Cavity Lining Materials (Acid-Base Cements) Flashcards
What are 5 general uses of acid-base dental cements?
- Cavity Liner
- Permanent/Temp. Filling
- Root Canal Sealer
- Permanent/Temporary luting of crown/ bridge
- Attachment of orthodontic appliances
Name some of the ideal properties of an acid0base 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
- An appropriate thermal expansion coefficient
- Good 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?
Acts as a filler
- Increases strength of the set cement
How does particle size affect setting of a cement?
Small size = Greater specific surface area = Faster setting reaction
How does powder:liquid affect setting of a cement?
Higher powder content = Faster set
How doers temperature affect setting of a cement?
Why does it have this affect?
- Increasing the temperature will increase setting rate
- Exothermic setting reaction
How does moisture affect setting of a cement?
Presence of moisture accelerates setting of some cements but slows for others
What are the 6 types of acid-base cements?
- Zinc Phopsphate
- 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 types of acid-base cements are phosphate bonded?
Zin Phosphate Cements
Which 2 types of acid-base cements are polycarboxylate bonded?
Chemical bond
- Zinc polycarboxylate cements
- GICs
Which 3 types of acid-base cements are phenolate boded?
- Calcium Hydroxide Cements
- ZOE cements
- EBA-based cements
Which 3 types of acid-base cements are water based?
- Zinc phosphate
- Zinc polycarboxylate
- Glass ionomer
Which 3 types of acid-base cements are oil-based?
- Calcium Hydroxide
- ZOE
- EBA
What powder do all cements except GIC use?
Zinc Oxide
What is the main reactant in a zinc phosphate cement?
What are the minor reactants?
- Roughly 90% ZnO
- 10% MgO, Aluminium Oxide and Silicon Dioxide
Advantages of having ZnO in based cements?
- Low cost
- Good radiopacity
- Low toxicity
- Reactivity can be controlled
What is the primary liquid component used in zinc phosphate cements?
Phosphoric Acid
What is the correct way to mix zinc phosphate cements?
Using a coal mixing slab and incorporate the powder in small amounts
What are some disadvantages of zinc phosphate in cements?
- 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
What are the 3 advantages of having SnF2 (Stannous Fluoride) in cements?
- Fluoride source
- Improves mixing
- Increases strength
What is the primary liquid component in Zinc Polycarboxyate cements?
Polyacrylic Acid
PAA
3 Disadvantages of Zinc Polycarboxyate cements?
- Lower compressive strength that Zinc Phosphate cements
- Short working time
- Not necessarily adhesive to all surfaces
What 3 things is cavity varnish designed to do?
- Seal Dentine
- Reduce diffusion through dentine
- Decrease microleakage
What 2 things is cavity liner designed to do?
- Seal exposed dentine
- Promotes health of pulp
What 4 things is cavity base designed to do?
- Act as dentine replacement
- Strengthens restoration
- Blocks out undercut
- Insulates tooth
What will happen to Zinc Eugenolate in the presence of excess water?
The complex is not stable and the setting reaction will reverse in the presence of excess water
What is the:
Mixing, working and setting time
of Zoe cement?
- 60-90 seconds
- 2-3 Minutes
- Less than 5 Minutes
4 Disadvantages of ZEO cements?
- Low compressive and tensile strengths
- High water solubility
- Eugenol is potential allergen
- Eugenol inhibits C=C polymerisation so cannot be used with composities
2 Ways in which ZOE cements are reinforced?
- 1040% of s synthetic resin is added to the powder
- Styrene of MMA is added to liquid
3 Advantages of reinforced ZOE?
- Increased compressive strength
- Increased tensile strength
- Reduced water sulbility
Compare EBA cements with ZOE cements. 2
- EBA have better strength
- EBA have lower water solubility
1 Disadvantage of EBA cements?
Poor handling characteristics
If a patient is allergic to eugenol what other oils can form a cement with ZnO instead?
Nonaoic Acid
What is the:
Mixing, working and setting time
of Calcium Hydroxide Cement?
- 5-30 Seconds
- 30-60 Seconds
- 1-2 Mins
4 Disadvantages of Calcium Hydroxide cements
- Low strength
- Weakened by moisture
- Dissolved by acidic conditions
- Can undergo plastic deformation at mouth temp.
Compared ZOE Cements to Calcium Hydroxide cements 4
- ZOE stronger and less soluble than CH
- ZOE has a calming effect
- CH is alkaline anti bac
- CH stimulates secondary formation
