restoring with amalgam Flashcards
When is amalgam indicated?
poor moisture control poor patient cooperation high occlusal loading cusp replacement financial constraints no enamel margins subgingival cavities
What did the high copper alloy compostion eliminate?
gamma 2 phase
tin/mercury phase
what occurs at the tin mercury phase?
weakest phase
causes expansion
what does the copper/tin phase do?
improves strength
reduces creep
what was the problem with mercury free alloys?
increased corrosion
excessive post setting expansion
what is the procedure for class 11 restoration?
outline form- access occlusally, leaving enamel slither
remove caries- tidy margins, remove unsupported enamel
restore- place band, pack and carve
What are therapist controlled variables when restoring with amalgam?
trituration
condensation
burnishing
polishing
what does over trituration cause?
hot mix- sticky
decreased working time
what does under trituration cause?
grainy, crumbly mix
what are condensation rules re. lathe cut alloy?
small condenser
high force
what are condensation rules re. spherical alloys?
larger conesner
easier to displace
requires less force
what are rules in general re. condensation?
condenser must fit
place amalgam in increments
condense with pressure
over pack
what doe carving do
removes mercury rich layer
removes gross gingival excess
what does burnishing do?
removes excess mercury, improves margin adaption
improves smoothness
less leakage
When should you polish?
after 24 hours
what does polishing do?
increases smoothness
decreases plaque retention
decreases corrosion
When should a bonded amalgam be used?
when not enough tooth structure for retention
missing cusp
achieve complete marginal seal
what does a good marginal seal do?
prevents ingress of bacteria
protect the pulp
what are the benefits of bonded amalgam compared with composite?
no polymerisation shrinkage
what are the advantages of a bonded amalgam?
reduces need for prep of retentive features
reduces marginal leakage
reinforced tooth structure
describe the technique for a bonded amalgam
vitrebond liner acid etch margins prime and bond rely x arc- uncured ( chemical cure resin based cement) pack amalgam
what is the toxic element in amalgam?
mercury
what allergic reactions can amalgam cause?
lichen planus
dermatitis
What is the theoretical risk of foetal damage?
Hg can cross the placental barrier
