lec 9 - Impression Procedures and Materials for Removable Partial Dentures

Question 1

• Negative likeness or an imprint made placing some soft, semifluid material in the mouth and allowing that material to set.

Answer 1

IMPRESSION

Question 2

usually used for cast restoration and are elastic when removed from the mouth.

Answer 2

Impression material

Question 3

IDEAL IMPRESSION MATERIAL (7)

Answer 3

1. Complete plasticity before cure (set)
2. Sufficient fluidity to record define detail
3. The ability to wet the oral tissues
4. Dimensional accuracy
5. Dimensional stability
6. Complete elasticity after cure
7. Optional utilities

Question 4

IMPRESSION MATERIAL CLASSIFICATION

Answer 4

(1) Rigid Impression Materials
(2) Thermoplastic Impression Materials
(3) Elastic Impression Materials

Question 5

• Set to rigid consistency
• Cannot be removed from the mouth without fracture and reassembly.

Answer 5

RIGID IMPRESSION MATERIALS

Question 6

RIGID IMPRESSION MATERIALS (2)

Answer 6

 Plaster of Paris
 Metallic Oxide Paste

Question 7

• One type of impression material is which has been used in dentistry for over 200 years.

Answer 7

plaster of Paris

Question 8

was once the only material available for removable partial denture impressions, but now elastic materials have completely replaced the impression plasters in this phase of prosthetic dentistry.

Answer 8

plaster of Paris

Question 9

usually some form of a zinc oxide–eugenol combination.

Answer 9

METALLIC OXIDE PASTE

Question 10

they are not used as primary impression materials and should never be used for impressions that include remaining natural teeth.

Answer 10

METALLIC OXIDE PASTE

Question 11

THERMOPLASTIC MATERIALS (2)

Answer 11

 Modelling plastic
 Impression waxes and natural resins

Question 12

• Modelling Compound

Answer 12

Modelling plastic

Question 13

• Oldest impression material used in prosthetic dentistry

Answer 13

MODELLING PLASTIC

Question 14

• Most often used for border correction (border molding) of custom impression trays for distal free end classifications. It is manufactured in several different colors, each color being an indication of the temperature range at which the material is plastic and workable.

Answer 14

MODELLING PLASTIC

Question 15

most commonly used modeling plastic for corrected impressions for extension base areas. (softens around 132°F/55.55°C)

Answer 15

• Red-brown

Question 16

obtainable in stick form used in border molding

Answer 16

Red, Gray, and Green

Question 17

• Used to record non-undercut edentulous portions of the oral cavity and are generally used in combination with other impression materials like polysulfide, ZOE impression paste or impression compound.

Answer 17

IMPRESSION WAXES AND NATURAL RESINS

Question 18

• May be used to correct the borders of impressions made of more rigid materials thereby establishing optimum contact at the border of the denture.

Answer 18

IMPRESSION WAXES AND NATURAL RESINS

Question 19

• All mouth temperature ____________ have the ability to record border detail accurately and include the correct width of the denture border.

Answer 19

wax impressions

Question 20

IMPRESSION WAXES AND NATURAL RESINS IS USED FOR (2)

Answer 20

 Corrective impression
 Bite Registration

Question 21

developed for used in recording the functional or supporting form of an edentulous ridge. May be used as a secondary impression materials

Answer 21

• Iowa Wax

Question 22

• Are those that remain in an elastic or flexible state after they have set and have been removed from the mouth

Answer 22

ELASTIC IMPRESSION MATERIALS

Question 23

• Only ones that can be withdrawn from tooth and tissue undercuts without permanent deformation and therefore are used generally for making impressions for removable partial dentures, immediate dentures, crowns, and fixed partial dentures when tooth and tissue undercuts and surface detail must be recorded with accuracy

Answer 23

ELASTIC IMPRESSION MATERIALS

Question 24

Elastic Materials (5)

Answer 24

 Reversible Hydrocolloids
 Irreversible Hydrocolloids
 Mercaptan Rubber-base Impression Materials
 Polyether Impression Materials
 Silicone Impression Materials

Question 25

* Agar-agar

Answer 25

REVERSIBLE HYDROCOLLOIDS

Question 26

* Which are fluid at higher temperatures and gel on reduction in temperature

Answer 26

REVERSIBLE HYDROCOLLOIDS

Question 27

* Are used primarily as impression materials for fixed restorations

Answer 27

REVERSIBLE HYDROCOLLOIDS

Question 28

* Demonstrate acceptable accuracy when properly used

Answer 28

REVERSIBLE HYDROCOLLOIDS

Question 29

can also be used for removable partial denture impressions and especially for secondary corrected or altered cast impressions

Answer 29

* Mercaptan rubber base/polysulfide polymer (thiokol) impression materials

Question 30

* Many of these materials have an unpleasant odor and can stain clothes.

Answer 30

RUBBER BASE IMPRESSION MATERIAL

Question 31

* Have high tear strength

Answer 31

RUBBER BASE IMPRESSION MATERIAL

Question 32

* Can be disinfected in liquid, cold-sterilizing solutions

Answer 32

RUBBER BASE IMPRESSION MATERIAL

Question 32

* Long working and setting times (8 to 10 minutes)

Answer 32

RUBBER BASE IMPRESSION MATERIAL

Question 33

* These materials are moderately inexpensive

Answer 33

RUBBER BASE IMPRESSION MATERIAL

Question 34

* Is an elastic-type material, as are the polysulfide and silicone materials.

Answer 34

POLYETHER IMPRESSION MATERIAL

Question 35

* These materials have demonstrated good accuracy in clinical evaluations and are thixotropic, which provides good surface detail and makes them useful as a border molding material.

Answer 35

POLYETHER IMPRESSION MATERIAL

Question 36

hydrophilic, which produces good wettability for easy cast forming.

Answer 36

POLYETHER IMPRESSION MATERIAL

Question 37

low to moderate tear strength and much shorter working and setting times, which can limit the usefulness of the material

Answer 37

POLYETHER IMPRESSION MATERIAL

Question 38

more accurate and easier to use than the other elastic impression materials.

Answer 38

SILICONE IMPRESSION MATERIALS

Question 39

* They have a pleasant odor, moderately high tear strength, and excellent recovery from deformation.

Answer 39

SILICONE IMPRESSION MATERIALS

Question 40

hydrophobic, which can make cast formation a problem.

Answer 40

SILICONE IMPRESSION MATERIALS

Question 41

can be disinfected in any of the disinfecting solutions with no alteration in accuracy. Ideally, these materials should be poured within 1 hour

Answer 41

SILICONE IMPRESSION MATERIALS

Question 42

Possible CAUSES of an INACCURATE and/or a Weak Cast of a Dental Arch (7)

Answer 42

1. Distortion of the hydrocolloid impression 2. A ratio of water to powder that is too high that will result in a weak cast. 3. Improper mixing. This also results in a weak cast or one with a chalky surface. 4. Trapping of air, either in the mix or in pouring, because of insufficient vibration. 5. Soft or chalky cast surface that results from the retarding action of the hydrocolloid or the absorption of necessary water for crystallization by the dehydrating hydrocolloid. 6. Premature separation of the cast from the impression. 7. Failure to separate the cast from the impression for an extended period.

Question 43

1. Distortion of the hydrocolloid impression a) By use of an impression tray that is ________ b) By _________ from the tray c) By ___________ caused by dehydration d) By __________ caused by imbibition (this will be toward the teeth and will result in an undersized rather than oversized cast e) By ____________ the cast with stone that has already begun to set.

Answer 43

not rigid partial dislodgment shrinkage expansion attempting to pour

Question 44

A STOCK TRAY SHOULD: * Be _________ to avoid distortion during the impression and cast forming procedures * Should fit the mouth about _________clearance * should be made of material that permits ___________ to fit the mouth

Answer 44

sufficiently rigid 4 to 5 mm trimming and shaping