Directly placed tooth-colored materials

Early composite materials were supplied as two pastes (Fig. 9.2), both containing mixtures of monomers and fillers, and one paste with a polymerization initiator (typically a peroxide), and the other with an activator 

2 Two-part, chemical cure paste composite filling material by 3M. 

3 Dimethacrylate monomers employed in dental resin composites. 

The use of a diluent monomer gives problems, however. Polymerization shrinkage is increased leading to problems of bonding at the adhesive interface with tooth dentin (Puckett et al., 2007). 

With added fillers - typically 70 wt% for early materials - the dimethacrylate monomers form very viscous pseudoplastic pastes (Watts et al., 1980). The manipulation of these materials was very technique-sensitive. Thorough mixing of the two pastes was essential, yet this was difficult to ensure, given that both pastes were of the same color. 

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Since the development of resin composites, other types of directly placed tooth-colored restorative materials have been developed, some of which are formulated to be capable of being syringed. These include ... 

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