Denture Base Materials Quiz

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
• Chairside Reline Materials:
  • Powder and liquid mixed, similar to autopolymerizing denture base material
  • Single cartridge placed into delivery gun
• 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

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.