Dental Amalgam

Question 1

What are cavity varnishes?

Answer 1

are natural rosins (such as copal, colophony or sandarac resin) or synthetic resins (polystyrene) dissolved in a solvent (alcohol, ether, chloroform or acetone)

applied to walls and floor of the cavity using a brush

Question 2

What is the purpose of varnishes?

Answer 2

bridge the gap between the dentine and restorative material - decrease post-operative sensitivity and decrease microorganism

Question 3

What materials were use in varnishes?

Answer 3

gold and amalgam

Question 4

What is the mechanical mixing of amalgam known as?

Answer 4

trituration

Question 5

What is the tray lined with in amalgamators?

Answer 5

aluminium foil

Question 6

Why is the amalgamator lined with aluminium foil?

Answer 6

in the event of a mercury spillage, the aluminium foil will retain the mercury and react with it (it will not vaporise)

• reduce mercury vapour

Question 7

What happens if you overtrituration the amalgam?

Answer 7

too wet and hot after mixing and is difficult to remove from the capsule

leads to…
excessive expansion
reduced strength

Question 8

What happens if you undertrituration?

Answer 8

dry crumbly mix (not reacted enough)

low strength

poor corrosion resistance

Question 9

How do you put amalgam into teh cavity?

Answer 9

incrementally, in layers

bring mercury to the top then remove

Question 10

How do you want to condense amalgam?

Answer 10

laterally and axially

Question 11

How do you prevent bonding the amalgam to the band?

Answer 11

apply a thin layer of Vaseline

Question 12

Do you carve towards or away from the marginal ridge?

Answer 12

away

Question 13

What is burnish?

Answer 13

plastic deformation of a surface due to sliding contact with another object. Burnishing smears the texture of a rough surface rendering it shiny

Question 14

Why is it important to polish amalgam?

Answer 14

amalgam is rough at a microscopic level, with pits that retain food debris ad acids

improves marginal adaptation of material - extend life of retoration

easier to clean

Question 15

What reaction can occur if amalgam is not polished?

Answer 15

galvanic activity on the surface leading to corrosion in extreme cases

Question 16

What speed and bur would you use for polishing amalgam?

Answer 16

slow speed polishing burs

brown and green

Question 17

After polishing, how do you finish an amalgam restoration?

Answer 17

use a mix of zinc oxide powder and alcohol in a rubber cup or on a brush for a final high-lustre polish

Question 18

Is elemental mercury toxic?

Answer 18

yes, highly toxic

Question 19

When is more mercury vapour released, what temperature?

Answer 19

over 80dc

Question 20

What are teh adverse effects of amalgam?

Answer 20

enamel discolouration

amalgam tattoo

lichenoid reaction

galvanic cell

Question 21

Why does enamel discolour with amalgam?

Answer 21

due to dentine structure being permeable

particularly when the restoration has been in situ for some time

corrosion by-products migrate into dentinal tubules

Question 22

Why can an amalgam tattoo form?

Answer 22

some fine particles of the material can migrate into the soft tissue

benign lesion

may mimic melanoma

diagnosis confirmed by biopsy

Question 23

What can cause the lichenoid reaction?

Answer 23

not uncommon

believed to be caused by electrochemical reactions and a Type IV hypersensitivity reaction

use a different material

Question 24

What is a galvanic cell?

Answer 24

2 dissimilar metals and saliva

mild electric shock or a silver paper experienced

effects reduce with time

Question 25

When would you not use dental amalgam fillings?

Answer 25

pregnant or breastfeeding women

primary teeth

children under 15years

allergy to constituents

aesthetics

patient objects

Question 26

What is the main reason for phasing down amalgam?

Answer 26

environment

water contamination

Question 27

In the USA (FDA) what age do they allow amalgam to be used?

Answer 27

6 years and above