Cavity lining materials Flashcards
What three cavity liners are there?
CaOH liner
Zinc oxide cements
GIC/RMGIC
What is a cavity base and what is a cavity liner?
When would they be used?
A cavity base is a thicker material typically used for dentine replacement. It is more common in metal restorations
A cavity liner is much thinner and used for coating over dentine or over pulp as a cap. Often used when pulpal protection is required
What disadvantages of restorative materials make liners essential?
Micro-leakage of some materials leaving gaps between material and tooth surface
Some unreacted materials leach toxins which can seep into the pulp
Not all restorative materials bond directly to tooth surfaces
What may we protect the pulp from with a liner?
Why else may we use one?
Strong thermal stimuli
Caries, bacteria and endotoxins
Chemical stimuli from unreacted restorative materials
Palliative treatment - decrease tooth sensitivity pre-treatment
Therapeutic treatment to reduce discomfort form inflammation
What are the ideal properties of a good liner?
Radiopaque - to see difference between liner and tooth
Cariostatic - fluoride release to prevent secondary caries
Low thermal conductivity and diffusivity
High compressive strength
Marginal seal and bond to tooth surfaces and restorative materials to prevent micro-leakage
Low solubility
Biocompatible and non-toxic to tooth tissue
Easy to mix and use
Pros of CaOH liner?
- initial pH of 12 so alkalinity means its bacteriocidal
- radiopaque
- fast setting
- ease of use
Cons of CaOH liner?
Irritation to odontoblast layer causing necrosis and tertiary dentine deposition
Unstable and soluble
Low compressive strength
When ideally should you use CaOH liner?
At close proximity to the pulp as an indirect or direct pulp cap
Should be covered with RMGIC
What is a zinc oxide cement? What are its benefits?
Acid + base reaction of liquid + powder
Chelation of ZnO with eugenol, this binds to unreacted ZnO
- pros are its a bulk mix with high compressive strength
- long working time
- provides a white colour and the shade can be matched to tooth material
Cons of zinc oxide cements?
Brittle and opaque
Not cariostatic
Not adhesive to tooth surface or restorative materials
Exothermic setting
Cannot withstand amalgam when used as a liner unless it is modified with resin
Pros of using GIC or RMGIC?
Can bond to tooth surface and composite
Fully seals dentine tubules
Lower thermal conductivity and diffusivity than dentine! - lower post treatment sensitivity
Easy to mix and place, light cure too so long working time
High compressive strength
Most radiopaque
Cons of RMGIC as a liner
Must etch prior to placing
Greatest initial solubility
Any unreacted can damage the pulp
PCS
