1
Q
What is Am?
A
An alloy of mercury, silver, tin, copper, zinc
2
Q
What is the setting reaction for Am?
A
y + Hg –> y + y1 + y2
y2 = weak, poor corrosion resistance
3
Q
What is the clinical implications of zinc in the use of Am in the mouth?
A
- Interacts with saliva/ blood
- Bubbles formed in Am –> pressure
- Downward press = pulpal pain
- upward pressure = proud restoration
4
Q
What operator factor will affect the properties of Am?
A
- Handling = condensation, carving & polishing
- Cavity design
- Brand variation
5
Q
What factors will decrease the strength of Am?
A
- Undermixing
- High Hg content after condensation
- Too low condensation pressure
- Slow packing (do not bond)
- Corrosion
6
Q
What are the advantages of using copper-enriched Am over conventional?
A
- Higher early strength
- Less creep
- Higher corrosion resistance
- Increased durability of margins
7
Q
What are the advantages of Am?
A
- Strong
- Long-lasting; good long term clinical performance
- Resistance to corrosion
- Radiopaque
- Cheap
8
Q
What are the disadvantages of Am?
A
- Corrosion
- Leakage; no bonding
- Aesthetics
- High thermal conductivity
- Galvanic resposnse
- Am tattoo
- Sensivities; lichenoid
- Mercury; toxicity? environmental impact
9
Q
What are the clinical indications for the use of Am as a restoration?
A
- Direct restoration; mod-large cavities of posterior teeth
- Core build ups for indirect restorations (crown/ bridge retainer)
10
Q
What are the clinical contra-indications for the use of Am as a restoration?
A
- Aesthetics paramount to pt
- Hx of sensitivity to mercury/ Am
- Retentive cavity cannot be produced (too little tooth tissue)
- Excessive amount of tooth tissue would be needed to be removed to creat a retentive cavity
Dental Materials & Operative Techniques
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