A clinical pilot study of the time-dependent composition of tooth bleaching systems.

This pilot study was undertaken to determine the compositional changes in tooth bleaching materials as a function of time in vivo. Ten patients were recruited and two bleaching systems were used - one a paste and the other a gel. Each material was placed in a custom bleaching tray and worn by each patient for each of four times - 15, 30, 60 and 120 min. The material was collected and chemically analysed for water by Karl Fischer titration and titrated for carbamide peroxide by the US Pharmacopoeia method. The paste material contained 18.66% water as supplied, and after 2 h this rose to between 28.6 and 64.4%. The gel material contained 2.85% water as supplied, and after 2 h this was diluted to between 28.5 and 73.4%. There was considerable difference in saliva uptake by the custom tray between patients. Most water uptake usually occurred within the first 30 min. Peroxide concentrations decreased in an approximately linear manner with time. There was a significant difference between the materials from baseline to 30 min and thereafter (P < 0.0009). This pilot study is an effective technique for chemical evaluation of bleaching materials. The effect of saliva is an important factor to consider, and is one that has hitherto not always been appropriately emphasized.