Cavity Lining (Acid-Base Cements) Flashcards
What are some general uses of acid-base dental cements? (5)
- Cavity liner
- Permanent/Temporary filling
- Root canal sealer
- Permanent/Temporary luting of crown/bridge
- Attachment of orthodontic appliances
Name some of the ideal properties of an acid-base cement (11)
- Non-irritant and non-toxic to the oral tissues
- Insoluble in oral fluids or anything taken into the mouth
- Adhesive to the tooth structure
- Adequate mechanical properties
- Thermally, chemically and electrically insulating
- Provide a therapeutic effect, e.g. bacteriostatic and obtundent
- An appropriate thermal expansion coefficient
- Good optical properties (aesthetics)
- Radio-opaque
- Appropriate rheological properties
- Easily manipulated
Definition of acid-base cement
Mixing of powder and liquid, which, through an acid-base reaction, produces a solid matrix that binds the mass together.
What does the unreacted powder in the set cement act as? What does this do?
The unreacted powder particles act as a filler. Increasing strength of the set cement
How does particle size affect setting of a cement?
The smaller the particle size the greater the specific surface area and the faster the setting reaction
How does powder:liquid affect setting of a cement?
A higher powder content will give a faster set
How does temperature affect setting of a cement?
Why does it have this affect?
- Increasing the temperature will increase the setting rate
- Setting reaction is exothermic so may further accelerate set
How does moisture affect setting of a cement?
Presence of moisture accelerates setting of some of the cements but slows it down for other cements
What are the 6 types of acid-base cements?
- Zinc phosphate cements
- Zinc polycarboxylate cements
- Glass ionomer cements (GICs)
- Zinc oxide eugenol (ZOE) cements
- Calcium hydroxide cements
- Ethoxybenzoic acid (EBAs) cements
Type I acid-base cements;
Use?
Particle size?
- Luting
- ~25µm
Type II acid-base cements;
Use?
Particle size?
- Restorative or a lining
- ~40µm
Type III acid-base cements;
Use?
Lining or base
Which acid-base cements are phosphate bonded?
Zinc phosphate cements
Which types of acid-base cements are polycarboxylate bonded? (2)
(Chemical bond!!)
- Zinc polycarboxylate cements,
- Glass ionomer cements
Which types of acid-base cements are phenolate bonded? (3)
- Calcium hydroxide cements
- Zinc oxide/eugenol cements (ZOE)
- EBA-based cements
Which types of acid-base cements are water based? (3)
- Zinc phosphate
- Zinc polycarboxylate,
- Glass ionomer
Which types of acid-base cements are oil based? (3)
- Calcium hydroxide
- Zinc oxide/eugenol (ZOE)
- EBA
What powder do all cements except GIC use?
Zinc oxide
What is the main reactant in a zinc phosphate cements?
What are the minor reactants?
- Roughly 90% ZnO
- 10% MgO, aluminum oxide and silicon dioxide
Advantages of having ZnO in based cements?
- Low cost
- Good radiopacity and whiteness
- Low toxicity
- Reactivity can be controlled
What is the primary liquid component used in zinc phosphate cements?
Phosphoric acid (H3PO4)
What is the correct way to mix zinc phosphate cements?
Mix using a cool mixing slab and incorporate the powder in small amounts
What are some disadvantages of zinc phosphate cements? (6)
- Low initial pH
- Slow to neutralise
- Brittle
- High acidic solubility
- No chemical adhesion
- Setting shrinkage
What can be used to modify the set of Zinc polycarboxylate cements?
Bismuth salts
