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BDS2 CDS DMS > 7. Clinical Application of Amalgam > Flashcards

7. Clinical Application of Amalgam Flashcards

1
Q

Definition of amalgam

A

An alloy of mercury with another metal or metals

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2
Q

Indications for amalgam ise (2)

A

A direct restoration in moderate and large sized cavities in posterior teeth
Core build-ups when the definitive restoration will be an indirect cast restoration such as a crown or bridge retainer

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3
Q

Contraindications for amalgam use (4)

A

If aesthetics is paramount to patient
The patient has a history of sensitivity to mercury or other amalgam components
Where the loss of tooth substance is such that a retentive cavity cannot be produced
Where excessive removal of sound tooth substance would be required to produce a retentive cavity

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4
Q

Advantages of amalgam (8)

A

Durable
Good long-term clinical performance (good bulk strength and wear resistance)
Long-lasting resistance to surface corrosion (can be used in load-bearing areas of the mouth)
Shorter placement time than composite (quick and easy, self-hardening at mouth temperature)
Corrosion products may seal the tooth restoration interface
Radiopaque
Colour contrast
Economical

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5
Q

Disadvantages of amalgam (12)

A 
Poor aesthetic qualities
Does not bond to tooth 
Thermal diffusivity high 
Cavity preparation may require destruction of sound tooth tissue
Marginal breakdown
Long-term corrosion at tooth restoration interface may result in “ditching” leading to replacement or repair
Local sensitivity reactions
Lichenoid lesions
Galvanic response can occur
Tooth discolouration
Amalgam tattoo
Concern about possible mercury toxicity
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6
Q

Definition of amalgam tattoo

A

Fine amalgam particles migrate into soft tissues (differential diagnosis; biopsy)

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7
Q

How does amalgam cause tooth discolouration

A

Corrosion products migrate into tooth surfaces which are porous (leading to darkened tooth)

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8
Q

Definition of Galvanism

A

Battery effect from two different amalgams or more likely amalgam and a cast metal restoration

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9
Q

Hypersensitivity associated with amalgam restorations

A

Type IV hypersensitivity

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10
Q

Treatment of Type IV hypersensitivity associated with amalgam

A

Remove amalgam and replace with gold/composite

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11
Q

Forms of cavity design (2)

A

Retention form

Resistance form

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12
Q

Definition of cavity design retention form

A

Features that prevent the loss of the restoration in any direction

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13
Q

Feature of amalgam cavity design retention form

A

In an occlusal direction, significant undercut is not required; parallel or minimal undercut is all that is necessary

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14
Q

Definition of cavity design resistance form

A

Features that prevent the loss of the material due to distortion or fracture by masticatory forces

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15
Q

Features of amalgam cavity design resistance form (2)

A

Ideally the cavity floor should be approximately parallel to the occlusal surface with sufficient depth of the cavity to give adequate mechanical strength (1.5-2mm)
The gingival floor of an interproximal box should be 90 to the axial wall. If it is greater than 90, this leads to a sloping inclined plane which makes the filling liable to slide out of the cavity

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16
Q

Cavity designs to treat interproximal caries (2)

A

Self-retentive box preparation (minimal preparation box)

Proximo-occlusal preparation

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17
Q

Self-retentive box preparation advantages (3)

A

Less tooth tissue removed than with a proximo-occlusal preparation
Reduced amount of amalgam placed
Sound tooth tissue retained between proximal box and any occlusal cavity

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18
Q

Self-retentive box preparation disadvantages (2)

A

Can be more technically challenging than proximo-occlusal preparation
Further treatment of any pit and fissure caries may be required

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19
Q

Proximo-occlusal preparation advantages (3)

A

(Should be) very retentive
Also treats any caries in pits and fissures
Less or no opportunity for future caries in pits and fissures

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20
Q

Proximo-occlusal preparation disadvantages (2)

A

Destruction of tooth tissue for retention

Increased risk of weakening of the tooth

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21
Q

Additional types of cavity preparation retention (2)

A

Mechanical retention

Adhesive technology

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22
Q

Types of cavity preparation mechanical retention (2)

A

Grooves or dimples

Pins

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23
Q

Definition of pins in cavity design

A

Titanium/stainless steel self-tapping screws and can work well in large restorations and for cores beneath crowns

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24
Q

Function of pins in cavity design

A

Used to increase the retention in large, non-retentive cavities, however use is controversial

25
Q

Features of pin placement (3)

A

Pins are placed into dentine in the greatest bulk of the tooth (never in enamel/at the DEJ)
Avoid the pulp and PDL
Pack amalgam around the pin. Never use pins with composite resins

26
Q

Problems with pins can be categorised into (2)

A

Initial

Long-term

27
Q

Initial problems with pins (3)

A

Stress in tooth around pin
Cracking of dentine
Sensitivity of tooth due to temperature transference

28
Q

Long-term problem with pins

A

Filling can leak but will not fall out because of the pin, leading to secondary caries which can progress further unto the tooth because of the pin

29
Q

Finishing of the preparation involves (4)

A

Ensuring all caries is removed
Smooth and round internal line angles
Check and finish cavo-surface angles
Smooth cavity margins

30
Q

Effect of moisture contamination (4)

A

Reduces strength
Increases creep
Increases corrosion
Increases porosity

31
Q

Definition of microleakage

A

Passage of fluid and bacteria in micro gaps (10um) between a restoration and tooth tissue

32
Q

Effects of microleakage (3)

A

Pulpal irritation and infection
Discolouration
Secondary caries

33
Q

Functions of matrices (4)

A

Recreate the wall(s) of the cavity
Allows the creation of proximal form
Allows adequate condensation
Confines amalgam to the cavity

34
Q

Ideal features of matrices (4)

A

Should be thin (<0.05mm)
Smooth
Strong to allow close adaptation (especially at cervical margin)
Good contact with adjacent tooth

35
Q

Functions of wedges (5)

A 
Essential to produce adaptation of the matrix at the cervical margin and can be inserted buccally or lingually (wizard/anatomical wedges)
Prevents excess amalgam gingivally
Aids proximal wall contour
Prevents movement of matrix band
Provide temporary tooth separation
36
Q

Mixing time affects (4)

A

Handling characteristics
Working time
Amalgam microstructure
Restoration longevity

37
Q

Functions of condensation (4)

A

Expels excess mercury bringing it to the surface where it will be carved off
Adapts material to cavity walls
Reduces layering (homogenous)
Eliminates voids

38
Q

Features of optimal condensation (5)

A

Requires the correct size of instruments
Easier to control the initial increment with a large plugger
Amalgam should be smeared into the cavity
Smaller plugger should be used for overlapping axial strokes
Condensation should be lateral as well as axial

39
Q

Condensation differences between amalgam particle types

A

Spherical alloys require less force for condensation

40
Q

Features of inadequate condensation (4)

A

Lack of adaptation to the cavity
Leads to poor bonding between layers
Causes inadequate mercury expression and consequently removal during carving
These restorations have inferior mechanical properties

41
Q

Function of carving

A

To recreate anatomical contour (including a marginal ridge, inter-proximal contact areas, fissure pattern, cusps and cuspal inclines and re-establishes occlusal contacts)

42
Q

Features of finishing (3)

A

May only be required to adjust anatomical contour after amalgam has set
Done using amalgam finishing burs with water (aspiration). Heat of finishing and risk of mercury should be considered
Polishing is unnecessary

43
Q

Definition of corrosion

A

Detrimental change in the character of amalgam due to reactions in the mouth
Associated with Gamma 2 phase

44
Q

Effects of corrosion

A

Can cause marginal ridge breakdown with creep and ditching

45
Q

How to prevent corrosion (2)

A

Expansion of amalgam during corrosive process may assist in the development of a marginal seal
Most amalgam is now non-gamma 2 (copper-enriched), so corrosion is less of a problem

46
Q

Definition of creep

A

The slow internal stressing and deformation of amalgam under stress

47
Q

How is creep reduced (2)

A

Creep is reduced by incorporating copper into amalgam (Ag-Sn-Cu phase is stronger)
Reduced creep should maintain marginal integrity

48
Q

Relationship between creep and strength

A

The greater the amount of creep, the weaker the amalgam

49
Q

Amalgam restorations may be used due to (3)

A

Secondary caries
Bulk fracture
Removal of an amalgam core within an extracoronal restoration

50
Q

Mercury can be absorbed into (5)

A 
Lungs (vapour)
Skin (contact)
Gastro-intestinal tract
Gingiva and mucosa
Dentine and pulp (metal ions)
51
Q

Content of mercury released by an amalgam restoration

A

0.5micrograms/surface/day

52
Q

Key points from the Minamata Convention on Mercury (4)

A

Encapsulated amalgam - mandatory from January 2019
Amalgam separators - mandatory from 2021; all amalgam separators installed from June 2017 must retain at least 95% of amalgam particles
All amalgam waste must be collected by an authorised waste management establishment
From July 2018, silver amalgam should not be used in children under 15 or pregnant or breastfeeding women (unless there is an appropriate reason for its use. Essentially the decision will be based on informed consent and clinical judgement)

53
Q

Types of Black’s cavity classification (6)

A 
Class I
Class II
Class III
Class IV
Class V
Class VI
54
Q

Black’s cavity class I

A

Pit and fissure caries

55
Q

Black’s cavity class II

A

Posterior approximal caries

56
Q

Black’s cavity class III

A

Anterior approximal caries

57
Q

Black’s cavity class IV

A

Approximal caries involving incisor angle

58
Q

Black’s cavity class V

A

Caries affecting cervical surfaces

59
Q

Black’s cavity class V

A

Caries affecting cusp tips

BDS2 CDS DMS (15 decks)

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