Composition and Properties of Dental Amalgam Flashcards
(39 cards)
Amalgam comes in different packagesAll the amalgam we use in clinic is ___ ____
___r to use
All the material is inside a capsule
Different materials have different structures so make sure you know what you are using
Amalgam comes in different packagesAll the amalgam we use in clinic is pre-capsuled
Easier to use
All the material is inside a capsule
Different materials have different structures so make sure you know what you are using
Composition of Dental Amalgam Capsule
___
___ ___ ___
There is a __ ___to separate both components
When you are ready to use it, there are ways to __ __ ___ and mix the two components so that a chemical reaction starts
Composition of Dental Amalgam Capsule
Mercury
Amalgam alloy powder
There is a thin film to separate both components
When you are ready to use it, there are ways to break the film and mix the two components so that a chemical reaction starts
Overview of ManipulationTime:
- Onset of ___
- The clock starts ticking
- ____: how we mix amalgam
- Done with a___r or ___
- ___ the capsule and then __ __ __ the amalgamator
- Onset of ___
- ___and ___
- Place the___ in your ___
- Onset of ___
- __
- When the material starts to set, you carve the amalgam
- ___of Setting
- Material is very ___ Can’t manipulate it
- 24 hours
- ___
- Don’t polish until after 24 hrs
- Steps:
- ____
- ____
- Proportion of 2 components is set in capsule
- ___
- Chemical rxn
- ____
- Your manipulation will influence the properties
- ___
Overview of ManipulationTime:Onset of Mixing
The clock starts ticking
Trituration: how we mix amalgam
Done with amalgamator or triturator
Activate the capsule and then put it in the amalgamator
Onset of Working
Placement and Condensation
Place the amalgam in your prep
Onset of Setting
Carving
When the material starts to set, you carve the amalgam
End of Setting
Material is very hard. Can’t manipulate it
24 hours
Polishing
Don’t polish until after 24 hrs
Steps:
Selection
Proportioning
Proportion of 2 components is set in capsule
Amalgamation
Chemical rxn
Manipulation
Your manipulation will influence the properties
Polishing
Classifications\
___content = __ ___
We use ___ copper clinically right now
___ content = ___ ____
Particle ___ (and ___) = ____, ___
___of particle ___ = __,___
Materials with both components inside are called___
ClassificationsCopper content = low copper, high copper
We use high copper clinically right now
Zinc content = Zn-containing, Zn-free
Particle size (and shape) = irregular, spherical
Number of particle types = 1 or 2
Materials with both components inside are called mixed.
Amalgamation
- Solution:
- Mercury ___ and ____in the ___ ___
- ___reaction
- Crystalization: ___ ___ ___ phases
- Once two components mix together, ____ occurs
- Different phases have started to form
- Creates a ___
- Microstructure: ___ ____bonded to___
- Microstructure of the set amalgam is unreacted __ ___ ___ embedded in the ___ formed by the __ ___
AmalgamationSolution:
Mercury diffuses and dissolves in the surface particles
Surface reaction
Crystalization: AgHg, SnHg, CuSn phases
Once two components mix together, crystallization occurs
Different phases have started to form
Creates a matrix
Microstructure: unreacted particles bonded to matrix
Microstructure of the set amalgam is unreacted metal alloy powders embedded in the matrix formed by the chemical reaction
Low-Copper Dental Amalgam
_____
__
___
____
There are different ways to describe the formula
___ ___ is mixed with ___
Gamma phase: ___ ___ ___. Still the powder
Gamma 1 phase: _____
___ AND ____
Gamma 2 phase: ____
Formed from ___ and ___
____ phase in this structure
_____ can happen along the gamma 2 phase
Normally long and penetrates throughout structure
If corrosion happens this wil ____ the __ ___.
Low-Copper Dental Amalgam
I/S-Alloy + Hg ® Residual Alloy + Matrix-1 + Matrix-2
Ag-Sn + Hg ® Ag-Sn + Ag-Hg + Sn-Hg
Ag3Sn + Hg ® Ag3Sn + Ag2Hg3 + Sn7-8Hg
Υ + Hg ® Υ +Υ1 + Υ2
There are different ways to describe the formula
Alloy powder is mixed with Hg.
Gamma phase: unreacted Metal alloys. Still the powder
Gamma 1 phase: Matrix 1
Silver and Mercury
Gamma 2 phase: Matrix 2
Formed from tin and mercury
Weakest phase in this structure
Corrosion can happen along the gamma 2 phase
Normally long and penetrates throughout structure
If corrosion happens this will weaken the structure greatly.
High-copper Dental Amalgam:
____=___=____
Newer and improved version
Copper can react with ____ and then form a __ __
Physically the final setting is to eliminate the ____ ___almost completely
That is why this (new) phase will increase the ___ ___ of the amalgam
That is why high copper version is on the market right now
High-copper Dental Amalgam:
Ag3Sn (g) + Ag-Cu + Hg
= Ag2Hg3 (Υ 1) + Sn7-8Hg (Υ 2) + unreacted particles
= Cu6Sn5 (η’) + Ag2Hg3 (Υ 1) + unreacted particles
Newer and improved version
Copper can react with gamma 2 and then form a new phase
Physically the final setting is to eliminate the gamma 2 almost completely
That is why this (new) phase will increase the mechanical strength of the amalgam
That is why high copper version is on the market right now
Composition of High Copper Alloy
Ag
Sn
Cu
Mercury Proportions
Admixed - ___% mercury (Hg)
Spherical - ___% Hg
Alloy particles: irregular particles have ____ surface area requiring____mercury
Mercury proportions in those materials depends on what types of alloys you are using
This is a ___ reaction so the larger SA you have the___ Hg you will need
Sphere has ____ SA so requires less Hg.
Mercury Proportions
Admixed - 50% mercury (Hg)
Spherical - 43-46% Hg
Alloy particles: irregular particles have larger surface area requiring more mercury
Mercury proportions in those materials depends on what types of alloys you are using
This is a surface reaction so the larger SA you have the more Hg you will need
Sphere has smallest SA so requires less Hg.
Microstructure
There are some ___ inside the material. We try to decrease the __ of ____ by doing condensation.
When dental amalgam fractures it fractures along the___ ____ inside the ___
So we try to minimize the amount of___in the material
Microstructure
There are some pores inside the material. We try to decrease the % of the pores by doing condensation.
When dental amalgam fractures it fractures along the unreacted powders inside the matrix
So we try to minimize the amount of matrix in the material
Unset vs Set Material
Unset material:
The particles are embedded in the __ of ___
Purpose of Condensation is to remove excess Hg
Matrix forms eventually.
Unset vs Set MaterialUnset material: The particles are embedded in the sea of Hg
Purpose of Condensation is to remove excess Hg
Matrix forms eventually.
Condensation
To ___ the ___ into the ___ ___
To attain the____ possible density (___ porosity)
To remove the ___ ___
During condensation the Hg rich layer will come on___
When you carve your restoration those layers will be___
Condensation
To compact the alloy into the prepared cavity
To attain the greatest possible density (reduce porosity)
To remove the excess mercury
During condensation the Hg rich layer will come on top.
When you carve your restoration those layers will be removed
Effects of Delayed Condensation
Amalgam ___ ____
You are breaking the structure and that will break the material
Lower____ (harder to ____ material)
Difficult to ___ ___ ___
Lower ___, higher ___ of the material
Effects of Delayed CondensationAmalgam partially sets
You are breaking the structure and that will break the material
Lower plasticity (harder to manipulate material)
Difficult to remove excess mercury
Lower strength, higher creep of the material
Physical PropertiesMetal
Thermal conductivity - ____
Coefficient of thermal expansion - ___ppm/ºC
- ___ than tooth structure
Electrical conductivity - ___
Radio____
It will be ___ on x-ray
Color - ___ ___ ____ (newly mixed material)
- __ ___
- Its diff then tooth color
Physical PropertiesMetal
Thermal conductivity - high
Coefficient of thermal expansion - 25 ppm/ºC
Higher than tooth structure
Electrical conductivity - high
Radiopacity
It will be light on x-ray
Color - Lustrous, shiny, white (newly mixed material)Metal white
Its diff then tooth color
Creep
Creep is the __ ___ ___e under ___
___ ___ ___ on amalgam cause creep.
Clinically associated with a ___ of the ___ ____ of restoration.
We load our restorations everyday
Repeated load can cause this material to have dimensional change
When you do your prep in operative, we have 90degree angles in the margin.
Overtime the material will expand and roll over to the margin to create a very__ ___for the restoration
Under load that ___ can ___
This material has ___ creep if you don’t manipulate it well
This doesn’t necessarily mean there will be ___ ___
In clinic you need to distinguish between___ ___ __n and ___ __
Creep
Creep is the gradual dimensional change under load.
Repeated chewing forces on amalgam cause creep.
Clinically associated with a breakdown of the marginal integrity of restoration.
We load our restorations everyday
Repeated load can cause this material to have dimensional change
When you do your prep in operative, we have 90degree angles in the margin.
Overtime the material will expand and roll over to the margin to create a very thin margin for the restoration
Under load that margin can break
This material has high creep if you don’t manipulate it well
This doesn’t necessarily mean there will be secondary decay
In clinic you need to distinguish between marginal break down and secondary decay
Properties of Dental Amalgam
Different clinicians prefer different material
Just preference
When you condense them you feel them differently
There really isn’t much difference
The compressive strength at 1 hour is very ___
So we tell patients “________________”
Wait until material completely sets. It will stand more load
Creep
High Copper is ___ ___ ___
All the red are in the standard
Different clinicians prefer different material
Just preference
When you condense them you feel them differently
There really isn’t much difference
The compressive strength at 1 hour is very lowSo we tell patients “don’t chew on this side for 24 hours”
Wait until material completely sets. It will stand more load
Creep
High Copper is not that much
All the red are in the standard
ANSI/ADA Specification No. 1
Creep at 4 hr - __% max
Compressive strength at 1 hr - ___ MPa
Dimensional change at 24 hr - +/-__ mm/cm
Determination of “___ and ____”
Dental Amalgam has been used in dentistry for a long time
That’s why the first specification is on this material
It tells us the ___ requirements for this material
Doesn’t necessarily mean ____
Note: Higher strength doesn’t translate directly to better ___ ___
ANSI/ADA Specification No. 1
Creep at 4 hr - 3% max
Compressive strength at 1 hr - 80 MPa
Dimensional change at 24 hr - +/-20 mm/cm
Determination of “safety and efficacy”
Dental Amalgam has been used in dentistry for a long time
That’s why the first specification is on this material
It tells us the minimum requirements for this material
Doesn’t necessarily mean longevity
Note: Higher strength doesn’t translate directly to better clinical performance
Clinical SignificanceAmalgam is generally considered a ___ material.
There is a certain requirement when we prep for those restorations
In operative class they will teach you how to prep
There are certain ____ for width, depth and now sharp angles
Clinical SignificanceAmalgam is generally considered a brittle material.
There is a certain requirement when we prep for those restorations
In operative class they will teach you how to prep
There are certain requirements for width, depth and now sharp angles
Galvanic Effect
When two metallic restorations consisting of metals with different degrees of _____are placed in close proximity, it is possible that a galvanic ___l will be set up.
The resultant currents can
Cause ___ ___
Leave a ___ ___ ___ in the mouth
Accelerate the ____ ______ of the ___ electronegative metal.
Galvanic Effect
When two metallic restorations consisting of metals with different degrees of electronegativity are placed in close proximity, it is possible that a galvanic cell will be set up.
The resultant currents can
Cause patients discomfort
Leave a strong metallic taste in the mouth
Accelerate the corrosive breakdown of the more electronegative metal.
Corrosion and Tarnish
Corrosion is the ____ of metals in the mouth and affects the ___ of the____
May also result from ___ ____ in foods or saliva.
Corrosion products ___ ____
Affects the ___ ____ of the material
Tarnish is a ___ ___of ___ ___.Tarnish is ___ but does ___ ____ amalgam (corrosion does).
Tarnish doesn’t influence the ___ of the ___
Mechanical property of material is __ ___. It just looks ugly
Old amalgam looks ___
They both occur more on amalgam with ___ ___
____ is necessary to avoid them.
Corrosion and TarnishCorrosion is the dissolution of metals in the mouth and affects the body of the amalgam.
May also result from chemical attack in foods or saliva.
Corrosion products seal margins
Affects the mechanical property of the material
Tarnish is a surface reaction of surface discoloration.Tarnish is unesthetic but does not destroy amalgam (corrosion does).
Tarnish doesn’t influence the body of the amalgam
Mechanical property of material is still good. It just looks ugly
Old amalgam looks black
They both occur more on amalgam with rough surfaces
Polishing is necessary to avoid them.
Carving and Polishing
After carving you need to polish the material
Need to bring patient back
Gives ____ to the amalgam
Carving and Polishing
After carving you need to polish the material
Need to bring patient back
Gives longevity to the amalgam
Clinical Performance
Longevity
___ yrs ideally, ___ yrs practically
Depends on situation. How you place them? Patient bite force? Cavity size?
Modes of failure
___, ___ ___, ___ ___
Main reason is ___
If your prep is good, the material doesn’t ___ as ___.
Theoretically this material will last 20-25 yearsPractically, because of manipulation and we cant achieve the ideal properties (sometimes we can)
Usually lasts only about 10 years
This is ___ the longevity of dental composites
Clinical PerformanceLongevity
20-25 yrs ideally, 8-12 yrs practically
Depends on situation. How you place them? Patient bite force? Cavity size?
Modes of failure
caries, margin fracture, bulk fracture
Main reason is decay!
If your prep is good, the material doesn’t fracture as easily.
Theoretically this material will last 20-25 yearsPractically, because of manipulation and we cant achieve the ideal properties (sometimes we can)
Usually lasts only about 10 years
This is double the longevity of dental composites
Advantages of Dental Amalgam
___
___ ___
___ to ___
- Less ___ ___
- ____
Takes ____ ____ for you to place than composites most of the time
Disadvantages of Dental Amalgam
Un____
Requires ___ ___ ___
____ (very rare)
___ __/____
Concerns about ___ ____
Advantages of Dental Amalgam
Durable
Cost effective
Easy to use
Less technique sensitive
Forgiveness
Takes less time for you to place than composites most of the time
Disadvantages of Dental Amalgam
Unaesthetic
Requires Complex tooth preparation
Allergy (very rare)
Galvanic effect / conductivity
Concerns about mercury toxicity
- Biological Properties
- Mercury Toxicity:
- OSHA maximum threshold limit value TLV = __ mg/m3 (vapor) per __ hr work week.
- Transient intraoral release (___ mg/m3).
- Mercury Hypersensitivity_____ evel allergic reaction.
- Very rare
- Estimated to be < 1 / ______
- Amalgam Tattoo:
- Can occur during ___ ___ if no ___ ____
- Embedded amalgam particles ___ and locally ___ gum.
- No known ___ ___
- Its just not ___
- You can see black spots on ___ or on ___
- Those are caused by small pieces of amalgam
- When you do restoration those amalgam pieces get into the___ ___ and then just stay there
- Just esthetically this doesn’t look good
Biological PropertiesMercury Toxicity:
OSHA maximum threshold limit value TLV = 50 mg/m3 (vapor) per 40 hr work week.
Transient intraoral release (<35 mg/m3).
Mercury Hypersensitivity:Low level allergic reaction.
Very rare
Estimated to be < 1 / 100,000,000
Amalgam Tattoo:
Can occur during amalgam removal if no rubber dam.
Embedded amalgam particles corrode and locally discolor gum.
No known adverse reactions.
Its just not esthetic
You can see black spots on mucosa or on gingiva
Those are caused by small pieces of amalgam
When you do restoration those amalgam pieces get into the soft tissue and then just stay there
Just esthetically this doesn’t look good
