Chapter 46: Impression materials and techniques

Question 1

three classifications of impressions

Answer 1

• preliminary
• final
• occlusal (bite registration)

Question 2

A preliminary impression is indicated for the following procedures:

Answer 2

diagnostic models/casts

custom trays

provisional coverage

orthodontic appliances

pretreatment and post treatment records

Question 3

who can take occlusal registrations or bite registrations

Answer 3

dentist and DA

Question 4

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

Answer 4

impression trays

Question 5

Impression trays are of two basic types:

Answer 5

stock trays custom trays

Question 6

Impression trays are supplied in one of the following ways

Answer 6

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

Question 7

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

Answer 7

perforated tray

Question 8

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.

Answer 8

smooth surface tray

Question 9

The correct size of tray accomplishes the following:

Answer 9

• patient comfort

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

Question 10

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

Answer 10

utility wax

Question 11

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

Answer 11

tray adhesives

Question 12

specific adhesives used with specific impression materials are as follows:

Answer 12

• 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

Question 13

a material used to obtain preliminary and final impressions

Answer 13

hydrocolloid

Question 14

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

Answer 14

sol (solution)

gel (solid)

Question 15

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

Answer 15

irreversible hydrocolloids.

Question 16

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

Answer 16

alginate

Question 17

The main components of alginate include the following:

Answer 17

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

Question 18

Hydrocolloid impression materials have two physical phases:

Answer 18

sol ( solution)

gel (solid)

Question 19

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).

Answer 19

elastomeric impression

Question 20

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

Answer 20

one hour

Question 21

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
:

Answer 21

imbibition

Question 22

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.

Answer 22

true

Question 23

Alginate is available in two settings:

Answer 23

normal set

fast set

Question 24

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

Answer 24

2

4 1/2

Question 25

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

Answer 25

1 1/4 1-2 mins

Question 26

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

Answer 26

working time

Question 27

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

Answer 27

no difference. The decision as to which type to use is based on time-related factor

Question 28

which temperature is best when mixing alginate

Answer 28

70 f / 21 c

Question 29

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

Answer 29

hysteresis

Question 30

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

Answer 30

85% | 13%

Question 31

also referred to as "tray-type materials"

Answer 31

regular and heavy body materials

Question 32

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

Answer 32

light bodied material

Question 33

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.

Answer 33

light bodied material

Question 34

polymerization stages

Answer 34

- initial - final set - final cure

Question 35

most common mixing technique for use with impression materials

Answer 35

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

Question 36

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

Answer 36

polysulfide polyether polysiloxane silicone

Question 37

Of concern when using elastomeric materials are:

Answer 37

dimensional stability permanent deformation

Question 38

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

Answer 38

dimensional stability

Question 39

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

Answer 39

deformation

Question 40

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

Answer 40

permanent deformation

Question 41

also reffered to as rubber base

Answer 41

polysulfide

Question 42

Disadvantages of rubber base material

Answer 42

strong odor and can easily stain clothing.

Question 43

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

Answer 43

Polysiloxane (polyvinyl siloxane)

Question 44

also referred to as rubber base.

Answer 44

polysulfide

Question 45

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

Answer 45

polyether

Question 46

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

Answer 46

elastomeric

Question 47

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

Answer 47

occlusal registration

Question 48

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

Answer 48

occlusal (bite) registration

Question 49

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

Answer 49

maxillary and mandibular teeth

Question 50

One of the most popular materials used for bite registrations:

Answer 50

Polysiloxane Bite Registration Paste

Question 51

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

Answer 51

Zinc Oxide–Eugenol Bite Registration Paste (ZOE)

Question 52

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

Answer 52

(1) The height of the teeth is missing | (2) must include more extensive tissue details.