There are three structural components in dental resin-based composites:
1. Matrix-A plastic resin material that forms a continuous phase and binds the filler particles
2. filler-Reinforcing particles and or fibers that are dispersed in the matrix
3. Coupling agent-Bonding agent that promotes adhesion between filler and resin matrix
Composite restorative materials contain a number of components in addition to the resin matrix, inorganic filler particles, and a coupling agent. An activator-initiator system is required to convert the resin paste from a soft, moldable filling material to a hard, durable restoration.
Other components are included to enhance the performance, appearance, and durability of the material. Pigments help to match the color of tooth structure. Ultraviolet (UV) absorbers and other additives improve color stability polymerization inhibitors extend storage life and provide increased working time for chemically activated resins.
Resin matrix is a blend of aromatic and/or aliphatic dimethacrylate monomers such as bis-GMA, one of the most widely used ingredients. This resin is commonly referred to as “Bowen’s resin”
triethylene glycol dimethacrylate (‘I’EGDMA) and Urethane dimethacrylate (UDMA), bis-GMA, and TEGDMA are widely used Resin matrix ingredients that form highly cross-linked polymer structures.
Resin matrix diluent monomers can be any fluid methacrylate but are usually dimethacrylates such as TEGDMA.
Incorporation of filler particles into a resin matrix greatly improves material properties, provided that the filler particles are well bonded to the matrix.
If not, the filler particles do not provide reinforcement and can actually weaken the material. the use of an effective coupling agent is extremely important to the success of a composite material.