Dental composites, also calle white fillings, are a group of restorative materials used in dentistry. As with other composite materials, a dental composite typically consists of a resin-based oligomer matrix, such as a bisphenol A-glycidyl methacrylate BISMA 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 begins the polymerization reaction of the resins when external energy (light/heat etc.) is applied. A catalyst package can control its speed.