Resin-Based Composites

Composite

solid that contains two or more different component materials/phases that have physical properties (strength/elasticity) that are significantly changed then when in a homogenous material

Resin-base composite (RBC)

dental materials used for restorations, such as fillings, veneers, inlays, and crowns

Three historical classifications of development for composite

1)Bonding

2)Fillers

3)Curing

Bonding history

1)Unbound composite (shrink and pop out)

2)Acid etch and enamel bonding

3)Dentin-bonded composite

Filler history

1)Original development (large filler particles)

2)Smaller filler particles

3)Nanohybrid composite

Curing history

1)Self cured

2)UV cured

3)Visible light cured (LED)

Basic composition of composite (6)

1)Resin matrix

2)Filler particles

3)Coupling agent

4)Initiator/inhibitors

5)Pigment

6)Other (antibiotics/stain)

Resin matrix monomers

they are the scaffolding that provides shape and stiffness for composite

Ex/Bis-GMA and TEGMA

Bis-GMA

most common matrix monomer

TEGMA

matrix monomer used to dilute Bis-GMA and allow for more particles/fillers

Filler particles

they reinforce the matrix, reduce shrinkage, reduce thermal expansion/contraction, decrease water sorption, radiopacity, and control workability/viscosity

Ex/quartz, glass Sol-gel ceramic, microfine silica, and silica nanoparticles

Coupling Agent (Silane)

provides bonding between inorganic filler particles and organic resin matrix to enhance mechanical properties and reduce clinical wear

Types of initiators (2)

1)Chemical initiators (redox)

2)Photo-initiators

Chemical initiator (redox)

polymerization begins when two components are mixed together, which releases a radical that breaks the double bond on the end of a monomer

Photo-initiator

Is a chemical/light that initiates the polymerization reaction. The key thing to remember here is that it takes the combination of the resin, photo-initiator, and the proper curing bulb to cause the gel to cure completely.

Inhibitors

prevent spontaneous polymerization to increase shelf-life and working time

Ex/Hydroquinone

Resin polymerization

causes shrinkage rate of 2-5.5%

Clinical implications of resin shrinkage (7)

1)Internal stress

2)Cusp deformities

3)Marginal gaps

4)Enamel cracks

5)Marginal leaks

6)Sensitivity

7)Secondary caries

Optical characteristics

multiple shades and translucency to appear like dentin/enamel

Classifications of resin-based composites

1)Filler particle (size/distribution)

2)Clinical usage (flowable/universal)

3)Polymerization reaction (light-cured, self-cured, dual-cured)

Filler particle classification (3)

1)Microfill

2)Mini/Midfill/Microhybrid

3)Nanofilled/Nanohybrid

Microfill

40-50 nm sized fillers, pre-polymerized with mixed monomers, polished, highest luster, smoothest surface, low stress bearing, and esthetic areas

Mini/Midfill or Microhybrid

<1μm sized filler, high strength, good wear, and used for anterior/posterior restorations

Nanofilled or Nanohybrid

<100 nm sized filler, high strength, esthetics, and polished

Clinical application classification (4)

1)Packable (high viscosity)

2)Flowable (low viscosity)

3)Conventional (regular viscosity)

4)Bulk-fill (conventional/low viscosity)

Packable composite

high viscosity, posterior teeth, difficult to adapt, rarely used, and similar to amalgam

Flowable composite

low viscosity, easy to adapt, inferior mechanical properties, and not load bearing

Convention composite

regular viscosity, universal composite, nanofiller/nanohybrid/microhybrid, higher resistance, low wear, load bearing, and increased polymerization shrinkage (stress)

Bulk-fill composite

conventional (high resistance and low wear) or low viscosity (low resistance and high wear), posterior restorations, reduced stress from polymerization shrinkage, and deeper curing depth

Type I polymerization restorative material

suitable for restorations of occlusal surfaces

Type II polymerization restorative material

suitable for restoration of all other surfaces besides occlusal surfaces

Class I restorative material

materials whose setting is initiated by mixing and initiator and activator (self-curing)

Class II restorative material

materials whose setting is initiated by application of external source (blue light/heat)

Group I: energy applied intra-orally

Group II: energy applied extra-orally

Class III restorative material

materials whose setting is initiated by an external energy source and also have self-curing mechanism (dual cure)

Desirable physical properties for composite (5)

1)Linear coefficient of thermal expansion (similar to teeth)

2)Water sorption (increase filler decrease water sorption)

3)Wear

4)Modulus of elasticity (increase filler increase stiffness)

5)Color stability (maintain color)