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Dental materials 1 > composite and amalgam > Flashcards

composite and amalgam Flashcards

1
Q

name 4 prop of composite

A

esthetically pleasing, strong, wear resistant, but have low to no fluoride release

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2
Q

what classes are composite recommended for

A

III to V

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3
Q

name the three phases of which composite is made of

A

resin matrix
dispersed inorganic filler particles
silane coupling agent

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4
Q

suggest a method to overcome or minimize the effect of polymerization shrinkage

A

insert and polymerize composite in layers

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5
Q

compressive and flexural strengths and elastic modulus or stiffness of microhybrid composites are dominated by what

A

the amount of filler and increases exponentially with the volume fraction of filler

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6
Q

name a downside to composite

A

loss of surface contour, which results from a combination of abrasive wear from chewing and toothbrushing and erosive wear from degredation of the composite in the oral environment

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7
Q

how to manipulate composite

A

with fourth abd 5th generation bonding agents:
1.enamel and dentin are etched with phosphoric acid
2.acid is flushed away with water
3.surface is dried gently with a steam of air
with 6th and 7th generation bonding agents:
etching and priming are accomplished at the same time and no rinsing is required

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8
Q

how are single paste composites activated

A

light activated thats why they come in an opaque plastic syringe to protect the material from exposure to light and thus provide adequate shelf life

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9
Q

name 4 direct esthetic restorative materials and name the date in which each one appeared

A

composite 1960
glass inomer 1972
Hybrid inomers 1990
compomer 1995

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10
Q

classify each material from the most releasing of fluoride to the least

A
  1. conventional glass inomer
  2. resin modified glass inomer
  3. compomer
  4. conposite
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11
Q

classify from most wear resistant to least

A
  1. composite
  2. compomer
  3. RMGi
  4. conventional glass inomer
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12
Q

what are Bis gma or UDMA (oligomers) characterized by

A

carbon double bonds

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13
Q

define an oligomer and give examples

A

it is a moderate molecular weight organic molecule made up of 2 or more molecules قليلة الحيدات

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14
Q

what is the principle system to achieve polymerization(setting) of composite

A

the visible light curing system

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15
Q

what is the exposure time to blue light

A

20 to 40 sec

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16
Q

what must be avoided when dealing with self-curing systems

A

the initiator and acceleratot must be kept separated and not mixed until just before the restoration is placed

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17
Q

describe the process of visible light curing systems

A

the composite is polymerized by exposure of it to intense blue light, the light absorbed by the diketone, which in tthe presence of an organic amine, starts the polmerization rxn.

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18
Q

what are the two types of composite

A

anatomical تشريحي

opaque كتيم

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19
Q

explain: the more the resin matrix, the higher the linear coeff of thermal expansion

A

because the polymers that are present i the resjn matrix have a hugher value than that of filler particles (molecules of filler particles are almost inert)

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20
Q

fill in the blank

most comosites are cosidered radiopaque when comapred with _____, and radiolucent when comapred with____

A
  1. dentin

2 .enamel

21
Q

in class V caries do we use a composite with less or more filler particles

A

less, because we want it to be somewhat elastic

22
Q

difference between coupling agents and bonding agents

A

coupling agents are used to bond resin matrix to inorganic filler particles while bonding agents are used to bond composite to prepared tooth

23
Q

why is the sixth and seventh generation bonding agents very practical,require no rinsing and are called self-etching

A

because they are self etching, as in the acid the primer and the bonding agent all come in one bottle so etching and priming are essentially done simultaneously
not that the acid used for etching is not phosphoric acid but a weaker acid beacause no rinsage will be done

24
Q

if a patient has sensitive teeth what bond generation is best to use and why

A

6th and 7th because the etchant is a weak acid which has a large molecular weight and thus a low likelihood of going into the dentinal tubules and to the pulp

25
Q

the silane bond is essentially bifunctional so it bonds to both composite and the prepared tooth,name the type of bonding with each

A

with the composite: chemical

with the tooth:micromechanical

26
Q

with time, how has amalgam developed

A

with time the percentage of copper in silver alloys increased, creating high-copper alloys which provied amalgam with higher strength and higher resistence to corrosion

27
Q

what is responsible for the superior properties of high cu amalgam over low-cu amalgam

A

the absence of gamma-2 product

28
Q

what is amalgamation

A

the rxn of the silver alloy with Hg

29
Q

what product results from the amalgamation of low-cu alloys with mercury

A

gamma-2 or (Sn-Hg) tin mercury which corrodes and leads to restoration failure

30
Q

write the amalgamation rxn of high-cu alloy with Hg

A

Hg + gamma= gamma + gamma-1 + eta

31
Q

what is gamma,gamma-1. and eta respectively,gamma-2

A

gamma: the silver alloy
gamma-1 : silver-mercury
eta: copper-tin
gamma-2: tin-mercury

32
Q

what are the 5 properties of amalgam with most clinical relevance

A

strength,dimensional change,creep,tarnish, corrosion

33
Q

how does amalgam manipulation attribute to its strength

A

inadequate condensation results in voids, which weaken the set mass.mixing the amalgam for too long or too short a time also weakens the final strength.

34
Q

define dimensional change

A

the net contraction(negative) or expansion(positive) of an amalgam during setting

35
Q

define creep, which has a higher creep range, high-copper or low-copper amalgams

A

progressive deformation of a material at constant stress(chewing). it occurs in positive dimensional change 9expansion of amalgam)
low copper amalgams

36
Q

what is the effect of negative dimensinal change of amalgam

A

means shrinkage of the restoration-aps at the margins-microleakage of oral fluids and bacteria,pulpal pain,and possibly recurrent decay

37
Q

what is the effect of positive dimensional change of amalgam

A

means expansion-pain,creep(deformation) of dentin,and fracture of the tooth

38
Q

clinical difference between tarnish and corrosion of amalgamn

A

tarnish-or the discoloration of amalgam with time-will not often cause the restoration to fail
whereas corrosion-or the dissolution of amalgam in moth- leads to failure of the restoration

39
Q

what is trituration

A

the process of mixing silver alloys with mercury

40
Q

does the amalgam bond to tooth structure

A

no, they have been retained by undercuts in the cavity design

https://pocketdentistry.com/wp-content/uploads/285/img0481.jpg

41
Q

ما هو الأملغم التقليدي

A

الفقير بالنحاس low-copper amalgam

42
Q

what form does the amalgam take if we are using an amalgamator(جهاز المعايرة الآلي)

A

capsules

43
Q

what is the percentage of both silver alloy and mercury in

  1. manual mixing
  2. mechanical mixing
A
  1. 40 % silver alloy, 60%mercury

2. 50 50

44
Q

which particles take up mercury more irregular or spherical

A

spherical

45
Q

what is the importance of adding 1 to 2 % of zinc in the silver alloy

A

to prevent oxidation of other metals

Ag2o (oxided silver) is highly unwanted

46
Q

what ia the importance of Sn or tin قصدير in the silver alloy

A

very important for الانسيابية/اللدونة

47
Q

what is the average condensation force

A

20N

48
Q

what is the purpose of polishing الصقل

A

removing excess Hg

Dental materials 1 (4 decks)

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