Surface hardness of a resin composite cured with a transparent cone.

The purpose of this study was to evaluate the surface hardness of a resin composite (TPH) polymerized with and without the use of a transparent light-curing cone. Twenty composite blocks were made on a Teflon mold with cylindrical holes of 3 mm depth and 6 mm radius, and were light cured following different procedures. Group 1: Ten samples were pressed with a glass slide and light cured for two 40-sec exposures without the plastic cone; Group 2: Ten samples were light cured using the transparent plastic cone which was pressed down into the composite until the tip was 1 mm from the floor of the cylindrical Teflon mold. The curing light was activated for 40 sec. The cone was then removed and the remaining part of the mold was filled in one portion, pressed with a glass slide, and light cured for 40 sec. After curing, the samples were placed in distilled water for 48 hr. The hardness of the samples was then measured with a Rockwell Hardness Tester at three different points on each composite block; therefore, 30 measurements per group were taken. The data were statistically analyzed using an unpaired Student's t test. The results revealed that the resin composite cured with the transparent plastic cone had a statistically significant higher surface hardness value (P < 0.0001) than the group cured without the cone.