Rigid Impression Dental Materials Question And Answers

Rigid Impression Materials Important Notes

1. Types of ZOE paste

• Type 1 – Hard – sets in 10 minutes
• Type 2 – Soft – sets in 15 minutes

2. Effect of adding water to ZOE paste

• Accelerates setting reaction
• Decreases setting time

3. Composition of ZOE paste

4. Uses of ZOE paste

• Making wash impression of edentulous ridges – most commonly used
• Bite registration
• Post-surgical pack
• Temporary relines
• Root canal filler
• Temporary filling material
• Luting agent

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5. Composition of impression compound

Rigid Impression Materials Long Essays

Question 1. Classify impression materials. Write in detail about the composition, manipulation, and uses of impression compound
Answer:

Impression materials Classification

1. Based on setting mechanisms

• Chemical reaction
  • Plaster of Paris
  • Zinc oxide eugenol
  • Alginate
  • Nonaqueous elastomers
• Thermally-induced physical reaction

1. Compound wax
2. Agar

2. Based on elasticity

• Rigid materials
  • Plaster of Paris
  • Zinc oxide eugenol
  • Compound wax
• Elastic material
  • Agar
  • Alginate
  • Nonaqueous elastomers

Impression Compound:

Impression Compound Composition:

Impression Compound Manipulation:

• Impression compound may be softened over a flame or by immersion in a warm water bath
• It is then removed and usually kneaded with the fingers in order to obtain uniform plasticity
• An oversized tray is selected
• Material is loaded over it and quickly seated onto the tissues to be recorded
• It should be held gently in position until the impression cools below the fusion temperature
• Under no circumstances the impression should be disturbed or removed until it reaches oral temperature

Impression Compound Uses:

• For making a preliminary impression of edentulous ridges
• To make a special tray for the construction of dentures
• For border molding of an acrylic custom tray during the fitting of the tray
• For individual tooth impression
• To check undercuts in inlay preparations

Question 2. Classify impression materials. Write a note on the composition, manipulation, and various uses of zinc oxide eugenol paste
Answer:

Zinc Oxide Eugenol Paste:

Zinc Oxide Eugenol Paste Composition:

Zinc Oxide Eugenol Paste Manipulation:

• Mixing is done on an oil-impervious paper or a glass mixing slab
• The proper proportion of the two pastes is obtained by squeezing two strips of paste of the same length onto the mixing slab
• Two strips of contrasting color are combined with the first stroke of a flexible stainless steel spatula
• Mixing is continued for 1 minute until a uniform color is achieved
• The material is loaded into the tray by swiping on the sides of the tray and then spread in a smooth uniform motion
• It is placed in the mouth till it sets

Zinc Oxide Eugenol Paste Uses:

• As impression material for edentulous ridges
• As surgical dressing
• As bite registration paste
• As temporary filling material
• Root canal filling material
• Cementing medium
• Temporary relining material for dentures

Rigid Impression Materials Short Essays

Question 1. Impression compound
Answer:

Impression compound

Impression compound is a rigid impression material

Impression compound Properties:

• Fusion temperature
  • The temperature below which a definite reduction in plasticity occurs during the heating of the impression compound is called the fusion temperature
  • Impression compound exhibits a fusion temperature range rather than a fixed point
• Thermal properties
  • Thermal conductivity
• It has a very low thermal conductivity
  • Coefficient of thermal expansion
  • It is high due to the presence of resin and wax
• Flow
  • Good flow is desirable while impression making
• Dimensional stability
  • Relaxation of impression compound occurs in a comparatively short period of time
  • To avoid it, the cast is poured immediately
• Detail reproduction
  • Due to low flow and high viscosity, it has less detailed reproduction

Question 2. Zinc oxide eugenol impression paste
Answer:

Zinc oxide eugenol impression paste Properties:

• Dimensional stability
• Slight shrinkage occurs during hardening
• Consistency and flow
• The thick paste can compress the tissues
• Zinc oxide eugenol has a very good flow
• Rigidity and strength
• Resist distortion and fracture when removed from the mouth
• Compressive strength -7 Mpa
• Biological properties
• Causes a burning sensation in the mouth
• Can cause tissue irritation

Rigid Impression Materials Short Question And Answers

Question 1. Impression compound
Answer:

Impression compound

Impression compound is a rigid, reversible impression material

Impression compound Classification:

• According to ADA specification no. 3, dental impression compounds are classified into two types as follows:
• Type 1- Impression compound
• Type 2-Tray compound

Impression compound Applications:

• For making a primary impression
• For individual tooth impression
• Peripheral tracing or border molding
• To check undercuts in inlay preparation

Question 2. Zinc oxide eugenol paste
Answer:

Zinc oxide eugenol paste

Zinc oxide eugenol is a rigid impression material

Zinc oxide eugenol paste Advantages:

• It has a sufficient body so as to make up for any minor under-extensions in the tray itself during impression making
• It has enough working time to complete border molding
• Can be checked in the mouth repeatedly
• Registers accurate surface details
• Does not require any separating media since it does not stick to the cast material
• Minor defects can be corrected locally without discarding a good impression

Zinc oxide eugenol paste Disadvantages:

• It requires a special tray for impression making
• It is sticky in nature and adheres to tissues
• Eugenol can cause a burning sensation and tissue irritation
• It cannot be used for making an impression of title and undercut areas as it is inelastic in nature

Question 3. Noneugenol paste
Answer:

Noneugenol paste

• Noneugenol pastes were developed to overcome the disadvantages of eugenol like
• Burning sensation
• Disagreeable taste
• Chronic gastric irritation

Noneugenol paste Composition

• Base Paste
  • Zinc oxide
  • Gum
  • Lorothiodol- fungicide
• Reactor
  • Coconut fatty acid
  • Rosin- a thickening agent
  • Chlorothymol- bacteriostatic
  • Antibiotics like tetracyclines may be incorporated
• Reaction
  • Zinc oxide reacts with carboxylic acid
  • This reaction is not affected by temperature and humidity

Question 4. Mention accelerator for ZOE paste.
Answer:

Mention accelerator for ZOE paste

Accelerators for ZOE paste are

1. Calcium chloride
2. Zinc acetate
3. Primary alcohols
4. Glacial acetic acid