Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

operative (morning) > Amalgam > Flashcards

Amalgam Flashcards

1
Q

advantage of dental amalgam?

A

IDK

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

disadvantage of dental amalgam?

A
  1. poor esthetics compared to resin composite
  2. weakening of tooth from removal of tooth structure
  3. recurrent carries
  4. no adhesive bonding, unless bonded restoration
  5. sensitivity of properties to manipulation
  6. brittle nature of material
  7. biocompatibility
  8. wastewater pollution w/ mercury
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

general setting reaction of amalgam?

A

alloy + Hg -> amalgam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Mercury/alloy ratio in dental amalgam

A

0.5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

mercury/alloy ratio range in commercial products

A

IDK

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

List the aspects of the alloy for dental amalgam particles that control the setting process

A

composition
shape
size of alloy particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

List the requirements for starting alloy particle composition and properties of the resulting dental amalgam that are given in American Dental Association Standard 1.

A

starting alloy particle:
-The total concentration of other elements cannot exceed 0.1 wt %, unless the manufacturer provides evidence of biocompatibility

resulting alloy properties:
creep 1.0 % maximum, dimensional change between -0.15 and +0.20 %, and compressive strength minimum of 80 MPa after 1 hour and 300 MPa after 24 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

State the two elements in greatest amount in the alloy for dental amalgam, along with other elements that are found in commercial products

A

2 primary elements:
Ag (primary) + Sn (secondary)
Also: 2-30% Cu and 0-1%Zn

May include: In and Pd

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Comment on whether the alloy particles mixed with mercury are single-phase or contain multiple phases

A

3 phases
gamma (Ag3Sn)
beta (Ag-Sn)
epsilon (Cu3Sn)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how are dental amalgams classified?

A

2 ways:

  1. Method of making Particles
    - Filing or lathe-cut
    - spherical
  2. composition of particles
    - all particles w/ same composition
    - different composition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the size range of the particles and the importance of this size range for condensation
of the dental amalgam mix

A

range:
- spherical particles range from 50micrometer diameter to over an order of magnitude smaller
- lathe-cut: wide range in sizes

intentionally done by manufacurer for optimum condensation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Explain the difference in mercury to alloy ratio that is needed for spherical alloy particles vs. lathe cut alloy particles.

A

spherical particles have lower mercury/alloy ratio than lathe cut

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

which one resists more force of condensation, spherical or lathe-cut?

A

lathe-cut

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

amalgam classification based on composition of particles?

A
  1. high copper vs low copper

2. zinc containing vs zinc free

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

high copper vs low copper, which one is better, why?

A

high copper bcz:
greater longevity
lower creep

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

zinc containing vs zinc free, which one is better? why?

A

either:

  • zinc improves corrosion resistance
  • if zinc, then less plastic amalgam mix
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what’s used in OSU?

A

60% spherical (50Ag, 30Sn, 20Cu, 0.5Pd)
40% lathe-cut (57Ag, 30Sn, 14Cu)

the product is classified as: fast, regular and slow setting time and ECT.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

relation btwn setting time and mercury/alloy ratio

A

slower setting times correspond to higher mercury/alloy ratio

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

why proprietary heat treatment?

A
  • eliminate compositional nonuniformaty
  • relieves stresses in alloy particles
  • provide manufacturer control of setting time (IMPORTANT)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

General form of setting rxn

A

gamma (starting alloy particles) + Hg (liquid) -> rxn phases (matrix) + unreacted particles (core)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

rxn of low copper amalgam

A

alloy (gamma) + Hg -> gamma 1 + gamma 2 + unreacted alloy particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

rxn of high copper amalgam

A

alloy (gamma) + Hg –> gamma 1 + n’ + unreacted alloy particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what’s present in both high copper and low copper amalgam?

A

gamma 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

No free mercury after _____

A

No free mercury after setting reaction

25
Q

stages of setting rxn

A

step one: both gamma 1 and gamma 2 form initially

step two: disappearance of gamma 2 and formation of n’

26
Q

what clinical problems would occur with an excessive setting expansion or contraction?

A

if expansion: loss of anatomy and postoperative pain

if contraction: microleakage

27
Q

general time period for the setting of a condensed dental amalgam?

A

24 hours

28
Q

core and matrix in terms of bricks and mortar

A 
bricks = alloy = core
mortar = rxn phases = matrix
29
Q

weakest microstructural phase ?

A

gamma 2 in low-copper amalgam

30
Q

which one corrodes? gamma 1 or 2

A

gamma 2

31
Q

what’s the strongest microstructural phase?

A

incompletely consumed starting alloy particles (gamma)

32
Q

what’s the major phase found in both low and high copper amalgam?

A

gamma 1

33
Q

amalgam: brittle or ductile?

A

brittle

34
Q

rate amalgam based on:

  • compressive loading vs. tensile loading
  • bending
A

compressive > tensile

cannot bend

35
Q

mechanical properties of amalgam after 1 hr, 1 day, and 1 wk

A

greater difference in strength after 1 hr compared to 1 day

final compressive strength = 1 wk (about the same as after 1 day)

36
Q

which amalgam sets most rapidly?

A

HCSS

37
Q

how is creep measured in lab?

A

cylindrical specimen
stored for 1 wk
compressed at 36 MPa
change in length measured from 1-4 hr

38
Q

which one has higher creep? low/high copper amalgam

A

low copper amalgam

39
Q

why is creep related to low copper amalgam?

A

creep mechanism is grain boundary sliding of gamma 1 phase (which is blocked by n’ in high copper amalgam)

40
Q

compare the compressive strength of LC, HCSS, and HCB

A

compressive strength:

HCSS > HCB > LC

41
Q

compare the tensile strength of LC, HCSS, and HCB

A

tensile strength:

HCSS > LC > HCB

42
Q

compare the creep of LC, HCSS, and HCB

A

creep (%)
LC > HCB > HCSS
(so LC sucks)

43
Q

compare tensile strength of amalgam, resin, alloy gold

A

tensile strength:

Gold alloy&raquo_space;> amalgam > resin

44
Q

what happens if you have too much mercury?

A

formation of greater amount of rxn phases

  • increases setting expansion
  • decreases strength
45
Q

why trituration?

A

decrease setting expansion

increase strength

46
Q

why condensation?

A

-adapt restoration to cavity walls
-minimize porosity
-control final mercury content
(also, decrease setting expansion and increase strength)

47
Q

what happen when we overtriturate?

A

makes mixed material hot
reduces working time
increases creep

48
Q

what’s the effect of small increase of condensation pressure?

A

-decrease setting expansion
-increase strength
(same reasons as the trituration reasons)

49
Q

problems of moisture contamination of Zinc-containing amalgam
-and what’s the mechanism for it?

A
  • excessive setting expansion
  • decreases strength

H2 released from Zn reduction of water

50
Q

Zn sucks, so why we may find it amalgam?

A

not economically feasible for manufacturer to eliminate Zn

-also, Zn eliminates corrosion

51
Q

types of corrosion and their possible location on the restoration

A
  • Galvanic corrosion: at interproximal contacts w/ gold alloys
  • electrochemical corrosion: b/c multiple phases
  • crevice corrosion at margins
  • chemical corrosion at occlusal (bcz of rxn w/ sulfide ions)

slide 35

52
Q

why do we prevent corrosion?

A

to reduce microleakage

to eliminiate decrease in strength

53
Q

what phases in low copper and high copper amalgams undergo corrosion?

A

low copper: gamma 2

high copper: n’

54
Q

why greater potential w/ low copper compared to high copper amalgam?

A

low copper has gamma 2 which results in bulk corrosion

high copper has n’ (n’ is not interconnected, so n’ corrosion only happens at the margin, w/o bulk corrosion)

55
Q

why polishing amalgam restoration would reduce corrosion?

A

bcz unpolished scratches or secondary anatomy = lower pH and O2 concentration of saliva = plaque = corrosion

56
Q

Zn containing amalgam vs. corrosion

A

Zn-containing amalgams have superior marginal integrity and longetivity
-preferential Zn corrosion may occur

57
Q

what are the routes of mercury exposure for dental office personnel and patients?

A

skin
inhalation of vapor
airborne droplets

58
Q

what’s the threshold limit value for mercury exposure?

A

0.05 mg Hg/m3

59
Q

what is recommended to do when placing amalgam?

A
  • use single use capsule
  • use a no-touch technique
  • clean up
  • discard any old or damaged mixing capsules
  • store amalgam scrap in cool space
  • store amalgam scrap in a jar of water and SULFUR
  • avoid baseboard heating in operatories where dental amalgam is used
  • use face mask and water spray with high vacuum evacuation
  • do not use ultrasonic condensers
  • office personnels should have their mercury levels checked by urinalysis

operative (morning) (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions