weakly acidic
What will produce a faster and stronger set of zinc oxide eugenol cement
Higher powder to liquid ratio and smaller particle size
Describe the pH changes in the zinc oxide eugenol setting process
Initial pH of 5.5-6 and then goes up 6-8 in the set cement
What are the advantages of zinc oxide eugenol cement
- Easy mix and handle
- Fast set in the mouth
- Moisture accelerates set
- Non irritant pH close to the neutral
- Obtudant (calming effect on the pulp) when placed on dentin
- Good sealing characteristics
- Protects the pulp from chemical irritation
- Good thermal insulator
What are the disadvantages of zinc oxide eugenol cement
- Low compressive and tensile strengthes
- High water solubility
- Eugenol is a potential allergen, smells strong and is a mild irritant when in direct contact with the pulp
- Eugenol inhibits vinyl polymerisation so can’t be used under composites and compomers
