Composite formulations, dental polymers

In the first portion of this section, we will focus on the materials and processes used to form polymer dental composites. This section will be followed by a discussion of the problems associated with polymer composite materials. An overview of the photopolymerization behavior and the polymer structure of these highly crosslinked materials is presented in Sects. 3 and 4. Lastly, some of the properties of current composite resin formulations are presented. 

For light-cured materials, the initiator system can be based on camphorquinone, so that cements can be cured with a conventional dental cure lamp emitting at a maximum wavelength around 470nm. Unlike formulations of composite resin, these materials cannot deploy amines as activators, because they would react with the carboxylic acid groups on the polymer, forming salts. Instead, a substance such as sodium p-toluene sulfinide is used as the activator. In addition, a photo-accelerator such as ethyl 4-NJ -dimethylamino benzoate is included [10]. 

The maximum value of Rp (between 10% and 30% conversion) is one of the reliable parameters to measure the reactivity of the formulation. FTIR profiles also provide the amount of unreacted functional groups remaining in the cured system, which is a parameter that strongly affects the final properties of the polymer. Real-time FTIR is also well suited for dark polymerization reactions that occur immediately after light exposure. One of the disadvantages of this technique appears in composite systems, in which the presence of additives may interfere with the transmission of the light by the polymer system, such as in dental composites. ... 

Poly(ether ether ketone) (PEEK), in various formulations, is found in a wide variety of applications as an alternative biomaterial to ceramic, metal and other polymer implants (such as UHMWPE). These applications include trauma fixation, as well as dental, orthopaedic and spinal implants and, as a result of ongoing research, the uses of PERK as a biomaterial continue to grow (Toth et al. 2006). Research conducted by Morrison et al. (1995) emphasised the biocompatibility of PEEK and its composites. This may mean that the probability of adverse tissue reactions induced by wear debris may be minimised through the use of PEEK as an implant material. 

All phenol polymers having free vinyl groups in the side chain (50, 56, and 57) could be furthermore subjected to thermal ciu ing due to cross-linking through the methacryhc groups [47,48]. A multi-methacrylate ohgomer was also prepared by polymer-analogous fimctionahzation of a poly(isopropylidenediphenol) (BPA) resin. Such materials could be of potential interest for the formulation of dental composites as direct esthetic restorative materials [15]. 

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