7. Amalgam Restorations Flashcards

1
Q

materials for direct restorations?

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

MERCURY + AMALGAMS

Definition of amalgam

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

MERCURY + AMALGAMS

  • why is mercury a suitable metal to use in amalgams?
A
  • 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

can all metals dissolve in mercury (Hg)?

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

Amalgam history

key element required for a successful amalgam filling?

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

Dental amalgam composition is based on what system?

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

Why may we add other metals to dental amalgam?

what other metals may we add and how will they affect the amalgam?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

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?

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

CONVENTIONAL AMALGAM

  • powder / liquid system

1
why are other metals added by manufacturers

2
- function of mercury added?

3
- max amount of mercury added?

4
- what happens to the mercury after amalgamation?

A

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

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

CONVENTIONAL AMALGAM

  • powder / liquid system

1
- function of silver + tin?

3
- max % amount of silver and tin added by weight?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

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?

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

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?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

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?

A
  • after the alloy has been produced, casted + cooled down, needs to be grinded down to powder to use for dental amalgams
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

ALLOY PREPARATION

1
what is a lathe cut?

2
How is a lathe cut done? (PICTURE)

3
what type/ shape of particles are produced?

A

1
cooling down and mechanically grinding alloy to powder form

2

3
irregular sized particles

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

ALLOY PREPARATION

1
what is a spherical manufacture?

2
How is a spherical manufacture done? (PICTURE)

3
what type/ shape of particles are produced?

A

1
- atomisation in an inert atmosphere to make alloy into powder form

2

3
- consistent sized particles
- spheroidal particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

PARTICLE MORPHOLOGY

1
in commercially available dental amalgams formulation, are lathe cut or spherical particles usually used?

2
why is this type used? (picture)

A

2
- many alloy powder are formulated by lathe-cut and spherical particles
(MIX OF BOTH)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

PARTICLE MORPHOLOGY

Differences between lathe-cut and spherical alloys?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

AMALGAMATION SETTING REACTION

1
initiated by?

2
Metals formed?

A

2
- metals are named gamma 1 and gamma 2 phases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

SETTING REACTION

what happens during the setting reaction?

CARD 1

A
  1. INITIAL DISSOLUTION
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

SETTING REACTION

what happens during the setting reaction?

CARD 2

A
  1. FORMATION OF GAMMA 1
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

SETTING REACTION

what happens during the setting reaction?

CARD 3

A
  1. FORMATION OF GAMMA 2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

SETTING REACTION

what happens during the setting reaction?

CARD 4

A
  1. SET AMALGAM
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

SETTING REACTION

electron microscope image

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

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)

A

1
- gamma
- gamma 1
- gamma 2
- amalgam

2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

PROPERTIES: RELATIVE STRENGTH OF DIFFERENT PHASES?

1
what phase is relatively the weakest

2
what will reducing this phase do?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

PROPERTIES: EVOLUTION OF STRENGTH WITH TIME

A
  • amalgamation reaction develops slowly
  • takes more than 24 hours to complete
  • this is of clinical relevance as amalgam restorations remain weak during that time
  • it usually good practice to recall the patient after 1 week of placing a restoration to refine the edges of the restoration + polish after the reaction is completely set
27
Q

PROPERTIES: STRENGTH COMPARED WITH DENTAL TISSUES

A
  • mechanical properties of amalgam restoration = similar to natural tooth substance

(NEED TO KNOW VALUES IN TABLE???? MAKE FCs FOR THESE??????)

28
Q

PROPERTIES - DIMENSIONAL CHANGE

  • what were some of the dimensional changes and why did some of these dimensional changes occur? (PICTURE)
A
  • early composition of amalgam released in the market demonstrated significant dimensional changes upon preparation of the amalgam mix + then after the reaction had completely set
29
Q

PROPERTIES: DIMENSIONAL CHANGES

MAKE Q

A
  • dimensional changes in amalgam (+ any other restoration) = significant clinical concern
  • contraction of the material results in marginal gaps
  • expansion results in protrusions or even tooth cracks
30
Q

what may contraction of the amalgam (or rest material) cause?

A
  • results in marginal gaps

this can allow:
- infiltration
- failure of restoration
- secondary caries

31
Q

new ISO standards for contraction and expansion of amalgam?

A
  • contraction should not exceed 0.1%
  • expansion should not exceed 0.2%
32
Q

THERMAL PROPERTIES

MAKE q’s

A
33
Q

THERMAL PROPERTIES

Thermal diffusivity and thermal expansion coef. of

  1. Dentine
  2. Amalgam

(NEED TO KNOW VALUES???)

A
34
Q

PROPERTIES: CORROSION

what happens when amalgam is placed in a wet environment?

A

CORROSION

35
Q

PROPERTIES: CORROSION

what does corrosion of amalgam lead to

A
  • can lead to the release of free mercury
36
Q

PROPERTIES: CORROSION

how can amalgam corrosion be reduced?

A

by polishing the restoration to a smooth surface

37
Q

PROPERTIES: CORROSION

what is a beneficial advantage of amalgam corrosion?

A
  • corrosion at interface between amalgam restoration and tooth can be beneficial
  • corrosion generates a less reactive species at the interface
  • this can create a microseal
  • this prevents microleakages
38
Q

PROPERTIES: PLASTIC DEFORMATION (CREEP)

  1. amalgam is subject to
  2. what may cause higher creep?
  3. what does creep cause?
A
39
Q

HIGH COPPER AMALGAM

  1. what does it eliminate?
  2. what does it do?
  3. how is copper added?
A

(- gamma 2 phase shows inferior mechanical properties)

40
Q

DISPERSED PHASE

  • EG of high copper amalgam where the final plan contains 2 additional dispersed phases
A
41
Q

High copper amalgam Vs conventional amalgam?

  • compressive strength
  • reaction set speed
  • creep
  • corrosion

copper is…

A
42
Q

Clinical procedure for amalgam restorations

A

1) Cavity preparation & pulp protection

  • crucial aspect of amalgam restoration
  • pulp protect if required (case by case)

2) Rubber dam, matrix and wedges application

  • to isolate the operating field

3) Amalgam trituration

  • NOT sure what he said (REWATCH AND FILL IN)
  • achieved by putting pre weighted ?? into ???
  • can regulate energy and timing of mixing procedure

4) Amalgam application (small quantity)

  • to fill all corners of cavity

5) Condensation

  • to remove excess mercury

6) Repeat 4 & 5 until cavity is filled (in slight excess)

7) Carving and burnishing

  • to shape we want to achieve
  • using natural remaining tooth structure as a guide
  • BURNISHING = important to achieve perfect marginal adaptation and remove any remaining unreacted mercury from the mix

8) Removing matrix

9) Refine carving in particular at the edges of restoration

  • ensures good marginal seal

10) Finishing & Polishing

  • ensure good contact points
  • to ensure ??? during chewing
  • polishing = important BUT can be done in second appointment (1 week after placement of 1st restoration)
43
Q

why is adequate cavity prep important for amalgam restorations?

A
  • key to maximise the long term success of amalgam restorations
44
Q

KEY ASPECTS TO CONSIDER WHEN CREATING CAVITY FOR AMALGAM RESTORATION

Why are these important to do/ how’re they beneficial

A
    • not leave any unsupported enamel structure under an amalgam restoration
  • as upon load this can lead to chipping + infiltration
    • lateral portion of cavity can be used to create a retentive structure like pit
  • can help avoid creep of the amalgam + overhanging of the amalgam structures
    • prep of corners of cavity not be wedge shaped, be more rounded
  • as shown in diagram, chewing force may be concentrated at corner and this can lead to cracking of residual dental structure
  • want a rounded corner of the cavity to have a more uniform stress pattern (stress of chewing would be dispersed over a large area + reduce risk of crack)
    • support of residual enamel structure + away from the vicinity of the pulp
45
Q

support of residual enamel structure + away from the vicinity of the pulp are KEY ASPECTS TO CONSIDER WHEN CREATING CAVITY FOR AMALGAM RESTORATION

In the diagrams which is the best and doing this and why?

A

C is the best

A- away from pulp so good in this sense BUT not good design for supporting residual enamel structure

B- residual enamel structure is well supported BUT too close to pulp

C- by exploiting a chamfer in the coronal part of the preparation, residual enamel is supported + is away from the pulp

46
Q

How was proportioning previously done + how is it done now?

A
  • PREVIOUSLY proportioning of powder + mercury of dental amalgam was done by dentist at dental chair

BUT

  • NOW done done by manufacturer and delivers capsules containing pre weighted amount of powder + mercury and is triturated using machinery
47
Q

MECHANICAL MIXING: TRITURATION

  1. why is correct trituration important?
  2. what is the correct trituration time dependent on?
  3. Under trituration causes…
  4. Over trituration causes…
A

1
- to ensure adequate properties of final amalgam mix
- hence in modern dent this is done automatically in machinery
- follow manufacturer instructions

48
Q

CONDENSATION

1
why is this an important step?

2
objectives? (IMAGE)

A

1
- to ensure quality of amalgam restoration

49
Q

CONDENSATION

1
when should it done

2
how should it be done

3
spherical Vs lathe cut amalgam condensation pressure?

A
50
Q

CARVING + FINISHING

1
working time?

2
spherical vs lathe cut - which produces a better surface

3
why should you avoid using too much pressure

4
advantage of a smooth surface

A
51
Q

Limitations of dental amalgams

A
52
Q

Concerns about using mercury alloy?

A
53
Q

Minimata treaty 2013

How safe is amalgam?

A
54
Q
A
  • some cases, mainly in incongruous amalgam restorations with sharp edges or particularly oxidised structures, can lead to mucositis + lesions in oral mucosa
55
Q
A
  • key result of minimata treaty of 2013, was phase down of use of dental amalgams in dental practise
56
Q
A
  • after safety concerns + minimata treaty + advancement of other materials like composite, amalgam usage has decreased significantly
57
Q

REMOVAL OF DENTAL AMALGAM RESTORATIONS

what to consider?

A
  • as many amalgam restorations have been placed some dentists may carry out amalgam restoration removal BUT this poses significant risk to operator and patient
    BECAUSE
  • Hg levels during removal of amalgams exceed governments’ safety limits
58
Q

REMOVAL OF DENTAL AMALGAM RESTORATIONS

Safety measures to minimise patient + operator exposure during removal?

A

1) (or slight incongruous ones)

2) (add for operator and team)

3) (+ possibly use more powerful aspiration system to minimise diffusion of microparticles in the environemtn)

59
Q

OVERALL
1
use of amalgam is strongly discourage in

2
general

A
60
Q
A

Minamata convention on mercury
http://www.mercuryconvention.org

Scientific Committee on Health and Environmental Risks (SCHER):

Opinion on the environmental risks and indirect health effects of mercury from
dental amalgam (update 2014)
https://ec.europa.eu/health/sites/health/files/scientific_committees/environmental_risks/docs/scher_o_165.pdf

Opinion on the safety of dental amalgam and alternative dental restoration
materials for patients and users
https://ec.europa.eu/health/scientific_committees/emerging/docs/scenihr_o_046.pdf

61
Q

FURTHER READING APPENDIX 1 -

CONCERN ABOUT MERCURY IN AMALGAM

  • why the concerns about mercury in amalgam?
  • so some people have reactions to amalgam?
  • if amalgam is safe, why does my dentist take precautions when handling it?
  • should I have my amalgam fillings removed?
A
62
Q

FURTHER READING APPENDIX 2 -

AMALGAM REMOVAL GUIDELINES

  • international association for oral med + tech
A
63
Q

FURTHER READING APPENDIX 3 -

POLICIES ON DENTAL AMALGAM

(BDA’s view)

A
64
Q

CONT.

FURTHER READING APPENDIX 3 -

POLICIES ON DENTAL AMALGAM

A