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
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
- Compound wax
- Agar
2. Based on elasticity
- Rigid materials
- Plaster of Paris
- Zinc oxide eugenol
- Compound wax
- Elastic material
- Agar
- Alginate
- Nonaqueous elastomers
Read And Learn More: Dental Materials Question and Answers
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
- Calcium chloride
- Zinc acetate
- Primary alcohols
- Glacial acetic acid