Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

DS1102 > Week 8 - Dental Amalgam > Flashcards

Week 8 - Dental Amalgam Flashcards

1
Q

What is the composition of conventional amalgam

A

alloy powder + triple distilled mercury

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the composition of the alloy powder

A

Silver 67-74%
Tin 25-27%
Copper <6%
Zinc 2-5%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the amalgam setting reaction

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is y phase (gamma phase)

A

the primary phase formed during the setting of dental amalgam. It consists mainly of silver tin alloy (Ag3Sn) and is responsible for most of the amalgam’s strength and durability. the y phase is the least prone to corrosion and is essential for the mechanical properties of the amalgam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the tensile strength of y phase

A

170 MPa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is y1 phase (gamma 1 phase)

A

A silver mercury alloy Ag2Hg3. It is formed when the mercury reacts with the silver present in the amalgam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the properties of y1 phase

A
  • provides some tensile strength (more than y2 but less than y)
  • more susceptible to corrosion than the y phase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the tensile strength of y1 phase

A

30 MPa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is y2 phase (gamma 2 phase)

A

A tin mercury alloy (Sn8Hg).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the properties of y2 phase

A
  • weakest tensile strength
  • most corrosion prone
  • lead to degradation of the amalgam over time
  • cause high creep resulting in ditching
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the tensile strength of y2 phase

A

20 MPa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What do you do to reduce the amount of y2 phase in amalgam

A

Increase Copper content: high copper amalgams

Adding Cu = 10-30%

  • In high copper amalgams some of the tin reacts with copper instead of mercury, forming the y phase (gamma 1) which is more stable and less prone to corrosion. this substitution reduces the formation of y2 phase.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the dimensional changes during the setting reaction of amalgam

A
  1. Primary contraction - slight contraction as amalgam particles react with mercury
  2. Expansion - due to formation of the y phase
  3. Delayed expansion (only occurs sometimes)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What causes delayed expansion

A

Amalgams that contain zinc can react with moisture (especially in the presence of saliva or other fluids) after they have set. This reaction can lead to the formation of zinc hydroxide and hydrogen gas, contributing to an increase in volume.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is dimensional changes of amalgam depend on

A
  • type of alloy
  • particle shape and size
  • manipulative variables
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the 2 types of amalgam cuts

A
  1. Lathe Cut
  2. Spherical
17
Q

What is lathe cute

A

type of amalgam alloy that produces irregular shapes which can help improve the mechanical interlocking of the particles, contributing to the strength of the final restoration

18
Q

What is spherical amalgam

A

spherical shaped amalgam alloy

19
Q

What are the properties of spherical amalgam (5)

A
  • Spherical shape
  • Reach full strength faster than in lathe cut
  • Easier to carve and polish than lathe cut
  • Lower mercury content than lathe cut
  • Harder to condense than lathe cut
20
Q

What is A

A

course grain lathe cut

21
Q

What is B

A

fine grain lathe cut

22
Q

What is C

A

spherical

23
Q

What is the consequence of galvanic corrosion in the mouth

A
  • metallic taste
  • electric shock
  • discolouration

Note: Avoid adjacent or opposing dissimilar metallic restorations, and polishing old amalgam as this may trigger it.

24
Q

What are the 3 classifications of dental amalgams

A
  • Conventional
    1. lathe cute Ag3Sn
    2. Spherical Ag3Sn
  • High Cu single phase
    1. All spherical AgSnCu
    2. Lathe cut AgSnCu
  • High Cu admix dispersed phase
    1. Lathe cut Ag3Sn + spherical AgCu
    2. Lathe cut AgSnCu + spherical AgSnCu
25
Q

What is high Cu single phase amalgam

A

Contains higher levels of copper with reduced amount of tin.

Primarily forms a single phase structure due to the higher copper content. y 1 phase

This has improved strength, wear resistance and lower corrosion compared to conventional amalgams. Also has less dimensional change and reduced delayed expansion.

26
Q

What is high Cu admix dispersed phase

A

This amalgam combines both high copper spherical and the cut particles in the amalgam formulation. The composition typically includes a mixture of higher copper and traditional low copper alloy components.

Contains both single phase and multiphase structures.

27
Q

What are benefits of dispersed phase amalgams(6)

A
  • reach full strength more quickly
  • easier to condense
  • easier to carve and polish
  • lower mercury content
  • higher strength
  • more resistant to corrosion
28
Q

What is the mixing ratio of lathe cut alloy

A

% lathe cut alloy = %mercury

29
Q

What is the mixing ratio of spherical alloy

A

%spherical alloy > %mercury

30
Q

What does under triturated amalgam look like

A

dull in colour and powdery

31
Q

what does over triturated amalgam look like

A

shiny

32
Q

What are reasons for the placement of amalgam restorations

A

Ranking

  1. Primary caries
  2. Secondary caries
  3. Poor margin
  4. Restoration fracture
  5. Tooth fracture
33
Q

What causes tooth fracturing with amalgam

A
  • due to amalgam not being bonded to the tooth structure
  • to prevent fracture you need convergent walls for all to provide retention - also dove tails
34
Q

What causes amalgam fracturing

A
  • thickness (not thick enough)
  • trituration (over trituration can affect properties, under trituration causes less crystals to forms also impacting the strength)
  • condensation (condensing the amalgam with a amalgam condenser, needs to be condensed well so that its adapted to the wall, the more you pack it squeezes out excess mercury which stops excess reaction from occurring which is good)
  • type of amalgam
  • occlusion (don’t want excess amalgam )
  • mature loading - ensure that amalgam is functional as soon as possible
35
Q

What causes marginal breakdown of amalgam

A
  • creep and corrosion
  • Wrong Cavo-surface angle
  • over filling - need to make sure that amalgam doesn’t extend on top of sound tooth structure because this is prone to fracture and can cause ditching on margins.
  • underfilling/over carving - underfilling is also prone to fracturing
  • delayed expansion - if you don’t control moisture it can be absorbed into the material and cause expansion in the material later - delayed expansion
36
Q

What causes recurrent caries in amalgam

A
  • poor matrix technique e.g. not mixing enough
  • Poor condensation - there are gaps at the bottom of the prep
37
Q

What are problems with amalgam

A
  • lack of aesthetics
  • non adhesive to tooth
  • lack of tensile strength and toughness
  • susceptible to corrosion
  • lack of biocompatibility -

Using a bond in between enamel and amalgam can reduce marginal leakage and sensitivity it however does really aid in bonding strength e.g. panavia - however this is not very popular

38
Q

What are the potential sources of mercury contamination

A
  • spills
  • leaky dispensers or capsules
  • removing or polishing amalgams
  • sterilizing Hg contaminated instruments
39
Q

What are mercury hygiene tips

A
  • Avoid direct skin contact with dental amalgam
  • use high volume evacuation when finishing or removing amalgams
  • use rubber dam
  • Store amalgam scrap under radiographic fixer solution in a designated container
  • Report and clean up skilled mercury immediately using a clean up kit
  • wear professional clothing only in the dental surgery
  • provide proper ventilation
  • monitor personnel
  • use proper work are design
  • use an amalgamator fitter covered during trituration

DS1102 (37 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions