CHEMICAL STRUCTURE OF COMPOSITE

[Anonymous]

As with other composite materials, a dental composite typically consists of a resin-based oligomer matrix, such as a bisphenol A-glycidyl methacrylate (BISGMA) or urethane dimethacrylate (UDMA), and an inorganic filler such as silicon dioxide (silica). Compositions vary widely, with proprietary mixes of resins forming the matrix, as well as engineered filler glasses and glass ceramics. The filler gives the composite wear resistance and translucency. A coupling agent such as silane is used to enhance the bond between these two components. An initiator package (such as: camphorquinone (CQ), phenylpropanedione (PPD) or lucirin (TPO)) begins the polymerization reaction of the resins when external energy (light/heat, etc.) is applied. A catalyst package can control its speed.

        

[Anonymous]

Composite resins have a notorious reputation for shrinking upon curing, however, uses as a dental restorative material focus on low shrinkage composites. Composite shrinkage can be reduced by altering the molecular and bulk composition of the resin. For example, UltraSeal XT Plus uses Bis-GMA without dimethacrylate and was found to have a shrinkage of 5.63%, 30 minutes after curing. On the other hand, this same study found that Heliomolar, which uses Bis-GMA, UDMA and decandiol dimethacrylate, had a shrinkage of 2.00%, 30 minutes after curing.[3] In the field of dental restorative materials, reduction of composite shrinkage is a "hot topic".[according to whom?] Soon to be introduced are patent pending, is a safe, non-leaching antimicrobial agent which minimizes recurrent decay of the tooth and reduces the harmful effects of micro-organisms and which some may cause gingivitis and periodontitis (periodontal disease).

        

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