Operative: Amalgam Flashcards
Define Amalgam
Mixture of elemental liquid mercury w/other metals
Eames Ratio
50% Mercury
50% Metal Alloy
* Silver: Strength
* Tin: Corrosion
* Copper: Strength
* Zinc: Plasticity & Deoxidizer (prevents oxidation of other metals), moisture contamination causes excess expansion
Trituration
mixes amalgam capsule
* alloy particle is coated by mercury
3 Phases:
Y (Gamma Phase): unreacted silver tin
* strongest w/least corrosion
Y1: Strong silver-mercury matrix:
* 2nd strongest and corrosion
* What we want
Y2: Weak tin-mercury
* weakest and most corrosion
* Susceptible to corrosion & creep
Trituration: Describe normal mix, over-trituration and under-trituration
Normal Mix:
* shiny
* smooth
Over Trituration:
* warm, wet, soft
* sets to quick
Under Trituration
* Dry, dull, crumbly
* sets too quick
Low-Copper vs High-Copper Amalgam
Low-Copper
* <12% Cu in Alloy
* results in Y, Y1, and Y2
High-Copper=IDEAL
* >/= 12% Cu in alloy
* Results in ONLY Y and Y1 (less corrosion and creep)
Define creep
XS Compression=deformed amalgam
Amalgam: Spherical vs Admixed Particles
Spherical:
* less overall surface area
* Microspheres of various sizes
* easier to condense
* Stronger
* sets faster
* great to use w/pins
Admixed:
* mixture of irregular lathe cut and spherical particles
* more condensation forces
* better proximal contacts
Amalgam: Indications vs Contraindications
Indications:
* Moderate to large lesions
* Heavy Occlusal loading
* Hard to isolate
* Non-esthetic
* Root Surface Lesion
* Foundation or abutment
Contraindications:
* very small class VI lesions
* High Esthetics
* Metal Allergy
When is the amalgam at its peak strength?
24 hours
What could cause a Marginal Ridge Fracture?
- Not rounded Axiopulpal line angle
- High Marginal Ridge
- Incorrrect occlusal embrasure (Overbulked)
- Improper matrix removal
- Over carving (< 2mm thick)
Class V Amalgam
Prep Walls:Diverge occlusally
* orientation of enamel rods
Secondary Retention:
* 4 corner coves
* occlusal and gingival line angle grooves
* circumferential grooves
Acute Mercury Toxicity
Inhalation=biggest risk
Acute Mercury Toxicity:
* muscle weakness (Hypotonia)
* Loss of hair (alopecia)
* Weight loss/GI Disorders
* Exhaustion
What should you do if there is a mercury spill?
Use a special vacuum system
* then apply sulfur powder on floor
What are the different forms of mercury?
Methylmercury
* organic (from seafood)
* most toxic
Elemental:
* liquid mercury
* dental amalgam
Mercury Salts:
* inorganic mercury
