Composite resin

Dental composite resins are types of synthetic resins which are used in dentistry as restorative material or adhesives. Synthetic resins evolved as restorative materials since they were insoluble, aesthetic, insensitive to dehydration, easy to manipulate and reasonably inexpensive. Composite resins are most commonly composed of Bis-GMA and other dimethacrylate monomers (TEGMA, UDMA, HDDMA), a filler material such as silica and in most current applications, a photoinitiator. Dimethylglyoxime is also commonly added to achieve certain physical properties such as flow ability. Further tailoring of physical properties is achieved by formulating unique concentrations of each constituent.

Many studies have compared the longevity of composite restorations to the longevity of silver-mercury amalgam restorations. Depending on the skill of the dentist, patient characteristics and the type and location of damage, composite restorations can have similar longevity to amalgam restorations. (See Longevity and clinical performance.) In comparison to amalgam, the aesthetics of composite restorations are far superior.

Traditionally composites set by a chemical setting reaction through polymerization between two pastes. One paste containing an activator (tertiary amine) and the other containing an initiator (benzoyl peroxide). To overcome the disadvantages of this method, such as a short working time, light-curing resin composites were introduced in the 1970’s. The first light-curing units used ultra-violet light to set the material, however this method had a limited curing depth and was a high risk to patients and clinicians. Therefore, UV light-curing units were later replaced by visible light-curing systems which used Camphorquinone as a light source and overcame the issues produced by the UV light-curing units.

The Traditional Period

In the late sixties, composite resins were introduced as an alternative to silicates and unfulfilled resins, which were frequently used by clinicians at the time. Composite resins displayed superior qualities, in that they had higher mechanical properties than silicates and unfulfilled resins. Composite resins were also seen to be beneficial in that the resin would be presented in paste form and, with convenient pressure or bulk insertion technique, would facilitate clinical handling. The faults with composite resins at this time were that they had poor aesthetics, poor marginal adaptation, difficulties with polishing, difficulty with adhesion to the tooth surface, and occasionally, loss of anatomical form.

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