Denture Base Resin: Properties, Benefits

Denture Base Resin

The most commonly used materials for the fabrication of denture bases are polymers such as polymethyl methacrylate or acrylic resin.

Requirements of an Ideal Denture Base:

Polymethyl methacrylate in dentistry

“Best Ways To Understand The Benefits Of Denture Base Resin”

Ideal denture base material The Material Should:

• Be tasteless, odorless, non-toxic, and non-irritant to the oral issue.
• Be aesthetically satisfactory, i.e. should be transparent or translucent and easily pigmented, the color should be permanent.
• Be dimensionally stable. It should not expand, contract or warp during processing and subsequent use by the patient.
• Have enough strength, resilience, and abrasion resistance.
• Be insoluble and impermeable to oral fluids.
• Have a low specific gravity and light in weight.
• Tolerate temperature well above the temperature of any hot foods or liquids taken in the mouth without undue softening or distortion.

“Importance Of Denture Base Resin In Prosthodontics”

• Be easy to fabricate and repair.
• Have good thermal conductivity.
• Be radiopaque (so that broken denture fragments can be detected by X-rays if accidentally aspirated or swallowed and also to examine the extensions of the resin restoration
  in a tooth).
• When used as a filling material it should bond chemically with the tooth.
• Have a coefficient of thermal expansion which match that of tooth structure.
• Be economical.

Denture polymerization process

“Risk Factors For Failure Of Denture Base Resin”

Acrylic Resin Of Ideal Denture Base

Popularity of polymethyl methacrylate occurs from the fact that the material exhibits favorable working characteristics, has acceptable physical, mechanical, and aesthetic properties, and is easy to fabricate with inexpensive equipment.

• Taste and odor: Completely polymerized acrylic resin is tasteless and odorless. On the other hand, poorly made dentures with a high amount of porosity can absorb food and bacteria, resulting in an unpleasant taste and odor.
• Esthetics: It is a clear transparent resin, which can be pigmented (colored) easily to duplicate the oral tissue. It is also compatible with dyed synthetic filers thus esthetics is acceptable.
• Strength: These materials are typically low in strength. However, they have adequate compressive and tensile strength for complete or partial denture applications.
• Modulus of Elasticity: They have sufficient stiffness (2400 MPa) for use in complete and partial dentures.
• Dimensional stability: A well-processed acrylic resin denture has good dimensional stability. The processing shrinkage is balanced by the expansion due to water sorption.

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• Solubility: Acrylic is virtually insoluble in water and oral fluids.
• Stability to heat: Polymethyl methacrylate is chemically stable to heat up to a point. It softens at 125°C.
• Radiopacity: There are instances of broken pieces of dentures being aspirated or swallowed. Radiopacity is a desirable property to enable easy location of fragments.
• Most denture base materials are radiolucent. Radiopacity is obtained by adding heavy metal salts such as bismuth or uranyl at a concentration of 10 to 15%

“The Role Of Polymerization In Improving Denture Base Resin Performance”

Dimensional stability of acrylic resin
Thermal properties:

• Stability to heat: Polymethyl methacrylate is chemically stable to heat up to a point. It softens at 125°C. However, above this temperature, i.e. between 125°C and 200°C it begins to depolymerize. At 450°C, 90% of the polymer will depolymerize to monomer.

Thermal conductivity: They are poor conductors of heat and electricity. This is undesirable because patients wearing acrylic complete dentures often complain that they cannot feel the temperature of food or liquids they ingest, thus reducing the pleasure. Replacing the palatal portion with metal is one solution because the metal is a better conductor of heat.

“Difference Between Heat-Cured And Cold-Cured Denture Base Resin”

• Coefficient of thermal expansion:
  • These materials have a high coefficient of thermal expansion (CTE).
  • The CTE for polymethyl methacrylate resin is 81 × 106/°C.
  • The addition of filers reduces CTE.
• Heat distortion temperature: This is the measure of the ability of a plastic to resist dimensional change when loaded under heat. It is measured by observing the temperature at which a specimen under 1.8 MPa load defects 0.25 mm.
  • Heat distortion temperature for PMMA  — 71 to 91°C.
  • Heat distortion temperature for vinyl resin  —  54 to 77°C.
  • Distortion is of concern during procedures like the repair or polishing of dentures.
  • The temperature should be kept low to avoid distortion.

“Understanding The Role Of Denture Base Resin In Modern Dentistry”

• Color stability: Heat-cure acrylic resins have good color stability. The color stability of self-cure resin is slightly lower.
• Biocompatibility: Completely polymerized acrylic resins are biocompatible.
• Adhesion: The adhesion of acrylic to plastic denture teeth is good chemical adhesion.
• Shelf life: Acrylic resins dispensed as powder and liquid have the best shelf-life.