Dental Resins and Polymerization Overview

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Questions and Answers

What type of resin cures through a process that takes hours?

Heat-cured Resin (correct)

Light-cured Resin

Self-cured Resin

Chemical Cured Resin

Which polymerization process does not produce by-products?

Chain-reaction Polymerization

Thermal Polymerization

Addition Polymerization (correct)

Condensation Polymerization

Which type of resin is chemically activated and cures at room temperature?

Self-cured Resin (correct)

Heat-cured Resin

Acrylic Resin

Light-cured Resin

What is a primary use of dental resins?

Elastomeric Impression Materials Signup and view all the answers

What is the primary component of the powder used in dental polymers?

Poly (Methyl Methacrylate) Signup and view all the answers

What type of polymerization is known as step-growth polymerization?

Condensation Polymerization Signup and view all the answers

What characteristic is required for addition polymerization to proceed?

Presence of a double bond Signup and view all the answers

Which property does Polymer Poly (Methyl Methacrylate) exhibit?

Remarkable clarity and stability Signup and view all the answers

What occurs during condensation polymerization?

Monomers combine while releasing by-products Signup and view all the answers

What might cause the fracture of a denture?

Inadequate curing time leading to lower strength Signup and view all the answers

Which of the following is NOT a cause of internal porosities in a denture base?

Polishing at controlled temperatures Signup and view all the answers

What is a purpose of trimming a processed denture base?

To remove excess resin and prevent injury to soft tissues Signup and view all the answers

What type of resin is typically used for repairing dentures?

Self-curing acrylic resin Signup and view all the answers

What is the purpose of using tissue conditioners in dental practice?

To promote healing and massage inflamed tissues Signup and view all the answers

Which of the following conditions would most likely require the use of soft liners in dentures?

Severe undercuts of the ridge Signup and view all the answers

What is the boiling point of methyl methacrylate?

100.8°C Signup and view all the answers

What is the first step in the denture base construction process using the double-pressing technique?

Impression making Signup and view all the answers

Which technique is used for packing resin into the mold space?

Compression and injection molding Signup and view all the answers

During the wax elimination step, what method is recommended to soften the wax?

Boiling water Signup and view all the answers

Which material is applied to prevent monomer penetration into the investing medium?

Colorgard Signup and view all the answers

What is the final step in the denture base construction process?

Trimming/Polishing Signup and view all the answers

Which component is NOT part of the metal flask used in investing?

Rubber liner Signup and view all the answers

What should be done after separating the upper and lower halves of the metal flask during wax elimination?

Pour hot water to create the mold space Signup and view all the answers

How many layers of high fusing pink wax are typically applied for the denture base wax pattern?

1-2 layers Signup and view all the answers

What is the purpose of the trial closure step in denture base construction?

To check for fit and alignment Signup and view all the answers

What is the ideal heating temperature for the resin during the rapid curing process?

74C Signup and view all the answers

Which of the following describes a potential consequence of cooling the flask too quickly?

Warpage due to differential thermal contraction Signup and view all the answers

What does crazing refer to in the context of denture processing?

Linear cracks on the surface Signup and view all the answers

What is a potential issue caused by external porosities on a denture base?

Trapping of food debris Signup and view all the answers

How long should the assembly be placed in the water bath during the rapid curing process?

1-1.5 hours Signup and view all the answers

What may happen if the heating rate of the resin is too high?

Boiling of the monomer Signup and view all the answers

What should be done after processing the denture to avoid warpage?

Cool it slowly to room temperature Signup and view all the answers

What is a consequence of too much pressure during the curing process?

Crazing in the denture Signup and view all the answers

What is the recommended time for bench cooling after removing the flask from the water bath?

30 minutes or more Signup and view all the answers

Which problem can arise from internal porosities in denture bases?

Difficulty in cleaning Signup and view all the answers

What is used as a separating medium to prevent adhesion between the investing medium and the upper and lower halves of the metal flask?

Colorgard Signup and view all the answers

What is the recommended monomer to polymer ratio by weight during the packing of resin?

2 – 2.5:1 Signup and view all the answers

In the injection molding technique, what purpose does the vent in the flask serve?

To attach an outside injector Signup and view all the answers

During what stage does the mixture become stringy and adhesive?

Sticky Stage Signup and view all the answers

What is the primary purpose of the monomer in the polymer process?

To produce a plastic mass Signup and view all the answers

What characteristic of the mold allows it to be filled properly in the injection molding technique?

Soft resin containment Signup and view all the answers

What happens during the damp sand stage of the packing process?

The polymer settles into the monomer Signup and view all the answers

What excess material issue can arise if too much resin is placed in the mold?

Overflow onto the land surrounding the mold Signup and view all the answers

What cleaning method is recommended for the land area created during the investment process?

Wet finger flattening Signup and view all the answers

What is an advantage of using the injection molding technique?

Trial closures are unnecessary Signup and view all the answers

Study Notes

Dental Resins: Curing and Polymerization

Types of Dental Resins
- Heat-cured Resins: Cured by applying heat for several hours.
- Self-cured Resins: Also known as auto-polymerizing resins, cure at room temperature with chemical activation
- Light-cured Resins: Cured using halogen light.

Polymerization: The Building Blocks of Dental Resins

Monomer: A single, small molecule
Polymer: A large molecule formed by the repeated joining of smaller monomers.

Types of Polymerization

Condensation Polymerization: (Step-growth polymerization)
- Monomers join together to form new molecules, releasing byproducts such as water, acids, or ammonia.
Addition Polymerization:
- Monomers add to each other without releasing byproducts.

Uses of Dental Resins in Dentistry

Elastomeric Impression Materials: Used to take impressions of teeth and oral tissues.
Individual Trays: Custom trays used to create a more accurate impression for dentures.
Denture Bases: Forms the foundation of dentures to support the artificial teeth.
Artificial Teeth (Pontics): Used to replace missing teeth.
Relining and Rebasing Materials: Utilized to repair and adjust the fitting of dentures over time.
Soft Liners: Soft, cushioning materials designed to provide comfort and prevent discomfort in dentures.
Crowns and Veneers: Used for restorations to improve the appearance of teeth.

Acrylic Resins: A Common Choice in Dentistry

Acrylic Resins: Polymers derived from ethylene. Composed of:
- Monomer (Methyl Methacrylate): A clear, liquid component that's volatile and sensitive to light.
- Polymer: The solid component formed by polymerization.

Denture Base Construction Using the Double-Pressing Technique

Impression Making: Process of capturing the shape and contours of the mouth to create a cast.
Construction of the Working Cast: A replica of the patient's mouth used to create the denture base.
Construction of a Wax Pattern: The shape of the denture base is modeled in wax.
Investing: Placing a wax pattern in a flask (metal mold) filled with plaster or investment material.
Wax Elimination: Removing the wax pattern from the flask to create a mold space.
Preparation of the Mold Space: The mold is prepared to receive the resin.
Packing Resin: The liquid resin mixed with polymer is packed into the mold space.
- Compression Molding (Dough-Molding Technique): Resin is manually packed and shaped into the mold.
- Injection Molding Technique: Resin is injected into the mold under pressure.
Trial Closure: The two halves of the flask are brought together to verify the mold is properly packed.
Curing: The resin is subjected to heat to solidify and harden.
- Rapid Curing: Rapid heating to cure the resin in a shorter time frame.
- Slow Curing: Slower, controlled heating method.
De-flasking: Separating the hardened denture base from the flask.
Trimming and Polishing: Excess resin is trimmed, and the denture base is polished for smoothness and aesthetics.

Denture Base Failures: Problems to Watch Out For

Porosities (Holes): Can lead to weakened dentures, difficulty cleaning, and food retention.
- Internal Porosities: Located within the denture base.
- External Porosities: Located on the surface of the denture base.

Common Denture Base Defects

Crazing (Cracks): Fine, white or hazy lines on the surface of the denture, often caused by excessive pressure during curing.
Fracture (Breakage): Can be caused by mishandling, too much pressure during separation from the cast, or inadequate curing.
Warpage or Distortion: Occurs when the denture base is subjected to uneven heat or pressure during processing or polishing.

Miscellaneous Resins and Techniques

Repair Resins: Self-curing resins used to fix minor cracks or damage in dentures.
Rebasing/Relining: Replaces the tissue surface of a denture to adapt to changes in the oral tissues or occlusion.
Soft Liners: Provide cushioning and comfort for dentures.
Resin Impression Trays: Custom trays for taking impressions, made from self-curing resins.
Tissue Conditioners: Soft tissue conditioners used to alleviate discomfort and promote healing of oral tissues.
Acrylic Resin Teeth/Pontics: Acrylic resins used in the creation of artificial teeth.

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Description

This quiz explores the various types of dental resins, their curing methods, and the basics of polymerization. Learn about heat-cured, self-cured, and light-cured resins, as well as the differences between condensation and addition polymerization. Test your understanding of these essential concepts in dental materials.