18 Questions
What is the primary function of the inert oils in Zinc Oxide-Eugenol impression materials?
To act as a plasticizer and decrease the irritating action of eugenol
Which component is responsible for imparting thermoplastic properties to the set Zinc Oxide-Eugenol impression?
Gum rosin
What is the primary component of the base paste (Tube 1) in Zinc Oxide-Eugenol impression materials?
Zinc oxide
What is the purpose of the accelerator (MgCl2 or CaCl2) in Zinc Oxide-Eugenol impression materials?
To hasten the setting reaction
What is the primary function of the filler (talc or kaolin) in Zinc Oxide-Eugenol impression materials?
To give the paste a specific consistency
What is the main reason for using oil of cloves instead of pure eugenol in Zinc Oxide-Eugenol impression materials?
Oil of cloves produces less of a burning sensation
What is the effect of a drop of water or alcohol on the setting time of a zinc oxide-eugenol impression material?
It decreases the setting time.
Which of the following statements about the dimensional changes of a zinc oxide-eugenol impression material is correct?
It undergoes a negligible shrinkage of less than 0.1% during hardening.
What is the relationship between the flow and setting time of a zinc oxide-eugenol impression material?
The relationship between flow and setting time is complex and depends on the specific product.
Which of the following properties of a zinc oxide-eugenol impression material is mentioned in the text?
Elasticity
What is the recommended disinfection procedure for a zinc oxide-eugenol impression material?
Immerse in 2% alkaline glutaraldehyde for the recommended time, then rinse.
What is the effect of increasing the mixing time within limits on the setting time of a zinc oxide-eugenol impression material?
Increasing the mixing time decreases the setting time.
Which of the following is a component of zinc oxide-eugenol impression materials?
Eugenol
What is the primary role of eugenol in zinc oxide-eugenol impression materials?
To initiate the setting reaction
Which of the following factors can affect the setting reaction of zinc oxide-eugenol impression materials?
All of the above
What is the primary advantage of zinc oxide-eugenol impression materials?
Low cost
Which of the following is a disadvantage of zinc oxide-eugenol impression materials?
Unpleasant taste
What is the purpose of zinc oxide in zinc oxide-eugenol impression materials?
To provide rigidity and strength
Study Notes
Introduction to Impression Materials
- Dental impression is a negative replica of hard and soft tissues of the mouth, made with a material that sets while still in contact with the tooth and tissues.
- A cast (model) is a positive replica of the oral hard or soft structures.
Purpose of Taking Impression
- To study alignment of teeth
- Construction of special (custom) tray
- Treatment planning
- Fabrication of indirect restorations
Types of Trays
- Stock trays
- Special tray
Desirable Properties of Impression Materials
- Pleasant odor, taste, and acceptable color
- Absence of toxic or irritant constituents
- Adequate shelf life for requirements of storage and distribution
- Not expensive
- Easy to use with the minimum of equipment
- Readily wets oral tissues
- Setting characteristics that meet clinical requirements
Zinc Oxide Eugenol (ZOE) Impression Material
Composition
- Tube 1 (Base): 80% Zinc oxide
- Tube 2 (Accelerator): Oil of cloves or eugenol (15%), Inert oil, Gum rosin and oils (65%), Filler (talc or kaolin) (16%), Accelerator (MgCl2 or CaCl2) and water (4%)
Properties
- Non-toxic, but eugenol can be irritant to patients
- Negligible shrinkage (less than 0.1%) during hardening
- Inelastic, cannot be used for recording undercuts
- Adequate working time for border molding in the mouth
- Adequate fine details and dimensionally stable
Manipulation
- Equal length of each paste is dispensed on the mixing pad or glass slap
- Mixed with a stiff stainless steel spatula for approximately 1 minute until a uniform color is achieved
Factors Affecting Setting Time
- Temperature: increased temperature decreases setting time
- Addition of water or alcohol: decreases setting time
- Inert oils: increases setting time
- Ratio of the two pastes: affects setting time depending on the product
- Mixing time: increased mixing time within limits decreases setting time
Advantages
- Adheres well to dried surfaces of compound, resin, and shellac bases
- Sufficient resistance to build up borders if the tray is slightly deficient
- Hard when set, can be taken in and out of the mouth repeatedly
- Can be repaired
Learn about the composition and properties of Zinc Oxide-Eugenol pastes, a rigid impression material used in dentistry for making complete dentures. Explore how the paste hardens by a chemical reaction and its applications in denture preparation.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
