clinical amalgam

Question 1

what is amalgam?

Answer 1

an alloy of mercury with another metal(s)

Question 2

what are the direct restorative materials?

Answer 2

amalgam
composite resin
glass ionomer/RMGI

Question 3

what are the indirect restorative materials?

Answer 3

gold
other metals
ceramic
composite resin

Question 4

what are the possible indications for amalgam?

Answer 4

direct rest. mod/large size cavity in posteriors

core build up when definitive rest. will be indirect cast restoration eg crown/bridge retainer

Question 5

when should amalgam not be used?

Answer 5

aesthetic important
history of sensitivity to mercury/other components
if retentive cavity cant be cut
excessive healthy tooth would have to be removed

Question 6

what are the advantages of amalgam?

Answer 6

durable
good long term performance
long lasting if good conditions
long term resistance to surface corrosion
short placement time
corrosion products may seal tooth rest. interface
radiopaque
colour contrast
economical

Question 7

what are the disadvantages of amalgam?

Answer 7

poor aesthetics
not easy bond
high thermal diffusivity
cavity prep may require destruction of sound tooth tissue
marginal breakdown
corrosion at interface may cause ditching
local sensitivity reactions
lichenoid lesions
-hypersensitivity 
galvanic response can occur
tooth discolouration
amalgam tattoo
mercury toxicity

Question 8

why is amalgam a ‘go to’?

Answer 8

quick and easy
self-hardening at mouth temp
load-bearing
bulk strength, wear resistance
1 visit
economical

Question 9

what is retention form?

Answer 9

features that prevent the loss of the restoration in any direction

Question 10

does an occlusal restoration need a significant undercut?

Answer 10

no a parallel or minimal undercut is all that is necessary

Question 11

what is resistance form?

Answer 11

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

Question 12

describe appropriate cavity floor in reference to resistance form

Answer 12

should be aprrox parallel to occlusal surface w/ sufficient depth to give adequate mechanical strength (1.5-2mm)

Question 13

describe the gingival floor of an interproximal box

Answer 13

approx 90 degrees to axial wall

if greater sloping incline make filling liable to sliding out

Question 14

what is a self-retentive box preperation?

Answer 14

minimal prep box

Question 15

what is a proximo-occlusal prep?

Answer 15

take out fissure as well as interproximal caries for better retention
-more healthy tissue removed

Question 16

what are the advantages of self-retentive box?

Answer 16

less tooth tissue removed
reduced amount of amalgam placed
sound tissue retained between proximal box and any occlusal cavity

Question 17

what are the disadvantages of self-retentive box?

Answer 17

can be more technically demanding that proximo-occlusal

further tx of any pit and fissure caries may be required

Question 18

what are the advantages of proximo-occlusal prep?

Answer 18

very retentive
treats pi & fissure caries
less/no opportunity for future caries in pit and fissures

Question 19

what are the disadvantages of proximo-occlusal prep?

Answer 19

destruction of tooth tissue for retention

increased risk of weakening the tooth

Question 20

describe mechanical additional retention

Answer 20

include grooves or dimples w/i cavity design
pin placement-titanium/stainless steel
used to increase retention in large non-retentive cavities or cores beneath crowns
self tapping screws
in dentine in greatest bulk of tooth
pack amalgam around pin

Question 21

what are initial problems with pins?

Answer 21

stress in tooth around pin
cracking of dentine
sensitivity of tooth due to temperature transference

Question 22

what are long term problems with pins

Answer 22

filling can leak but not fall out

-secondary caries can progress further into tooth

Question 23

describe adhesive technology (additional retention)

Answer 23

sealing and bonding restorations
bonding
RMGIC

Question 24

how is an amalgam cavity prep finished?

Answer 24

ensure all caries is removed
smooth and round internal line angles
check and finish cavo-surface angles
smooth cavity margins

Question 25

what are the consequences of moisture contamination

Answer 25

reduces strength
increases creep
increases corrosion
increases porosity
not as critical as in bonded composite rest

Question 26

how is dentine sealed?

Answer 26

cavity varnished

RMGIC

Question 27

what is microleakage?

Answer 27

passage of fluid and bacteria in micro gaps between rest and tooth

• pulpal irritation and infection
• discolouration
• secondary caries

Question 28

how does microleakage occur?

Answer 28

over time mechanical loading and thermal stress

Question 29

what is the function of a matrix?

Answer 29

recreate walls of cavity
allows creation of proximal form
allows adequate condensation
confines amalgam to cavity

Question 30

what does mixing time (trituration) affect?

Answer 30

handling characteristics
working time
amalgam microstructure
rest. longevity

Question 31

what is condensation?

Answer 31

expels excess mercury bringing it to the surface where it will be carved off
adapts material to cavity walls
reduces layering
eliminates voids

Question 32

how is optimal condensation achieved?

Answer 32

require correct size of instruments
easier to control initial increment with large plugger
-smear into cavity
-smaller plugger
-overlapping axial strokes
lateral as well as axial condensation
spherical alloys require less force for condensation

Question 33

what are the consequences of inadequate condensation?

Answer 33

lack of adaptation to cavity
poor bonding between layers
inadequate mercury expression and consequently removal during carving
inferior mechanical properties

Question 34

should the cavity be overfilled?

Answer 34

yes

Question 35

what is recreated during carving?

Answer 35

marginal ridge
inter-proximal contact areas
fissure pattern
cusps and cuspal inclines
re-establishes occlusal contacts

Question 36

describe finishing

Answer 36

only if required to adjust anatomical contour after amalgam has set
amalgam finishing burs with water spray
aspiration
unnecessary - can create heat

Question 37

what is corrosion?

Answer 37

detrimental change in the character of amalgam due to reactions in the mouth
associates with gamma 2 phase
-can cause marginal breakdown with creep and ditching
-expansion may assist in development in marginal seal

Question 38

what is creep?

Answer 38

slow internal stressing and deformation of amalgam under stress
-copper decreases
-more creep-weaker amalgam
correct cavo-surface angle is essential

Question 39

how are amalgam restorations removed

Answer 39

dental dam 
high volume aspiration
minimal cutting
selective cutting
hand instruments
-break up with handpiece then remove, least drill possible

Question 40

when is the greatest amount of mercury released?

Answer 40

during the insertion and removal of restorations

Question 41

what is the usual mecury hygiene?

Answer 41

dental dam
high volume aspiration
amalgam traps-seperators
spillage kit
correct disposal of waste amalgam
correct disposal of unused amalgam

Question 42

what are the signs of mercury toxicity?

Answer 42

neuro-toxicity
kidney dysfunction
reduced immunocompetence
effects on the oral and intestinal bacterial flora
effects on general health
foetal and birth defects

Question 43

who can amalgam not be used on without appropriate reson?

Answer 43

children under 15
pregnant women
breastfeeding women

Question 44

what are blacks cavity classifiacations?

Answer 44

I- pit and fissure caries
II approximal caries posterior
III - approximal caries anterior
IV - approximal caries involving incisal angle
V - caries affecting cervical surfaces
VI caries affecting cusp tips