Dental resin composites dimethacrylate monomers

Dimethacrylate monomers employed in dental resin composites. 

The general approach of graded radiation exposure can also be used to examine light driven processes such as photopolymerization [19]. For example, Lin-Gibson and coworkers used this library technique to examine structure-property relationships in photopolymerized dimethacrylate networks [38] and to screen the mechanical and biocompatibility performance of photopolymerized dental resins [39]. In another set of recent studies, Johnson and coworkers combined graded light exposure with temperature and composition gradients to map and model the photopolymerization kinetics of acrylates, thiolenes and a series of co-monomer systems [40 2]. 

The majority of resins are composed of two dimethacrylate monomers, 2,2 -bis [4(2-hydroxy-3-methacryloyloxypropyloxy)phenyl] propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) [22-28]. Typically, TEGDMA or other methacrylate monomers are added as viscosity modifiers to Bis-GMA to make the solution less viscous and more appropriate for clinical use. These diluents also allow for better distribution of the components during manufacture of these composite systems. Another common monomer used to make dental composites, especially those manufactured in Europe, is urethane dimethacrylate [24,29, 30], Ethoxy bisphenol A dimethacrylate is another modification of the Bis-GMA monomer that can be used to make a more hydrophobic polymer that would better withstand the wet oral environment. Other diluents include low viscosity diacrylates and dimethacrylates. Table 1 lists some of these monomers [31-37]. 

Their concentration in the cured resin is considerably higher for dimethacrylate monomers than for those with a single methacrylate group in the molecule. Infrared reflectance measurements indicate that the residual methacrylate group in commercial dental composites with dimethacrylate ingredients ranges from 30 to 48 percent. 

Most of the dental composite resin materials and denture-base polymers are diluted with the less viscous difunctional acrylates. These are the met-hacrylic monomers of which EGDMA, DEGDMA, triethylene glycol dimethacrylate (TREGDMA) (Fig. 3) and 1,4-butanediol dimethacrylate (BUDMA) (Fig. 4) are the most widely used (Table 2). The use of acrylates in dentistry is an expanding field. Some are... 

The resin matrix of commercial dental composites has bis-GMA (bisphenol-A-glycidyldimethacrylate) as its predominant base monomer. Due to its high viscosity, bis-GMA is mixed with other dimethacrylates, such as TEGDMA, UDMA or other monomers of lower molecular weight [26, 50] to reduce viscosity. The monomers are heavily reinforced with filler particles, which add dimensional stability, improve wear and strength of the material, also reducing polymerization shrinkage [51]. 

There is a need to further enhance the durability of dental composite restorative and sealant materials. Dimethacrylates such as BIS-GMA (the diadduct of bisphenol A and glycidyl methacrylate) are now widely used to formulate the resin component of these materials. Some of the deficiencies of dental composites and sealants are traceable to impurities and inherent structural imperfections in the monomer systems. Structure-property studies are needed to explore ways of achieving minimal shrinkage on polymerization, reducing water sorption, promoting adhesion, generally optimizing the chemical,... 

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