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all topics Flashcards

1
Q

What is the medical devices directive? What year was it brought about?

A

Statement of manufacture offered to all patients receiving dental appliances. March 2010.

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2
Q

What is the oral enviroment subject to?

A
  • loading (6kg)
  • on/off cyclical forces
  • chemicals
  • temp. changes in microseconds
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3
Q

What does the pdl act as for teeth?

A

shock absorber

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4
Q

what is tensile strength?

A

tensile=pulling strength

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5
Q

what is the unit of strain?

A

It has no unit because it is a ratio

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6
Q

what is compressive strength?

A

measuring how brittle something is

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7
Q

what is diametral tensile strength?

A

useful for brittle materials where conventional strength is not aceptable

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8
Q

what is flexural strength?

A

how much bend it has

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9
Q

what is shear bond strength?

A

test used to measure the overall strength of a material

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10
Q

what is cyclical stress?

A

application of cyclical loading for a defined number of cycles. Material will either fail/survive

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11
Q

how is surface roughness measured?

A

profilometer

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12
Q

what is meant by rheological properties?

A

study of materials flow properties eg. composite in syringe, impression materials. how viscous things are

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13
Q

biological properties are measured at three levels. What are these three levels?

A
  1. lab testing
  2. limited lab(in.vivo) usage testing
  3. human randomised controlled clinical trial
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14
Q

what properties would the ideal material have?

A

non-toxic
non irritant
harmless to dental pulp
no carcinogenic potential or irritancy

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15
Q

metals at an ambient temperature are what?

A

hard and lustrous
closely packed
opaque
conductors of heat and electricity

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16
Q

what is an alloy?

A

a mixture of metals

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17
Q

what is an alloy system?

A

the consideration of all possible combinations of that alloy

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18
Q

what are crystals termed in a metal?

A

grains

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19
Q

what is a grain boundary?

A

where the crystals in a metal meet, its a source of tension

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20
Q

nucleation of a metal may be heterogenous or homogenous. what is meant by:

  1. heterogenous
  2. homogenous
A
  1. many sites of nucleation

2. single site of nucleation

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21
Q

in a metal, what does grain size influence?

A

physical properties

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22
Q

how do you visualise grain boundaries?

A
  • light reflecting microscope

- application of acid etch as the etch will attack the grain boundaries

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23
Q

what is malleability?

A

the max. degree of compression in response to an applied compressive force

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24
Q

what is ductility?

A

the max. degree of extension in response to an applied tensile force

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25
Q

there are three types of solid solution. what are these three types?

A
  1. ordered solid solution
  2. random solid solution
  3. interstitual solid solution
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26
Q

what is ordered solid solution?

A

atoms have specific sites in common lattice

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27
Q

what is random solid solution?

A

atoms have random sites in common srystal lattice

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28
Q

what is interstitual solid solution?

A

atoms lie within the primary lattice sites of the other

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29
Q

what do phase diagrams do?

A

phase diagrams construct a series of cooling curves for alloys of different compositon

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30
Q

what is a eutectic alloy?

A

very specific composition of 2 binary alloys

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31
Q

what are the two different compositions of amalgam?

A

conventional and high copper

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32
Q

what is the composition of conventional amalgam?

A

65% Ag, 29% Sn, 6% Cu, 2% Zn, 3% Hg

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33
Q

what is the composition of high copper amalgam?

A

40% Ag, 32% Sn, 30% Cu, 2% Zn, 3%Hg

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34
Q

what are the two variations in amalgam morphology?

A

lathe cut or spherical

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35
Q

is the gamma 2 phase present in both conventional and high copper amalgam?

A

yes, but is much less in the high copper amalgam

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36
Q

what effect does Cu have on amalgam?

A

strengthening effect

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37
Q

what does Zn act as in alloy production?

A

Zn acts as a scavenger for oxygen

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38
Q

what is the mixing of amalgam termed?

A

mixing of amalgam = trituration

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39
Q

Does the net expansion/contraction of amalgam balance itself out

A

yes

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40
Q

What is the percentage of expansion/contraction set by the ISO?

A

+/- 0.1%

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41
Q

the release of hydrogen gas results in what?

A

uncontrolled expansion

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42
Q

amalgam is fully set after how many hours?

A

24 hours

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43
Q

is amalgam strong or weak in thin sections?

A

weak

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44
Q

spherical amalgam has a larger what that results in it setting faster?

A

spherical amalgam has a larger surface area

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45
Q

what is creep?

A

protrusions at restoration margins

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46
Q

creep causes what?

A

ditching. Bits of amalgam to fracture of

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47
Q

what is largely, but not exclusively responsible for creep?

A

gamma 2 phase

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48
Q

How is the gamma 2 phase reduced?

A

adding more copper

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49
Q

corrosion of alloy exacerbates the release of what at the marginal crevise?

A

mercury

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50
Q

what is the theory of mercuroscopic expansion?

A

localised expansion of amalgam. Where the amalgam wants to create small balls of mercury and trap them between the restoration and the tooth

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51
Q

why is an advantage of corrosion?

A

corrosion provides marginal seal

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52
Q

does amalgam have a high thermal diffusivity?

A

yes

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53
Q

what are four properties of amalgam?

A
  1. creep
  2. corrosion
  3. thermal
  4. biological
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54
Q

mercury compounds are known to be toxic to what part of the body?

A

CNS

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55
Q

some reports have linked amalgam to what?

A
  • ms
  • behavioural problems
  • psychiatric disturbances
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56
Q

drier mixes are achieved by what?

A

mechanical mixing

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57
Q

nowadays, how is amagalm normally dispensed?

A

its normally encapsulated

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58
Q

what was the earliest tooth coloured restorative material?

A

silicates

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59
Q

what are some of the properties of silicates?

A
  • release flouride
  • moisture sensitive
  • erosion prone
  • brittle
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60
Q

what was used as a restorative material between the 1960s and 1980s?

A

acrylics

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61
Q

what were the components of the powder in acrylic restorative materials?

A

Pmma(polymethylmethacrolate)

  • chemical initiator(usually peroxide)
  • pigment(makes it tooth coloured)
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62
Q

what was in the liquid component of acrylics?

A
  • mma monomer( methyl methacrolate monomer)

- chemical activator(amine)

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63
Q

what was the initial thing that set of the acrylic setting reaction?

A

amine (chemical activator)

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64
Q

what are the four stages of free radical polymerisation of methyl methacrolate?

A
  1. activation
  2. initiation
  3. propogation
  4. termination
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65
Q

what do the stages of free radical polymerisation mean for the clinician?

A
  • material contracts on setting

- reaction is exothermic

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66
Q

how were acrylics better than silicates?

A

acrylics are:

  • less prone to erosion
  • less soluble
  • less acidic
  • less brittle
  • low thermal diffusivity
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67
Q

In 1951, what did Knock & Glen do to acrylics?

A

they introduced inert filler particles that reduced shrinkage

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68
Q

In 1963, what did Bowen do?

A

covered the filler particles in a coupling agent, this overcame weaknesess. It was now known as composite.

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69
Q

laser light curing technology was developed to give what?

A

command curing

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70
Q

what are resin matrix generally based upon?

A

methacrolate or dimethacrolate monomers.

eg. BISGMA, Urethane, dimethacrolate

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71
Q

carbon to carbon double bond in the matrix takes part in what?

A

free radical polymerisation

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72
Q

what is a silorane?

A

where there is a ring and it opens up

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73
Q

what is the photosensitiser in composites?

A

camphorquinone

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74
Q

what in a silorane, is involved with the ring opening polymerisation?

A

oxirane

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75
Q

what in the filler causes radiopacity?

A

quartz

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76
Q

what are some examples of the glasses used as fillers?

A
  • aluminosilicates
  • boro silicate
  • barium oxide
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77
Q

what is the most common coupling agent used?

A

gamma silane(gamma-methacryloxypropyltrimethoxysilane) only need to know gamma silane!!

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78
Q

more filler results in what?

A

less contraction

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79
Q

how does the polymerisation of camphorquinone begin?

A

camphorwuinone yeilds the necessary free radicals to begin polymerisation

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80
Q

what is the most readily generated light that is used?

A

quartz halogen lights

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81
Q

what does the coupling agent do?

A

coupling agent transfers the stress generated under loading from the rigid brittle filler to the more flexible and ductile polymer matrix.

82
Q

what types of resin composites are there?

A

conventional, microfilled, hybrid, nano composites

83
Q

what is hybrid?

A

mix of conventional and microfilled

84
Q

what is the difference between type 1 and type 2 classifications according to ISO 4049?

A

type 1. restoration of cavities including occlusal surfaces

type 2. all other polymer based filling and restorative materials

85
Q

does the viscosity of resin composite increase when leaving the tube?

A

yes it does.

86
Q

what are three mechanisms that result in wear?

A
  1. abrasive
  2. erosive
  3. fatigue
87
Q

polycarboxylated cements replace what?

A
  • ion leachable glass
  • polycarboxylic acid
  • set cement
88
Q

the setting reaction in glass polyalkenoate, powder & liquid is essentially what?

A

acid based

89
Q

the powder in glass polyalkenoate is what?

A

sodium aluminosilicate glass

90
Q

porosity causes stress. stress causes what?

A

stress causes cracks

91
Q

what is the setting reaction in glass polyalkenoate?

A

glass + acid =cored structure

92
Q

what is the outer layer in the cored structure of glass polyalkenoate?

A

outer layer = rich in calcium

93
Q

what is the inner layer in the cored structure of glass polyalkenoate?

A

inner layer = aluminium

94
Q

what is the charge in the calcium and aluminium ions in glass polyalkenoates?

A

Ca2+

Al 3+

95
Q

how do the calcium and aluminium ions play a part in the setting reaction of glass polyalkenoate?

A

the cross link acid chains

96
Q

in the initial set, is it the calcium or aluminium ions that are predoinant?

A

calcium ion is predominant over aluminium

97
Q

why is the calcium ion predominant over aluminium ion in the initial set?

A
  • calcium is on the outer surface of glass so its the first thing that the acid meets
  • calcium is more mobile in solution than aluminium
  • -more statistically likely that two chains will come along rather than three chains( transport analogy)
98
Q

why is vaseline used after placing glass polyalkenoate?

A

as the final set (aluminium) has to be protected from water

99
Q

how does the glass polyalkenoate bond to tooth substance?

A

via calcium inos

100
Q

what does citric acid do?

A

citric acid removes the smear layer

101
Q

what does polyalcrylic acid do?

A

increases bond strength

102
Q

what are some of the properties of glass polyalkenoate?

A
  • thermal diffusivity is close to dentine
  • chemical set is exothermic
  • flouride release
  • brittle
  • poor abrasion resistance
  • susceptible to acid erosion
  • good appearance
103
Q

in modified composites, the filler is replaced with what?

A

aluminosilicate glass. This encourages flouride release

104
Q

what is a giomer?

A

modified composite, however aluminosilicate glass is pre-reacted with polyacid to form a pre reacted glass polyalkenoate complex

105
Q

what are the two types of reaction involved with giomers?

A
  1. surface reaction

2. full recation

106
Q

what is dark cure?

A

-doesnt really work, where both setting reactions have occured and the last setting reaction (dark cure) is where it sets in the presence of no light. But this doesnt actually happen!!

107
Q

is there a greater release of flouride when the pH is lower?

A

yes

108
Q

what are some advantages of composite?

A

strong, tough, insoluble, radiopaque, quick setting

109
Q

what are some disadvantages of composite?

A

no inherent adhesion, shrinkage, no flouride release

110
Q

what are some advantages of glass polyalkenoate?

A

inherent adhesion, little shrinkage, flouride release, bicompatible

111
Q

what are some disadvantages of glass polyalkenoate?

A

brittle, soluble, not radiopaque, slow set

112
Q

where does the setting reaction happen in phosphoric acid based cements?

A

at the surface of the powder

113
Q

Phosphoric acid based cements have a low pH and low molecular weight, what does this mean?

A

it can penetrate more dentinal tubules

114
Q

Phosphoric acids are radiopaque, what is the constituent of phosphoric acid that causes it to be radiopaque?

A

zinc oxide

115
Q

does phosphoric acid based cements have an obtundent effect?

A

no

116
Q

how does zinc oxide eugenol cements set? by what reaction?

A

chelation

117
Q

are reinforced zinc oxide eugenol cements obtundant?

A

yes

118
Q

are reinforced zinc oxide eugenol cements strong that just zinc oxide eugenol cements?

A

yes

119
Q

is VLC exothermic or endothermic?

A

exothermic

120
Q

what are some of the properties of calcium hydroxide cements?

A
  • high pH gives beneficial irritancy and renders it bacteriocidal
  • thermal and electrical insulator
  • radiopaque
  • not adhesive so there is no coronal seal
121
Q

polycarboxylates are acidic but have a gih molecular weight, what does this reduce?

A

reduces penetration and therefor it is mildly irritant to the pulp

122
Q

glass ionomers are bacteriostatic due to what?

A

flouride release

123
Q

what cements have zinc oxide in them?

A

poly F, calcium hydroxide, zinc oxide eugenol, phosphoric acid based cements

124
Q

poly F cross links with what ions?

A

calcium ions

125
Q

what is the test that can be done to measure strength?

A

shear bond strength test

126
Q

glass polyalkenoates have a cord structure, what is this due to?

A

this is due to the concentration gradients

127
Q

where does the setting reaction happen in glass polyalkenoates?

A

setting reaction happens at the surface

128
Q

what is the C factor?

A

ratio of unbound to bound surfaces, most unfavourable = occlusal

129
Q

hydrocolloid impressionmaterials are hydrophobic. what does this mean?

A

moist surfaces will repel against it. Tissues that are moist will come close to the tissue but not actually touch it

130
Q

what would the ideal impression material be?

A
  • no changes when exposed to disinfectants
  • no interaction with model/die materials
  • non toxic
  • easily manipulated
  • palatable taste
  • realistic working/setting time
131
Q

what are the classifications of hydrocolloid impression materials?

A

non elastic or elastic

132
Q

is non elastic hydrocolloid materials highly mucostatic?

A

yes

133
Q

is non elastic or elastic hydrocolloid impression materials more commonly used?

A

elastic is more commonly used

134
Q

hydrocolloid are either reversible or irreversible. What is an example of them both.

A
  1. reversible=agar

2. irreversible=alginate

135
Q

what features do reversible and irreversible hydrocolloids both have in common?

A

both colloidal suspensions of polysaccharides in water

136
Q

alginate can only go from sol to gel, is agar the same?

A

no. Alginate can go from sol to gel, and from gel to sol.

137
Q

what is agar?

A

complex polysaccharide from seaweed

138
Q

what does borax do in agar?

A

borax gives it more body

139
Q

what are the temperatures that agar requires water bath conditioning?

A
  1. 65 and then to 45 which is the clinical usage temperature
140
Q

what are some of the disadvantages of agar?

A
  • cost
  • cross infection concerns of reuse
  • low tear strength
  • dimensionally unstable due to water content
141
Q

what is the composition of alginate, an irreversible hydrocolloid?

A
  1. sodium or pottasium salt
  2. calcium sulphate dihydrate
  3. sodium phosphate
  4. inert filler
  5. reaction indicator in some to signify set
142
Q

give two examples of mucostatic materials.

A

plaster and alginate

143
Q

in alginate, sodium phosphate limits the availability of what?

A

calcium ions

144
Q

what units is strain?

A

doesnt have a unit because it is a ratio

145
Q

why are impressions disinfected?

A

to prevent the transmission of blood borne viruses to patients, potential workers and members of the dental team

146
Q

what impression disinfection is used in DDH?

A

artichlor tablets, rinse and immerse in solution for 2 minutes

147
Q

give two examples of alternatives to impressions?

A
  • CAD CAM

- Intra oral scanner

148
Q

what are the 3 gypsum products?

A
  1. dental plaster
  2. dental stone
  3. densite
149
Q

at what temperature does gypsum turn into dental plaster?

A

120 degrees

150
Q

at what temperature is gypsum steam into dental stone?

A

steamed at 125 degrees

151
Q

what is gypsum boiled in to make densite?

A

calcium chloride

152
Q

does plaster or densite have larger particle size?

A

densite has larger particle size and has more porosities than plaster

153
Q

does plaster require more water than stone when mixing?

A

yes

154
Q

on mixing gypsum, air incorporation leads to what?

A
  • loss of detail

- weakness

155
Q

what happens in the 1st stage of setting in gypsum?

A

water becomes saturated with hemihydrate

156
Q

what happens in the 2nd stage of setting in gypsum?

A

conversion of hemihydrate to dihydrate

157
Q

what happens in the 3rd stage of setting in gypsum?

A

dihydrate crystalises out initiated by exposure to nuclei of crystallisation

158
Q

what is meant by the gilmore needles in gypsum setting?

A

where the initial set goes to intermediate set but not final

159
Q

what increases solubility of hemihydrate in gypsum?

A

hydrogen sulphate

160
Q

what is the retarder in gypsum?

A

borax

161
Q

Dyes are often added to gypsum, what colour is related to the following

  1. plaster?
  2. stone?
  3. die stone?
A
  1. white
  2. yellow
  3. blue/pink
162
Q

what are some of the properties of gypsum?

A
  • brittle
  • low flexural strength
  • good detail reproduction
  • soluble in water
163
Q

what are some of the advantages of gypsum?

A
  • inexpensive

- easy to use

164
Q

what are some of the disadvantages of gypsum?

A
  • may interact with the borax in alginate(Rare)

- hypochlorite may interact if not rinsed off implression before casting

165
Q

what are the three approaches to adhesion?

A
  1. micromechanical attachment
  2. chemical adhesion to enamel/dentine
  3. complex adhesion
166
Q

low contact angle means what?

A

high wetting ability

167
Q

what are the 3 factors effecting acid etch?

A
  1. etching time
  2. washing
  3. drying
168
Q

what does washing acid etch do?how long do you wash?

A

washing acid etch removes any debris. Wash for 60 seconds

169
Q

what does drying acid etch do?

A

drying enable hydrophobic resin to penetrate and attach

170
Q

what are some features of an ideal resin?

A
  • high bond strength to enamel and dentine
  • immediate,durable and reliable bond
  • prevent bacterial ingress
  • simple and safe to use
  • fit for purpose
171
Q

what are some of the problems that may occur in dentine bonding?

A
  • dentine is hydrophilic but adhesives are hydrophobic
  • dentine is a vital tissue
  • consists of inorganic and organic compounds
  • covered by a smear layer
  • smear layer occludes the dentinal tubules
172
Q

what do sealers do?

A

sealers flow into the dentinal tubules.
Seal the dentine with surface layer rich in methacrolates
ensures bonding to the resin composite

173
Q

what do dentine conditioners do?

A

dentine conditioners open dentinal tubules and demineralize surface dentine to a depth of 4 microns

174
Q

what do primers act as?

A

adhesives.

175
Q

what is the general formula of primers?

A

M-R-X
M=methacrolate group
R=spacer to allow system to move
X=interacts in some way to help dentine move

176
Q

What is a popular primer?

A

HEMA

177
Q

what are sealers a mix of?

A

BIS-GMA and HEMA

178
Q

There are three approaches to etching. What is involved in each of these approaches?

A
  1. 3 stage- etch prime and seal on different stages
  2. 2 stage- etch and then prime and seal together
  3. 1 stage- etch prime and seal all in the same stage
179
Q

what is an ormocer?

A

monomer free nanohybrid composite material

180
Q

what are the three components of an ormocer?

A

silicones, organic polymers and ceramic glasses

181
Q

what is meant when it is said that hydrocolloid impression materials are hydrophobic?

A

moist surfaces will repel against the material

182
Q

what are some ideal features of hydrocolloid impression material?

A
  • non toxic
  • easily manipulated
  • palatable taste
  • realistic working/setting time
  • no interaction with model/die materials
183
Q

there are two classifications of impression materials. What are they?

A

non-elastic or elastic

184
Q

is non elastic used regularly?

A

no, not commonly used anymore

185
Q

give an example of elastic impression materials.

A

hydrocolloids

186
Q

there are two types of hydrocolloid impression material. What are these two types?

A

reversible and irreversible

187
Q

what is an example of 1. reversible hydrocooloid and 2. irreversible hydrocolloid

A

reversible=agar

irreversible=alginate

188
Q

what features do reversible and irreversible hydrocolloids both have?

A

they are both colloidal suspensions of polysaccharides in water

189
Q

ISO4823 classifies according to what?

A
  • chemical nature

- consistency

190
Q

in the base paste of polysulphides, what makes it smell very bad?

A

thiol

191
Q

as cross linking occurs in polysulphides, what increases?

A

increased viscosity and elasticity

192
Q

what are some properties of polyshulphides?

A
  • high tear resistance
  • reaction continues with water loss
  • bad odour and taste
  • impression is easily read
193
Q

what is the setting reaction of silicon rubbers (condensation)?

A

cross linking of hydroxyl terminated polydimethylsiloxane chains

194
Q

what is the by product of silicon rubbers(condensation)?

A

alcohol. specifically ethyl

195
Q

what are some of the properties of silicon rubbers(condensation)?

A
  • set time is less than polysulphides
  • hydrophobic
  • tear resistance is adequate
  • good elastic recovery
  • considered non toxic in intra oral application
196
Q

what is the setting reaction of silicon rubbers addition curing?

A

platinum catalysed addition reaction

197
Q

is there a by product from silicon rubbers addition curing?

A

no. there is only a by product from condensation curing.

198
Q

what is the setting reaction of polyethers?

A

sets by cationic ring opening addition polymerisation

199
Q

how many types of ISO standards for dental gypsum products are there?

A

5

200
Q

what are the 3 types of gypsum products?

A

plaster, stone, densite

dental materials mixed (1 decks)

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