Denture Bases and Resins in Dentistry

Types of Denture Bases

• Available types of denture bases include: heat activated resins, chemically activated resins (cold or self-cured), light activated resins, soft denture liners, acrylic resin teeth, and obturators for cleft palates/maxillofacial prosthetic devices.

History of Denture Bases

• Earlier materials used for denture bases include: Vulcanite (1839), nitrocellulose, phenol formaldehyde, vinyl plastics, and porcelain.
• In 1937, Poly(methyl methacrylate) (PMMA) polymers were introduced by Walter Wright.
• By 1946, 95-98% of dentures were constructed from PMMA or copolymers.
• Other polymers developed during the Thermoplastic development period (1910-1950) include: vinyl acrylic, polystyrene, epoxy, nylon, vinyl styrene, polycarbonate, polysulfone, polyurethane, polyvinylacetate-ethylene, hydrophilic polyacrylate, silicones, and light activated urethane dimethacrylate.

Acrylic Resins

• Since the mid-1940s, the majority of denture bases have been fabricated using PMMA resins.
• PMMA is a colorless, transparent solid that can be tinted with pigments, dyes, fillers, and fibers to provide various colors, shades, and degrees of translucency.
• The color, optical characteristics, and dimensional properties of PMMA remain stable under normal intraoral conditions.
• Acrylic resins are commonly supplied as a powder-liquid system, which can be mixed in the proper proportions to form a workable mass.
• Polymerization can be activated by chemical, heat, and light energy, as well as microwave energy.

Stages of Acrylic Resin Polymerization

• The mixture enters a stringy stage when the monomer attacks the surfaces of individual polymer beads and is absorbed into the beads, causing swelling of the beads and dissolution of non-crosslinked polymer chains into the liquid monomer.
• The mass enters a doughlike stage when an increased number of polymer chains enter the solution, making it behave as a pliable dough.
• The mixture enters a rubbery or elastic stage when some monomer is dissipated by evaporation, and some penetrates further into remaining polymer beads.
• The mixture becomes stiff and resistant to mechanical deformation when it reaches the final stage.

Soft Lining Materials

• Acrylic soft liner (Vertex) has high peel strength to acrylic denture base, high rupture strength, and some can be polished or cooled.
• Silicone soft liners (RTV and Heat Cured) have resilience, but low tear strength and low bond strength to denture base.

PEEK

• PEEK is a material used for CAD-CAM dentistry, introduced by Whitty in 2013.
• It has properties suitable for dental applications, including strength, durability, and aesthetics.

References

• List of references cited in the text, including Alqurashiab et al. (2021), Aunsavice (2003), Shen (2022), Powers and Wataha (2017), Craig and Powers (2002), Skirbutis et al. (2017), Van Noort (2002), and O'Brien (2002).

This quiz covers different types of denture bases, including heat, chemically, and light activated resins, as well as soft denture liners and acrylic resin teeth. It also touches on obturators for cleft palates and maxillofacial defects.