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Composite Resins

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Dental composites are polymeric materials used in restorative dentistry as adhesives and filling materials. They are insoluble, easy to manipulate, and do not dehydrate. The term composite refers to a material that is composed of two different materials. In the case of dental materials, one of the components is a polymer such as Bis-GMA, TEGMA, UDMA, HDDMA, etc., which are di-methyacrylates monomers. Another component is a filler which provides strength to the polymer matrix, such as silica or finely ground glass particles. Dimethyglyoxine could be added in controlled amounts to modify physical properties like viscosity of the resin.

Composites have an advantage over the mercury amalgam filling materials in that they can be color matched to the tooth being worked upon and the surrounding teeth. Thus, they have a much greater cosmetic appeal. For this reason composites may be the material of choice when dealing with the front teeth. Composites can be bonded. This gives them an edge over the amalgam in that they can be used to restore minor fractures or chip-offs. Composite restorations are possible in many situations where sufficient natural tooth structure is not left to hold an amalgam filling. Since composites are to be bonded to the affected area, minimum tooth preparation is necessary.

Composites have several disadvantages.  The main disadvantage is, of course, cost. Composite fillings are more expensive. Such fillings have to be applied layer by layer, and demand much more time and much more expertise on the part of the dentist. This is the primary reason for their high cost. Another shortcoming is their slightly lower physical strength in comparison to amalgam filling materials. They will not withstand as much of chewing stress as amalgam fillings do.

Some insurance plans do not cover composite fillings for this same reason. It may be expected that indirectly placed composites (inlays) may show a better survival rate because they have prepared and cured in the lab with all due care. Studies have, however, not shown any major difference. Indirect application will normally demand an extra visit for the inlay.