Purpose: To compare in vitro the bleaching effects obtained with and without the use of the various lights on power bleaching systems.
Methods: 19 groups of five tooth specimens were prepared and allocated randomly to treatments. Only specimens with shade C4 were accepted for the study. Three commercial bleaching products all based on 35% hydrogen peroxide were used with and without four different light sources. Shade assessments were made using a Shade Guide (SG), Shade Vision System (SVS) and chromometer.
Results: For SG, all but the light only treatment resulted in measurable improvement in shade ranging from 4.6 to 14.6 shade guide units. Similar findings were apparent with SVS and chromometer. No change was seen in the light only treatments by SVS or SG with very small changes by chromometer. In mean terms with all three gels, least change was noted when there was no light used. For SG, SVS and chromometer data analysis over all treatment groups, excluding light only treatments, revealed highly significant differences. Within bleach product treatment differences were only significant with one gel both with and without light activation. Differences between gels with the same light and no light revealed some significant differences in SG and chromometer data but not SVS. In mean terms the order of efficacy of gels with each light and no light was the same for the majority of data sets.