Clinical Amalgam Flashcards
What is amalgam made of?
Amalgam is an alloy of mercury with another metal/metals
Name examples of direct restorative materials (3)
- Amalgam
- Composite Resin
- Glass ionomer + RMGI
Name examples of indirect restorative materials (4)
- Gold
- Other metals
- Ceramic
- Composite resin
Name examples of possible indications for amalgam (2)
- A direct restoration I moderate and large sized cavities in posterior teeth
- When definitive restoration will be an indirect cast restoration
( i.e. a crown or bridge retainer)
Name examples of amalgam contra-indications (4)
- Aesthetics
- Patient has a history of sensitivity to mercury or other amalgam components
- When loss of the tooth substance is such that a retentive cavity can’t be produced
- Where excessive removal of sound tooth substance would be required to produce a retentive cavity
Name advantages of amalgam (6)
- Durable
- Good long term performance
- Long lasting if placed under ideal conditions (12-15 years)
- Long term resistance to surface corrosion
- Shorter placement time than composite
- Good bulk strength and wear resistance
Name disadvantages of amalgam (9)
- Aesthetics
- Does not bond easily to tooth substance
- Thermal diffusivity high (1.7cm2 to 0.0026 of dentine)
- Cavity prep may require destruction of sound tooth tissue
- Marginal breakdown
- Long term coronation at tooth restoration interface may result in ditching (leading to replacement or repair)
- Tooth discolouration
- Corrosion products migrate into tooth surfaces which is porous and leads to a darkened tooth - Amalgam tattoo
- Fine amalgam particles migrate into soft tissues - Galvanic response can occur
- effect from 2 diff amalgams
Why has amalgam been used for over 100 years? ( 5)
- Quick + easy
- Self hardening at mouth temperature
- Can be used in load-bearing areas of the mouth
- Good bulk strength and wear resistance
- Usually placed at one visit
Describe the sequence for placing an amalgam restoration (8)
- Caries risk, assessment + diagnosis
- Likely material choice
- Informed consent
- Caries access + removal
- Cavity design
- Removal of deep caries
- Cavity toilet
- Restoration placement
Describe the term retention form, in terms of cavity design
Features that prevent the loss of the restoration in any direction
Are undercuts required for an occlusal direction amalgam restoration?
Undercuts are not required, parallel or minimal undercut is all that is necessary
Describe the term resistance form in terms of cavity design
Features that prevent loss of the material due to distortion or fracture by masticatory forces
What depth is required for an amalgam cavity?
1.5-2mm to give adequate mechanical strength
What feature of the cavity design ensures resistance form is maintained? (2)
- The gingival floor of an inter proximal box should be approx 90 degrees to the axial wall
If its greater than this a sloping inclined plane makes the filling liable to slide out of the cavity
- The cavity floor should be approximately parallel to the occlusal surface
Name the cavity designs used to treat inter proximal caries (2)
- Self retentive box preparation (minimal prep required)
2. Proximo-occlusal preparation
Advantages of self retentive box preparation (2)
- Less tooth tissue removed than with a proximo-occlusal preparation (sound tooth tissue retained between proximal box and occlusal cavity)
- Reduced amount of amalgam placed
Disadvantages of self retentive box preparation
- Can be more technically demanding
2. Further treatment of any pit and fissure caries may be required
Advantages of a proximo-occlusal box preparation (2)
- Should be very retentive
2. Also treats any caries in pits and fissures (so less/no opportunity for future pits and fissure caries)
Disadvantages of a proximo-occlusal box preparation (2)
- Destruction of tooth tissue for retention
2. Increased risk of weakening of the tooth