Resin-Based Composites Vocabulary

Flashcards defining key vocabulary, chemical components, and physical properties of resin-based composites as discussed in the lecture notes.

Activation

The process by which sufficient energy is provided to induce an initiator to generate free radicals and cause polymerization to begin.

Activator

The source of energy used to produce free radicals, which can be an electron-donating chemical, light, and/or heat.

C-factor

Configuration factor; the ratio between the bonded surface area of a resin-based composite restoration and the nonbonded or free surface area.

Coupling agent

A compound, such as an organosilane, that provides professional chemical bonds between two dissimilar materials, like silicate-based fillers and the resin matrix.

Degree of conversion ($DC$)

The percentage of carbon-carbon double bonds ($-C=C-$) converted to single bonds ($-C-C-$) during curing to form a polymeric resin.

Depth of cure

The thickness of a light-cured resin that has attained adequate mechanical strength when exposed to a light source under specific conditions.

Dual-cured resin

A dental composite containing both chemical-activated and light-activated components to initiate polymerization.

Filler

Inorganic, glass, and/or organic-resin particles dispersed in a resin matrix to increase rigidity and strength while decreasing thermal expansion and polymerization shrinkage.

Gel point

The point in the polymerization reaction where sufficient crosslinks have formed to produce a rigid, glassy state and internal flow among the polymer chains has stopped.

Inhibitor

A chemical, such as butylated hydroxytoluene ($BHT$) at $0.01\%$ by weight, added to resin systems to minimize spontaneous polymerization and extend storage life.

Initiator

A free radical-forming chemical, like benzoyl peroxide or camphorquinone ($CQ$), used to start the polymerization reaction.

Matrix

A plastic resin material that forms a continuous phase upon curing and binds the reinforcing filler particles.

Oxygen-inhibited layer

A thin surface region of polymerized resin containing unreacted methacrylate groups due to dissolved atmospheric oxygen.

bis-GMA

Bisphenol-A glycidyl dimethacrylate, a high-molecular-weight monomer ($800\,Pa\cdot s$) that forms a crosslinked, durable matrix.

TEGDMA

Triethylene glycol dimethacrylate, a lower-molecular-weight fluid monomer ($0.005$ to $0.05\,Pa\cdot s$) used as a diluent to adjust the viscosity of resin pastes.

UDMA

Urethane dimethacrylate, a resin based on monomers containing urethane groups ($-NH-CO-O-$) and two methacrylate end groups.

Ormocer

Acronym for organically modified ceramics; molecule-sized hybrid structures consisting of inorganic-organic copolymers.

POSS

Acronym for polyhedral oligomeric silsesquioxane; molecules comprising 12-sided silicate cages with the chemical composition $R_nSi_nO_{1.5n}$.

Camphorquinone ($CQ$)

A photosensitizer that absorbs blue light between $400$ and $500\,nm$ to initiate polymerization in light-cured resins.

Macrofillers

Reinforcing filler particles with a size range of $10$ to $100\,\mu m$.

Microfillers

Reinforcing filler particles with a size range of $0.01$ to $0.1\,\mu m$ ($agglomerated$).

Nanofillers

Nonagglomerated reinforcing filler particles with a size range of $0.005$ to $0.1\,\mu m$ ($5$ to $100\,nm$).

Two-body wear

A mode of wear caused by direct contact of the restoration with an opposing cusp or adjacent proximal surfaces.

Three-body wear

A mode of wear simulating the loss of material in noncontact areas due to the abrasive action of food.

Soft-start technique

A clinical curing approach where polymerization begins at low light irradiance and ends with high irradiance to allow for stress relaxation before the gel point.