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MOD C: Dental Materials > Chapter 46: Impression materials and techniques > Flashcards

Chapter 46: Impression materials and techniques Flashcards

1
Q

three classifications of impressions

A
  • preliminary
  • final
  • occlusal (bite registration)
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2
Q

A preliminary impression is indicated for the following procedures:

A

diagnostic models/casts

custom trays

provisional coverage

orthodontic appliances

pretreatment and post treatment records

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3
Q

who can take occlusal registrations or bite registrations

A

dentist and DA

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4
Q

these are used to hold the impression material within the mouth.

A

impression trays

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5
Q

Impression trays are of two basic types:

A

stock trays custom trays

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6
Q

Impression trays are supplied in one of the following ways

A
  • quadrant trays (cover half the arch)
  • section trays (covers anterior portion of arch)
  • full arch trays
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7
Q

thisi tray allows the impression material to ooze through the holes of the tray, creating a mechanical lock to hold the material in place.

A

perforated tray

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8
Q

when this tray is used, there is no mechanical lock, so the interior of the tray is painted or sprayed with an adhesive to hold the impression material securely in the tray.

A

smooth surface tray

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9
Q

The correct size of tray accomplishes the following:

A
  • patient comfort

- Extends 2 to 3 mm beyond the third molar, retromolar, or tuberosity area of the arch

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10
Q

how would you extend an impression tray ? what material would you use

A

utility wax

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11
Q

____ helps ensure that an impression remains firmly attached to the tray on removal from the mouth so as not to cause deformity.

A

tray adhesives

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12
Q

specific adhesives used with specific impression materials are as follows:

A
  • VPS adhesives (blue)—used with polyvinyl siloxane (polysiloxane) and polyether impression materials
  • Rubber base adhesives (brown)—used with rubber base impression materials
  • Silicone adhesives (orange-pink)—used with silicone impression materials
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13
Q

a material used to obtain preliminary and final impressions

A

hydrocolloid

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14
Q

Depending on the type of hydrocolloid, the physical change from ______to ______can be irreversible (changed by chemical factors) or reversible (changed by thermal factors).

A

sol (solution)

gel (solid)

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15
Q

Hydrocolloid impression materials that cannot return to the sol state after they become a gel are termed

A

irreversible hydrocolloids.

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16
Q

an irreversible hydrocolloid that is most widely used for preliminary impressions.

A

alginate

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17
Q

The main components of alginate include the following:

A
  • Potassium alginate,
  • Calcium sulfate
  • Trisodium phosphate
  • Diatomaceous earth
  • Zinc oxide
  • Potassium titanium fluoride
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18
Q

Hydrocolloid impression materials have two physical phases:

A

sol ( solution)

gel (solid)

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19
Q

The gel strength of hydrocolloid is not as great as that of _____ impression materials. The hydrocolloids have difficulty withstanding tensile stress (tearing) and elastic strain (stretching).

A

elastomeric impression

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20
Q

Alginate impression materials must be “poured up” within _ hour of taking the impression

A

one hour

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21
Q

If an alginate impression is stored in water or in a saturated paper towel, the alginate acts like a sponge and will absorb the additional water and expand. This condition is called
:

A

imbibition

22
Q

Storage of the disinfected impression in a plastic biohazard bag covered with a slightly moistened towel will provide an atmosphere close to 100% relative humidity, which causes the least amount of distortion

t or f.

A

true

23
Q

Alginate is available in two settings:

A

normal set

fast set

24
Q

Normal-set alginate has a working time of _ minutes and a setting time of up to __ minutes after mixing.

A

2

4 1/2

25
Q

Fast-set alginate has a working time of __ minute and a setting time of _ to _ minutes .

A

1 1/4

1-2 mins

26
Q

time allowed for mixing the alginate, loading the tray, and positioning the tray in the patient’s mouth is called :

A

working time

27
Q

what is the difference in the makeup of the completed impression between the two setting types of alginates.

A

no difference.

The decision as to which type to use is based on time-related factor

28
Q

which temperature is best when mixing alginate

A

70 f / 21 c

29
Q

the term used to describe the change in temperature that causes the reversible hydrocolloid material to transform from one physical state to another.

A

hysteresis

30
Q

Reversible hydrocolloid material is approximately __% water and __%
agar

A

85%

13%

31
Q

also referred to as “tray-type materials”

A

regular and heavy body materials

32
Q

also referred to as syringe-type or wash-type material, is dispensed directly onto the prepared and surrounding teeth.

A

light bodied material

33
Q

This material is less
viscous (has a lower
viscosity) than tray material and is used because of its ability to flow into and around the details of the prepared tooth.

A

light bodied material

34
Q

polymerization stages

A
  • initial
  • final set
  • final cure
35
Q

most common mixing technique for use with impression materials

A

preparing the light-bodied material first, then the heavy-bodied material.

36
Q

The four types of elastomeric impression materials most often used in dental practice are

A

polysulfide
polyether
polysiloxane
silicone

37
Q

Of concern when using elastomeric materials are:

A

dimensional stability

permanent deformation

38
Q

the ability of the material to keep its shape after it has been removed from the mouth.

A

dimensional stability

39
Q

the ability of the material to resist permanent change caused by stresses during removal from the mouth.

A

deformation

40
Q

means that the material was changed and will not regain its previous shape.

A

permanent deformation

41
Q

also reffered to as rubber base

A

polysulfide

42
Q

Disadvantages of rubber base material

A

strong odor and can easily stain clothing.

43
Q

this elastomeric material has high dimensional stability and low tear resistance, making them easy to handle when taking final impressions

A

Polysiloxane (polyvinyl siloxane)

44
Q

also referred to as rubber base.

A

polysulfide

45
Q

this elastomeric material includes a third component called a thinner to reduce thickness and improve finished impression

A

polyether

46
Q

The term ______indicates “having elastic or rubber-like qualities.”

A

elastomeric

47
Q

Reproduction of a patient’s bite with the use of wax or elastomeric material

A

occlusal registration

48
Q

a registration of the normal centric relationship of the maxillary and mandibular arches

A

occlusal (bite) registration

49
Q

A wax bite registration is used to show the occlusal relationship of the :

A

maxillary and mandibular teeth

50
Q

One of the most popular materials used for bite registrations:

A

Polysiloxane Bite Registration Paste

51
Q

When a more durable material is needed for a bite registration, _________ material may be selected.

A

Zinc Oxide–Eugenol Bite Registration Paste (ZOE)

52
Q

Taking an alginate impression of an edentulous arch differs from taking other alginate impressions in two ways:

A

(1) The height of the teeth is missing

(2) must include more extensive tissue details.

MOD C: Dental Materials (5 decks)

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