RESUMO
The aim of this study was to compare the effectiveness of three different types of commonly used bleaching techniques using an in-vitro model. Five groups of 10 tooth specimens were prepared and allocated randomly to treatment groups. The four treatment groups tested were a home tray bleaching product, an 'in surgery' tray bleaching product and an 'in surgery power bleaching' product for use with an activating light. The bleaching agent in the latter group was also tested without light activation to assess the additional benefit of the bleaching lamp. A placebo group treated with water was also included. Colour change was assessed using a Vita shade guide and an electronic chromometer. The mean change in shade guide units ranged from 10.9 to 13.2 units, with the 'in surgery' tray bleaching system producing the largest change. For the chromometer readings the mean change in tooth colour ranged from 3.6 to 25.6 units, with the night guard vital bleaching product producing the largest change. This study has demonstrated in vitro that all the different bleaching systems tested produced comparable changes in tooth colour.