Resistance to condensation of 'condensable' resin composites as evaluated by a mechanical test.

This study compared the resistance-to-condensation forces of recently introduced condensable resin composites to that of amalgams and conventional resin composites. Using the flat platens of a servohydraulic testing machine, cylindrical specimens of each material 2.8 mm in diameter and 5.5 mm in length were compressed diametrally over two seconds to a thickness of 0.75 mm. Peak forces generated during compression were recorded. This method ranked the various classes of restorative material for resistance to condensation in the same order as most clinicians subjectively reported, with the highest forces observed with admixed dental amalgams, followed in order by spherical amalgams, condensable resin composites and conventional resin composites. Although peak forces observed with the condensable resin composites were generally higher than those observed with conventional resin composites, these were significantly lower than the peak forces observed with amalgams.