139 Questions
Why is it recommended to use a non-perforated tray painted with an adhesive?
To assure retention of the impression to the acrylic tray
What is the percentage of shrinkage exhibited by addition silicone during the first 24 hours?
0.05%
What is the elasticity percentage of polysulfide impression material?
98%
What occurs when a rubber impression is cooled from mouth to room temperature?
Thermal contraction
Why should impressions be poured 30-60 minutes after removal from the mouth?
To allow for highest elastic recovery and least polymerization shrinkage
What happens to rubber impressions during storage?
They undergo a small contraction
What is the primary reason for using a non-perforated tray?
To prevent distortion of the impression
What is the percentage of shrinkage exhibited by polyether during the first 24 hours?
0.1%
What is the elasticity percentage of condensation and addition silicones?
99.5%
What is the primary reason for the contraction that occurs when a rubber impression is cooled from mouth to room temperature?
Thermal contraction
What is the benefit of pouring impressions 30-60 minutes after removal from the mouth?
Both A and B
What is the main advantage of using a non-perforated tray painted with an adhesive?
Reduced distortion of the impression
What happens to impressions made with condensation silicone during storage?
They contract due to evaporation of volatile constituents
Why should a perforated tray not be used for rubber impressions?
It causes distortion of the impression
What is the primary cause of dimensional changes in rubber impressions during storage?
Both A and B
What is the elasticity percentage of polyether impression material?
98.9%
What happens to the rubber impression material during the first 24 hours?
It shrinks due to polymerization
Why is it important to have good adhesion between the impression material and the tray?
To reduce distortion
What is a significant advantage of polyether impression materials?
Better wettability to soft tissues and gypsum products
What is the composition of the base of polyether materials?
80% polyether liquid polymer and 20% silica
What type of reaction occurs in the setting of polyether rubber?
Addition polymerization
What affects the fluidity of polyether impression materials?
Consistency of the material
What is a characteristic of polyether impression materials?
High stiffness and short working time
What is the catalyst used in the setting reaction of polyether rubber?
Sulfonic acid ester
What is the significance of the dimensional change during polymerization?
It affects the accuracy of the impression
What is the comparison of dimensional change between polysulfide and condensation silicone?
Polysulfide has 0.3% shrinkage, condensation silicone has 0.6% shrinkage
What is the primary reason for the contraction that occurs when a rubber impression is cooled from mouth to room temperature?
Thermal contraction
What is the benefit of pouring impressions 30-60 minutes after removal from the mouth?
Both A and B
What is the result of poor adhesion between the impression material and the tray?
Distortion of the impression
What is the elasticity percentage of condensation and addition silicones?
99.5%
What is the dimensional change that occurs in rubber impressions during storage?
Contraction
What is the significance of using a non-perforated tray painted with an adhesive?
Improved adhesion
What is the primary cause of the dimensional change in rubber impressions during storage?
Both B and C
What is the elasticity percentage of polysulfide impression material?
98%
What is the result of using a perforated tray instead of a non-perforated tray painted with an adhesive?
Distortion of the impression
What is a disadvantage of polyether impression materials mentioned in the text?
Short setting time
How are polyether materials presented?
As two pastes
What is the setting reaction involved in the formation of polyether rubber?
Addition polymerization
Which factor affects the fluidity of polyether impression materials?
Consistency
What is a general property of rubber impression materials?
High shrinkage during polymerization
What is the main advantage of polyether impression materials according to the text?
Better wetting ability
Which component is responsible for catalyzing the setting reaction of polyether rubber?
Sulfonic acid ester
What characteristic makes polyether impression materials have better wetting properties?
High hydrophilicity
What is a key disadvantage of polyether impression materials mentioned in the text?
Difficult handling properties
How are polyether rubber impression materials presented?
As two pastes
Which component is NOT part of the composition of polyether rubber impression materials?
Polydimethylsiloxane
What type of polymerization results in the setting reaction of polyether rubber?
Addition polymerization
Which general property of rubber impression materials is dependent on their consistency?
Fluidity
What is a benefit of polyether impression materials being highly hydrophilic?
Better surface detail reproduction
What is the primary function of the catalyst in the polyether rubber setting reaction?
Initiate polymerization
Which dimensional change occurs in polysulfide during the first 24 hours?
0.3% shrinkage
What is the purpose of painting a tray with an adhesive material for rubber impressions?
To prevent distortion of the impression.
Which rubber impression material exhibits the highest percentage of elasticity?
Polyether
Why should a rubber impression ideally be poured 30-60 minutes after removal from the mouth?
To allow maximum elastic recovery.
Which type of tray should be used to assure retention of the impression to the acrylic tray?
Non-perforated tray painted with an adhesive.
What is one of the main disadvantages of polyether rubber impression materials due to their viscoelastic nature?
Lack of elasticity over time.
What is the primary reason why the thermal contraction of rubber impressions is significantly reduced by adhesion to the tray?
To avoid distortion during cooling.
Which rubber impression material has the lowest percentage of dimensional changes during storage due to further polymerization shrinkage and evaporation?
Condensation silicone
What is the primary consequence of using a perforated tray instead of a non-perforated one painted with adhesive for rubber impressions?
Distortion of the impression.
What property of rubber impressions ensures the ability to withdraw over undercut areas?
Elastic recovery
What is the primary reason for the contraction that occurs when a rubber impression is cooled from mouth to room temperature, significantly reduced by?
the adhesion of the impression material to the tray
What happens to rubber impressions during storage due to further polymerization shrinkage and evaporation of volatile constituents?
They contract slightly
What is the significance of pouring impressions 30-60 minutes after removal from the mouth?
To allow for minimum polymerization shrinkage
What is the elasticity percentage of polysulfide impression material?
98%
What is the consequence of poor adhesion between the impression material and the tray?
Distortion of the impression
Addition silicone shrinkage during the first 24 hours is 0.05%.
True
Polyether shrinkage during the first 24 hours is 0.05%.
False
The thermal contraction of rubber impressions from mouth to room temperature is not reduced by adhesion to the tray if a perforated tray is used.
False
Rubber impressions made with polysulfide exhibit 100% recovery over the undercut areas due to their elastic nature.
False
Dimensional changes can occur on storage of a rubber impression after removal from the mouth due to polymerization shrinkage for all types of rubber impression materials.
False
Polyether impression material has a higher percentage of shrinkage during the first 24 hours compared to addition silicone.
False
Thermal contraction of rubber impressions from mouth to room temperature is completely eliminated by the adhesion of the impression material to the tray.
False
Polyether impression materials exhibit higher elasticity percentage than polysulfide impression material.
True
Storage of rubber impressions after removal from the mouth does not lead to any dimensional changes.
False
Rubber impressions should be poured immediately after removal from the mouth to ensure the highest polymerization shrinkage.
False
Using a perforated tray instead of a non-perforated tray painted with adhesive does not cause distortion of the impression.
False
Contraction of rubber impressions from mouth to room temperature is mainly due to poor adhesion between the impression material and the tray.
False
Elastic recovery in rubber impressions is 100% in all types of rubber materials due to their highly elastic nature.
False
Polyether rubber impression materials have a longer working time compared to polysulfides.
False
Polyether impression materials are less hydrophilic compared to polysulfides.
False
The base of polyether materials contains 20% low M.W. polyether liquid polymer.
False
Polyether rubber is formed through condensation polymerization with the catalyst.
False
Heavy body consistencies of polyether impression materials are used for injection by syringe.
False
Polysulfide impressions exhibit more shrinkage during the first 24 hours compared to condensation silicones.
False
Polyether impression materials are not suitable for creating restorations with excellent surface details.
False
The _______ barked
dog
Elastic recovery in rubber impressions is not 100% due to their _______ nature
Viscoelastic
A non perforated tray painted with an adhesive should be used to assure retention of the impression to the _______ tray
acrylic
Rubber impressions should be poured 30-60 minutes after removal from the mouth to allow the highest _______ recovery
elastic
The thermal contraction of rubber impressions from mouth to room temperature is significantly reduced by the adhesion of the impression material to the _______
tray
On storage of a rubber impression after removal from the mouth, a small contraction can occur due to further polymerization shrinkage and evaporation of volatile constituents if _______ types are used
condensation
The magnitude of thermal contraction of rubber impressions is reduced by the adhesion of the impression material to the tray if the tray is painted with an _______ material
adhesive
Polyether impressions have an elasticity percentage of _______
98.9%
Polyether rubber impression materials have a combination of better mechanical properties than those of ______ along with less dimensional change than those of condensation silicone impression materials.
polysulfides
The base of polyether materials contains ______% low M.W.polyether liquid polymer containing ethylene amine terminal group and 20% Fillers as silica.
80
Polyether impression materials are supplied in different ______ e.g. light body for injection by syringe, medium for use alone in a special tray and heavy body for use as a tray for the light body.
consistencies
There is a little ______ on setting due to polymerization in polyether impression materials.
shrinkage
Polyether impression materials are highly ______ and therefore, better wetting to soft tissues as well as to wet gypsum products during pouring the models resulting in restorations with excellent surface details.
hydrophilic
Polyether (liquid polymer) + ______ give Polyether (rubber) by Addition polymerization.
Sulfonic acid ester
The ______ of polyether impression materials depends on their consistency.
fluidity
Polyether exhibits a shrinkage of 0.1% during the first 24 hours, which is __________ than addition silicone.
higher
Adhesion of the impression material to the tray reduces the thermal contraction that occurs on cooling the rubber impressions from mouth to room temperature, significantly minimizing the ________ of this thermal contraction.
magnitude
Rubber impressions are sufficiently elastic to be withdrawn over the undercut areas with varying degrees of recovery: Polysulfide = 98%, Condensation and addition silicones = 99.5%, Polyether = ________%.
98.9
On storage of a rubber impression after removal from the mouth, a small contraction may occur due to further polymerization shrinkage and evaporation of volatile constituents, especially if ________ types are used.
condensation
Impressions should be poured 30-60 minutes after removal from the mouth to allow the highest elastic recovery and the least ________ shrinkage.
polymerization
What is the shrinkage percentage of polyether during the first 24 hours?
0.1%
How is the thermal contraction of rubber impressions from mouth to room temperature affected by adhesion to the tray?
It is significantly reduced
What happens if a perforated tray is used instead of a non-perforated one painted with adhesive?
Distortion of the impression takes place
What is the elasticity percentage of polysulfide rubber impressions?
98%
Why should rubber impressions ideally be poured 30-60 minutes after removal from the mouth?
To allow the highest elastic recovery and least polymerization shrinkage
What is the contraction that can occur in rubber impressions during storage due to further polymerization shrinkage and evaporation of volatile constituents?
Small contraction
What is the elasticity percentage of condensation and addition silicones in rubber impressions?
99.5%
What is the primary function of the catalyst in the polyether rubber setting reaction?
Initiate polymerization
What are rubber impressions sufficiently elastic to be withdrawn over, despite not achieving 100% recovery due to their viscoelastic nature?
Undercuts areas
What are the two main disadvantages of polyether impression materials?
Short working time and high stiffness
What is the role of sulfonic acid ester in polyether impression materials?
It acts as a catalyst
What is the benefit of polyether impression materials being highly hydrophilic?
Better wetting to soft tissues and wet gypsum products
What is the primary reason for minimal dimensional change in polyether impression materials?
Low polymerization shrinkage
What is the composition of the base of polyether materials?
80% low M.W.polyether liquid polymer containing ethylene amine terminal group and 20% Fillers as silica
What type of polymerization occurs in the setting reaction of polyether rubber?
Addition polymerization
What is the significance of the fluidity of polyether impression materials?
It depends on their consistency
What is the benefit of using polyether impression materials over others?
Better mechanical properties and less dimensional change
What is the benefit of polyether impression materials being highly hydrophilic?
better wetting to soft tissues and to wet gypsum products during pouring the models resulting in restorations with excellent surface details
What is the composition of the catalyst used in polyether rubber impression materials?
Sulfonic acid ester
What is the main advantage of polyether impression materials?
Combination of better mechanical properties than polysulfides along with less dimensional change than condensation silicones
What is the significance of fluidity in polyether impression materials?
Depends on their consistency, with different consistencies suitable for different uses
What is the general property of rubber impression materials related to their consistency?
Fluidity
What is the reaction that occurs when polyether impressions are set?
Addition polymerization
What is the consequence of the dimensional changes that occur during polymerization in rubber impressions?
Shrinkage
What is the main disadvantage of polyether rubber impression materials?
Short working time and high stiffness
What type of contraction occurs when a rubber impression is cooled from mouth to room temperature?
thermal contraction
Why should rubber impressions be poured 30-60 minutes after removal from the mouth?
to allow the highest elastic recovery and the least polymerization shrinkage
What type of impression material exhibits a shrinkage of 0.1% during the first 24 hours?
polyether
What property of rubber impressions ensures the ability to withdraw over undercut areas?
elasticity
What types of rubber impressions are affected by further polymerization shrinkage and evaporation of volatile constituents during storage?
condensation types
Why is adhesion of the impression material to the tray important?
to minimize thermal contraction
What is the primary cause of dimensional changes in rubber impressions during storage?
further polymerization shrinkage and evaporation of volatile constituents
What is the benefit of using a non-perforated tray painted with an adhesive?
to assure retention of the impression to the acrylic tray
What is the elasticity percentage of polyether impression material?
98.9%
Study Notes
Polyether Rubber Impression Materials
- Polyether impressions offer better mechanical properties than polysulfides and less dimensional change than condensation silicone impression materials.
- Disadvantages of polyether impression materials: short working time and high stiffness.
- Polyether impression materials are highly hydrophilic, which provides better wetting to soft tissues and wet gypsum products, resulting in restorations with excellent surface details.
Presentation and Composition
- Polyether materials are supplied as two pastes.
- Composition:
- Base: 80% low M.W.polyether liquid polymer containing (ethylene amine) terminal group and 20% Fillers as silica.
- Catalyst: Sulfonic acid ester.
Setting Reaction
- Polyether (liquid polymer) + Sulfonic acid ester give Polyether (rubber) by Addition polymerization.
General Properties of Rubber Impression Materials
- Fluidity: depends on consistency, supplied in different consistencies (e.g. light body for injection by syringe, medium for use alone in a special tray, and heavy body for use as a tray for the light body).
- Dimensional changes during polymerization:
- Polysulfide shrinkage: 0.3% during the first 24 hours.
- Condensation silicon shrinkage: 0.6% during the first 24 hours.
- Addition silicone shrinkage: 0.05% during the first 24 hours.
- Polyether shrinkage: 0.1% during the first 24 hours.
- Contraction also occurs on cooling the rubber impressions from mouth to room temperature.
- Adhesion to the tray: a non-perforated tray painted with an adhesive should be used to assure retention of the impression to the acrylic tray.
- Elasticity: sufficiently elastic to be withdrawn over the undercuts areas (no 100% recovery because of their viscoelastic nature):
- Polysulfide: 98%.
- Condensation and addition silicones: 99.5%.
- Polyether: 98.9%.
- Dimensional changes on storage:
- Small contraction can occur due to further polymerization shrinkage and evaporation of volatile constituents (if condensation types are used).
- Should be poured 30-60 minutes after removal from the mouth to:
- Allow the highest elastic recovery.
- Allow the least polymerization shrinkage.### Shrinkage and Contraction
- Addition silicone shrinkage is 0.05% during the first 24 hours.
- Polyether shrinkage is 0.1% during the first 24 hours.
- Contraction also occurs on cooling the rubber impressions from mouth to room temperature.
Adhesion to the Tray
- A non-perforated tray painted with an adhesive should be used to assure retention of the impression to the acrylic tray.
- If a perforated tray is used instead, distortion of the impression will occur.
Elasticity
- Polysulfide = 98%.
- Condensation and addition silicones = 99.5%.
- Polyether = 98.9%.
- They are sufficiently elastic to be withdrawn over the undercuts areas (no 100% recovery due to their viscoelastic nature).
Dimensional Changes on Storage
- A small contraction can occur due to further polymerization shrinkage and evaporation of volatile constituents (if condensation types are used).
- They should be poured 30-60 minutes after removal from the mouth to allow the highest elastic recovery and least polymerization shrinkage.
Polyether Rubber Impression Materials
- They offer a combination of better mechanical properties than polysulfides and less dimensional change than condensation silicone impression materials.
- Disadvantages include short working time and high stiffness.
- Highly hydrophilic, allowing better wetting to soft tissues and wet gypsum products, resulting in restorations with excellent surface details.
- Composition: 80% low M.W.polyether liquid polymer containing ethylene amine terminal group and 20% Fillers as silica; Catalyst: Sulfonic acid ester.
- Setting reaction: Polyether (liquid polymer) + Sulfonic acid ester give Polyether (rubber) by Addition polymerization.
General Properties of Rubber Impression Materials
- Fluidity: Depends on consistency, supplied in different consistencies (e.g., light body, medium, heavy body).
- Dimensional changes during polymerization:
- Polysulfide shrinkage is 0.3% during the first 24 hours.
- Condensation silicon shrinkage is 0.6% during the first 24 hours.
- Addition silicone shrinkage is 0.05% during the first 24 hours.
- Polyether shrinkage is 0.1% during the first 24 hours.
Explore the advantages and disadvantages of polyether rubber impression materials compared to other types of impression materials. Learn about their mechanical properties, dimensional changes, working time, stiffness, and hydrophilicity.
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