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
How can retention be achieved when preparing a cavity (2)
- Include grooves/dimples within the cavity design
2. Pin placement
- Titanium / stainless steel
Used to increase retention in large non-retentive cavities
How are pins used to create retention? (4)
Pins are self tapping screws
Place pin into dentine in the greatest bulk of the tooth (never in enamel or at the ADJ)
Avoid pulp and PDL
Pack amalgam around the pin
Disadvatanges of pins for:
Initial (3)
Long term effects (2)
On the restoration
- Initial:
- Stress in tooth around the pin
- Cracking of dentine
- Sensitivity of tooth due to temperature transference - Long term:
- Filling can leak but will not fall out because of the pain
- Secondary caries can progress further into tooth because of the pin
When should pins NEVER be used?
With composite resins
How is finishing of a cavity prep achieved? (4)
- Ensure all caries is removed
- Smooth and round internal line angles
- Check and finish Cavo-surface angles
- Smooth cavity margins
Moisture contamination disadvantages (4)
- Reduces strength
- Increases creep
- Increases corrosion
- Increases porosity
Critical for amalgam but not as critical as in bonded composite restorations
Define micro leakage
Passage of fluid and bacteria in micro grams (10 microns) between the restoration and the tooth
What can micro leakage lead to? (3)
- Pulpal irritation and infection
- Discolouration
- Secondary caries
What can cause microleakage over time?
Mechanical loading and thermal stresses
Advantages of matrices (3)
- Recreate the walls of the cavity
- Allow close adaption especially at the cervical margin
- Allows good contact with adjacent tooth
How thick should a matrix be?
<0.05mm thick
Function of wedges (3)
- Essential to produce adaptation of the matrix at the cervical margin
- Prevent movement of the band
- Prevent excess placement of amalgam gingival
Function of condensation (4)
- Expels excess mercury bringing it to the surface, where it will be carved off
- Adapts material to the cavity walls
- Reduces layering
- Eliminates voids
What does mixing time of amalgam affect? (4)
- Handling characteristics
- Working time
- Amalgam microstructure
- Restoration longevity
Affects of inadequate condensation
- Lack of adaptation to cavity
- Poor bonding between layers
- Inadequate mercury expression leading to removal during carving
- Worse mechanical properties
What does amalgam carving reproduce? (5)
- Marginal ridge
- Interproximal contact areas
- Fissure pattern
- Cusps and cuspal inclines
- Occlusal contacts
What is corrosion associated with
Gamma 2 phase
> Can cause marginal breakdown with creep and ditching
Define creep
Slow internal stressing and deformation of amalgam under stress
In terms of amalgam, how is creep avoided?
Correct cave-surface angle
Reduced creep maintains marginal integrity
Why are amalgam restorations removed? (3)
- Secondary caries
- Bulk fracture
- Removal of an amalgam core within an extracoronal restoration
Disadvantages of mercury absorption (4)
- Vapour into lungs
- Contact with skin
- GI tract
- Gingiva and mucosa
How is mercury hygiene achieved? (4)
- Dental dam
- High vol aspiration
- Spillage kit
- Correct disposal of waste/unused amalgam
Class 1
Pits and fissure caries
Class II
Approximal caries (posterior teeth)
Class III
Approximal caries (anterior teeth)
Class IV
Approximal caries involving the incisal angle
Class V
Caries affecting cervical surfaces
Caries VI
Caries affecting cusp tips
From 2018, when should amalgam NOT be used? (3)
- Children under 15
- Pregnant woman
- Breastfeeding woman
What component of amalgam helps avoid creep?
Copper
