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Questions and Answers
What is the primary purpose of a denture base?
Which of the following materials is commonly used for denture base construction?
Which polymerization method is NOT a technique used for producing denture bases?
What phenomenon affects dimensional changes in dentures during the polymerization process?
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Which property of metallic base dentures is an advantage over polymeric bases?
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What is the reason for keeping dentures wet?
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What stage indicates that acrylic is ready for use in denture construction?
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Which method of polymerization utilizes light to initiate the process?
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What is a disadvantage of porcelain teeth when used in dentures?
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What advantage do polymer (plastic) teeth have over porcelain teeth?
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What is a common consequence of wearing an ill-fitting denture?
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What is a key advantage of lab-processed relines compared to soft relines?
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When deciding between making a new denture or performing a denture reline, what factor is most significant?
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What is true about chairside reline materials?
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Why do tissue conditioners need to be frequently replaced?
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What are the implications of using silicone-based reline materials?
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Which statement is a disadvantage of using polymer (plastic) teeth?
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In the context of denture retention, what is considered a mechanical undercut?
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What is the primary purpose of a denture tissue conditioner?
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What happens to the strength of heat-polymerized repairs compared to unbroken material?
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Why might metal-based maxillary dentures compromise retention?
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What is a common method to accelerate the setting of alginate impression materials?
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What type of resin is commonly used in denture repair?
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What leads to the irritation of the residual ridge when tissue conditioners harden?
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What should be used for disinfection of Polyvinyl Siloxane (PVS) material?
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Which type of dental stone is the strongest and most wear-resistant?
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Which viscosity of PVS impression material is recommended for unsupported and movable tissues?
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What characteristic of Polyether requires it to be disinfected differently than Polyvinyl Siloxane?
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What is the primary use of Type I wax in dental procedures?
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Which statement about all types of dental stones is true?
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Which type of wax is used to capture sections of oral mucosa in a nonfunctional state?
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What determines the viscosity of Polyvinyl Siloxane (PVS) to be used for making impressions?
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What is the primary purpose of hypochlorites in denture cleaning?
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Which of the following is a potential drawback of using oxygenating agents on dentures?
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In which scenario are denture adhesives typically recommended?
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What is a characteristic of paste-based denture cleansers?
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What is one of the risks associated with certain denture cleansers in patients with natural teeth?
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What is the recommended approach to clean delicate or distortable tissues in denture impressions?
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Which type of denture cleanser is designed to be sprinkled over a wet denture base?
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For what type of patients are denture adhesives least likely to be necessary?
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Study Notes
Denture Base Materials
- Denture bases are fabricated from polymers or metals
- Polymeric materials are most popular because they are easy to shape, form, and have less weight than metals
- The purpose of the denture base is to cover the residual ridge, provide facial contour, hold denture teeth in the correct position, and provide intimate contact with mucosa without interfering with movements of cheeks and tongue
Polymethyl Methacrylate (PMMA)
- PMMA is a common material used for denture base construction
- PMMA can be polymerized using heat, chemical reaction, microwave energy, and light activation
Stages of Acrylic Polymerization
- The dough stage is the stage where the acrylic is ready to work with
- Dentures must be kept wet to prevent shrinkage
- Resin shrinkage during polymerization is between 0.3 to 0.5%
- Dentures are slightly smaller due to shrinkage and absorb water from their storage fluid, expanding slightly to almost the original dimensions
Tooth Retention
- Mechanical undercuts with no chemical bonding and micromechanical retention are used for tooth retention
Porcelain Teeth
- Advantages: hard and wear-resistant, less likely to demonstrate a loss of occlusal vertical dimension
- Disadvantages: hard, can lead to excessive wear of natural teeth, transmits impact forces to the underlying mucosa increasing bone resorption, susceptible to fracture with minimal trauma, can produce a clicking sound, difficult to contour and adjust
Polymer (Plastic) Teeth
- Advantages: softer than porcelain, less stress on the residual ridge, easily contoured, less likely to fracture
- Disadvantages: less wear resistant, occlusal surfaces wear more rapidly than porcelain teeth
Denture Liners
- Denture liners are used to address ill-fitting dentures due to residual bone resorption
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Chairside Reline Materials:
- Powder and liquid mixed, similar to autopolymerizing denture base material
- Single cartridge placed into delivery gun
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Laboratory Reline Materials:
- Old surface is roughened, impression material is placed on denture base, and inserted into the patient's mouth
- New denture base material is added and polymerized against the old base under heat and pressure
- Soft, silicone-based reline material for longer flexibility
Denture Tissue Conditioners
- Temporary denture liners that cushions the underlying residual ridge and allows tissues to heal
- Used for irritated and inflamed tissues
- Must be frequently replaced as it can become hardened, lose resiliency, and leach out plasticizers
Denture Repair
- Autopolymerizing resin is used for denture repair of lost teeth or fractured base
- Create locks or undercuts using liquid and acrylic for a stronger polymer
- Transverse strength of heat-polymerized repairs: 80% of unbroken material
- Transverse strength of chemically polymerized repairs: 60% of original strength
Impression Materials
- Alginate Hydrocolloid (Irreversible Hydrocolloid): frequently used for preliminary impressions
- Polyvinyl Siloxane (PVS) and Polyether: elastomeric impression materials used for final impressions
PVS
- Available in light-bodied, medium-bodied, heavy-bodied, and putty viscosities
- Viscosity selection depends on the consistency of tissue
- More unsupported and movable tissue requires lighter-bodied material to minimize distortion
- Hydrophobic, can be soaked in disinfectant
Polyethers
- Hydrophilic, must be spray disinfected
- Impressions do not need to be poured immediately
Dental Stones
- Different types of stones vary in hardness, strength, surface detail reproducibility, and setting expansion
- Maximal properties are achieved through correct proportions of water and powder, and mixing techniques
- Stones release heat during curing (exothermic)
Types of Stones
- Type I (Impression Plaster): very soft, weak
- Type II (Model Plaster, Mounting Stone): highest setting expansion, weaker than Types III and IV
- Type III (Dental Stone): less strong than Type IV, slightly more expansion, used to fabricate master casts
- Type IV (High-Strength Stone): very hard, strong, wear-resistant, and low expansion
Interocclusal Registration Materials
- Moldable thermoplastic material or Polyvinyl Siloxane used for registration materials
Dental Waxes
- Baseplate Wax: available in three hardness levels with varying flowability at different temperatures
- Sticky Wax: used to attach parts of a denture during processing
- Low-Melting Impression Wax: used to capture delicate tissues in a nonfunctional state
Denture Cleansers
- Abrasive Cleansers: soft-bristled brushes recommended for removing debris
-
Solution Cleansers:
- Hypochlorites: antibacterial agent, removes protein, but corrosive to metal and can cause discoloration
- Oxygenating Agents: perborates, peroxides, perarbonates effective but should not be used with soft liners as they can harden it
- Mild Acids: use caution as they can potentially etch natural teeth
Denture Adhesives
- Used primarily for denture stabilization in emergency situations
- Indications: little to no remaining ridge, cleft palates, post-cancer treatment prostheses
- Denture cleaners should not be used with adhesive materials as they can dissolve the adhesive
Denture Adhesive Product Types
- Powder-Based Products: sprinkled on a wet denture base and inserted into the mouth
- Paste-Based Products: water-resistant, spread in a thin layer
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Description
Test your knowledge on denture base materials, focusing on polymeric materials like PMMA, the stages of acrylic polymerization, and their applications in dental prosthetics. This quiz covers essential concepts and details important for understanding the fabrication and function of dentures.
