7 - Amalgam restorations Flashcards
materials for direct restorations/ fillings?
Mercury + amalgams
Definition of amalgam
Mercury + amalgams
- why is mercury a suitable metal to use in amalgams/ why is mercury used?
- is the only metal which is liquid a normal temperature and atmospheric pressure and can dissolve other metals at room temperature
- mercury is therefore used in manufacture of dental amalgams
Why do we use mercury (Hg)?
Amalgam history
key element required for a successful amalgam filling?
- key element of successful amalgam filling material was an adequate proportion of mercury with other alloys in the mix and in the mixing procedure itself
Dental amalgam composition is based on what system?
Why may we add other metals to dental amalgam?
what other metals may we add and how will they affect the amalgam?
Conventional amalgam
1
what is conventional amalgam based on?
2
- what is the liquid part?
3
- what is the powder part
4
- what does the powder part form?
CONVENTIONAL AMALGAM
- powder / liquid system
1
why are other metals added by manufacturers
2
Function of mercury?
3
- max amount of mercury added?
4
- what happens to the mercury after amalgamation?
1
- to change the properties of the final restorations
2
- pre amalgamation
3
- 3% max by weight
4
- during condensation phase and blemeshing phase of the restoration (after amalgamation), a significant portion of the mercury is removed from the amalgam
CONVENTIONAL AMALGAM
- powder / liquid system
1
- function of silver + tin?
3
- max % amount of silver and tin added by weight?
CONVENTIONAL AMALGAM
- powder / liquid system
1
why are other metals may be added by manufacturers
2
- function of the metals added added?
3
- max % amount of metals added by weight?
ALLOY MANUFACTURING
1
how is the gamma phase alloy used in dental amalgams manufactured?
2
what are problems you may face during this stage
3
how could you overcome this problem?
ALLOY PREPARATION
1
what form must the final alloy be so we can use it?
2
what are the 2 possible ways to grind the alloy into powder form?
- after the alloy has been produced, casted + cooled down, needs to be grinded down to powder to use for dental amalgams
ALLOY PREPARATION
1
what is a lathe cut?
2
How is a lathe cut done? (PICTURE)
3
what type/ shape of particles are produced?
1
cooling down and mechanically grinding alloy to powder form
2
3
irregular sized particles
ALLOY PREPARATION
1
what is a spherical manufacture?
2
How is a spherical manufacture done? (PICTURE)
3
what type/ shape of particles are produced?
1
- atomisation in an inert atmosphere to make alloy into powder form
2
3
- consistent sized particles
- spheroidal particles
PARTICLE MORPHOLOGY
1
in commercially available dental amalgams formulation, are lathe cut or spherical particles usually used?
2
why is this type used? (picture)
2
- many alloy powder are formulated by lathe-cut and spherical particles
(MIX OF BOTH)
PARTICLE MORPHOLOGY
Differences between lathe-cut and spherical alloys?
Amalgamation setting reaction
1
initiated by?
2
Metals formed?
2
- metals are named gamma 1 and gamma 2 phases
SETTING REACTION
what happens during the setting reaction?
CARD 1
- INITIAL DISSOLUTION
SETTING REACTION
what happens during the setting reaction?
CARD 2
- FORMATION OF GAMMA 1
SETTING REACTION
what happens during the setting reaction?
CARD 3
- FORMATION OF GAMMA 2
(Ignore the crossing out that madeeha has done in the pic)
SETTING REACTION
what happens during the setting reaction?
CARD 4
- SET AMALGAM
SETTING REACTION
electron microscope image
Properties: Relative strength of different phases?
1
what are the phases?
2
in terms of the mechanical properties of the different systems, different phases have different relative strength
phases tensile strength order? (what do we assume when having this order) (PICTURE)
1
- gamma
- gamma 1
- gamma 2
- amalgam
2
Properties: relative strength of different phases?
1
what phase is relatively the weakest
2
what will reducing this phase do?