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What is the primary purpose of a denture base?
Which of the following is NOT a method of polymerizing denture base resin?
What is the result of resin shrinkage during polymerization?
What is an advantage of metal-based dentures?
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What do denture bases typically cover?
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Which of the following materials is most commonly used for denture base construction?
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Why must dentures be kept wet?
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What does polymerizing denture base resin involve?
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What is a disadvantage of porcelain teeth in dentures?
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What should a clinician consider if there is a large space due to ridge loss?
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Which of the following is an advantage of polymer (plastic) teeth over porcelain teeth?
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What are the two types of chairside reline materials mentioned?
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What would be a drawback of using porcelain teeth in dentures?
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Which type of retention is described as mechanical undercut?
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What should be done if the occlusal vertical dimension has been lost due to ridge resorption?
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What is a major benefit of using polymer (plastic) teeth over porcelain?
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What type of polyvinyl siloxane impression material is preferred for unsupported and movable tissues?
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How do polyethers differ from polyvinyl siloxane in terms of disinfection?
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Which type of dental stone has the highest setting expansion?
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What is a characteristic of Type IV dental stone?
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Which statement is true regarding the setting of dental stones?
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What is the primary use of Type 1 baseplate wax?
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Which impression material is known for being moldable thermoplastic?
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What is true about low-melting impression wax?
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What is a key advantage of lab-processed relines using heat and pressure?
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What is a primary disadvantage of soft, silicone-based reline materials?
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Why must tissue conditioners be frequently replaced?
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What is the function of denture repair using autopolymerizing resin?
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What is the transverse strength of heat-polymerized repairs compared to unbroken material?
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What type of denture cleansers are abrasive cleansers categorized as?
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What type of impression material is alginate?
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What happens to alginate when breaking the seal around an impression?
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Which agent is known for its antibacterial properties in denture cleaning?
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What is a notable characteristic of a temporary denture liner?
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Why should oxygenating agents not be used on dentures with a soft liner?
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In what situation are denture adhesives typically recommended?
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What can result from using certain denture cleaners on patients with natural teeth?
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How is the powdered denture cleanser applied?
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What is the primary function of paste-based denture cleansers?
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Which group of denture cleansers would include hypochlorites?
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Study Notes
Denture Base Materials
- Denture bases are fabricated from either polymeric materials or metal.
- The most common material is a polymer, which is easily shaped and formed.
- The denture base serves five key functions:
- Covers the residual ridge.
- Provides facial contour.
- Holds denture teeth in place.
- Provides intimate contact with the mucosa.
- Allows for movement of cheeks and tongue.
- Polymethyl Methacrylate (PMMA) is commonly used for denture base construction.
Polymerization
- Polymerization is the process of joining monomers (small molecules) to form polymers (large molecules). There are four types of polymerization used in denture construction:
- Heat Polymerization: Acrylic is heated to activate chemical bonds, forming a solid structure.
- Chemical Polymerization (Auto-Polymerized): Chemical initiators are mixed with acrylic monomers, triggering a chemical reaction to form a polymer.
- Microwave Energy: Micro-waves heat the acrylic, accelerating polymerization.
- Light Activation: UV or LED light triggers a chemical reaction in acrylic monomers to form a polymer.
Resin Shrinkage
- Resin shrinkage during polymerization is a natural occurrence, ranging from 0.3% to 0.5%.
- Denture dimensions will be subtly smaller after polymerization.
- The denture will absorb water from its storage fluid, expanding slightly (0.1%-0.2%). This compensates for the initial shrinkage.
Metal-Based Dentures
- The tissue-bearing side of the denture is made of metal for improved fit and heat transfer.
- Polymers are used on the outside of the denture to mimic gingiva and hold the teeth.
- Metal dentures offer the following advantages:
- More accurate fit.
- Transfer heat from food and beverages to the palate.
- Added weight can aid in denture stability, especially in the mandible.
- Metal-based maxillary dentures may compromise retention due to added weight.
Tooth Retention
- Denture teeth are retained through two primary methods:
- Mechanical Retention: Using undercuts in the base to physically lock the teeth into the denture.
- Micromechanical Retention: Using a textured surface on the base to create a grip that holds the teeth in place.
Porcelain Teeth
- Porcelain teeth are hard and wear-resistant, less likely to show a loss of occlusal vertical dimension.
- Some disadvantages of porcelain teeth include:
- Their hardness can lead to excessive wear on opposing natural teeth.
- They transmit forces to the residual ridge, increasing bone resorption.
- They are prone to fracturing with minimal trauma.
- They can produce a clicking sound.
- They are challenging to contour to fit ridges and adjust during insertion.
Polymer (Plastic) Teeth
- Polymer teeth are softer than porcelain teeth and are less likely to stress the residual ridge.
- Advantages of Polymer teeth:
- They are softer than porcelain teeth.
- They transmit less stress to the residual ridge.
- They are easy to contour to fit the ridge and adjust during insertion.
- They are less prone to fracture than porcelain teeth.
- Disadvantages of Polymer teeth include:
- They wear faster than porcelain teeth.
Denture Liners
- Denture liners are used to address the gaps that occur between the denture base and the residual ridge due to bone resorption.
- Solutions to address these gaps include:
- New Denture: When the ridge loss and space are significant, a new denture is necessary.
- Denture Reline: A thin layer of new plastic is added to the existing denture base to fill the gaps, either at the chairside or in a laboratory setting.
Chairside Reline Materials
- Chairside reline materials are either hard or soft, and come in two forms:
- Powder and Liquid: Similar in composition to autopolymerizing denture base materials.
- Single Cartridge: Dispensed through a delivery gun, offering both hard and soft options.
Laboratory Reline Materials
- Laboratory relines involve roughening the denture surface, taking an impression, and adding new material under heat and pressure.
- Laboratory relines offer the benefit of greater strength and resistance to color change.
Denture Tissue Conditioners
- Denture tissue conditioners are temporary liners used to cushion the residual ridge, promote healing, and reduce irritation.
- Frequent replacement is essential for continued efficacy.
Denture Repair
- Autopolymerizing resin is commonly used for denture repair, such as replacing missing teeth or rejoining fractured denture bases.
- Undercuts or locks are created using the resin to strengthen the repair.
- Heat-polymerized repairs are stronger than chemically polymerized repairs.
Impression Materials
- Alginate Hydrocolloid, an irreversible hydrocolloid, is a popular choice for impressions.
- Setting time can be accelerated by increasing the temperature of the water.
- The impression should be removed with a rapid snapping motion, breaking the seal around the impression.
Polyvinyl Siloxane (PVS)
- PVS is an elastomeric impression material commonly used for final impressions.
- PVS is available in various viscosities:
- Light-bodied: More fluid-like consistency.
- Medium-bodied: Mid-range viscosity.
- Heavy-bodied: Thicker consistency.
- Putty: Non-fluid, very dough-like consistency.
- The viscosity chosen depends on the tissue being captured. More movable tissues require a lighter-bodied material for minimal distortion.
- PVS is hydrophobic and can be safely disinfected with any disinfectant, as it does not absorb water.
Polyethers
- Polyethers are another elastomeric material. They are hydrophilic and absorb water, so they require spray disinfection and should be placed in a plastic bag for storage.
- Polyether impressions do not need to be poured immediately.
Dental Stones
- Dental stones vary significantly in hardness, strength, detail reproducibility, and setting expansion.
- The properties of stones are influenced by the water-to-powder ratio and mixing technique.
- For optimal results, vacuum spatulation using a motor-driven mixing device can be used.
- Dental stones are exothermic, releasing heat during setting.
Types of Stones
- Type I (Impression Plaster): Very soft and weak; used in specific situations.
- Type II (Model Plaster, Mounting Stone): Has the highest setting expansion but is weaker than Types III and IV.
- Type III Stone (Dental Stone): Offers a relatively high strength and is used for master models.
- Type IV Stone (High-Strength Stone): Very hard, strong, wear-resistant, and with low expansion.
Interocclusal Registration Materials
- Registration materials help to determine the relationship between the upper and lower dentures.
- They are available in two forms:
- Moldable Thermoplastic Material: A wax-like material easily manipulated and adaptable.
- Polyvinyl Siloxane (PVS): A flexible material offering greater accuracy, especially in situations with limited interocclusal space.
Dental Waxes
- Baseplate wax is available in varying levels of hardness and flowability at different temperatures (room temperature, body temperature, and elevated temperatures).
- Type 1 wax is commonly used in denture base construction.
Other Waxes
- Sticky Wax: Used to attach components, especially in denture fabrication.
- Low-Melting Impression Wax: Used to capture delicate, distortable tissues in impressions. It is warmed and painted onto the impression tray.
Denture Cleansers
- Denture cleansers are categorized into two groups: abrasives and solutions.
Abrasive Cleansers
- Abrasive cleansers are paste-based formulations with soft-bristled brushes to gently remove debris.
Solution Cleansers
- Solution cleansers include:
- Hypochlorites: Antibacterial agents, remove protein, but can be corrosive to metal dentures; can cause loss of color and whitening.
- Oxygenating Agents: Peroxides, perborates, and percarbonates are dissolved in solutions to cleanse dentures.
- Mild Acids: Used in some denture cleaners, but can potentially etch natural teeth.
Denture Adhesives
- While generally not necessary with well-made dentures, denture adhesives can be used in emergency situations to stabilize dentures.
- Adhesives are used in cases of:
- Minimal residual ridge.
- Cleft palates.
- Patients with post-cancer treatment intraoral prostheses.
Cautions on Denture Cleansers
- Some denture cleansers can contribute to acid buildup in saliva, which could erode natural teeth.
- Cleaning solutions can also harden soft denture liners.
Denture Adhesive Products
- Powder-based adhesives are sprinkled over the wet denture base prior to insertion.
- Paste-based adhesives are water-resistant and spread thinly over the denture base.
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Description
Explore the essential materials used in denture bases, focusing on polymeric and metal options. Learn about the key functions of denture bases and the various types of polymerization processes involved in their construction. This quiz covers the fundamentals necessary for understanding denture fabrication.
