Session 9-17 (Quiz 2) Flashcards
1
Q
When do we use a FMC?
A
First and second molar
Heavy grinder
2
Q
Define dental impression
A
A negative imprint of an oral structure used to produce a a positive replica of the structure used as a permanent record or in the production of a dental restoration or prosthesis.
3
Q
Primary Requirements of clinical impression materials: Sufficiently _____ to adapt to oral tissues
A
Fluid
4
Q
Primary Requirements of clinical impression materials: Viscous enough to be _____ in a tray
A
Contained
5
Q
Primary Requirements of clinical impression materials: Able to set to a rubbery or rigid consistency in < ____ min
A
7 min
6
Q
Primary Requirements of clinical impression materials: ____ ____ enough to allow one or more pourings
A
Dimensionally stable
7
Q
Primary Requirements of clinical impression materials: ___compatible
A
Biocompatible
8
Q
Primary Requirements of clinical impression materials: ___ ___ including any associated equipment
A
Cost effective
9
Q
Elastic material returns to ____ ______
A
Original shape
10
Q
Plastic (Non-elastric) material undergoes _____ _____
A
Permanent Deformation
11
Q
What are the two types of impression material?
A
Elastic and non-elastic
12
Q
What are two subtypes of elastic impression material?
A
Aqueous hydrocolloid
Non-aqueous elastomers
13
Q
What are two types of aqueous hydrocolloid?
A
Agar (Reversible)
Alginate (irreversible)
14
Q
Agar is reversible, while alginate is ____
A
Irreversible
15
Q
What are three types of non-aqueous elastomer?
A
Polysulfide, polyether, polyvinyl siloxane
16
Q
Define elastomers
A
A group of rubbery polymers which are either chemically or physically cross-linked.
17
Q
What occurs with final impression material elastomeric when applied stress is released?
A
Can rapidly recover to its original dimensions
18
Q
Define yield strength
A
The stress at which a test specimen exhibits a specific amount of plastic strain.
19
Q
Define elastic strain
A
Deformation that is recovered upon removal of an externally applied force or pressure
20
Q
Define plastic strain
A
Deformation that is not recoverable when the externally applied force is removed.
21
Q
Define Elastic Modulus
A
Relative stiffness of a material; ratio of elastic stress to elastic strain.
22
Q
Define viscosity
A
Property of a fluid that tends to prevent it from flowing when subjected to an applied force
23
Q
____ viscosity fluids resist flow
A
High
24
Q
____ viscosity fluids flow easily
A
Low
25
Define Colloid
Mixture in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance.
26
What are the base ingredients in polysulfide impression?
Polysulfide polymers
Fillers
Plasticizers
27
What are the two catalysts of the polysulfide impression material?
Lead dioxide
| Fillers
28
What is the byproduct of the polysulfide impression material?
Water
29
Polysulfide impression material is also known as ____ base
Rubber base
30
Polysulfide impression material has the ____ tear strength
Highest
31
Describe working and set time of polysulfide impression material
Long working and set time
32
Why should polysulfide impression material be poured within one hour after setting?
Not dimensional stable
33
What are the two pastes that contain polyether impression material?
Base and accelerator
34
Describe ingredients in polyether impression base paste
Polyether polymer
Filler: Colloidal silica
Plasticizer: Glycolether/Phthalate
35
Describe the ingrediants in polyether impression accelerator paste
Contains alkyl-aromatic sulfonate
| Filler and plasticizer
36
Polyether is hydro___
Phillic
37
What can you do with polyether impression material multiple times?
Can be poured multiple times
38
Why is polyether impression material hard to remove from the mouth?
It is rigid
39
What is polyether similar to?
PVS
40
What is the main advantage of polyether compared to PVS?
Hydrophilicity
41
What is the most rigid elastomeric impression material?
Polyether
42
What are two disadvantages of polyether material?
It may get locked in patient's mouth.
| High cost
43
What are the two pastes that condensation PVS comes in?
Base and accelerator paste
44
PVS: What does the base contain?
Poly(dimethylsiloxane)
| Tetraethylorthosilicate filler
45
PVS: What does the accelerator paste contain?
Metal organic ester
46
PVS Consistency
Putty like; highly viscous
47
PVS Byproduct
Ethanol
48
PVS is hydro___
Phobic
49
Cost of PVS
Inexpensive
50
What is the most accurate material available?
PVS
51
Define Working time
The total time from the start of mixing to the final time at which an impression tray can be fully seated without distortion.
52
Polyvinyl siloxane: Working time
1 min 10 secs
53
Polyvinyl siloxane: Setting time
5 min
54
Define Setting Time
The elapsed time from the start of mixing until the impression material becomes firm enough to resists permanent deformation
55
What does the setting time represent for elastic impression material?
Time at which the impression can be taken out of the mouth
56
What happens to the poly vinyl siloxane material if the working time is violated?
The light body will not set with the tray material, will separate and the impression will be distorted.
57
PVS comes in what four types of viscosities
XLV (Extra light viscosity)
LV (Light viscosity)
Medium
Heavy
58
What does a lighter viscosity allow material to do?
Flow easily into the sulcus and to capture the fine surface detail of the prep
59
The lighter body material has a ____ tear strength compared to a heavier body
Lighter
60
What does a heavier viscosity provide?
Adequate rigidity to prevent distortion and to minimize deformation
61
Low viscosity -> Light body -> ______ -> Syringeable material
Wash
62
Medium viscosity -> Regular body -> Wash -> ______ Phase
Single
63
High viscosity -> Heavy body -> ____ material -> Single phase
Tray material
64
Very high viscosity -> ______ -> Tray Material
Putty
65
Define Viscoelasticity
Property of materials that exhibit both viscous and elastic characteristics when undergoing deformation
66
When stress is applied how do viscous materials react with time?
Resist sheer flow and strain linearly with time
67
When stress is applied, how do elastic materials react when stress is removed?
Strain when stretched and quickly return to their original state once the stress is removed.
68
Viscoelastic materials exhibit a ____-dependent strain
Time
69
How should PVS impression material be removed to minimize distortion?
Quickly to minimize distortion
70
List out impression material in decreasing flexibility
Polysulfides> Condensation silicone > or equal to Addition silicone > or equal to Polyether
71
List out impression material in decreasing elastic recovery
Addition silicone > or equal to condensation silicone > or equal to polyether > polysulfides
72
Polysulfides have the ____ tear strength
Best
73
Condensation silicones have ____ dimensional stability
Poor
74
Addition silicone is the _______ accurate
Most
75
What is the foundation of any successful impression
Time management
76
What are two necessary things to do in order to achieve tissue management
Bleeding must be controlled.
| Ample space must be created for the impression material.
77
What needs to be acceptable before beginning fixed prosthodontic treatment?
Periodontal condition
78
What may the patient need to be on prior to the impression being made for 10-14 days?
Chlorohexidine
79
What are three requirements that must be considered before making the master impression?
Tissue health
Saliva control
Displacement of gingival tissues
80
Tissue health: What do you want to minimize during tooth preparation?
Tissue trauma
81
What is critical related to saliva control?
Isolation
82
What types of instruments/tools can be used to control saliva?
LA, Cotton rolls, saliva ejector, dry angle, dry tip
83
What are two examples of medications that can be used to control saliva?
Anticholinergics, antihypertensive drugs
84
What type of material may not be affected by moisture?
Reversible hydrocolloid
85
What type of drug controls crevicular fluids?
Viscostat
86
What are four things that can stimulate saliva flow?
Being in patient's mouth
Pain
Gingival manipulation
Anxiety
87
What are three methods of gingival tissue displacement?
Retraction cord
Laser
Electrosurgery
88
Two types of retraction cords
1. Woven or braided cord impregnated with chemicals (Gingi-pak)
Knitted (Ultradent) 100% cotton with no impregnated chemicals
89
What is an example of a packing instrument?
Fischer's UltraPak Packers
90
Fischer's UltraPak Packers: Sizes
Regular and small
91
Fischer's UltraPak Packers: Angles
45 and 90 degrees
92
Use of the double cord technique
Predictable way to achieve hemostasis and to create space for the impression material to flow beyond the margin
93
What type of cord is packed into the gingival sulcus first?
Smaller cord Size 000 or 00
94
What is the purpose of the first packing cord?
Achieve hemostasis
| Prevent any heme or gingival cervicular fluid from contaminating the tooth surface during impression making procedure
95
How should the first packing cord be cut?
Cut to the circumference of the tooth so that there is no extra material above the tissue
96
Where is the large second cord packed
Into the sulcus
97
Function of largest packing cord
Maximize the retraction of the tissue
98
Purpose of second cord
To create space between the tissue and the tooth so the impression material can flow beyond the crown margin in order to facilitate die trimming
99
Length of second cord
Should be slightly longer than the circumference of the tooth so that the tail of the cord sticks out for ease of removal
100
Define Hemodent
Buffered aluminum chloride hemostatic liquid
101
Function of hemodent
Works as a vasoconstrictor that effectively stops minor gingival bleeding
102
What is not in Hemodent to avoid cardiac reaction?
Epi
103
What is socked in hemodent prior to packing into the sulcus?
Retraction cord
104
Define Viscostat clear
Aluminum chloride
105
Difference between hemodent and viscostat clear
Viscostat clear is a gel; hemodent is a liquid
106
How are retraction cords used to capture surface detail of tooth?
Top cord is removed -> bottom is left in sulcus -> light body impression material is injected into sulcus and around surrounding teeth -> Captures portion of tooth apical to margin as well
107
An acceptable final impression always starts with an _____ crown prep
Acceptable
108
What can be used in order to get the opposing arch?
Alginate impression
109
Describe a Diode
Any device which electricity can flow in one direction
110
Diodes are fabricated out of ______ crystals
Semiconductor
111
When do semiconductor crystals emit light?
When an electrical current is passed through them and the light can be focuses into a small dot
112
Define electrosurgery
Passage of a high frequency current through the tissue from a large electrode to a small electrode
113
What works similar to a microwave?
Electrosurgery
114
Electrosurgery uses ____ as medium
Electricity
115
Electrosurgery generates ______
Heat
116
Electrosurgery:
| More power=
More damange
117
Electrosurgery:
| More recession=
Rebound
118
Contraindications to electrosurgery
```
Cardiac patients w/ arrhythmias
Cardiac pacemakers
TENS units
Insulin pumps
Metal implants
Ortho brackets
```
119
How should the laser be used in order to minimize tissue trauma?
Quick short strokes using the least amt of power
120
Define what is occurring when Mounting
Turn the impression into stone and put it on an instrument that simulates the movements of the mouth
121
Three characteristics for Plaster Type I/II
B-hemihydrate
Large particles
Irregularly shaped
122
Three characteristics for Stone Type III-V
a-hemihydrate
Small particles
Prism/rod shaped
123
Why is more water required when with Plaster Type I/II
Because it contains large and irregularly shaped particles
124
The smaller/regularly shaped particles in Stone Types III-V need less water, which can _____ the strength of the stone
Increase
125
Which type of plaster used to be used for final impressions of complete dentures?
Type One
126
What is an advantage of Type One Plaster
It replicated the surface detail of the soft tissue well.
127
Why did we stop the use of Type One Plaster
It fell out of favor once elastomeric materials were introduced.
128
What is type II plaster sometimes referred to?
Lab plaster
129
What is Type II plaster used for?
Investment and processing of the denture
130
Why is Type II Plaster used for devesting of a denture?
Because it is a softer stone
131
What is Type III Dental Stone used for?
When pouring up final impressions for dentures
132
Why is Type III Dental Stone used for pouring up final impressions for dentures?
It is necessary to break the stone in order to recover the denture after processing, and a weaker stone facilitates breaking with minimal distortion upon removal.
133
Type IV Stone has _____ strength and ___ expansion
High strength
| Low expansion
134
Type IV Stone is referred to as ____
Die stone
135
What is Type IV stone used for?
used in the fabrication of crown and bridge work
136
Why is the hardness of Type IV dental stone preferred?
It resists abrasion throughout the fabrication steps
137
Type V has ____ strength and ___ expansion
High strength
| High expansion
138
What is the extra expansion of Type V Stone used to compensate for?
The larger shrinkage upon cooling when a base metal is used.
139
Gypsum: The amounts of water and hemihydrate should be gauged accurately by ______
Weight
140
Gypsum: The ratio of water to hemihydrate powder is usually expressed as the ___ ratio
W/P
141
Gypsum: As the W/P ratio increases, the setting time ___, the strength of the gypsum ___ and the setting expansion _____
Increases; decreases; decreases
142
Example of Type I Plaster
Mounting Plaster
143
Example of Type II Plaster
Microstone
144
Example of Type III Plaster
Snap-stone
145
When the patient has a ____ MIP, the maxillary and mandibular casts will lock in to one position, with no rock.
Stable
146
What is the purpose of a bite registration?
Assist in mounting the maxillary and mandibular casts together.
147
What is the bite registration also referred to? Why?
Jaw relation record; because it helps to relate the jaws to each other accurately.
148
What are some reasons why MIP may not be achievable? What is needed to mount the casts correctly?
Flat worn teeth, unable to tripodize due to missing teeth
| Bite Registration
149
What can occur if the bite registration is not trimmed?
It will not seat fully
150
Why are the casts not a perfect replica of the teeth?
Dimensional change with impression material and stone
151
What do you want to trim away on the bite registration in order for the casts to come in contact?
Tooth to tooth contacts
152
Why do you not want a bite registration between to contacting teeth that are in stable MIP?
It is more accurate to have the stone casts touch each other directly instead.
153
Describe when a record base is needed
When there is a rocking or tipping that exists between two casts when not enough teeth are present to tripodize them.
154
What can a record base be made out of?
TRIAD UDMA
155
Regisil has a working time of _____ but is not as _____
1 Minute; rigid
156
What type of material can be used to make provisional templates because of its faster setting time?
Regisil
157
_____ sets up extremely firm but has a short working time.
Take One Advanced
158
What is Take One Advanced reserved for?
Straight forward cases such as single unit crowns
159
What does the pindex system prepare us for?
The master cast for crown fabrication
160
What is an advantage of the pindex system?
The die can be removed individually for ease of waxing.
161
Pindex System: A properly trimmed die will mimic the ____ form of the prepared tooth
Root
162
On a pindex system, the margin is mixed with a ______ to clearly define the junction of the crown and the tooth.
Red Pencil
163
Pindex System: What is added into the die to create space for cement upon delivery of crown?
Die Spacer
164
Pindex System: Recommended thickness of die spacer
20 to 40 um
165
What is Performed when fabricating a full metal crown?
A full contour wax up
166
Define Spruing
Involves the flow of molten metal straight from the casting crucible to the pattern area in the ring
167
Where is the sprue attached to?
The thickest portion of the wax pattern, usually the nonfunctional cusps 6 mm from the top
168
Define investment
Pour investment around the wax pattern
169
When casting multiple restorations, a _____ is added to act as a resevoir for molten metal
Runner bar
170
What can occur when a hot spot retains a localized pool of molten metal?
Creates shrinkage void or suck back porosity
171
First requirement of an investment
Must reproduce precisely the detailed form of the wax pattern
172
Second requirement of an investment
Must provide sufficient strength to withstand the heat of burnout and the actual casting of the molten metal
173
Third requirement of an investment
Must expand sufficiently to compensate for the solidification shrinkage of the alloy
174
Investment: 25-35% binder ->
Provides rigidity
175
Investment: Binder made up of
Gypsum, phosphate or ethyl silicate
176
Investment: 65-75% Refractory ->
Regulates thermal expansion
177
Investment: Refractory is made out of
Silica
178
An investment material is made up of what two things?
Binder and refractory material
179
Function of binder
Holds ingredients together and provides rigidity.
180
Gypsum is used below ____ degrees celsius
1000
