Prosthodontic Applications of Polymethyl Methacrylate (PMMA): An Update

Abstract

A wide range of polymers are commonly used for various applications in prosthodontics. Polymethyl methacrylate (PMMA) is commonly used for prosthetic dental applications, including the fabrication of artificial teeth, denture bases, dentures, obturators, orthodontic retainers, temporary or provisional crowns, and for the repair of dental prostheses. Additional dental applications of PMMA include occlusal splints, printed or milled casts, dies for treatment planning, and the embedding of tooth specimens for research purposes. The unique properties of PMMA, such as its low density, aesthetics, cost-effectiveness, ease of manipulation, and tailorable physical and mechanical properties, make it a suitable and popular biomaterial for these dental applications. To further improve the properties (thermal properties, water sorption, solubility, impact strength, flexural strength) of PMMA, several chemical modifications and mechanical reinforcement techniques using various types of fibers, nanoparticles, and nanotubes have been reported recently. The present article comprehensively reviews various aspects and properties of PMMA biomaterials, mainly for prosthodontic applications. In addition, recent updates and modifications to enhance the physical and mechanical properties of PMMA are also discussed.

Keywords: CAD/CAM PMMA; artificial teeth; dental base; obturators; polymers; prosthesis; prosthodontics.

Figure 1

Classification of denture base polymers based on polymerization activation and according to the ADA specifications.

Figure 2

Manipulation and various stages of PMMA manual mixing and handling for denture fabrication: (a) PMMA powder in a mixing bowl; (b) pouring of the monomer solution into PMMA for mixing; (c) sandy stage, whereby the monomer solution has full wetted and saturated the PMMA particles; (d) start of stringy stage; (e) progression of the stringy stage; (f) dough stage ready for packing and plastic molding; (g) rubbery stage followed by the hardened PMMA, whereby plastic deformation is no longer possible; (h) fabricated denture using heat-cured PMMA and acrylic teeth after finishing and polishing.

Figure 3

Ideal properties required for the PMMA materials for denture base applications.

Figure 4

Key applications of PMMA: (a) in various biomedical disciplines; (b) secondary impression tray; (c) acrylic artificial teeth; (d) denture with acrylic teeth; (e) provisional fixed partial denture, crown; (f) orthodontic retainer; (g) occlusal splint; (h) palatal obturator replacing lost tissue following maxillectomy.

Figure 5

Various representative examples of PMMA modifications and associated outcomes: (a) randomly distributed filler particles allowing crack propagation; (b) uniformly dispersed particles that enhance fracture toughness through crack diversion [66]; (c) impregnation with ZrO₂ resulted in increased Vickers hardness values [51] and (d) flexural properties [30]; (e) silica nanoparticle surface modification using trietoxyvinylsilane and chemical bonding to MMA to enhance the fracture toughness (f) of modified PMMA (from [240] with permission), PMMA (control), PMMA reinforced with silica (SiO₂) nanoparticles measuring ~12 nm (PMMA-SIL), and PMMA containing trietoxyvinylsilane-modified SiO₂ nanoparticles (PMMA T-SIL); (g) antimicrobial functionalization of PMMA by adding zinc oxide, potassium sorbate (PS), and sodium metabisulfite (SM) (from [241] with permission) showed no remarkable effects on L929 cell viability (h), however resulted in a significant antimicrobial action against bacteria and Candida albicans (I).