Dental Composite Materials

Dental composite materials fill in areas where decayed tooth matter was removed. This procedure is commonly known as a filling. Many materials comprise a single filling, each with a distinct role. A resin is used as the base material for the composite. Coupling agents increase the adherence of the resin to the tooth. Dental composites require free radicals to start polymerization. This can be achieved by heat, chemical or photochemical catalysts.

Resins

• Since the late 1950s, dentists have used bisphenol glycidylmethacrylate (BIS-GMA) as the resin in fillings. It is mixed with a diluting agent, which makes it easier for the dentist to shape and work with. According to Dentalcomposites.com, the most common diluting agents are methylmethacrylate (MMA), bisphenol dimethacrylate (BIS-DMA) and urethane dimethacrylate (UDMA).

Coupling Agents

• According to Dentalcomposites.com, coupling agents chemically coat filler surfaces and increase strength. Silanes, a silicon chemical compound, are a common coupling agent that has been used since the 1950s. Common silane agents are vinyl triethoxysilane and methacryloxypropyltrimethoxysilane.

Heat Catalysts

• Heat catalysts initiate the polymerization process, which combines monomers (single components) into a polymer (a mixture of components). This process joins the molecules of the various materials used in a filling so that they form a strong structure. The most commonly used heat catalyst is hydroquinone. Other common heat catalysts are benzoylperoxide, t-butylperoxide and t-cumythydroxyperoxide.

Chemical Catalysts

• Chemical catalysts also initiate polymerization. One drawback of chemical catalysts is that they aren't very color-stable, which results in filling pigmentation. Common chemical catalysts are dimethyl p-toludine and N,N-bis(hydroxy-lower-alkyl)-3,5-xylidine.

Photochemical Catalysts

• Photochemical catalysts also acheive polymerization. They require light to cure the filling, which results in the adherence and hardening of the filling. Different catalyst materials require different wavelengths of light to cure, from ultraviolet to visible blue light. Common photochemical catalysts include camphoroquinone, acenaphthene quinone and benzyl.

Plasticizers

• Plasticizers make the composite more flexible so that it is easier to shape and work with. Many plasticizers are a form of phthalate (dibutyl, dioctol, dinonyl, etc.) or polyethylene glycol.