Clinical Amalgam Flashcards
What is amalgam?
- An alloy of mercury with another metal or metals
What are 3 examples of direct restorative materials?
- Amalgam
- Composite resin
- Glass ionomer & RMGI
What are 4 examples of indirect restorative materials?
- Gold
- Other metals
- Ceramic
- Composite resin - Ceromeric
What are possible indications for using amalgam as a resotra tive material? (2 points)
- A direct restoration in moderate and large sized cavities in posterior teeth
- Core build ups when the definitive restoration will be an indirect cast restoration such as a crown or bridge retainer
What are possible contraindications for using amalgam as a restorative material? (4 points)
- IF aesthetics are paramount to the patient
- The patient has a history of sensitivity to mercury or other amalgam components
- Where the loss of tooth substance is such that a retentive cavity cannot be produced
- Where excessive removal of sound tooth substance would be required to produce a retentive cavity
What are advantages of using amalgam? (9 points)
- Durable
- Good long term clinical performance
- Long lasting if placed under ideal conditions (median survival 12-15 years)
- Long-term resistance to surface corrosion
- Shorter placement time than composite
- Corrosion products may seal the tooth restoration interface
- Radiopaque
- Colour contrast (can be a good thing)
- Economical (it is cheap - takes less time for you to place so not as expensive for you to place)
What are some disadvantages of amalgam? (5 points)
- Poor aesthetic qualities
- Does not bond easily to tooth surface
- Thermal diffusivity high
- Cavity preparation may require destruction of sound tooth tissue
- Marginal breakdown
What may long term corrosion at the tooth restoration interface of amalgam result in?
- ‘ditching’ leading to replacement of repair
Can local sensitivity reactions happen at amalgam restoration s?
- Yes
Lichenoid lesions can occur at amalgam restorations. What are these and what would you do? (3 points)
- Type IV hypersensitivity reactions
- Remove amalgam and replace
- Gold or composite
One disadvantage of using amalgam is that a galvanic response can occur. What does this mean?
- Battery effect from 2 different amalgams more likely amalgam and a cast metal restoration (tingly effect in the mouth - rare)
One disadvantage of using amalgam is that it can cause tooth discolouration. How does it do this?
- Corrosion products migrate into tooth surfaces which is porous -> darkened tooth
- (not rare)
One disadvantage of using amalgam as a restorative material is that is can cause an amalgam tattoo. How does this happen?
- Fine amalgam particles migrate into soft tissues
- Not a problem - only problem potentially is the differential diagnosis - need to make sure it is definetly an amalgam tattoo and not something more serious
- (can biopsy or use an x-ray, however x-ray is seldom helpful)
What advantageous properties has caused amalgam to be used for over 100 years? (6 points)
- Quick and easy
- Self hardening at mouth temp.
- Can be used in load-bearing areas of the mouth
- Good bulk strength and wear resistance
- Usually placed at one visit
- Economical
What is the caries restoration sequence? (8 points)
- Caries risk, assessment and diagnosis
- Likely material choice
- Informed consent
- Caries access and removal
- Cavity design
- Removal of deep caries
- Cavity toilet
- Restoration placement
What is meant by retention form?
- Features that prevent the loss of the restoration in any direction
- In an occlusal direction significant undercut is not required, parallel or minimal undercut is all that is necessary
What is meant by resistance form? (3 points -long)
- Features that prevent loss of the material due to distortion or fracture from masticatory forces
- Ideally the cavity floor should be approx. parallel to the occlusal surface with sufficient depth of the cavity to give adequate mechanical strength (approx. 1.5-2mm) (place a lining in the lower parts rather than taking tooth away in the upper parts)
- The gingival floor of a proximal box should be approx. 90 degrees to the axial wall. IF it is greater than this -> a sloping inclined plane which makes the filling liable to slide out of the cavity (doesn’t slide out at any speed but will creep out)
What are the 2 possible cavity designs to treat interproximal caries?
- Self-retentive box preparation
- Proximo-occlusal preparation
What are the advantages of a self-retentive box preparation? (3 points)
- Less tooth tissue removed than with a proximo-occlusal restoration
- Reduced amount of amalgam placed
- Sound tooth tissue retained between proximal box and any occlusal cavity
What are the disadvantages of a self-retentive box preparation? (2 points)
- Can be more technically demanding than a proximo-occlusal preparation
- Further treatment of any pit and fissure caries may be required
What are the advantages of a proximo-occlusal preparation? (3 points)
- (should be) very retentive
- Also treats any caries in pits and fissures
- Less or no opportunity for future caries in pits and fissures
What are the disadvantages of a proximo-occlusal preparation?
- Destruction of tooth tissue for retention
- Increased risk of weakening the tooth
What additional mechanical retention can be added to a cavity? (2 points)
- Include grooves or dimples within the cavity design
- Pin placement - titanium/stainless steel (pin use is controversial BUT used to increased retention is large)
When placing a pin for extra mechanical retention, what must you consider? (5 points)
- Pins are self tapping screws
- Place pin into dentine in the greatest bulk of the tooth
- Never in enamel or at the
ADJ - Avoid the pulp and periodontal ligament
- Pack amalgam around the pin
What are the initial problems with using pins as added mechanical retention? (3 points)
- Stress in tooth around the pin
- Cracking of dentine
- Sensitivity of tooth due to temperature transference
What are the long term problems with using pins as added mechanical retention? (1 point)
- Filling can leak but will fall out because of the pin -> secondary caries which can progress further into the tooth because of the pain
What filling material should you never use pins with?
- Composite resins
What are examples of adhesive technology which can be used for additional retention? (3 points)
- Sealing + bonding restorations (resin) (must be dual curing bonding agent) e.g. scotchbond, prime&bond
- Bonding - resin cement e.g. PANAVIA
- Resin modified GIC e.g. Vitrebond
When finishing the cavity prior to a restoration what do you need to do? (4 points)
- Ensure all caries is removed
- Smooth and round internal line angles
- Check and finish cavo-surface angles
- Smooth cavity margins
What does moisture contamination do to restorative materials (especially composite)? (4 points)
- Reduces strength
- Increases creep
- Increases corrosion
- Increases porosity
What would you use for sealing dentine?(3 points)
- Cavity varnishes
- Normally with RMGIC
- Can use DBA but this complicates the process
What is microleakage?
- Passage of fluid and bacteria in micro gaps (10 microns) between restoration and tooth
What can microleakage cause? (3 points)
- Pulpal irritation and infection
- Discolouration
- Secondary Caries
Over time, what can lead to microleakage? (2 points)
- MEchanical loading and thermal stresses
What are 2 examples of matrices?
- KerrHawe Matrices
- Omni-matrix
What are examples of uses of a matrix? (4 points)
- Recreate wall(s) of the cavity
- Allows creation of proximal form
- Allows adequate condensation
- Confines amalgam to the cavity
What properties should a matrix have? (4 points)
- Should be <0.5mm thick
- Smooth and strong
- Allow close adaptation especially at the cervical margin
- Allow good contact with adjacent tooth
What are wedges essential for?
- To produce adaptation of the matrix at the cervical margin buccal or lingual approach
What are 2 examples of wedges?
- Wizard wedges
- Anatomical wedges
What are 4 uses for wedges when using amalgam?
- Temporary tooth separation
- Prevents excess amalgam gingivally
- Aids proximal wall contour
- Prevents movement of matrix band
What does the mixing time of amalgam affect? (4 points)
- Handling characteristics
- Working time
- Amalgam microstructure
- Restoration longevity
Is condensation pressure important?
- Yes, very important
- Vertical and lateral pressure needed
What does condensation of amalgam do? (4 points)
- Expels excess mercury bringing it to the surface where it can be carved off
- Adapts material to cavity walls
- Reduces layering (homogenous)
- Eliminates voids
What do you require to get optimal condensation of amalgam? (4 points)
- Require correct size of instruments
- Easier to control initial increment with a large plugger (smear into cavity, smaller plugger, overlapping axial strokes)
- Lateral as well as axial condensation
- Spherical alloys require less force for condensation
What can inadequate condensation of amalgam lead to? (4 points)
- Lack of adaptation to cavity
- Poor bonding between layers
- Inadequate mercury expression and consequently removal during carving
- Inferior mechanical properties
Do you want to overfill the cavity when placing amalgam?
- Yes
There is a higher mercury content in the surface amalgam which needs to be removed. How can we do this? (3 points)
- Carving
- Burnishing
- Using high volume aspiration
When carving amalgam you want to recreate the anatomical contour. What do you want to recreate? (5 points)
- Marginal ridge
- Inter-proximal contact areas
- Fissure pattern
- Cusps and cuspal inclines
- Re-establishes occlusal contacts
What is the finishing of amalgam used to do?
- Only do it if required to adjust anatomical contour after the amalgam has set
What is meant by the term ‘corrosion’?
- Detrimental change in the character of amalgam due to reactions in the mouth
What is corrosion of amalgam in the mouth associated with and what can this cause? (4 points)
- Associated with gamma 2 phase
- Can cause marginal breakdown with creep and ditching
- Expansion of amalgam during corrosive process may assist in the development of a marginal seal
- Most amalgam is now non-gamma 2, high copper, so less of a problem
What is meant by the term ‘creep’?
- Slow internal stressing and deformation of amalgam under stress
What is incorporated into amalgam to reduce creep?
- Copper
What should reduced creep of amalgam maintain?
- Marginal integrity
What is essential to reduce creep in amalgam restorations?
- Correct cavo-surface angles
In which situations would you remove an amalgam restoration? (3 points)
- Secondary caries
- Bulk fractures
- Removal of an amalgam core within an extra-coronal restoration
When is the greatest amount of mercury released from an amalgam restoration?
- During the insertion and removal of amalgam restorations
During insertion
- Amount is proportional to the restorations free surface area
During removal
- Vapour + particles
How can you absorb mercury? (5 points)
- Vapour into lungs
- Contact with skin
- GIT
- Gingival and mucosa
- Dentine and pulp as metal ions (not a lot do this)
How much mercury is absorbed from a filling?
- Inorganic mercury vapour is released very slowly from an amalgam (about 0.5 microgrammes/surface/day)
What protection would you use to ensure mercury hygiene? (6 points)
- Dental dam
- High volume aspiration
- Amalgam traps - separaotrs
- Spillage kit
- Coreect disposal of waste amalgam
- Correct disposal of unused amalgam
Does dental amalgam produce delayed hypersensitivity contact reactions on the skin and mucous membranes?
- Yes
What can higher levels of mercury than found in dentistry cause to happen to the body? (6 points)
- Neuro-toxicity
- Kidney disfunction
- Reduced immunocompetence
- Effects on the oral and intestinal bacterial flora
- Effects on general health
- Foetal and birth defects
What is Black’s classification?
- Classifications of a CAVITY
What is blacks class I cavity?
- Pit and fissure caries
What is blacks class II cavity?
- Approximal caries (posterior teeth)
What is blacks class III cavity?
- Approximal caries (anterior teeth)
What is blacks class IV cavity?
- Approximal caries involving incisal edge
What is blacks class V cavity?
- Caries affecting cervical surfaces
What is blacks class VI cavity?
- Caries affecting the cusp tips
