Amalgam

Question 1

what is amalgam made up of?

Answer 1

An amalgam is a mixture of two metals, mercury and silver based alloy

reaction of liquid (Mercury) and powder (Silver, Tin, Copper (10 – 30%)and other metals such as Palladium & Indium).

Question 2

what are the indications of use for amalgam?

Answer 2

Cavities in permanent teeth

For patients with inadequate oral hygiene

Extent of caries

poor moisture control

Question 3

what are the advantages and disadvantages of amalgam fillings?

Answer 3

advantages- strong under occlusal load, long lasting, easy to use not moisture or technique sensitive , good abrasion resistance to TB, cheap.

Disadvantages- aestheticly unpleasing, mercury toxicity, may need to remove healthy tooth to retain amalgam, thermal conductor.

Question 5

what are principles of amalgam cavity preparation?

Answer 5

outline form- gain access to caries using high speed and fissure bur.

remove peripheral caries and clear ADJ

Retention ( hold the substance)

resistance ( occlusal forces biting down)

correct cavity margins

Question 6

what do you place amalgam in?

Answer 6

Mixed amalgam is transferred to the tooth by an amalgam gun or carrier.

Question 7

what are 3 types of matrix bands?

Answer 7

Tofflemire

Siqveland – narrow/wide

Omni-Matrix

Kerr Hawe Adapt Super Cap Matrix

Automatrix

Sectional matrices

Question 8

what are 5 functions of matrix bands?

Answer 8

Replaces missing walls

Helps retain material during placement

Prevents material entering subgingivally

Provides moisture control

Prevents joining teeth together with restoration

Question 9

what are functions of wedges?

Answer 9

prevents overhangs

Prevents excess material at the cervical area of the cavity forming a ledge

Helps retain the matrix band

Absorbs Crevicular fluid

Question 10

reasons for carving amalgam?

Answer 10

Removes excess mercury

Removes excess amalgam

Restores tooth morphology

Restores tooth function

Produces a smooth surface

Question 11

ways for good mercury hygiene?

Answer 11

good ventilation in surgery

no carpets or tiles on surgery floor

mix and store away from heat

Question 12

what are reasons for replacing older amalgams?

Answer 12

secondary caries

fracture of filling

pulpal involvement/ endo treatment

Question 13

what are the 2 types of amalgam? ad are they high or low copper content

Answer 13

Traditional high copper content 12 - 13% copper
reduces the chance of marginal ditching creep and corrosion

Conventional low coper content 4-6% causes creep corrosion leads to marginal ditching

Question 14

what is amalgam creep?

Answer 14

ditch between tooth surface and amalgam caused by an overload on occlusal forces over a long period of time

Question 15

what is micro leakage in amalgam?

Answer 15

Caused by a gap between cavity wall and amalgam
Leads to secondary caries

Question 16

what is amalgam corrosion? what can it be minimised by?

Answer 16

Oxidation of amalgam from substances in saliva causes amalgam to breakdown impacting the properties

corrosion can be minimised by polishing

Question 17

what are the 3 phases of traditional low coper content amalgam setting reaction?

Answer 17

gamma phase - strongest phase

gamma phase1- not as strong as gamma phase

gamma phase 2- weak corrodes easily can take up to 24 hours to set

Question 18

amalgam setting high coper content phases?

Answer 18

gamma phase

gamma 1 phase

Eta phase

The eta phase reduces creep

Question 19

what are the different shapes of amalgam?

Answer 19

Lathe cut - Strong
Slow setting

spherical- Less wear resistance
Sets faster than lathe cut

Admixed-

Question 20

Properties Affecting Chemical Performance?

Answer 20

Thermal –due to the metal content, amalgam conducts heat and cold and usually requires a lining

Strength is affected by under mixing,poor condensation and high mercury content after condensation