Dental Composite is a Synthetic Resin which has gained popularity as a restorative material as it is insoluble (saliva and other fluids), aesthetic, insensitive to dehydration, easy to manipulate and reasonably inexpensive. Earlier used restorative materials needed excessive tooth preparation to obtain a specific cavity shape and form to give the restorative material structural support to bear occlusal forces. But with Composites which involve multiple steps like acid etching, dentin bonding agent and then Composite Resin the need for excessive tooth preparation or cavity extension is minimized and bond strength is high as well.
Definition of Composite Resin: “It is a three dimensional combination of two or more chemically different materials with a distinct interphase between them. In combination, the properties are superior to those of the individual components”
Dental Composite consists of Organic phase – resin matrix which is reinforced by inorganic phase – fillers. A Saline coupling agent is included to provide interfacial bonding between two different chemical agents. Activators, initiators and inhibitors are also included to control the time and other factors of polymerization reaction. Various coloring agents are also incorporated to give the proper shade, opacity, translucency available.
Generations of Dental Composites:
1st Generation Composite:
It consists of macro-ceramic reinforcing phases in resin matrix.
Due to macro-ceramic phase this generation has the highest surface roughness and at the same time good mechanical properties.
2nd Generation Composite:
Consists of colloidal and micro-ceramic reinforcing phases in resin matrix.
Due to the presence of micro-ceramic phase this generation exhibits a very smooth texture
The coefficient of thermal expansion is unfavorable due to less filler loading.
In terms of wear resistance it is better than first generation, while strength is low.
3rd Generation Composite:
hybrid composites in which there is combination of macro and micro (colloidal) ceramics as reinforces in 75:25 ratio.
Good surface smoothness due to presence of micro ceramics while strength is reasonable due to macro ceramics
Overall properties are in between 1st and 2nd generation
4th Generation Composite:
These are also a type of hybrid composite, but instead of macro-ceramic fillers, these contain heat cured irregularly shaped, highly reinforced composite macro particles, along with micro (colloidal) ceramics.
As compared to previous generations, it has better surface characteristics and mechanical properties.
They produce superior restorations but are very technique sensitive.
5th Generation Composite:
Hybrid system in which resin phase is reinforced with micro ceramics and macro, heat cured spherical, highly reinforced composite particles. Because of specific shapes of macro-molecules, it is easier to work with and gives better final shape and finish. Surface texture and wear of these materials are comparable to 2nd generation composites, which is smooth and gives a natural and the required finish. When it comes to Physical and mechanical properties are similar to 4th generation composites.
6th Generation Composite:
It is a Hybrid Composite consisting of heat-cured, spherical, highly reinforced macro composite, particles with micro (colloidal) ceramics. It has the best mechanical properties of all generations due to the presence of reinforcing particles. It also has good finishing and polishing properties because of different shapes of macro molecules.