Marginal seals in composite restorations may be improved with the use of less viscous resin material. Although not as durable due to less filler, these composites may be used with materials higher in filler. Heating the composite material to lower the viscosity reduces the film thickness, which may improve the adaptation of the material when it is inserted into the preparation. A study by Wagner, et al assessed the effects of preheating composite resin, followed by immediate or delayed light-curing, in terms of microleakage of class II restorations. Previous studies have shown that heating has no negative effects on the composite’s physical properties, and preheating appears to improve polymerization and hardness of filled composite resins. This in vitro study consisted of class II preparation of extracted teeth, placement of the composite restoration, thermocycling, dye exposure, sectioning, and measuring microleakage. The composite material was heated to 130°F. After allowing the material to cool for 15 seconds, it was either immediately or was delayed light-curing. Thermocycling was done after the cavity was filled and light-cured with the test materials to simulate oral conditions. The study concluded that delaying light-curing of preheated composite material results in greater microleakage than immediate light-curing of preheated composite.
(Source: Oakstone Medical Publishing; study published in Operative Dentistry, January/February 2008)
