Chapter 5 B: Restorations With Amalgam. Clinical Phases Flashcards
The steps of an amalgam restoration are?
- Selection of amalgam alloy
- Mercury-amalgam ratio
- Trituration
- Mulling
- Application of matrix band
- Insertion of amalgam
- Condensation
7a. Precarve burnishing - Burnishing
- Carving
9a. Postcarve burnishing - Finishing and polishing
What are the factors considered when selecting an alloy for restoration?
- type of alloy:
1. High or lower copper alloys
2. Zinc free or zinc containing alloys
3. Size and shape of the particles
Which amalgam would you chose for a restoration that would undergo high occlusal stresses?
One with high resistance to marginal fracture
Mercury is required to?
Wet the alloy particles before they can react
Ratio of alloy/mercury is usually?
5:8 or 5:7
What happens if the mercury is more than the required amount?
The resultant mix will be weaker
What happens if the mercury is less than the required amount?
It might not be sufficient to wet the alloy particles
____ amalgam alloys require more (45%) of mercury to wet than the ____ alloys (40%)
Lathecut , spherical
The purpose of trituration is
To remove oxide layers from the alloy particles so as to coat each alloy particle with mercury, resulting in a homogenous mass for condensation
Mechanical trituration is done by a?
Amalgamator
Trituration by hand is done by?
Mortar and pestle
Objectives of trituration:
- achieve a workable mass of amalgam within minimum time
- increase direct contact between the particle and mercury by removing oxides from powder
- reduce particle size of powder so that fast and more complete amalgamation can be done
- help in dissolving the particles of powder in mercury
___ and ____ applied for trituration, affect the quality of trituration?
Speed and force
Good mix amalgam:
Shiny, homogenous mass that adheres together
Undertrituration results in?
Weak crumbly mix
Over trituration results in?
A mix that is warm and has a shiny surface that sticks to the capsule and is difficult to remove
Mulling is?
So that the particles are properly coated with mercury
Mulling by hand?
Squeezing the freshly mixed amalgam collected in the chamois skin with gloves
Mechanical mulling?
With amalgamator by triturating it for 1-2 seconds
What actually happens before, trituration or application of matrix band ?
Practically, application of matrix band
In what classes do you not use a matrix band?
Classes 1, 3
The aim of the matrix is?
To avoid overhanging restorations and to make the shape of the missing wall
Allows us to insert the restoration without exceeding the limits of the normal tooth structure
What happens if you over tighten the matrix band?
The cusps will flex
Do you have to burnish the contact area of the band against the adjacent tooth?
Yes
Which part do you fill first, the proximal or the occlusal?
Proximal
Where is the first increment of amalgam placed?
In the deepest proximal part
What kind of pressure has to be applied for adequate condensation?
Firm
Do we overfill for amalgam?
Yes
Rules of condensation?
- start condensation within 3 minutes of trituration
- condense continuously
- condense laterally as well as apically
- apply adequate force for condensation
- have a constant supply of amalgam
Objectives of condensation?
- bring excessive mercury on the surface of the restoration
- reduces the number and size of the voids
- prepares the surface of the restoration for carving
- to adapt amalgam to the preparation walls and floors
Condensation depends on?
- plasticity of the mass
- size of the amalgam in cement: larger mass—> incomplete condensation
- condenser size
- direction of the force (apically and laterally)
- amount of force
- type of alloy
The smaller the condenser working end, the ____ (weaker/greater) the force?
Greater
When condensing spherical alloys which condenser size should be used and why?
Larger because the smaller ones displace the spherical particles rather than condensing them
Lathecut alloy
Spherical alloy
Blended alloy
Which condenser sizes should be used for each?
Lathecut and blended —> small
Spherical—> large
When is precarve burnishing done?
After condensation
When is Postcarve burnishing done?
After carving
Burnishing is?
The process of rubbing, generally done to make the surface shiny
Burnishing is done with what kind of strokes?
Heavy strokes to improve marginal adaptability of the restoration and remove excess mercury from overpacked amalgam
Advantages of precarve burnishing?
- improves the marginal integrity of restoration
- shapes the restoration according to the contours and curvatures of the tooth
- helps in reducing the mercuric content of amalgam
Advantages of Postcarve burnishing?
- reduces the number and size of voids
- produces dense amalgam at margins
- improves the marginal seal
- increases surface hardness
- decrease rate of corrosion
Postcarve burnishing is?
Done after condensation with the help of small sized Burnishers using light strokes
Objectives of carving?
- no over and underhangs
- proper size, location, and good inter-proximal contact
- adequate marginal ridges
- proper contours
- optimal occlusal anatomy
- adequate embrasures
- enhancing the health of the periodontium
Carving instruments should have what type of design?
Discoid, cleoid
Trim the axial margins towards? Using?
Gingiva downward, with a sharp carver
What happens if you over-carve amalgam?
Acute angles and stress concentration which can fracture the restoration
What is used to carve the occlusal surface?
Sharp carver like a hollen back
How should the instruments be held?
Half on tooth and half on restoration
What should be used to define marginal ridge and occlusal embrasures ?
Sharp explorer
How to check the contact points?
Floss
In high copper amalgam, postcarve burnishing has ?
No significant effect on the clinical performance
In low copper amalgam, post carve burnishing produces?
Denser amalgam at the margins
Finishing amalgam restorations involves?
Removal of marginal irregularities, defining anatomical contours, and smoothening the surface roughness
When should finishing and polishing be done?
24 hours after
Premature finishing and polishing causes?
Interferes with the crystalline structure of the hardening amalgam
Advantages of finishing and polishing?
- improve marginal adaptation of restoration
- reduces tarnish and corrosion
- polished surface is plaque resistant
- polished surface is smoother and easier to clean
- prevention of recurrent decay
- prevention of amalgam deterioration
- maintenance of periodontal health
- prevention of occlusal problems
What is the most important precaution to be taken ?
Minimzaiton of heat production
Why is the heat generated during polishing dangerous ?
- it can cause thermal damage to the pulp
- heat brings the mercury to the surface of the restoration, resulting in a dull, cloudy surface, and makes it more susceptible to corrosion
To minimise heat production ?
- Use light intermittent pressure with rotary instruments
- Use slow speed with rotary instruments
- Use abrasive agents that are wet
What do u use to evaluate the cavosurface margins for marginal integrity?
Explorer
Steps for finishing and polishing?
- evaluate the cavosurface margins for marginal integrity
- determine the presence of any marginal discrepancies and evaluate the contour of the restoration
- identity the occlusal pattern and areas that need to be reduced
- smoothen the margins with a round bur
- eliminate the scratches and graininess with a large round bur
- smoothen the occlusal surface and marginal ridges with a finishing bur
- smoothen and polishing the gingival cavosurface margins and inter proximal space with a finishing strip
- smoothen the facial and lingual surfaces with a finishing disk
- polish surface with abrasive agents
A polished amalgam restoration should have the following features?
- surface is smooth with no scratches or graininess
- surface is lustrous with a mirror like shine
- there is no break between margins and the tooth surface
- restoration has proper contact and contour
- there is no damage to the restoration or adjacent tooth surface
How long is the life of a properly manipulated and restored silver amalgam restoration?
10-12 years
What changes occur with time?
Tarnish, corrosion, recurrent marginal caries, discolouration of teeth, fracture of restoration or tooth and ultimately loss of restoration
Reasons for amalgam restoration failure?
- poor case selection: amalgam should be placed in small to moderate size carious lesions
- defective tooth preparation: inadequate occlusal extension, under extension of the proximal box, over extended tooth preparation, depth of preparation, not flat pulpal floor
- defective amalgam manipulation: inappropriate condensation, incorrect mercury alloy ratio, contamination during manipulation, faulty finishing and polishing
- defective matrix adaptation
- post restorative fail: post restorative pains, premature fracture of restoration
