Cavity Lining Materials Flashcards
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
What are the uses of Zinc oxide eugenol cement
ZOE cements are used in applications where strength isn’t important but low irritancy is
- Not in direct contact with the pulp
- Thermal insulating base
- Temporary restorations
- Intermediate restorations
- Long term cementation
- Endodontic use
- Periodontal dressing
Describe the composition of the powder component of EBA cement
ZnO - 60-75%
Fillers - SiO2, Al2O3 - 20-35%
Hydrogenated rosin - 6%
Describe the composition of the liquid component of EBA cement
- 50-65% of the eugenol in ZOE cement is replaced by o-ethoxybenzoic acid
- 35-50% eugenol
Is o-ethoxybenzoic acid more acidic than eugenol
yup
What are the properties and uses of EBA cements
- Properties similar to ZOE
- EBA cements have better strength
- EBA cements have lower water solublility
- Poor handling characteristics
- Uses similar to ZOE cements but used little in reality as other materials are available
What are the 2 pastes for calcium hydroxide cements called
Base and catalyst
What can the base pastes for calcium hydroxide cements be made of
Salicylate ester 40% e.g. butylene glycol disalicylate
Filler e.g. TiO2, CaSO4, BaSO4
What can the catalyst pastes for calcium hydroxide cements be made of
Ca(OH)2 50%
ZnO 10%
Plasticiser 40% e.g. toluene sulphonamide, zinc stearate
Describe the calcium hydroxide cement setting reaction
Acid-base reaction:
- Disalicylate reacts with Ca(OH)2 and ZnO
- Calcium and zinc disalicylate forms
What are the advantages of calcium hydroxide cements
- Easy to mix and handle
- Rapid hardening in thin layers
- Moisture accelerates set
- Good seal
- Alkaline pH 9-12, can neutralise acid materials e.g. zinc phosphate cements
- Antibacterial
- Stimulate reparative/sclerotic/ secondary dentin - contact with pulp causes necrosis layer that calcifies
- compatible with composites
What are the disadvantages of calcium hydroxide cements
- Low strength even when fully set
- Weakened by exposure to moisture
- Can dissolve completely acid conditions where marginal leakage occurs
- Can undergo plastic deformation at mouth temperature
What are the uses of calcium hydroxide cement
- Cavity lining, especially in deep cavities, pulp capping
- With composites as ZOE cements inhibit setting of composites
- Care must be taken when acid etching
- Strong enough to withstand amalgam condensation pressures
- Thermal insulating agents
- Endodontic use
What accelerates the setting of ZOE and CH cements
Moisture in the mouth
AY BAWS CAN I HABE DE NOTE PLZ
CH cements stimulate secondary dentin formation
What is a suspension liner and what is it made of
This is a non-setting, thick layer of a suspension of calcium hydroxide in water. Methyl or ethyl cellulose can be added for strength
What visible light cured dental composites can be used as cavity liners
BisGMA
UDMA
Phosphonated
Name some fillers that are used in visible light cured resins
Ca(OH)2
Fluoride releasing glass
Hydroxtapatite
Calcium Silicate
What are the advantages of using visible light cured resins as cavity liners
- Tougher and less soluble
- Increased resistance to etchants
- Can have alkaline surface pH~11 but not antibacterial
What are the properties and uses of Calcium Silicate base or MTA cements
- Mainly used in endodontic applications
- High Strength
- Alkaline pH
- Bioactive pulp repair
What is added to reinforce ZOE cements
10-40% of a synthetic resin is added to the powder and coated round the powder particles. Styrene or MMA is added to the liquid.
What does reinforcing ZOE cement result in
- Increased compressive strength 40 MPa
- Increased tensile strength
- Reduced water solubility
