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Fixed Prosth 3rd year > L5- Impressions > Flashcards

L5- Impressions Flashcards

1
Q

die and why

A

positive reproduction of prepared teeth in a suitable accurate hard substrate

need because

  • accurate representation of the tooth preparation and adjacent structure
  • die must be strong enough to withstand the fabrication process
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2
Q

requirements for die material

A

accurate

dimensionally stable

minimum setting contractions and expansions

fine detail reproduction

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3
Q

good impression requires

A
  1. tooth prep that follow biomechanical principles
  2. carefult soft tissue management
  3. knowledge of the handling properties of the impresion material
  4. avoiding common problems
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4
Q

biologic width
1mm for
1mm for
plus?

A

1mm for connective tissue

1mm of junctional epithelium

plus 1 to 2 mm of tooth structure for the crown margin placement and terminiation

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5
Q

ferrule requirements

A

requires 2mm BEYOND a core material finish line

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6
Q

ferrule requirements

A

requires 2mm BEYOND a core material finish line

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7
Q

mechanical displacement he highlighted

A

knitted – ultradent – type of cord used

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8
Q

breakdown of careful soft tissue management

A
  1. mechanical- often most common - like PLACING cord
  2. hemostasis in the sulcus
  3. tissue removal
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9
Q

Most popular form of retraction

A

mechanical dispalcemnt

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10
Q

small 000-00 use?

A

anterior with thin tissue areas – lower cord in 2 technique

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11
Q

medium 0-1

A

osterior - lower cord in 2 cord technique - premolar - molar

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12
Q

large 2-3

A

uper cord in 2 cord technique - thick gingiva

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13
Q

UP cords thickness from thinness to largest?

A

0.5 - 1.4mm

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14
Q

first cord is?

A

smaller in diameter and equal or slightly less in length than the circumference of the tooth

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15
Q

second cord is? - in general

A

larger than first

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16
Q

prior to light bodty impression material?

A

only the second cord is removed

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17
Q

first cord must?

A

secure in the sulcus and exposes the finish line

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18
Q

correct cord placement

A

tucking it in - general

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19
Q

leave cord in for how long?

A

5-10 minutes

leave enough length of cord to easily capture with cotton pliers

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20
Q

cord he suggests

A

knitted - ultradent

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21
Q

twisted cord

A

tends to be separated by the packing instrument and it has BIAS AND MEMORY

  • first cord should disappear into sulcus
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22
Q

braided cord

A

is RIGID macking the packing into the sulcus challenging

has memory

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23
Q

knitted cord

A

more flexible and exerts an outward pressure once placed

will hold more hemostatic solution

NO MEMORY

easier to place

place and leave for 3-8 minutes

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24
Q

retarction and sulcular width - study?

A

Laufer et al - affect of marginal thicknesss on the distortion of different impression materials

“sulcus must be of enough width for the impression material”

0.2 mm SULCUS WIDTH IS MINIMUM REQUIRED

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25
Q

Class I hemostatic agents

A

vasoconstrictors

adrenergics

action – constricting blood vessels

can HAVE SYSTEMIC AFFECTS

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26
Q

class II hemostatic in the sulcus

A

hemostatic

ASTRINGENTS – action is precipitating proteins causing coagulation

**he suggests using this one due to no systemic affects

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27
Q

examples of class II

A

alumnimum chloride

ferric sulphate

ferric chloride

aluminum chloride gel

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28
Q

cord with epi?

A

class 1 - with systemic effects

0.2 to 1 mg/ in

max for healthy patient is 0.2mg (10 carpules)

NOT RECOMMENDED

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29
Q

GINGI-PAK

A

cord with epi – has .5 mg / in

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30
Q

implication of hemostatis agent OF CLASS II

A

changes pH – low

so need to rinse it out

because it ADVERSELY AFFECTS THE SURFACE DETAIL REPRODUCTION OF PVS IMPRESSION

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31
Q

% used class 1 in 1985?

A

79.39%

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32
Q

% used class 1 in 1999

A

14% – huge decline

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33
Q

electro- surgery / cautery

A

another way to remove tissue for impression

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34
Q

laser advantages

A

no bleeding / no referral to perio

make impression that day

makes wider area for impression materials with poor tear strength such as reversible hydrocolloid - like poly ether material

safe with implants if contacted

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35
Q

disadvantages of laser

A

can cause GINGIVAL RECESSION therefore NEVER recommended for anteriors or thin gingiva

cannot use on patients with delayed healing

does not involve osseous - no bone change = no tissue change - so not for CLP

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36
Q

laser vs bur

A

speed
- laser is slow (advantage) vs fast

bur will cause bleeding

bur – cannot use on implants – will damage implants if contacted

bur is fast – could be a disadvantage

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37
Q

polyether aka

A

impregum

polyether + sulphonic acid ester = cross linked rubber

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38
Q

impregum made of

A

polyether + sulphonic acid ester = cross linked rubber

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39
Q

polyvinylsiloxane

A

hydrogen contaiing siloxane + vinyl siloxane + chloroplatinic acid = silicone rubber

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40
Q

alter technique for gaggers

A

USE A CUSTOM TRAY

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41
Q

what do we want from an elastomeric impression

A

accurte reproduction of detail of the tooth prep and surrounding hard and soft tissue

dimensional stability to allow delayed pouring

ease of handeling

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42
Q

allergies?

A

no polyether

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43
Q

intitially fluid?

A

need this to get into the areas at first

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44
Q

tear resistance?

A

if this is adequate then wwhen remove it wont tear and remain in tact

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45
Q

working means

A

begin at START OF MIX and ENDS BEFORE ELASTIC PROPERTIES HAVE DEVELOPED

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46
Q

setting =

A

mix to removal

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47
Q

viscosity increase?

A

decreases in time

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48
Q

warm environemtn?

A

impression material is sensitive to changes in temperature - especially pvs

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49
Q

PVS set time in regular set

A

into mouth is 2:30 – do not remove for 5 mins

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50
Q

thixotropic means

A

flows smoothly under pressure in critical areas and remians fixed without pressure

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51
Q

snap set properties

A

reduces the potential for distortion during the setting process and removal from the mouth to assure a precise - fitting final restoration

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52
Q

polyvinl snap set?

A

NO - so hold in patietns mouth - if trey moves - will be distorted

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53
Q

thixotropic under pressure?

A

materials viscosity will REDUCE when it is placed under stress

54
Q

greatest flow?

A

polyehter

impressions with deep subgingival margins and / or multiple preparations mayh be better captured wit a polyether impression material

55
Q

advanatges to polyether

A

SNAP SET
good working time

very STIFF when set - Hi shore hardness

sets 5-6 mins

thixotropic

hydrophillic

excellent accuracy and wetting

56
Q

complete wetting?

A

contact angle of 0 degrees

57
Q

higher contact angle

A

greater than 90 – means lower wetting

58
Q

higher contact angle

A

greater than 90 – means lower wetting

59
Q

custom trey requires?

A

tray requires approximately 3mm of relief over the diagnositc cast and at least 3 vertical stops

60
Q

custom trey requires?

A

tray requires approximately 3mm of relief over the diagnositc cast and at least 3 vertical stops

61
Q

advantages of custom treys

A

reduced volme of the material

take advantage of the fluid dynamics of non-newtonian materials

reduced cost of the impression –(15+ estimated cost of impression in a stock trey)

improved accuracy by reducing stress due to thermal contraction and having an eve amount of material around the prepared teeth

IMPROVED ACCURACY by reducing the potential for the tray to flex

62
Q

_____ the stock trey

A

customize the stock trey

63
Q

_____ the stock trey

A

customize the stock trey

64
Q

order of loading?

A

load the tray first

then load the syringe second

65
Q

dual arch /triple trey

A

bad

FLEXIBLE – which is a very bad trait

so impression is made in an unstable situation

also bad with the triple tray dies

66
Q

disadvantages of the dual arch impressions

A

DISTORT B-L

LACKS SUPPORT AND CONFINEMENT of impression material

VARIATION in impression MATERIAL THICKNESS

difficult to determine if patient “closed” correctly = occlusal contacts suspect

cannot be re-poured

cannot evaluate patietn’s occluson

67
Q

implant impressions recommendationss

A

open trey

recommend custom tray often the impression coping cannot be accessed in a stock trey

68
Q

transfer impression?

A

can use monophasic or single mix

69
Q

dual phase or

A

heavy / light body mix

used in fabrication of INDIRECT RESTORATIONS

70
Q

technique used for indirect restorations

A

dual-phase or heavy / light body mix

71
Q

advantages of pentamix

A

consistent mix of material

decrease waste

ease of loading tray and syringe

decrease in air bubbles in mix

72
Q

bleed material?

A

YES – always bleed the material first so that unmixed material does not get int the way

73
Q

tip of the dispenser?

A

must NOT come out of the maine body of the material, keep tip in the material to prevent folds and bubbles

74
Q

syringing the material? - details

A

DRY the field but DO NOT DESICCATE

small tips are the best

place tip in the MOST DIFFICULT area first

DO NOT LIFT THE TIP OUT OF THE BODY OF THE MATERIAL AS THIS INCOPORATES BUBBLES

allow the material to push forward around the tooth

air syringe? – need to know technique

75
Q

streaks from

A

not mixing well

76
Q

big contributoe to inadequate margins- loss of detail

A

poor fitting tray or tray movement upon placement

77
Q

main reason we see poor bond between light and heavy body material

A

***too much time elapsed between mixing these materials

premature removal

latex contamination

vaseline contamination

expired material

78
Q

gypsum is

forms?

A

calcium sulfate dehydrate

5 forms

Beta hemihydrate to alpha hemihydrate

from plaster to high strength dental stone

79
Q

control we have with gypsum

A

ratio of POWDER TO WATER , mixing time, setting time and working time

80
Q

add water to powder?

A

NO - add powder to water

81
Q

go past the diameter on round ended bur?

A

created a ski slope / bad margin

82
Q

connective tissue needs

A

1 mm of sound tooth structure

83
Q

junctional epithelium needs

A

1 mm of tooth structure

84
Q

000-00 corresponds to

A

small cord size

- anterior and thin tissue area

85
Q

0-1 corresponds to

A

medium cord size – posterior lower cord in 2 cord

pre-molar / molar

86
Q

thinnest to largest cord

A

0.5 to 1.4 mm

87
Q

bias in cord means

A

theres a rotation to it – characteristic of twisted cord

88
Q

end cord in interproximal?

A

NO – never

89
Q

implication of cord having memory

A

wants to spring open once not tucked into sulcus - can be challengin

90
Q

memory in terms of knitted cord

A

NO - knitted cord does NOT have memory to it

91
Q

miscellaneous forms of tissue retraction

A

pastes – traxodent

impression- bite regitration material – hold cord in place too

retraction caps / compression caps – with or without gels - inject into sulcus then put it on top of prep and bite down

92
Q

action of class II hemostatic agents

A

precipitate proteins – causing coagulation on the superficial layer of mucosa and make it mechanically stronger

93
Q

aluminum chloride is example of? details

A 
class II ASTRIGENT 
- AlCl2 -- shrinks or constricts tissue and extracts fluid from tissues

concentrations of 5-25% has minimum systeimc side effects

94
Q

Alcl2 vs Alcl3

A

AlCl 3 is LESS irritating / least of the hemostatic agents used with cords but it DISRUPTS THE SETTING OF PVS IMPRESSION

95
Q

hemostatic agent can disrput PVS set?

A

ye – like AlCl3 – so must rinse out adequatley

96
Q

implications if use type I

A

restriction of arteries by binding alpha - adrenergic receptors - contraciton of smooth msucle

blood pressure rises due to vascular resistance

increase chances of hypertensive crisis, agina pectoris, myocardial infarcation, cardiac arrythmias

DO NOT COAGULATE - but CONSTRICT

97
Q

wash and dry with cord?

A

YES – the alumnium chloride, ferric sulfate, and ferric sub sulfate ADVERSELY affet the surface detail reproduction of PVS impressions

98
Q

hemostatic agents pH?

A

tend to be low and can affect surface detail of PVS - rinse and dry priot to impression

99
Q

GP’s vs prosth with getting finish line?

A

only 14% used epi treated and 44% used PLAIN CORD if a prosth vs 79.39 GP (bad)

100
Q

bur curettage induce bleeding?

A

yes and can DAMAGE IMPLANTS and can be too fast a method n

101
Q

biological reasons for having difficulty making an impression?

A
  1. we invaded bio width
  2. not allowed tissue healing
  3. tissue trauma
  4. POOR marginal adaption of PROVISONAL restoration (temp crown)***
  5. no room in the sulcus for the impression material
102
Q

undercuts, thin teeth and thin prep probably going to use?

A

PVS

103
Q

PVS set time - quick

A

into the mouth 1 min do not remove for 5 minutes (6 total)

104
Q

snap set?

A

polyether impression characteristic
- ensures that the material will not start setting before the working time ends - and then when it does set - it does so immediatley resulting in precise fitting restorations without distrotion

  • reduces the potential of distortion upon removal
105
Q

if use light and heavy body together process and timing?

A

mix heavy body - put in trey then inject light body around thetooth and put he tray in

106
Q

impression material that is HYDROPHOBIC and implication

A

aquasil / PVS

- so if drying area is a concern may want to use poly-ether for impression

107
Q

wetability

A

ability of liquid ro spread over a surface

108
Q

complete wetting angle?

A

0 degrees

109
Q

poly ether with wetting

A

more hydrophillic - spreads out more

110
Q

disadvantages of polyether

A

LOW TEAR STRENGTH

  • adhesive required
  • unpleasant taste
  • very STIFF when set
  • 0.5% of patients allergic to catalyst

CAN NOT BE STORED WET

111
Q

impression material to use for small dies?

A

PVS – less stiff

112
Q

disadvantages of PVS

A

requires perforated trays

adhesive is not strong

HYDROPHOBIC

inhibited by latex / sulfur containing materials

inhibited by certain astringidents

avoid hydrogen peroxide materials

retraction cord contamination

113
Q

do we need a second pour?

A

YES - says we should

like for adjusting contacts

114
Q

custom trey vs diagnostic cast

A

trey needs approx 3mm of relief over the diagnostic cast and at least 3 vertical stops

115
Q

advantages of custom trays

A

reduced volume of the material

take advantage of the fluid dynamics of non-newtownian materials

reduced cost of impression

IMPROVED ACCURACY BY REDUCING TRESS DUE TO THERMAL CONTRACTION and having an even amount of material around the prepared teeth

116
Q

reduces the potential for the trey to flex?

A

if use a custom trey – can IMPROVE ACCURACY

117
Q

high vs low viscosity materials in terms of seating

A

the hi viscosity material will displace the low viscosity material according to the non-Newtownian properties of viscous materials under stress

118
Q

do not use triple trey for?

A

FPD’s – there is NOT enough information regarding the occlusion in order to deliver a resotration that has the correct function built in

not a good way to figure out the A-P orientation or the B-L

119
Q

his opinion for impressions with implants

A

open trey – and use custom tray as often the impression coping cannot be accessed in a stock trey

120
Q

monophasic or single mix impression can be used for?

A

transfer impression

121
Q

which displaces the other in terms of materials?

A

heavy displaces the light body

122
Q

putty wash

A

silicone materials
want more back pressure because of sub-gingival margin

but it is flexible – so distortions can be incoporated and then restoration does not fit

123
Q

regular set PVS set vs fast

A

within 60 seconds – need to get on trey and into patients mouth (can remove after 5 mins)

fast - get to pt mouth by 35 seconds (Can remove in 2.5 mins)

124
Q

second pours can be used for?

A

proximal contacts

as reference for a fixed splint case - like a 3 -unit FPD

reference for die trimming

back up in case of damage to 1st pour

125
Q

inadequate retraction implication in impression

A

likely going to get tears in impression

126
Q

polymerization problems with impression likely due to

A

maybe it is expired – CHECK DATE

127
Q

important aspect to inadequate margins / lost details

A

make sure the trey fits

this is oftne due to poor fitting tray or tray movement

128
Q

reasons material does not set fully

A

contamination (like to latex )

hemostasis material contamination

exposure to residue from custom temporary material

poor mix

expired material

material will look discolored

129
Q

PVS voids or pulls likely due to

A

saliva in the way

130
Q

voids or pulls due to

A

waited to long to put into patient mouth and may get separation of material

131
Q

main reason for poor bond between light and heavy body material

A

too much TIME ELAPSED BETWEEN MIXING these materials

132
Q

reaons crown does not fit

A

tray moved or rocked

margin was not captured

disposable tray was too flexible

did not use tray adhesive, cast is distorted upon pouring

premature setting of impression material prior to seating intra-orally

premature removal

Fixed Prosth 3rd year (17 decks)

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