Discuss the function of a liner in pulp protection
- chemical stimuli - unreacted monomer etc
- thermal stimuli - exothermic setting of composite or conductivity of amalgam
- Bacterial stimuli - stops ingress of bacteria and endotoxins near pulp
- some liners stimulate formation of reparative dentine
- Therapeutic role- reduces symptoms
- Palliative role - for patients with irreversible pulpitis
What should a liner be? clue- 3 things
should be command set
workable
easy to mix
Discuss the Thermal properties of a liner
- as low thermal conductivity as possible!
- should have a thermal expansion coefficient matching the tooth
- Should have a similar or lower thermal diffusivity than enamel
Discuss the mechanical properties of a liner
- high compressive strength (filling on top dentine below)
- allow placement of restoration without breakage
- similar modulus to dentine
What other properties should a liner have
radiopaque good marginal seal low solubility cariostatic biocompatibility
Calcium hydroxide components
Made of a …
Base- Calcium Hydroxide, Zinc Oxide filler and plasticiser
Catalyst- Butylene glycol disalicylate, filler and radiopaquer
Calcium Hydroxide setting reaction
Butylene glycol disalicylate and zinc oxide filler undergo chelation together at pH12
Calcium Hydroxide Mode of action
Irritates odontoblast layer, forms reparative dentine
calcium from pulp helps form a bridge
high alkaline content = bactericidal
Zinc Oxide Eugenol setting reaction
Zinc Oxide + Eugenol > Zinc Oxide Eugenolate + Water
Base + Acid > Salt + Water
Resin Modified ZOE - what does it do to the properties of the material
reduces solubility
What is the advantage of using GIC as a liner with amalgam
It acts as a middle man for the tooth tissue and amalgam by bonding to both the amalgam and the tooth
Contraindications for using ZOE?
As a liner for composite it inhibits the addition polymerisation process meaning the composite doesn’t set properly
