Cavity Lining Materials Flashcards
What is the purpose of a cavity liner?
Pulpal protection from
- chemical stimuli
- Thermal stimuli (exothermic setting reaction of comp)
- Bacteria and endotoxins due to microleakage
Therapeutic (calms down inflammation within pulp and promote pulpal healing)
Palliative (reduce pts symptoms prior to txt being carried out)
What is the difference between a cavity base and cavity liner? When would they be used?
Cavity Base
- Thick mix placed in bulk
- Dentine replacement used to minimised bulk of material or block out undercuts
- More common in metal rest
Cavity liner
- thin coating <0.5mm over exposed dentine
- useful as a pulp cap to protect exposed pulp
Give some types of Cavity base and liners
Setting Calcium hydroxide - Liner
Zinc oxide based cements - Base
GIC and RMGIC - Base or Liner
What disadvantages of restorative materials makes 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 Setting calcium hydroxide liners are there? What type of setting reaction is it?
- Life or Dycal
- Settiing reaction is chelation reaction between ZnO and butylene glycol disalicylate
- Results in cement with initial pH 12
What is the MOA of CaOH?
- Highly alkaline liner is bactericidal to cariogenic bacteria
- Irritates odontoblast layer leading to necrosis and ultimately tertiary dentine layer being produced. Forms a calcified bridge walling the base of cavity off from the pulp
What are the properties of CaOH liner?
- Quick setting time
- Radiopaque
- Easy to use
- Low compressive strength :(
- Unstable and soluble so if cavity leaks then lining disappears
When ideally should you use a CaOH liner?
At close proximity to the pulp as an indirect or direct pulp cap
Should be covered with RMGIC
What is the setting reaction of Zinc Oxide eugenol Cement (ZOE)?
- Chelation reaction of ZnO with Eugenol to form Zinc eugenolate matrix
- Matrix bonds the unreacted ZnO particles
Acid base reaction (Base ZnO) Acid eugenol
Pros and cons of ZOE properties
- adequate working time
- Rapid setting time
- Low thermal conductivity
- Radiopaque
- But Low strength 20MPa as weak hydrogen bonds between eugenolate mols and not strong enough to use as a base beneath amalgam filling
- Brittle and opaque
- Not cariostatic
- Not adhesive to tooth surface or restorative materials
- Exothermic setting
What two types of ZOE do we use now and in the dental hospital and what is the differences?
Resin modified ZOE (Kalzinol)
- Polystyrene added as resin and gives increased strength of >40MPa and decreases solubility
EBA - modified ZOE so same setting reaction
- encourages crystalline structure = stronger 60MPa and less soluble
Pros of GIC and RMGIC
Can bond to tooth surface and composite
Fully seals dentine tubules (decreases microleakage and helps prevent post txt sensitivty)
Lower thermal conductivity and diffusivity than dentine!
Easy to mix and place, light cure too so long working time
High compressive strength 170MPa
Most radiopaque (see 2caries radiographically)
Fluoride release and may be cariostatic
Cons of RMGIC
Must etch prior to placing
Greatest initial solubility
Any unreacted HEMA can damage the pulp (ensure complete cure)
PCS
What is the Dental Hospital Lining guidelines?
Cavities in dentiine
- Consider use of Lining of RMGIC such as Vitrebond for amalgam and larger cavities filled with composite
CaOH used only when cavity approaches pulp as either direct or indirect pulp cap
CaOH covered with RMGIC prior to final rest being placed as it protect CaOH and prevent dissolution beneath restoration
