Elastomers for maxillofacial applications.

Systematic evaluations of the properties of prosthetic facial materials began to appear in 1969 with a report by Cantor et a/. ’ They reported that plasticized poly(methyl methacrylate) was the best material with respect to resistance to tearing and degree of elongation. A year later, Walter2 reported the specific gravity, water sorption, thermal conductivity, strain in compression, and permanent deformation on an acrylic ester resin, two silicone rubbers and a pourable latex rubber. The laboratory results and clinical trials indicated that the ‘high compressibility and good tissue compatibility of the acrylic polymer made it the choice over the other elastomers. In 1971, Roberts3 published the physical properties of a heat-cured silicone material and two room-temperature cured silicone elastomers and found tensile strengths from 300-1000 Ibs/in*, ultimate elongations from lOO-350%. tear strengths from 20-100 Ibs/in and hardnesses from 45-50 Shore A numbers. The following year, Sweeney et aL4 determined the properties of a poly(vinyl chloride) maxillofacial material and proposed a set of requirements for such materials including an accelerated aging test for evaluating changes in colour but not mechanical properties. In 1973 a symposium was held to discuss priorities in dental biomaterials research5. At that symposium Castleberry discussed the choices and challenges of materials for external maxillofacial prostheses. Materials reviewed at that time were poly(vinyl chloride), heatand room-temperature cured silicones, silphenylene[poly(siIphenylenedimethylsiloxane)] , and polyurethanes. The next year, Lontz et aL7 reported how the properties of polysiloxanes could be modified by oils and crosslinking agents to approximate the stress-strain profiles of human tissues such as aorta and tendon. Since 1974 there has been a significant increase in research on maxillofacial materials by Koran and Craig8, Goldberg et a/.g-1 l, Yu et al. ‘*, May et al. 13, Gonzalez14, and Koran and co-workers15-20. It is the purpose of this paper to review the developments of maxillofacial materials in the 1970’s.