Artificial Teeth Composition

Diacrylate monomers have been prepared that are photocurable in visible light and that have small polymerization shrinkage and high X-ray contrast properties. When polymerized with 0.01 to 0.04 pm glass powder, these dental composites were easily machined into artificial teeth. 

Dental appUcations (composites, artificial teeth and dentures)... 

The various dental polymers discussed in this article include impression materials, dentures and denture liners, artificial teeth, crown and bridge materials, mouth protectors, maxillofacial materials, restoratives (consisting of glass polyalkenoates or glass-ionomers and composites), adhesives, and sealants. Specifications and standards for dental materials are also briefly mentioned in the text. 

Commercial interpenetrating polymer networks (not including thermoplastic compositions) include artificial teeth (Dentsply) made Ifom crosslinked PMMA mixed with MMA monomer and polymerized (sequential IPN), sound and vibration damping compositions (e.g., vinyl-phenolic Hitachi) and sheet molding compositions (acryhc/urethane/polystyrene Ferro Chemical) [164]. Water-borne acrylic methane semi-IPNs are commercial Ifom several sources where acrylate monomers are polymerized in the presence of a polymethane water dispersion. A silicone/polytetrafluoroethylene composition described as an IPN is offered by Biomed Sciences under the Silon tradename. The fluoropolymer provides the mechanical strength and the silicone rubber offers the softness and oxygen and moisture permeability for applications in the wound care area. 

Implantation of artificial teeth has received some study. The approach has been to attach a suitable replica of the original tooth to an artificial, porous base. This serves as a root that permits the ingrowth of new living tissue to fix the prosthesis in place. Greenberg and Kamel (6) proposed the use of a porous composite prepared from aluminum oxide particles dispersed in 50 volume % of aqueous poly(acrylic acid). A composite filled with 0.3 microns alumina is said to have a porosity of 38% and compressive strength of 18,000 psi (124 MPa) while a composite filled with 0.05 microns alumina had a porosity of only 15% and a compressive strength of 28,000 psi (192 MPa). 

Nanostructured materials are nothing new. Chrysotile fibers are an example (Fig. 16.22), as are bones, teeth and shells. The latter are composite materials made up of proteins and embedded hard, nanocrystalline, inorganic substances like apatite. Just as with the imitated artificial composite materials, the mechanical strength is accomplished by the combination of the components. 

The largest voliune of polsrmeric materials used in dentistry is in prosthetic applications. Polymeric materials are also important in operative dentistry, being used to produce composite resins, dental cements, adhesives, cavity liners, and as a protective sealant for pits and fissures. Elastomers are employed as impression materials. Resilient prosthetic devices are oft en fabricated to restore external soft-tissue defects. Mouth protectors are fabricated to prevent injury to teeth, as well as prevent head and neck injinaes. Other polymer applications include fabricating patterns for metal castings and partial denture frameworks, impression trays, orthodontic and periodontal devices, space maintainers, bite plates, cleft palate obdurators, and oral implants. Polymeric materials may also be used to fabricate an artificial tongue, when disease results in its loss. 

It should be noted that biological structural materials occurring in nature are typically composites. Common examples are wood, bamboo, bone, teeth, and shell. Furthermore, use of artificial composite materials is not new. Bricks made from straw-reinforced mud were employed in biblical times. This material also has been widely used in the American Southwest for centuries, where it is known as adobe. In current terminology, it would be called an organic fiber-reinforced ceramic matrix composite. 

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